Does light exist as a distinct right circularly polarized or left circularly polarized state?
If it does exist in these states, does that mean that the passage of a right circularly polarized light through a Left circular polarizer will result in no light passing through it similar to what happen when we use a linear polarizer?
If you are speaking of light from a hot object, such as the Sun, then that light is a mixture of all linear polarizations. Such light is incoherent. The radiators (generally electrons in the outer shells of atoms making up the object, although there are other possible sources) are multitudinous, and are at random orientations.
There are three types of polarization: linear, circular, and elliptical. I'll begin with linear, since it's the easiest to visualize, and since, as I said above (and here's part of the answer to your question), when considered as single photons, all incoherent white light behaves as if it were a mixture of linear polarizations at all angles, and phases, and a continuous range of frequencies.
Linear polarization occurs when the component fields that make up the light are in phase with one another; that is, they reach their maxima, minima, and zero-crossings at the same times. This results in an oscillation of the light wave in a single, preferred direction which is in a straight line. Such light is monophasic and monochromatic, as well as being of linear polarization; if it were not monophasic, then its components would result in elliptical polarization, and if it were not monochromatic, they would fall in and out of phase with one another or "beat" (this last term refers to a phenomenon that will be familiar to musicians who play stringed instruments, as the absence of beat frequencies signifies perfect tuning). The light from lasers is like this, if it is polarized (laser light is by definition monochromatic and monophasic, but the radiators are still randomly arranged as to their angle). White light can also be linearly polarized, but due to the fact that it is a mix of frequencies, it is actually a collection of linearly polarized photons that are not all necessarily linearly polarized with respect to one another, but are linearly polarized with all other photons in the stream that are of the same frequency.
Circular polarization occurs when the component fields are precisely 90 degrees out of phase, one component reaching its maximum when the other is reaching its zero-crossing; in addition, the two components (unlike in linear polarization) must be of equal amplitudes. In this case, there are two distinct topological possibilities: either one field leads, or the other does. These two cases are called "left-" and "right-handed" polarization. But this is actually an artificial polarization; it is a mix of equal amounts of two linear polarizations at right angles to one another, and 90 degrees out of phase to one another. You can see this kind of light (and see that this description must be so) by placing a quarter-wave plate in a linearly polarized beam with the plane of linear polarization oriented at 45 degrees to the quarter-wave plate. CD players use this kind of light to decode the information on a CDROM or audio CD. Currently, this is the only method we know of for creating circularly polarized light; and the method implies that the linearly polarized light is split into two components, one of which is retarded by just enough to put it 90 degrees out of phase with the other.
Elliptically polarized light is a combination of two linear polarizations that are neither precisely in phase nor precisely 90 degrees out of phase, or the components are not of equal amplitude if it is 90 degrees out of phase. Just as with circular polarization, elliptically polarized light can be either right- or left-handed.
Now, all of that said, it is not necessary to decompose light as plane waves (as all three above descriptions have done). Instead, one can construct all other polarizations from combinations of left- and right-handed circularly polarized light; and I expect this is the source of your question. In that case, in the meaning of your first question, no, light does not generally exist as right- and left-handed circularly polarized components; this is merely a convenient method for describing the characteristics of the light as a combination of simpler (and therefore more mathematically tractable) entities, but these entities have no real physical existence. In the case of linear polarization, however, the electromagnetic field (and its electric component, upon which the polarization is based) appears to have actual physical existence (or as much "existence" as such an entity that cannot be directly sensed can have- we cannot directly sense electrons either, after all).
To answer your second question, no, it is not possible to exclude right-hand polarized light with a left-hand polarizer, as can be done with two prisms or two sheets of polaroid film with linearly polarized light; this is because circularly polarized light is by definition a mixture of two rectilinearly polarized linear components, and the device which is used to make circularly polarized light uses a half-wave plate which will exercise its behavior on any incident light of the correct polarization angle. And the same is true of elliptically polarized light and left- and right-hand polarizers. At least, no material we know of is capable of this. However, it is not physically impossible, merely technically impossible, as far as I know; certainly, we do know how to detect right-hand polarized microwaves while excluding left-hand polarized ones of the same frequency. So I suppose there is some chance we might find a means of creating and handling circularly polarized light as conveniently as we do linearly polarized light with polaroid.
And to be entirely honest, polarization is a complex and evolving subject, and it is possible that there have been recent developments of which I have not heard that could allow something like this.
There are three types of polarization: linear, circular, and elliptical. I'll begin with linear, since it's the easiest to visualize, and since, as I said above (and here's part of the answer to your question), when considered as single photons, all incoherent white light behaves as if it were a mixture of linear polarizations at all angles, and phases, and a continuous range of frequencies.
Linear polarization occurs when the component fields that make up the light are in phase with one another; that is, they reach their maxima, minima, and zero-crossings at the same times. This results in an oscillation of the light wave in a single, preferred direction which is in a straight line. Such light is monophasic and monochromatic, as well as being of linear polarization; if it were not monophasic, then its components would result in elliptical polarization, and if it were not monochromatic, they would fall in and out of phase with one another or "beat" (this last term refers to a phenomenon that will be familiar to musicians who play stringed instruments, as the absence of beat frequencies signifies perfect tuning). The light from lasers is like this, if it is polarized (laser light is by definition monochromatic and monophasic, but the radiators are still randomly arranged as to their angle). White light can also be linearly polarized, but due to the fact that it is a mix of frequencies, it is actually a collection of linearly polarized photons that are not all necessarily linearly polarized with respect to one another, but are linearly polarized with all other photons in the stream that are of the same frequency.
Circular polarization occurs when the component fields are precisely 90 degrees out of phase, one component reaching its maximum when the other is reaching its zero-crossing; in addition, the two components (unlike in linear polarization) must be of equal amplitudes. In this case, there are two distinct topological possibilities: either one field leads, or the other does. These two cases are called "left-" and "right-handed" polarization. But this is actually an artificial polarization; it is a mix of equal amounts of two linear polarizations at right angles to one another, and 90 degrees out of phase to one another. You can see this kind of light (and see that this description must be so) by placing a quarter-wave plate in a linearly polarized beam with the plane of linear polarization oriented at 45 degrees to the quarter-wave plate. CD players use this kind of light to decode the information on a CDROM or audio CD. Currently, this is the only method we know of for creating circularly polarized light; and the method implies that the linearly polarized light is split into two components, one of which is retarded by just enough to put it 90 degrees out of phase with the other.
Elliptically polarized light is a combination of two linear polarizations that are neither precisely in phase nor precisely 90 degrees out of phase, or the components are not of equal amplitude if it is 90 degrees out of phase. Just as with circular polarization, elliptically polarized light can be either right- or left-handed.
Now, all of that said, it is not necessary to decompose light as plane waves (as all three above descriptions have done). Instead, one can construct all other polarizations from combinations of left- and right-handed circularly polarized light; and I expect this is the source of your question. In that case, in the meaning of your first question, no, light does not generally exist as right- and left-handed circularly polarized components; this is merely a convenient method for describing the characteristics of the light as a combination of simpler (and therefore more mathematically tractable) entities, but these entities have no real physical existence. In the case of linear polarization, however, the electromagnetic field (and its electric component, upon which the polarization is based) appears to have actual physical existence (or as much "existence" as such an entity that cannot be directly sensed can have- we cannot directly sense electrons either, after all).
To answer your second question, no, it is not possible to exclude right-hand polarized light with a left-hand polarizer, as can be done with two prisms or two sheets of polaroid film with linearly polarized light; this is because circularly polarized light is by definition a mixture of two rectilinearly polarized linear components, and the device which is used to make circularly polarized light uses a half-wave plate which will exercise its behavior on any incident light of the correct polarization angle. And the same is true of elliptically polarized light and left- and right-hand polarizers. At least, no material we know of is capable of this. However, it is not physically impossible, merely technically impossible, as far as I know; certainly, we do know how to detect right-hand polarized microwaves while excluding left-hand polarized ones of the same frequency. So I suppose there is some chance we might find a means of creating and handling circularly polarized light as conveniently as we do linearly polarized light with polaroid.
And to be entirely honest, polarization is a complex and evolving subject, and it is possible that there have been recent developments of which I have not heard that could allow something like this.
Dear Schneibster,
Thank you for your comprehensive replies.
I am having problem with some textbooks in Quantum Mechanics where they define circularly polarized state as somewhat analogous to the linealy polarized state. They have stated that a right circularly polarized light will be cut-off by a Left circular polarizer but pass through a right circular polarizer without any loss in intensity.
Is their assertion correct?
You have mentioned that a circular polarizer is in fact a combination of a linear polarizer and a quarter-wave plate that somehow retard the propagation of light after it has been polarized. Would you please explain what essentially constitute a right circularly polarized state from a left circularly polarized state based on how the circular polarizer are made?
Cheers.
Thank you for your comprehensive replies.
I am having problem with some textbooks in Quantum Mechanics where they define circularly polarized state as somewhat analogous to the linealy polarized state. They have stated that a right circularly polarized light will be cut-off by a Left circular polarizer but pass through a right circular polarizer without any loss in intensity.
Is their assertion correct?
You have mentioned that a circular polarizer is in fact a combination of a linear polarizer and a quarter-wave plate that somehow retard the propagation of light after it has been polarized. Would you please explain what essentially constitute a right circularly polarized state from a left circularly polarized state based on how the circular polarizer are made?
Cheers.
Well, I guess I should have checked the camera guys out!
Apparently, they make circular polarizers for cameras- a screw-on glass standard filter, which you can rotate with a slip-ring after it's on the lens, to modify the polarization plane. It is a piece of polaroid over a quarter-wave plate, with the polaroid's polarization plane oriented at 45 degrees to the quarter-wave plate's axis. So it looks like I was indeed wrong, and you can make a simple circular polarizer.
Now, I was correct that it only works precisely for one frequency; this is because the quarter-wave plate is only a quarter-wave plate for one frequency. This frequency in cameras is apparently chosen to be the yellow-green at the center of the optical spectrum. So that frequency is the only one that's truly circular; the remaining frequencies, up to violet and down to red, are elliptically polarized.
The article says that you can tell a linear polarizer from a circular polarizer by looking through the polarizer at its image in a mirror. The mirror reverses the handedness of the filter; if you think for a moment, you'll see why this must be so. If you look in a mirror and move your right hand, the image in the mirror moves its left; mirrors "flip" things. So if you look through the polarizer into the mirror, the image of a linear polarizer will look just the same through the polarizer or without it; but the image of a circular polarizer will be darker through the polarizer than without it, because the circular polarizer rejects light of the opposite handedness. Note however that because only the yellow-green light is perfectly circularly polarized, only that light will be completely excluded; the elliptically polarized red and violet light will only be partially excluded, because the handedness of elliptically polarized light and its exact phase relationship will not perfectly cancel after reflection from a mirror.
So, it looks like I was wrong, and your textbook is right; but with a caveat: this is only precisely true for the exact frequency for which the quarter-wave plate is a quarter-wave plate. I don't understand the underlying mechanism, and I'll have to think about why. I'll do so and try to explain it once I understand it.
In regard to a quarter-wave plate, what is going on is due to the crystalline structure of the minerals used to construct the plate. Basically, the atoms in some crystals (hexagonal, trigonal, and tetragonal crystals; orthorhombic, monoclinic, and triclinic crystals do not have this property) are "constrained" in certain directions, but not in others, from moving (the orthorhombic, monoclinic, and triclinic crystals have not one, but two such directions and therefore don't act differently along different axes). As a result, the direction where the atoms are not constrained has one speed of light, and the direction where they are constrained has another. (The speed of light inside of a transparent material is always slower than the speed of light in open space; the difference is the cause of various optical effects lumped together as "refraction.") Thus, linearly polarized light that is oriented along the direction of the constraint has one speed, and linearly polarized light oriented perpendicularly to the direction of the constraint has another. If the thickness of the plate is very, very carefully adjusted, and the optical axis (the direction of the constraint) very, very carefully oriented before the crystal is cut, then the plate can be made to make the perpendicularly polarized light come out with a precise phase difference from the parallel polarized light; and if that phase difference is 90 degrees, then you have a quarter-wave plate. It is also possible to make half-wave plates, which make a phase difference of 180 degrees between the perpendicularly and parallel polarized waves; or eighth-wave, three-quarter-wave, and so forth plates; the difference being the thickness of the plate.
Since the wavelength of light varies with its color, and varies inversely as the frequency, the precise thickness of the plate implies that it is only of the desired phase difference for one frequency of light; the phase delay is less for lower frequencies with their longer wavelengths, and greater for higher frequencies with their shorter wavelengths, since the time delay is constant for a particular plate for all frequencies.
HTH. I'll post later on why a circular polarizer excludes the opposite handedness.
Apparently, they make circular polarizers for cameras- a screw-on glass standard filter, which you can rotate with a slip-ring after it's on the lens, to modify the polarization plane. It is a piece of polaroid over a quarter-wave plate, with the polaroid's polarization plane oriented at 45 degrees to the quarter-wave plate's axis. So it looks like I was indeed wrong, and you can make a simple circular polarizer.
Now, I was correct that it only works precisely for one frequency; this is because the quarter-wave plate is only a quarter-wave plate for one frequency. This frequency in cameras is apparently chosen to be the yellow-green at the center of the optical spectrum. So that frequency is the only one that's truly circular; the remaining frequencies, up to violet and down to red, are elliptically polarized.
The article says that you can tell a linear polarizer from a circular polarizer by looking through the polarizer at its image in a mirror. The mirror reverses the handedness of the filter; if you think for a moment, you'll see why this must be so. If you look in a mirror and move your right hand, the image in the mirror moves its left; mirrors "flip" things. So if you look through the polarizer into the mirror, the image of a linear polarizer will look just the same through the polarizer or without it; but the image of a circular polarizer will be darker through the polarizer than without it, because the circular polarizer rejects light of the opposite handedness. Note however that because only the yellow-green light is perfectly circularly polarized, only that light will be completely excluded; the elliptically polarized red and violet light will only be partially excluded, because the handedness of elliptically polarized light and its exact phase relationship will not perfectly cancel after reflection from a mirror.
So, it looks like I was wrong, and your textbook is right; but with a caveat: this is only precisely true for the exact frequency for which the quarter-wave plate is a quarter-wave plate. I don't understand the underlying mechanism, and I'll have to think about why. I'll do so and try to explain it once I understand it.
In regard to a quarter-wave plate, what is going on is due to the crystalline structure of the minerals used to construct the plate. Basically, the atoms in some crystals (hexagonal, trigonal, and tetragonal crystals; orthorhombic, monoclinic, and triclinic crystals do not have this property) are "constrained" in certain directions, but not in others, from moving (the orthorhombic, monoclinic, and triclinic crystals have not one, but two such directions and therefore don't act differently along different axes). As a result, the direction where the atoms are not constrained has one speed of light, and the direction where they are constrained has another. (The speed of light inside of a transparent material is always slower than the speed of light in open space; the difference is the cause of various optical effects lumped together as "refraction.") Thus, linearly polarized light that is oriented along the direction of the constraint has one speed, and linearly polarized light oriented perpendicularly to the direction of the constraint has another. If the thickness of the plate is very, very carefully adjusted, and the optical axis (the direction of the constraint) very, very carefully oriented before the crystal is cut, then the plate can be made to make the perpendicularly polarized light come out with a precise phase difference from the parallel polarized light; and if that phase difference is 90 degrees, then you have a quarter-wave plate. It is also possible to make half-wave plates, which make a phase difference of 180 degrees between the perpendicularly and parallel polarized waves; or eighth-wave, three-quarter-wave, and so forth plates; the difference being the thickness of the plate.
Since the wavelength of light varies with its color, and varies inversely as the frequency, the precise thickness of the plate implies that it is only of the desired phase difference for one frequency of light; the phase delay is less for lower frequencies with their longer wavelengths, and greater for higher frequencies with their shorter wavelengths, since the time delay is constant for a particular plate for all frequencies.
HTH. I'll post later on why a circular polarizer excludes the opposite handedness.
Thank you Schneibster for your replies. In the meanwhile, I hope other learned members could help in providing some light on this topic.
From your explanation, you seem to put undue emphasis on the frequency of light passing through a circular polarizer. Unfortunately, the way some of these textbooks have written seems to suggest that a circular polarizer does not make this distinction with regards to whether one circularly polarized state of light will be cancelled by a second circular polarizer.
Indeed, if one were to conduct an experiment using two circular polarizers, you sometime get total cancellation of light as if they are two linear polarizers, but sometime you don’t whichever angle you rotate between the two circular polarizers. However, by rotating two circular polarizers, you do get a variation in the color of the light that gets through both the circular polarizers.
What does these observations tell us with regards to how we define the term--circularly polarized states in physics?
I will look forward to your subsequent clarification on the construction of a circular polarizer.
From your explanation, you seem to put undue emphasis on the frequency of light passing through a circular polarizer. Unfortunately, the way some of these textbooks have written seems to suggest that a circular polarizer does not make this distinction with regards to whether one circularly polarized state of light will be cancelled by a second circular polarizer.
Indeed, if one were to conduct an experiment using two circular polarizers, you sometime get total cancellation of light as if they are two linear polarizers, but sometime you don’t whichever angle you rotate between the two circular polarizers. However, by rotating two circular polarizers, you do get a variation in the color of the light that gets through both the circular polarizers.
What does these observations tell us with regards to how we define the term--circularly polarized states in physics?
I will look forward to your subsequent clarification on the construction of a circular polarizer.
QUOTE (hexa+)
From your explanation, you seem to put undue emphasis on the frequency of light passing through a circular polarizer.
The only method I have seen described of making a circular polarizer uses a quarter-wave plate, and a quarter-wave plate is only a quarter-wave plate for a very narrow range of frequencies. The reason is because the relative velocities of the ordinary (parallel) and extraordinary (perpendicular) polarized components must be maintained for a very precise amount of time for that velocity difference to result in a quarter-wave (90 degree) difference in phase. As far as I have been able to discover, there is absolutely no other means of making a circular polarizer but to combine a linear polarizer with a quarter-wave plate. If this is true, then a circular polarizer will be extremely narrow in the range of frequencies it will actually circularly polarize; frequencies outside that range will be elliptically polarized, because the phase difference between the two components will be other than 90 degrees.
QUOTE (hexa+)
Unfortunately, the way some of these textbooks have written seems to suggest that a circular polarizer does not make this distinction with regards to whether one circularly polarized state of light will be cancelled by a second circular polarizer.
If they do not, then what method besides the use of a quarter-wave plate combined with a linear polarizer do they suggest is used to create circularly polarized light?
Perhaps you should review this, which gives practical instructions for using a circular polarizer on a camera and states, "If you're wondering whether your polarizer is circular or not, look through your polarizer at a mirror and look at how dark the polarizer is that the guy in the mirror is holding. Reverse the polarizer in your hand so the other side of the glass is pointing toward the mirror. With a circular polarizer, one direction will be significantly darker than the other. With a linear polarizer, both sould be the same. The reason is that linearly polarized light will still be linearly polarized in the same direction after bouncing off the mirror. Clockwise circularly polarized will be counter-clockwise after bouncing off a mirror, and will be cancelled when it comes back."
It also states, "Of course, a quarter-wave plate is only exactly a quarter wave for one frequency of light. That frequency is usually chosen to be a yellow in about the middle of the visible spectrum so that on the average, the light will be circularly polarized with various degrees of elliptical polarization mixed in. I suppose if you were photographing something that was primarily red, or primarily violet, your metering might be slightly off, even using a circular polarizer." So I suggest that you will find that your physics textbook may not be giving you all of the story.
You might also review this and this which have descriptions of circular polarization and circular polarizers.
Perhaps you should review this, which gives practical instructions for using a circular polarizer on a camera and states, "If you're wondering whether your polarizer is circular or not, look through your polarizer at a mirror and look at how dark the polarizer is that the guy in the mirror is holding. Reverse the polarizer in your hand so the other side of the glass is pointing toward the mirror. With a circular polarizer, one direction will be significantly darker than the other. With a linear polarizer, both sould be the same. The reason is that linearly polarized light will still be linearly polarized in the same direction after bouncing off the mirror. Clockwise circularly polarized will be counter-clockwise after bouncing off a mirror, and will be cancelled when it comes back."
It also states, "Of course, a quarter-wave plate is only exactly a quarter wave for one frequency of light. That frequency is usually chosen to be a yellow in about the middle of the visible spectrum so that on the average, the light will be circularly polarized with various degrees of elliptical polarization mixed in. I suppose if you were photographing something that was primarily red, or primarily violet, your metering might be slightly off, even using a circular polarizer." So I suggest that you will find that your physics textbook may not be giving you all of the story.
You might also review this and this which have descriptions of circular polarization and circular polarizers.
OK, now first off we're going to have to step back and understand a couple of things better about precisely what happens when photons interact with the electron shells of atoms in a birefringent crystal; I've explained it as best it can be explained from the wave point of view, but the way that photons interact (and in fact, the way that all subatomic particles interact) has some features that are unlike the way that we are used to thinking of things. So you're going to have to clear your mind of preconceptions about "particles" being "little balls;" there are things that particles do that little balls cannot. Quantum physics describes things that simply cannot happen in classical mechanics. As Richard Feynman once said, "Do not keep saying to yourself, if you can possibly avoid it, "But how can it be like that?" because you will get "down the drain" into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that."
Whenever you measure the spin of a photon, you will find that you can only measure that spin in a single direction with unlimited accuracy; the spin of a photon (or, for that matter, any particle) in two different axes is complementary under Heisenberg uncertainty. Now, momentum and position are also complementary, and we can measure both with some accuracy, as long as we don't try to be too accurate; but momentum and position are (relatively) continuous parameters. Spin, on the other hand, is a discrete parameter; so there isn't a continuum of answers, there are only two possible answers when we measure spin: UP, or DOWN. That's because all photons have exactly the same spin; the only difference is whether the spin is thisaway or thataway.
So if we measure the spin of a photon in a particular axis, we know the spin in that axis; but we do not and cannot know the spin in any other axis at that time, and in fact the fact that we have measured it in a particular axis guarantees that the spin in any other axis will be random. That's because of uncertainty; that's what it means to say that the spin in one axis is complementary under uncertainty to the spin in any other.
When we send photons through a linear polarizer, what we are doing is measuring the spin of each and every photon along a single axis, the optical axis of the polarizer. Now, if the photons come from an incoherent source, their spins will be random; and because there are only two possible values, that means that half of the photons (plus or minus a standard deviation or so) will be measured having spin UP, and the other half will be measured having spin DOWN. The linear polarizer will only pass one of these two alternatives; therefore, it will pass half of the photons, and trap the other half (actually, if it is polaroid film, it absorbs most of them, and scatters a few; on the other hand, if it is a single birefringent crystal, it sends half of them in one direction and half in another at an angle to the first). Thus, all of the photons emerging from a linear polarizer have had their spins measured along a particular axis, and their spins have been found to have the same value.
Now, the spin axis of a photon points along the photon's direction of travel; this is because if the axis did not point along the direction of travel, the spin of the photon would make one side of the photon move faster than the speed of light, and that is impossible. So actually, what we have measured is whether, looking at the photon along its spin axis (i.e., along its direction of movement), is it spinning clockwise, or counterclockwise. And the arrangement of the atoms in the crystal lattice of a birefringent crystal causes clockwise-spinning photons to have a different speed than counterclockwise-spinning photons. The reasons for this are deeply embedded in the equations that describe the geometry of the electron shells of the atoms, and describing this would consume a great deal of time; if you are interested in the underlying mechanisms, I suggest you prepare for a career in physics, because by the time you are done figuring it out, you will be a physicist. If that is your goal, go for it; but I'm not going to go that far because it's not merely a single post, or even a single thick book; you'll need literally scores of books, and several very good teachers. So for the moment, simply accept that the geometry of the situation enforces a different speed of light on these two alternatives.
Refraction of light is caused by a difference in the speed of propagation of light in different materials. The easiest example to understand is that of an army marching in a column from a flat surface onto a broken surface, at an angle to the boundary between the surfaces. To the soldiers on one side of the column, the angle of the boundary to the direction they are marching will appear acute, as it runs away from the column; to the soldiers on the other side of the column, it will appear obtuse. As the soldiers cross the boundary from the smooth surface to the broken surface, they will slow down. The soldiers on the acute side of the column, however, will come to the boundary first; they will therefore slow down before the soldiers on the obtuse side. If the soldiers are taught to stay in a straight line with the soldier(s) next to them, what will happen? Obviously, the soldiers on the acute side will have to turn toward the line perpendicular to the boundary as the soldiers who have not yet crossed it outdistance them; so once the soldiers have crossed the boundary, their lines will be turned toward the boundary from the angle they had before they crossed it. This means that the column will be bent toward the line perpendicular to the boundary.
Exactly the same thing happens to light as it crosses the boundary between (for example) air and glass; the speed of light inside glass is less than the speed of light in air. So if light hits glass at an angle to the boundary, it will be bent toward the line perpendicular to the boundary; this line is called the "normal" in optics. So light crossing a boundary from higher speed to lower is bent toward the normal.
If you think about it a moment, you'll see that if the column of soldiers is marching on broken ground and crosses another boundary to smooth ground, and their speed increases, exactly the opposite will happen. And so it is for light: crossing a boundary from slower to faster speed, the light is bent away from the normal.
Finally, thinking just a little more, you'll see that light crossing a boundary parallel to the normal, no matter whether from slower to faster or vice versa, will not be bent at all.
The above is an intuitive (though not necessarily correct in terms of the quantum mechanical description, it is correct in terms of the observed behavior of the light) description of a law of nature named "Snell's Law" after one of the people who discovered the mathematics that describes it. Snell's Law is the first Law of optics; the behavior of prisms and lenses follows from Snell's Law. And, as a matter of fact, so does the behavior of light inside a birefringent crystal; here's how.
Since the two kinds of photons (UP and DOWN) have different speeds inside the birefringent crystal, we can see that Snell's Law will cause them to have different angles; and this means that a beam of light entering a birefringent crystal will be split into two halves, that will emerge from the crystal in different directions. If we only take one of the two halves, no matter which one, we will find that it is linearly polarized; and if we compare them, we will find that they are linearly polarized at a right angle to one another. Remember, the polarization depends only on whether the spin is clockwise or counterclockwise.
Now, here is the part where what Feynman said about not wondering how it can be like that but just accepting it comes into play: If we measure the spin of the photons from a different angle, the distributions will again be random, but the probability will no longer be 50%. This randomness will depend upon the angle between the two measurements in a very specific way. Because all of the photons have been measured along a particular line to have spin (for example) UP, we know that none of them have spin UP along the perpendicular line. Similarly, because they have all been measured along a particular line to have spin UP, if we measure them again along that same line, they will still all have spin UP. And this is "just how it works;" to understand precisely why, you will have to study physics for many years, and even then the ultimate answer remains unknown (unless, of course, you discover it and win the Nobel Prize). We do not know precisely why these two probabilities depend upon one another; we only know that they do.
The manner in which the spin at a second angle varies with the spin at the first angle is related to the angle between the two measurement planes; to be precise, it is the square of the cosine of that angle. At 30 degrees, 75% of the photons will have the spin that is passed; at 45 degrees, 50%; at 60 degrees, 25%; and at 90 degrees, 0%.
Thus, if we have a birefringent crystal that passes all the photons with spin UP along a vertical plane, sending the photons with spin DOWN into (for example) a layer of black paint, and we send the passed photons to another birefringent crystal that passes all the photons with spin UP along a plane at 45 degrees to the vertical, then only half of the photons that made it through the first crystal will make it through the second; if the two crystals both pass spin UP along the vertical plane, then all the photons that made it through the first crystal will make it through the second; and if one passes spin UP along the vertical plane and the other spin UP along the horizontal, then none of the photons will be passed.
A sheet of polaroid film is actually a piece of plastic filled with tiny birefringent crystals, all aligned so that their optical axes point in the same direction, and all made with a material which has the characteristic that it absorbs the photons that are not passed (rather than simply transmitting them in a different direction). As it turns out, these particular crystals are electrically asymmetric (which means that although they are neutral, they have a preferred alignment to an electric field) which means that simply by subjecting the plastic filled with crystals to an electric field before the plastic hardens, all the crystals can be easily aligned, and once the plastic is hard they will not change their orientation.
So if we take two pieces of polaroid film, and orient them so that the optical axes are parallel, they will pass 50% of the light, and all of that light will be linearly polarized along the optical axes; if we then rotate the second piece of film, as the angle increases, the amount of light passed will decrease, so that at 30 degrees, only 37.5% passes, at 45 degrees only 25%, at 60 degrees only 12.5%, and at 90 degrees none of the light passes at all.
That concludes the discussion of refraction, birefringence, and linear polarization; in the next post, I will discuss retardation plates, and in a final post, I will discuss why a combination of a linear polarizer with a quarter-wave retardation plate yields circularly polarized light and why a circular polarizer will not pass circularly polarized light of the opposite handedness.
Whenever you measure the spin of a photon, you will find that you can only measure that spin in a single direction with unlimited accuracy; the spin of a photon (or, for that matter, any particle) in two different axes is complementary under Heisenberg uncertainty. Now, momentum and position are also complementary, and we can measure both with some accuracy, as long as we don't try to be too accurate; but momentum and position are (relatively) continuous parameters. Spin, on the other hand, is a discrete parameter; so there isn't a continuum of answers, there are only two possible answers when we measure spin: UP, or DOWN. That's because all photons have exactly the same spin; the only difference is whether the spin is thisaway or thataway.
So if we measure the spin of a photon in a particular axis, we know the spin in that axis; but we do not and cannot know the spin in any other axis at that time, and in fact the fact that we have measured it in a particular axis guarantees that the spin in any other axis will be random. That's because of uncertainty; that's what it means to say that the spin in one axis is complementary under uncertainty to the spin in any other.
When we send photons through a linear polarizer, what we are doing is measuring the spin of each and every photon along a single axis, the optical axis of the polarizer. Now, if the photons come from an incoherent source, their spins will be random; and because there are only two possible values, that means that half of the photons (plus or minus a standard deviation or so) will be measured having spin UP, and the other half will be measured having spin DOWN. The linear polarizer will only pass one of these two alternatives; therefore, it will pass half of the photons, and trap the other half (actually, if it is polaroid film, it absorbs most of them, and scatters a few; on the other hand, if it is a single birefringent crystal, it sends half of them in one direction and half in another at an angle to the first). Thus, all of the photons emerging from a linear polarizer have had their spins measured along a particular axis, and their spins have been found to have the same value.
Now, the spin axis of a photon points along the photon's direction of travel; this is because if the axis did not point along the direction of travel, the spin of the photon would make one side of the photon move faster than the speed of light, and that is impossible. So actually, what we have measured is whether, looking at the photon along its spin axis (i.e., along its direction of movement), is it spinning clockwise, or counterclockwise. And the arrangement of the atoms in the crystal lattice of a birefringent crystal causes clockwise-spinning photons to have a different speed than counterclockwise-spinning photons. The reasons for this are deeply embedded in the equations that describe the geometry of the electron shells of the atoms, and describing this would consume a great deal of time; if you are interested in the underlying mechanisms, I suggest you prepare for a career in physics, because by the time you are done figuring it out, you will be a physicist. If that is your goal, go for it; but I'm not going to go that far because it's not merely a single post, or even a single thick book; you'll need literally scores of books, and several very good teachers. So for the moment, simply accept that the geometry of the situation enforces a different speed of light on these two alternatives.
Refraction of light is caused by a difference in the speed of propagation of light in different materials. The easiest example to understand is that of an army marching in a column from a flat surface onto a broken surface, at an angle to the boundary between the surfaces. To the soldiers on one side of the column, the angle of the boundary to the direction they are marching will appear acute, as it runs away from the column; to the soldiers on the other side of the column, it will appear obtuse. As the soldiers cross the boundary from the smooth surface to the broken surface, they will slow down. The soldiers on the acute side of the column, however, will come to the boundary first; they will therefore slow down before the soldiers on the obtuse side. If the soldiers are taught to stay in a straight line with the soldier(s) next to them, what will happen? Obviously, the soldiers on the acute side will have to turn toward the line perpendicular to the boundary as the soldiers who have not yet crossed it outdistance them; so once the soldiers have crossed the boundary, their lines will be turned toward the boundary from the angle they had before they crossed it. This means that the column will be bent toward the line perpendicular to the boundary.
Exactly the same thing happens to light as it crosses the boundary between (for example) air and glass; the speed of light inside glass is less than the speed of light in air. So if light hits glass at an angle to the boundary, it will be bent toward the line perpendicular to the boundary; this line is called the "normal" in optics. So light crossing a boundary from higher speed to lower is bent toward the normal.
If you think about it a moment, you'll see that if the column of soldiers is marching on broken ground and crosses another boundary to smooth ground, and their speed increases, exactly the opposite will happen. And so it is for light: crossing a boundary from slower to faster speed, the light is bent away from the normal.
Finally, thinking just a little more, you'll see that light crossing a boundary parallel to the normal, no matter whether from slower to faster or vice versa, will not be bent at all.
The above is an intuitive (though not necessarily correct in terms of the quantum mechanical description, it is correct in terms of the observed behavior of the light) description of a law of nature named "Snell's Law" after one of the people who discovered the mathematics that describes it. Snell's Law is the first Law of optics; the behavior of prisms and lenses follows from Snell's Law. And, as a matter of fact, so does the behavior of light inside a birefringent crystal; here's how.
Since the two kinds of photons (UP and DOWN) have different speeds inside the birefringent crystal, we can see that Snell's Law will cause them to have different angles; and this means that a beam of light entering a birefringent crystal will be split into two halves, that will emerge from the crystal in different directions. If we only take one of the two halves, no matter which one, we will find that it is linearly polarized; and if we compare them, we will find that they are linearly polarized at a right angle to one another. Remember, the polarization depends only on whether the spin is clockwise or counterclockwise.
Now, here is the part where what Feynman said about not wondering how it can be like that but just accepting it comes into play: If we measure the spin of the photons from a different angle, the distributions will again be random, but the probability will no longer be 50%. This randomness will depend upon the angle between the two measurements in a very specific way. Because all of the photons have been measured along a particular line to have spin (for example) UP, we know that none of them have spin UP along the perpendicular line. Similarly, because they have all been measured along a particular line to have spin UP, if we measure them again along that same line, they will still all have spin UP. And this is "just how it works;" to understand precisely why, you will have to study physics for many years, and even then the ultimate answer remains unknown (unless, of course, you discover it and win the Nobel Prize). We do not know precisely why these two probabilities depend upon one another; we only know that they do.
The manner in which the spin at a second angle varies with the spin at the first angle is related to the angle between the two measurement planes; to be precise, it is the square of the cosine of that angle. At 30 degrees, 75% of the photons will have the spin that is passed; at 45 degrees, 50%; at 60 degrees, 25%; and at 90 degrees, 0%.
Thus, if we have a birefringent crystal that passes all the photons with spin UP along a vertical plane, sending the photons with spin DOWN into (for example) a layer of black paint, and we send the passed photons to another birefringent crystal that passes all the photons with spin UP along a plane at 45 degrees to the vertical, then only half of the photons that made it through the first crystal will make it through the second; if the two crystals both pass spin UP along the vertical plane, then all the photons that made it through the first crystal will make it through the second; and if one passes spin UP along the vertical plane and the other spin UP along the horizontal, then none of the photons will be passed.
A sheet of polaroid film is actually a piece of plastic filled with tiny birefringent crystals, all aligned so that their optical axes point in the same direction, and all made with a material which has the characteristic that it absorbs the photons that are not passed (rather than simply transmitting them in a different direction). As it turns out, these particular crystals are electrically asymmetric (which means that although they are neutral, they have a preferred alignment to an electric field) which means that simply by subjecting the plastic filled with crystals to an electric field before the plastic hardens, all the crystals can be easily aligned, and once the plastic is hard they will not change their orientation.
So if we take two pieces of polaroid film, and orient them so that the optical axes are parallel, they will pass 50% of the light, and all of that light will be linearly polarized along the optical axes; if we then rotate the second piece of film, as the angle increases, the amount of light passed will decrease, so that at 30 degrees, only 37.5% passes, at 45 degrees only 25%, at 60 degrees only 12.5%, and at 90 degrees none of the light passes at all.
That concludes the discussion of refraction, birefringence, and linear polarization; in the next post, I will discuss retardation plates, and in a final post, I will discuss why a combination of a linear polarizer with a quarter-wave retardation plate yields circularly polarized light and why a circular polarizer will not pass circularly polarized light of the opposite handedness.
Thanks again Schneibster.
Let me restate my question.
From our physical observation, a linear polarizer performs a definite action on a stream of unpolarized light (which we will designate as lψ> state) by realigning the orientation of the photons along its polarizing axis. Hence, a source of non-polarized photons when operated upon by a vertical or v-state polarizer (Mv) will produce photons polarized along this polarizing axis or in the lv> eigen state. Quantum Mechanics express this operation and its projection probabilities as follows: l<v l Mv l ψ>l 2 = ˝. If we pass this polarized light in the lv> state through another v-state polarizer (Mv), we will get 100%: l<vl Mv lv>l 2 = 1. However, if we rotate the second polarizer by 90 degree and turn it into a horizontal or h-state operator (Mh), the projection probability will be zero: l<hl Mh lv>l 2 = 0.
The question I am raising is whether there is a distinct Right circularly polarized state or lR> eigen state and a Left circularly polarized state or lL> eigen state when light passes through a Right Circular Polarizer and a Left Circular polarizer respectively.
Quantum Mechanics appears to treat the lR> state and the lL> state as somewhat similar to the lv> state and the lh> state as it expresses the projection probabilities when light in the lR> state passes through a Right Circular polarizer as: l<R l MR l R>l 2 = 1 and through a Left circular polarizer as: l<Ll ML lR>l 2 = 0
Is it correct for Quantum Mechanics to make this prediction?
I thank you in anticipation of your clarification.
Let me restate my question.
From our physical observation, a linear polarizer performs a definite action on a stream of unpolarized light (which we will designate as lψ> state) by realigning the orientation of the photons along its polarizing axis. Hence, a source of non-polarized photons when operated upon by a vertical or v-state polarizer (Mv) will produce photons polarized along this polarizing axis or in the lv> eigen state. Quantum Mechanics express this operation and its projection probabilities as follows: l<v l Mv l ψ>l 2 = ˝. If we pass this polarized light in the lv> state through another v-state polarizer (Mv), we will get 100%: l<vl Mv lv>l 2 = 1. However, if we rotate the second polarizer by 90 degree and turn it into a horizontal or h-state operator (Mh), the projection probability will be zero: l<hl Mh lv>l 2 = 0.
The question I am raising is whether there is a distinct Right circularly polarized state or lR> eigen state and a Left circularly polarized state or lL> eigen state when light passes through a Right Circular Polarizer and a Left Circular polarizer respectively.
Quantum Mechanics appears to treat the lR> state and the lL> state as somewhat similar to the lv> state and the lh> state as it expresses the projection probabilities when light in the lR> state passes through a Right Circular polarizer as: l<R l MR l R>l 2 = 1 and through a Left circular polarizer as: l<Ll ML lR>l 2 = 0
Is it correct for Quantum Mechanics to make this prediction?
I thank you in anticipation of your clarification.
Hi Schneibster,
Based on its construction, a circular polarizer comprises a linear polarizer and a quarter wave plate, I am curious how does Quantum Mechanics define a Right or Left Circularly polarized state of light? Is this a mistake on the part of the authors of some of these books to state that a Right polarized state of light will pass through a right circular polarizer unaffected (i.e with 100% transmission) whereas it will be obscured (i.e with 0% transmission) if it is made to pass through a Left circular polarizer?
Hope other members could help. Thanks.
Based on its construction, a circular polarizer comprises a linear polarizer and a quarter wave plate, I am curious how does Quantum Mechanics define a Right or Left Circularly polarized state of light? Is this a mistake on the part of the authors of some of these books to state that a Right polarized state of light will pass through a right circular polarizer unaffected (i.e with 100% transmission) whereas it will be obscured (i.e with 0% transmission) if it is made to pass through a Left circular polarizer?
Hope other members could help. Thanks.
Hey, sorry I didn't respond quickly- I've been out of town. I'm busy this evening, but I'll get back to you shortly.
It looks to me like you're studying some pretty serious physics, if you're using bracket notation. I'll try to keep that in mind; but you keep in mind that I'm not just writing for you, there is more audience out there who are reading this, so I'm keeping it simple for them as well.
Rather than just up and respond to your question, I'll feel better finishing the two other subjects I intended to cover first, then deriving principles and showing how to apply them to figure out what's going on. Hope you're patient for that!
It looks to me like you're studying some pretty serious physics, if you're using bracket notation. I'll try to keep that in mind; but you keep in mind that I'm not just writing for you, there is more audience out there who are reading this, so I'm keeping it simple for them as well.
Rather than just up and respond to your question, I'll feel better finishing the two other subjects I intended to cover first, then deriving principles and showing how to apply them to figure out what's going on. Hope you're patient for that!
Hi Schneibster,
Thanks for your replies.
The topic on Circular polarization raises some problem in my effort to understand Quantum Mechanics. We were told by Richard Feynman and other experts that we must not question why quantum objects behave the way they do using our macroworld logic and commonsense. What matters is that Quantum mechanics allow us to make prediction that is otherwise impossible be it the rules developed for classical particles or waves. Apparently, this is also the current paradigm of quantum physics that is taught in schools and universities and adopted by the majority in the Science community.
Unfortunately, the Quantum Mechanical predictions shown in some of the books on circular polarization does not seem to agree with observation. Is this a mistake on the part of the authors or there is something more to it pertaing to what we meant by a circularly polarized state of light?
I would certainly look forward to your explanation.
Thanks for your replies.
The topic on Circular polarization raises some problem in my effort to understand Quantum Mechanics. We were told by Richard Feynman and other experts that we must not question why quantum objects behave the way they do using our macroworld logic and commonsense. What matters is that Quantum mechanics allow us to make prediction that is otherwise impossible be it the rules developed for classical particles or waves. Apparently, this is also the current paradigm of quantum physics that is taught in schools and universities and adopted by the majority in the Science community.
Unfortunately, the Quantum Mechanical predictions shown in some of the books on circular polarization does not seem to agree with observation. Is this a mistake on the part of the authors or there is something more to it pertaing to what we meant by a circularly polarized state of light?
I would certainly look forward to your explanation.
QUOTE (hexa+)
From our physical observation, a linear polarizer performs a definite action on a stream of unpolarized light (which we will designate as lψ> state) by realigning the orientation of the photons along its polarizing axis.
Not exactly. Polarization is a measurement of a property of the photons; it is a discrete property, in that there are only two possible measurements. The property in question is whether, when measured along a particular axis, their spin is UP or DOWN. If it is UP, then the photons go thisaway; if DOWN, then they go thataway. One way or the other leads to them being absorbed; the other way leads to them being transmitted.
Assuming that the now-polarized photons do not encounter anything that changes their spin states, then when their spin is measured again, later, along a different axis, there will be a probability based on the angle of the two measurement axes (specifically, the square of the cosine of the angle between them) for the photon to have an UP or DOWN spin along that other axis.
I do not know Dirac notation, so I will not give this in that notation.
Assuming that the now-polarized photons do not encounter anything that changes their spin states, then when their spin is measured again, later, along a different axis, there will be a probability based on the angle of the two measurement axes (specifically, the square of the cosine of the angle between them) for the photon to have an UP or DOWN spin along that other axis.
I do not know Dirac notation, so I will not give this in that notation.
QUOTE (hexa+)
The question I am raising is whether there is a distinct Right circularly polarized state or lR> eigen state and a Left circularly polarized state or lL> eigen state when light passes through a Right Circular Polarizer and a Left Circular polarizer respectively.
The answer to this question is, "Yes, there are distinct right and left circular polarizations that are also distinct from vertical and horizontal polarizations."
The circular polarization states correspond to a dynamic change over time and distance of the states that you have denoted |h> and |v>. In other words, at a particular distance from the circular polarizer, the light is horizontally polarized; at a certain other distance, it is vertically polarized; and its plane of polarization changes with the distance from the circular polarizer in a regular manner; in other words, it oscillates.
Just as with the quarter-wave plate, this distance varies with the wavelength of the light, because it is dependent upon it; similarly, the quarter-wave plate is only precisely a quarter-wave plate for one particular frequency of light, and thus, only that particular frequency is precisely circularly polarized; other frequencies above and below it are elliptically polarized. In terms of the dynamic change, this means that the oscillation is uneven, and the light spends more time in (for example) the vertical polarization domain than in the horizontal (or vice-versa).
The way that a quarter-wave plate oriented at 45 degrees to the plane of polarization of a linear polarizer can make circularly polarized light is due to the fact that a quarter-wave plate delays photons that have one polarization relative to those that have the other polarization by precisely 1/4 of a wave, or 90 degrees; and we already know that polarized light that is sent through a second polarizer with its optical axis at 45 degrees to the plane of polarization will detect 1/2 of the light with one polarization and 1/2 with the other. Thus, 1/2 of the plane-polarized light will be delayed by precisely 1/4 wavelength over the other half, yielding two equal waves 90 degrees out of phase, which is exactly what circularly polarized light is. Contrary to the operation of a linear polarizer which merely detects the polarization of photons, we have actively modified the wave by delaying half of it by 90 degrees; in this way, circular polarization is essentially different from linear polarization.
Whether the light that emerges from the circular polarizer is left- or right-hand polarized depends upon the orientation of the quarter-wave plate's optical axis with respect to the linear polarizer's optical axis; looking into the device in the direction the light will travel, if the quarter-wave plate's axis is clockwise from the linear polarizer's, then the light will be right-hand polarized. If it is counter-clockwise, then the light will be left-hand polarized.
The arguments that show why left-hand circularly polarized light is transmitted by a left-hand polarizer and blocked by a right-hand polarizer is very complex, and I do not have time now for it. I will try to make time sometime this week.
The circular polarization states correspond to a dynamic change over time and distance of the states that you have denoted |h> and |v>. In other words, at a particular distance from the circular polarizer, the light is horizontally polarized; at a certain other distance, it is vertically polarized; and its plane of polarization changes with the distance from the circular polarizer in a regular manner; in other words, it oscillates.
Just as with the quarter-wave plate, this distance varies with the wavelength of the light, because it is dependent upon it; similarly, the quarter-wave plate is only precisely a quarter-wave plate for one particular frequency of light, and thus, only that particular frequency is precisely circularly polarized; other frequencies above and below it are elliptically polarized. In terms of the dynamic change, this means that the oscillation is uneven, and the light spends more time in (for example) the vertical polarization domain than in the horizontal (or vice-versa).
The way that a quarter-wave plate oriented at 45 degrees to the plane of polarization of a linear polarizer can make circularly polarized light is due to the fact that a quarter-wave plate delays photons that have one polarization relative to those that have the other polarization by precisely 1/4 of a wave, or 90 degrees; and we already know that polarized light that is sent through a second polarizer with its optical axis at 45 degrees to the plane of polarization will detect 1/2 of the light with one polarization and 1/2 with the other. Thus, 1/2 of the plane-polarized light will be delayed by precisely 1/4 wavelength over the other half, yielding two equal waves 90 degrees out of phase, which is exactly what circularly polarized light is. Contrary to the operation of a linear polarizer which merely detects the polarization of photons, we have actively modified the wave by delaying half of it by 90 degrees; in this way, circular polarization is essentially different from linear polarization.
Whether the light that emerges from the circular polarizer is left- or right-hand polarized depends upon the orientation of the quarter-wave plate's optical axis with respect to the linear polarizer's optical axis; looking into the device in the direction the light will travel, if the quarter-wave plate's axis is clockwise from the linear polarizer's, then the light will be right-hand polarized. If it is counter-clockwise, then the light will be left-hand polarized.
The arguments that show why left-hand circularly polarized light is transmitted by a left-hand polarizer and blocked by a right-hand polarizer is very complex, and I do not have time now for it. I will try to make time sometime this week.
In case it was unclear, I made a mistake in my first post: a right-hand polarizer WILL exclude left-hand polarized light.
Thanks again Schneibster.
You are stating that a right circular polarizer is made of a linear polarizer (1st filter) followed by a quarter wave plate (2nd filter) that somehow rotates the spin of the photons in a clockwise direction, whereas, a left circular polarizer is made of another linear polarizer (1st filter) followed by another quarter wave plate (2nd filter) that somehow rotates the spin of the photons in the anti-clockwise direction. We will be able to detect different linear polarized state depending on the phase we observe these photons.
You have also stated that the photons passing through a Right or Left circular polarizer will be transformed into a distinct right or left circularly polarized state. It is governed by the frequency of light passing through the polarizer if it is to remain in the circular polarized state (otherwise it will be in the elliptically polarized state).
You further state that a right circular polarizer will exclude a left-handed polarized light but allow unhindered passage for a right-handed polarized light. The converse, I presume is also true.
Unfortunately, the observation one gets in playing around with two circular polarizers is contrary to what you have just described, no matter which frequency of light we use. It is for this reason that I am asking whether it is correct to make the hypothesis that there is a distinct right or left circularly polarized state of light.
If a circular polarizer is a combination of two filters, shouldn’t we define the light passing through these filters based on what the last filter dictates?
This is the case when we pass light through a series of linear polarizers (10 or more linear polarizers inclined at angle other than 90 degree between two adjacent polarizers). It does not matter which state of light it may be in after passing though the intermediate filters. The last filter is the one that define the state of light passing through the series of linear polarizers.
If this is the case, then I see it as redundant if not technically incorrect to define that there is a circularly polarized state of light, since no amount of adjustment will yield the result predicted by Quantum mechanics.
I hope you could help in clarifying this disturbing and apparent disparity between theory and observation. Thanks.
Cheers.
You are stating that a right circular polarizer is made of a linear polarizer (1st filter) followed by a quarter wave plate (2nd filter) that somehow rotates the spin of the photons in a clockwise direction, whereas, a left circular polarizer is made of another linear polarizer (1st filter) followed by another quarter wave plate (2nd filter) that somehow rotates the spin of the photons in the anti-clockwise direction. We will be able to detect different linear polarized state depending on the phase we observe these photons.
You have also stated that the photons passing through a Right or Left circular polarizer will be transformed into a distinct right or left circularly polarized state. It is governed by the frequency of light passing through the polarizer if it is to remain in the circular polarized state (otherwise it will be in the elliptically polarized state).
You further state that a right circular polarizer will exclude a left-handed polarized light but allow unhindered passage for a right-handed polarized light. The converse, I presume is also true.
Unfortunately, the observation one gets in playing around with two circular polarizers is contrary to what you have just described, no matter which frequency of light we use. It is for this reason that I am asking whether it is correct to make the hypothesis that there is a distinct right or left circularly polarized state of light.
If a circular polarizer is a combination of two filters, shouldn’t we define the light passing through these filters based on what the last filter dictates?
This is the case when we pass light through a series of linear polarizers (10 or more linear polarizers inclined at angle other than 90 degree between two adjacent polarizers). It does not matter which state of light it may be in after passing though the intermediate filters. The last filter is the one that define the state of light passing through the series of linear polarizers.
If this is the case, then I see it as redundant if not technically incorrect to define that there is a circularly polarized state of light, since no amount of adjustment will yield the result predicted by Quantum mechanics.
I hope you could help in clarifying this disturbing and apparent disparity between theory and observation. Thanks.
Cheers.
Gah! It posted when it was supposed to be previewing! Go to the next page for the full post.
QUOTE (hexa+)
You are stating that a right circular polarizer is made of a linear polarizer (1st filter) followed by a quarter wave plate (2nd filter) that somehow rotates the spin of the photons in a clockwise direction, whereas, a left circular polarizer is made of another linear polarizer (1st filter) followed by another quarter wave plate (2nd filter) that somehow rotates the spin of the photons in the anti-clockwise direction.
No. The spin of the photons is not altered by the first operation. It is merely measured. And the effect is not to rotate the spin. It is the field that undergoes rotation, and only half of it; this is not the same as the photon's spin being rotated. It is the spin that is being measured, and in the second case, based on that measurement, some of the photons are delayed; however, "rotating" the spin of a photon is not something that happens in this situation.
Remember, the model of the spin of a photon is that it is longitudinal; that means that the spin axis must point along the direction of travel. The reason is that if it were transverse, in other words if the axis were pointing in any other direction, one side of the photon would have to move faster than the speed of light while the other would have to move slower than the speed of light, and both of these movements are impossible for a photon. Therefore, when viewed from any particular angle, the photon can only have one of two spins: UP, or DOWN. If it is spinning clockwise (viewed from the direction it came from), and you view it from its right, then you will perceive the photon as having spin UP. If you view it from the left, you will perceive its spin to be DOWN.
Remember also, however, that spin is not actually the way I am asking you to visualize it here; it is a quantum mechanical degree of freedom, which is discrete and has only two values. The spin viewed from any particular angle is complementary under uncertainty with the spin viewed from any other angle simultaneously. But what that spin means in real physical terms merely acts the same way as a longitudinal spin; we don't know what is actually happening to the particle that acts this way, we only know that the math that describes spins works perfectly to describe this degree of freedom.
Photons represent the electromagnetic field, and are electromagnetic radiation. In fact, they are the exchange particle of the electromagnetic interaction. Having gone to all this trouble to explain spin, I now have to tell you that it isn't directly spin that determines polarization. It is indirect. First, you need to understand magnetism.
If you think about it, you'll see that if some object (think particle) that exhibits an electric field (IOW is "charged") passes something else that exhibits one, then they will interact. You'll also be aware that time dilation occurs as a result of high velocities; this is part of relativity. Now consider a pair of charged particles speeding along relative to some observer. These particles will interact by the electric force, since they are charged; it doesn't matter whether they're charged the same and push each other apart, or charged differently and attract one another, the magnitude of the force will be the same, right? Well, first imagine that the observer is speeding along with them; their attraction will be precisely the Coulomb force:
F = eqq'/d^2
where,
F is the force vector,
e is the electric constant,
q is the charge of the first particle,
q' is the charge of the second particle, and
d is the distance between them.
Now a force results in an acceleration that depends upon the mass of the object the force is exerted against, as Newton tells us:
F = ma
where,
m is the mass of the object, and
a is the acceleration the object experiences.
So that means that an object acted upon by the Coulomb force will accelerate according to its mass. But acceleration is the second-order derivative of distance with respect to.... time! And that means that if the two particles are moving very fast with respect to the observer.... and they undergo time dilation.... then.... the force will APPEAR to be REDUCED BECAUSE THEY AREN'T EXPERIENCING TIME AS FAST AS THE OBSERVER. Remember: the force isn't REALLY reduced- it's just that to the observer it SEEMS to be reduced. This reduction in the electric force is interpreted as an opposing force to the electric field that varies with the direction an object is moving, and the velocity it is moving at, and is exerted at right angles both to the electric field (NOT the electric force!) and to the direction of movement.
But what have I just described? MAGNETISM! Operates only on moving electrically charged objects... at right angles to the motion... and at right angles to the electric field. Just precisely so. So what magnetism is is a relativistic effect on the electric force caused by the motion of an object subject to that force- it's a relativistic correction for the time dilation's APPARENT effect on the action of the force.
So you can see that every moving charged particle that has an electric field MUST have a magnetic field as well. And that this magnetic field MUST be at right angles both to the electric field and to the direction of motion.
OK, what about a spinning particle?
You can see where I'm going here.
OK, now what about the very particle that is the electromagnetic field? That is, what about the photon? Well, it must represent both the electric and magnetic fields- and since the photon is moving, those fields must be perpendicular to one another and they also must be perpendicular to the direction the photon is moving. In other words, as a photon propagates through space, we can also describe its propagation as the propagation of an electromagnetic wave through that same space, with its electric and magnetic components oscillating transversely to the direction of travel, and perpendicularly to one another. Either description will do, and the two descriptions are precisely identical in their substance. BUT THEY ARE NOT IDENTICAL IN THEIR FORM. And this is the most important point. The first description is a quantum description; the second is a field description. These two descriptions are EQUIVALENT, but not IDENTICAL. What we must do is pick the description that is the most useful to our particular problem!
Where does the magnetic component come from? Well, let us suppose that the photon represented the electric force. Now, the magnetic force is the RELATIVISTIC CORRECTION to the electric force. So what phase angle will they have to one another at the speed of light? A quick calculation using the Lorentz factor will convince you that it must be 90 degrees. A little topology will show you that for two waves oscillating at right angles to one another, 90 degrees out of phase, there are two possible configurations: either the electric wave LEADS the magnetic wave, or it LAGS behind it. And if you think about the spinning photon, you'll see that these two possible WAVE STATES must correspond to the two QUANTUM STATES of spin UP and spin DOWN! And that is the relationship of the electric and magnetic fields, and the spin of the photon.
In this particular case, the photons are going through a polarizer. Polarizers are made of atoms; and atoms are surrounded by a cloud of charged electrons. In fact, these electrons form standing waves around the nucleus; we call the various standing wave patterns that electrons can take up shells and subshells. And when we talk about how these shells and subshells are arranged spatially around the nucleus, we are talking about how the atoms will interact with one another via their electron clouds. OK, now we're talking about polarizers, and we already discussed the fact that they are made from birefringent crystals. Let's remember the fact that a crystal is a lattice of atoms, arranged in a regular pattern in space. That means that their electron shells must also be arranged in a regular pattern in space; that is, of course, what holds them together in the lattice in the first place. So what happens when the photons interact with these atoms? Obviously, that will depend upon the WAVE STATE of the photons- but the WAVE STATE depends upon the QUANTUM STATE of the spin of the photon, right? So it follows that there will be two alternatives: either the electric wave is LEADING, or it is LAGGING- either the spin is UP, or the spin is DOWN. And if the spin is thisaway, then the photons will bounce off the atoms thisaway, and if it is thataway, then they will bounce off thataway. Or, if the electric wave is leading, then they will bounce off thisaway, and if it is lagging, then thataway. Same thing, two different ways of describing it. See what I mean about picking the right description? In this case, either description works; you can see how it does.
As it turns out, it's easier to visualize the selection of the photons by the electron standing waves in the crystal lattice in terms of the spin they have than it is to visualize how the alignment of the electric field happens. You can describe polarization in terms of the alignment of the electric field; but if you just think of it as sorting the spin of the photons, it's easier to visualize. So basically, what we're talking about here is the spin; but remember, the spin is DIRECTLY CONNECTED to whether the electric field oscillation leads or lags, because it determines the orientation of the magnetic field with respect to the electric field.
Now it gets weird. Now we have to take into account how this "spin" degree of freedom actually works in quantum terms; and this description completely removes our photons from the implicit visualization as little balls moving along at the speed of light spinning so their axes point in the direction they are moving. Because, you see, spin measured at different angles is complementary under uncertainty! What we're saying is that if we measure the spin of a photon at one angle, we cannot simultaneously know its spin at another angle because they are complementary. This is a property that little balls cannot have; if they are spinning UP when viewed from the left, they MUST be spinning DOWN when viewed from the right. But Heisenberg uncertainty tells us WE CAN'T EVER KNOW THAT about photons!
What CAN we know? Well, as it turns out, what we can know is that, given a measurement of the spin along one angle, if we later measure the spin at another angle, we will get the same value for a percentage of the photons that is dependent upon the relationship of the two angles. Specifically, it is dependent upon the square of the cosine of the angle between them. The first measurement will ALWAYS find that about half the photons in incoherent light are polarized UP, and half polarized DOWN. The second will always find that, if we measure all the UP photons, then the cosine of the angle between the measurements squared will be the fraction of the photons that will be measured to be UP at the second angle. Similarly for the DOWN photons measured DOWN a second time. Why, you ask, is it like that? NOBODY KNOWS! That's just the way it IS. This is Feynman's "hole" that you will "get down" by asking WHY. We've checked it and found it to be that way. That's what we know.
So when you say to me, "the polarizer somehow rotates the spin," I have to say, "No, that's not what happens at all."
Remember, the model of the spin of a photon is that it is longitudinal; that means that the spin axis must point along the direction of travel. The reason is that if it were transverse, in other words if the axis were pointing in any other direction, one side of the photon would have to move faster than the speed of light while the other would have to move slower than the speed of light, and both of these movements are impossible for a photon. Therefore, when viewed from any particular angle, the photon can only have one of two spins: UP, or DOWN. If it is spinning clockwise (viewed from the direction it came from), and you view it from its right, then you will perceive the photon as having spin UP. If you view it from the left, you will perceive its spin to be DOWN.
Remember also, however, that spin is not actually the way I am asking you to visualize it here; it is a quantum mechanical degree of freedom, which is discrete and has only two values. The spin viewed from any particular angle is complementary under uncertainty with the spin viewed from any other angle simultaneously. But what that spin means in real physical terms merely acts the same way as a longitudinal spin; we don't know what is actually happening to the particle that acts this way, we only know that the math that describes spins works perfectly to describe this degree of freedom.
Photons represent the electromagnetic field, and are electromagnetic radiation. In fact, they are the exchange particle of the electromagnetic interaction. Having gone to all this trouble to explain spin, I now have to tell you that it isn't directly spin that determines polarization. It is indirect. First, you need to understand magnetism.
If you think about it, you'll see that if some object (think particle) that exhibits an electric field (IOW is "charged") passes something else that exhibits one, then they will interact. You'll also be aware that time dilation occurs as a result of high velocities; this is part of relativity. Now consider a pair of charged particles speeding along relative to some observer. These particles will interact by the electric force, since they are charged; it doesn't matter whether they're charged the same and push each other apart, or charged differently and attract one another, the magnitude of the force will be the same, right? Well, first imagine that the observer is speeding along with them; their attraction will be precisely the Coulomb force:
F = eqq'/d^2
where,
F is the force vector,
e is the electric constant,
q is the charge of the first particle,
q' is the charge of the second particle, and
d is the distance between them.
Now a force results in an acceleration that depends upon the mass of the object the force is exerted against, as Newton tells us:
F = ma
where,
m is the mass of the object, and
a is the acceleration the object experiences.
So that means that an object acted upon by the Coulomb force will accelerate according to its mass. But acceleration is the second-order derivative of distance with respect to.... time! And that means that if the two particles are moving very fast with respect to the observer.... and they undergo time dilation.... then.... the force will APPEAR to be REDUCED BECAUSE THEY AREN'T EXPERIENCING TIME AS FAST AS THE OBSERVER. Remember: the force isn't REALLY reduced- it's just that to the observer it SEEMS to be reduced. This reduction in the electric force is interpreted as an opposing force to the electric field that varies with the direction an object is moving, and the velocity it is moving at, and is exerted at right angles both to the electric field (NOT the electric force!) and to the direction of movement.
But what have I just described? MAGNETISM! Operates only on moving electrically charged objects... at right angles to the motion... and at right angles to the electric field. Just precisely so. So what magnetism is is a relativistic effect on the electric force caused by the motion of an object subject to that force- it's a relativistic correction for the time dilation's APPARENT effect on the action of the force.
So you can see that every moving charged particle that has an electric field MUST have a magnetic field as well. And that this magnetic field MUST be at right angles both to the electric field and to the direction of motion.
OK, what about a spinning particle?
You can see where I'm going here.
OK, now what about the very particle that is the electromagnetic field? That is, what about the photon? Well, it must represent both the electric and magnetic fields- and since the photon is moving, those fields must be perpendicular to one another and they also must be perpendicular to the direction the photon is moving. In other words, as a photon propagates through space, we can also describe its propagation as the propagation of an electromagnetic wave through that same space, with its electric and magnetic components oscillating transversely to the direction of travel, and perpendicularly to one another. Either description will do, and the two descriptions are precisely identical in their substance. BUT THEY ARE NOT IDENTICAL IN THEIR FORM. And this is the most important point. The first description is a quantum description; the second is a field description. These two descriptions are EQUIVALENT, but not IDENTICAL. What we must do is pick the description that is the most useful to our particular problem!
Where does the magnetic component come from? Well, let us suppose that the photon represented the electric force. Now, the magnetic force is the RELATIVISTIC CORRECTION to the electric force. So what phase angle will they have to one another at the speed of light? A quick calculation using the Lorentz factor will convince you that it must be 90 degrees. A little topology will show you that for two waves oscillating at right angles to one another, 90 degrees out of phase, there are two possible configurations: either the electric wave LEADS the magnetic wave, or it LAGS behind it. And if you think about the spinning photon, you'll see that these two possible WAVE STATES must correspond to the two QUANTUM STATES of spin UP and spin DOWN! And that is the relationship of the electric and magnetic fields, and the spin of the photon.
In this particular case, the photons are going through a polarizer. Polarizers are made of atoms; and atoms are surrounded by a cloud of charged electrons. In fact, these electrons form standing waves around the nucleus; we call the various standing wave patterns that electrons can take up shells and subshells. And when we talk about how these shells and subshells are arranged spatially around the nucleus, we are talking about how the atoms will interact with one another via their electron clouds. OK, now we're talking about polarizers, and we already discussed the fact that they are made from birefringent crystals. Let's remember the fact that a crystal is a lattice of atoms, arranged in a regular pattern in space. That means that their electron shells must also be arranged in a regular pattern in space; that is, of course, what holds them together in the lattice in the first place. So what happens when the photons interact with these atoms? Obviously, that will depend upon the WAVE STATE of the photons- but the WAVE STATE depends upon the QUANTUM STATE of the spin of the photon, right? So it follows that there will be two alternatives: either the electric wave is LEADING, or it is LAGGING- either the spin is UP, or the spin is DOWN. And if the spin is thisaway, then the photons will bounce off the atoms thisaway, and if it is thataway, then they will bounce off thataway. Or, if the electric wave is leading, then they will bounce off thisaway, and if it is lagging, then thataway. Same thing, two different ways of describing it. See what I mean about picking the right description? In this case, either description works; you can see how it does.
As it turns out, it's easier to visualize the selection of the photons by the electron standing waves in the crystal lattice in terms of the spin they have than it is to visualize how the alignment of the electric field happens. You can describe polarization in terms of the alignment of the electric field; but if you just think of it as sorting the spin of the photons, it's easier to visualize. So basically, what we're talking about here is the spin; but remember, the spin is DIRECTLY CONNECTED to whether the electric field oscillation leads or lags, because it determines the orientation of the magnetic field with respect to the electric field.
Now it gets weird. Now we have to take into account how this "spin" degree of freedom actually works in quantum terms; and this description completely removes our photons from the implicit visualization as little balls moving along at the speed of light spinning so their axes point in the direction they are moving. Because, you see, spin measured at different angles is complementary under uncertainty! What we're saying is that if we measure the spin of a photon at one angle, we cannot simultaneously know its spin at another angle because they are complementary. This is a property that little balls cannot have; if they are spinning UP when viewed from the left, they MUST be spinning DOWN when viewed from the right. But Heisenberg uncertainty tells us WE CAN'T EVER KNOW THAT about photons!
What CAN we know? Well, as it turns out, what we can know is that, given a measurement of the spin along one angle, if we later measure the spin at another angle, we will get the same value for a percentage of the photons that is dependent upon the relationship of the two angles. Specifically, it is dependent upon the square of the cosine of the angle between them. The first measurement will ALWAYS find that about half the photons in incoherent light are polarized UP, and half polarized DOWN. The second will always find that, if we measure all the UP photons, then the cosine of the angle between the measurements squared will be the fraction of the photons that will be measured to be UP at the second angle. Similarly for the DOWN photons measured DOWN a second time. Why, you ask, is it like that? NOBODY KNOWS! That's just the way it IS. This is Feynman's "hole" that you will "get down" by asking WHY. We've checked it and found it to be that way. That's what we know.
So when you say to me, "the polarizer somehow rotates the spin," I have to say, "No, that's not what happens at all."
QUOTE (hexa+)
We will be able to detect different linear polarized state depending on the phase we observe these photons.
No, it's not dependent upon their phase. It's dependent upon their spin. The two are totally different, and one need not depend upon the other. It is the sense of the phase difference, lead or lag, not the phase itself. And that sense is dependent upon the spin.
Let me explain that a little further: let's suppose that the electric field leads. In that case, we'll have the electric field going up (positive), followed by the magnetic field going right (positive), followed by the electric field going down (negative), followed by the magnetic field going left (negative), and then the electric field will go up again. Think about this and you'll see that it's as if the field were rotating clockwise; this is the right-handed spin of the photon. If the magnetic field leads, you'll see how the spin is counter-clockwise, corresponding to the left-handed spin.
The phase itself is merely the state of the electric field at any given point in space, and only for one particular photon (unless the light is coherent, in which case it is monophasic and monochromatic, which means it all has the same frequency and the same phase).
Let me explain that a little further: let's suppose that the electric field leads. In that case, we'll have the electric field going up (positive), followed by the magnetic field going right (positive), followed by the electric field going down (negative), followed by the magnetic field going left (negative), and then the electric field will go up again. Think about this and you'll see that it's as if the field were rotating clockwise; this is the right-handed spin of the photon. If the magnetic field leads, you'll see how the spin is counter-clockwise, corresponding to the left-handed spin.
The phase itself is merely the state of the electric field at any given point in space, and only for one particular photon (unless the light is coherent, in which case it is monophasic and monochromatic, which means it all has the same frequency and the same phase).
QUOTE (hexa+)
You have also stated that the photons passing through a Right or Left circular polarizer will be transformed into a distinct right or left circularly polarized state. It is governed by the frequency of light passing through the polarizer if it is to remain in the circular polarized state (otherwise it will be in the elliptically polarized state).
To be very precise, only light of one particular frequency- that at which the quarter-wave plate is precisely a quarter-wave plate- will be circularly polarized; the remaining light (if any) will be elliptically polarized. Unless you want this post to get a hell of a lot longer, we had best ignore the elliptically polarized light. We'll stick to our monophasic, monochromatic light, and stipulate that the quarter-wave plate is precisely a quarter-wave plate for that exact frequency.
QUOTE (hexa+)
You further state that a right circular polarizer will exclude a left-handed polarized light but allow unhindered passage for a right-handed polarized light. The converse, I presume is also true.
That is correct- but I have to stop you here and point out that from the point of view of that light, the second circular polarizer is only a circular polarizer from one direction. And that direction is the direction from which the quarter-wave plate comes first.
The reason is because, at any particular distance from the first circular polarizer, assuming that the light is monophasic, the light will have two linear polarization components whose orientations are constant at that distance, and perpendicular. If that light encounters the linear polarizer first, then its transmission will depend upon the squared cosines of the two angles. Now, remember, one half of the light will be polarized one way, and the other half at right angles to the first; that is the effect of the quarter-wave plate in the first circular polarizer. These two planes of polarization will rotate with distance from the circular polarizer, but they will always be at right angles to one another. If you do the calculations, you will find that precisely one half of the light will always be transmitted. It doesn't matter what angle the planes of polarization are at; if they are at 45 degrees, then half of each will be transmitted, giving half of the whole; if they are at 30 and 60 degrees, then one will transmit 75% of its light and the other 25%, making half; and any other combination of angles will yield the same results. Do the calculations yourself, and you'll see it's true. This half of the light will be linearly polarized in the optical axis of the linear polarizer; and when it encounters the quarter-wave plate at 45 degrees to this linear polarizer, it will all be transmitted. One half of it will be delayed by the quarter-wave plate; but it will all make it through; and it will be circularly polarized in the sense of the second polarizer no matter what its polarization state was before it started, and it will be of precisely half the intensity of the original circularly polarized light.
OK, now let's turn things around and pass the light through the quarter-wave plate first instead.
The action of a quarter-wave plate on circularly polarized light depends upon the handedness of the light; this is because of what happens to the light as it passes through the quarter-wave plate. Let us begin with light whose instantaneous linear polarization of the advanced wave is parallel to the slow axis, and the retarded wave is parallel to the fast axis. As the advanced wave proceeds through the quarter-wave plate, it will be delayed at first, since it is parallel to the slow axis. However, by the time it makes it through the plate, its direction will have changed. So it will not be delayed by the full 90 degrees that light linearly polarized parallel to the slow axis normally would be; if you do the math for this case, what you'll find is that it will be delayed by 45 degrees. I'm sure you can see this coming, but the retarded wave is parallel to the fast axis, and therefore moves faster, but as it rotates, it slows down- and so instead of a 90 degree advance, it only gets a 45 degree advance. Now, that means that the advanced wave has been retarded by 45 degrees, and the retarded wave has been advanced by 45 degrees; so, since they started out 90 degrees apart, they are of course now in phase. Now in addition to this, they both rotated; because that's what circularly polarized light does. And not too surprisingly, they rotated by 45 degrees. And the direction they rotated in depends upon their handedness, of course; so one handedness will yield light that is polarized at 45 degrees to the fast axis in one direction, and the other handedness will yield light that is polarized at 45 degrees the other way from the fast axis. In addition, this result obtains for all instantaneous linear polarizations that strike the plate; this is because of the sums of the squares of the cosines, as already described, added to the partial rotation that occurs while the wave traverses the plate. And in addition, all the light will be in phase, whether it was advanced or retarded, and that means it will no longer be circularly polarized; it is now linearly polarized. Right-hand circular polarization will yield linearly polarized light that will traverse a following linear polarizer if it is oriented so that it forms a right-hand polarizer with the quarter-wave plate; but it will be oppositely polarized from a linear polarizer that forms a left-hand polarizer with the plate, and vice-versa for left-hand polarized light.
The reason is because, at any particular distance from the first circular polarizer, assuming that the light is monophasic, the light will have two linear polarization components whose orientations are constant at that distance, and perpendicular. If that light encounters the linear polarizer first, then its transmission will depend upon the squared cosines of the two angles. Now, remember, one half of the light will be polarized one way, and the other half at right angles to the first; that is the effect of the quarter-wave plate in the first circular polarizer. These two planes of polarization will rotate with distance from the circular polarizer, but they will always be at right angles to one another. If you do the calculations, you will find that precisely one half of the light will always be transmitted. It doesn't matter what angle the planes of polarization are at; if they are at 45 degrees, then half of each will be transmitted, giving half of the whole; if they are at 30 and 60 degrees, then one will transmit 75% of its light and the other 25%, making half; and any other combination of angles will yield the same results. Do the calculations yourself, and you'll see it's true. This half of the light will be linearly polarized in the optical axis of the linear polarizer; and when it encounters the quarter-wave plate at 45 degrees to this linear polarizer, it will all be transmitted. One half of it will be delayed by the quarter-wave plate; but it will all make it through; and it will be circularly polarized in the sense of the second polarizer no matter what its polarization state was before it started, and it will be of precisely half the intensity of the original circularly polarized light.
OK, now let's turn things around and pass the light through the quarter-wave plate first instead.
The action of a quarter-wave plate on circularly polarized light depends upon the handedness of the light; this is because of what happens to the light as it passes through the quarter-wave plate. Let us begin with light whose instantaneous linear polarization of the advanced wave is parallel to the slow axis, and the retarded wave is parallel to the fast axis. As the advanced wave proceeds through the quarter-wave plate, it will be delayed at first, since it is parallel to the slow axis. However, by the time it makes it through the plate, its direction will have changed. So it will not be delayed by the full 90 degrees that light linearly polarized parallel to the slow axis normally would be; if you do the math for this case, what you'll find is that it will be delayed by 45 degrees. I'm sure you can see this coming, but the retarded wave is parallel to the fast axis, and therefore moves faster, but as it rotates, it slows down- and so instead of a 90 degree advance, it only gets a 45 degree advance. Now, that means that the advanced wave has been retarded by 45 degrees, and the retarded wave has been advanced by 45 degrees; so, since they started out 90 degrees apart, they are of course now in phase. Now in addition to this, they both rotated; because that's what circularly polarized light does. And not too surprisingly, they rotated by 45 degrees. And the direction they rotated in depends upon their handedness, of course; so one handedness will yield light that is polarized at 45 degrees to the fast axis in one direction, and the other handedness will yield light that is polarized at 45 degrees the other way from the fast axis. In addition, this result obtains for all instantaneous linear polarizations that strike the plate; this is because of the sums of the squares of the cosines, as already described, added to the partial rotation that occurs while the wave traverses the plate. And in addition, all the light will be in phase, whether it was advanced or retarded, and that means it will no longer be circularly polarized; it is now linearly polarized. Right-hand circular polarization will yield linearly polarized light that will traverse a following linear polarizer if it is oriented so that it forms a right-hand polarizer with the quarter-wave plate; but it will be oppositely polarized from a linear polarizer that forms a left-hand polarizer with the plate, and vice-versa for left-hand polarized light.
QUOTE (hexa+)
Unfortunately, the observation one gets in playing around with two circular polarizers is contrary to what you have just described, no matter which frequency of light we use. It is for this reason that I am asking whether it is correct to make the hypothesis that there is a distinct right or left circularly polarized state of light.
So we see where your problem came from: you have shone the circularly polarized light through the linear polarizer first, and so you get half the light; if you want to block it all, or pass it all, it has to precisely reverse its course, going through the quarter-wave plate first and then the linear polarizer. This is why the light going one way through a circular polarizer into the mirror and back out the circular polarizer remains unchanged, but light going the other way is blocked: the handedness changes, but only if the quarter-wave plate side of the circular polarizer faces the mirror. If the linear polarizer side faces the mirror, then you will get linearly polarized light reflecting from the mirror and coming back through the linear polarizer at the same angle, and therefore passing, and only being converted to circular polarization after it has already traversed both filters. Not only that, but you can see that in fact, circularly polarized light is in a different quantum state based on its handedness; left and right circular polarization are distinct states.
QUOTE (hexa+)
If a circular polarizer is a combination of two filters, shouldn’t we define the light passing through these filters based on what the last filter dictates?
Yes, that is correct; but it is only a circular polarizer if the order is correct. Circularly polarized light is only excluded by an opposite-handed filter if it enters from the quarter-wave plate side; from the linear polarizer side, it is merely converted to whatever the polarization of the last filter is.
QUOTE (hexa+)
This is the case when we pass light through a series of linear polarizers (10 or more linear polarizers inclined at angle other than 90 degree between two adjacent polarizers). It does not matter which state of light it may be in after passing though the intermediate filters. The last filter is the one that define the state of light passing through the series of linear polarizers.
If this is the case, then I see it as redundant if not technically incorrect to define that there is a circularly polarized state of light, since no amount of adjustment will yield the result predicted by Quantum mechanics.
I hope you could help in clarifying this disturbing and apparent disparity between theory and observation. Thanks.
If this is the case, then I see it as redundant if not technically incorrect to define that there is a circularly polarized state of light, since no amount of adjustment will yield the result predicted by Quantum mechanics.
I hope you could help in clarifying this disturbing and apparent disparity between theory and observation. Thanks.
In fact, provided that the polarizers are oriented correctly, we can get either one effect or the other; but not both! Either the polarization plane can be rotated, or the light can be excluded; which effect we see depends on which direction we pass the light through in. With a linear polarizer, the same thing happens both directions; and both effects are seen in the same direction, and in fact in both directions. With a circular polarizer, however, we see one effect one way, and the other effect the other way; this is because linearly polarized light cannot be distinguished from its mirror image, but circularly polarized light can be so distinguished. Nothing could be simpler, once you work your way through how it all works.
I hope you have found this conversation helpful. Please let me know if it remains unclear to you, and be sure to try the experiment with the circular polarizer(s) both directions, so you see both effects.
It is probably worth mentioning that Heisenberg uncertainty is proven by the fact that you can place several linear polarizers one after another, and eventually rotate the plane of the resultant light by 90 degrees, although it cannot be done with only two filters; crossed polarizers will exclude the light, but add a 45 degree polarizer between them, and light is transmitted. This is one of the most elegant demonstrations of Heisenberg uncertainty I know of, and only Heisenberg uncertainty can explain it. So have fun, because when you play with polarizers, you can see quantum effects in the macroscopic world, and this is one of the very few ways you can see this.
I hope you have found this conversation helpful. Please let me know if it remains unclear to you, and be sure to try the experiment with the circular polarizer(s) both directions, so you see both effects.
It is probably worth mentioning that Heisenberg uncertainty is proven by the fact that you can place several linear polarizers one after another, and eventually rotate the plane of the resultant light by 90 degrees, although it cannot be done with only two filters; crossed polarizers will exclude the light, but add a 45 degree polarizer between them, and light is transmitted. This is one of the most elegant demonstrations of Heisenberg uncertainty I know of, and only Heisenberg uncertainty can explain it. So have fun, because when you play with polarizers, you can see quantum effects in the macroscopic world, and this is one of the very few ways you can see this.
Thanks again Schneibster.
I cannot thank you enough for providing me with such vivid description of the problem I am facing with Circular polarization of light.
You have stated that in order to observe the cancelling of light passing through two circular polarizers, we can consider using a mirror. Is this set up identical if we use two circular polarizers? The first circular polarizer comprises v-linear polarizer (position-1) + quarter-wave plate (position-2) and second circular polarizer comprises quarter-wave plate (position-1) + h-linear polarizer (position-2).
If this is correct, then can I assume the followings:
R-polarizer = v-polarizer + QWP
L-polarizer = QWP + h-polarizer
Appreciate that you could clarify this point.
Cheers.
I cannot thank you enough for providing me with such vivid description of the problem I am facing with Circular polarization of light.
You have stated that in order to observe the cancelling of light passing through two circular polarizers, we can consider using a mirror. Is this set up identical if we use two circular polarizers? The first circular polarizer comprises v-linear polarizer (position-1) + quarter-wave plate (position-2) and second circular polarizer comprises quarter-wave plate (position-1) + h-linear polarizer (position-2).
If this is correct, then can I assume the followings:
R-polarizer = v-polarizer + QWP
L-polarizer = QWP + h-polarizer
Appreciate that you could clarify this point.
Cheers.
QUOTE (hexa+)
Thanks again Schneibster.
I cannot thank you enough for providing me with such vivid description of the problem I am facing with Circular polarization of light.
I cannot thank you enough for providing me with such vivid description of the problem I am facing with Circular polarization of light.
It's my pleasure. The research has taught me a few new things, as well. Polarization is not an area I have studied extensively, and looking into it has improved my knowledge. So, thank you for the motivation to learn something new!
QUOTE (hexa+)
You have stated that in order to observe the cancelling of light passing through two circular polarizers, we can consider using a mirror. Is this set up identical if we use two circular polarizers?
It is only identical if the second circular polarizer is reversed and of the opposite handedness. If it is reversed and of the same handedness, then all the light coming from the first polarizer will be passed by the second; if it is non-reversed, then half of the light coming from the first polarizer will be passed, and it will be passed whether the polarizer is the same handedness or the opposite handedness, and will have the polarization of the second polarizer.
Technically speaking, because the second polarizer is reversed, it is not a circular polarizer any more; it is a circular de-polarizer, or perhaps it would be better to say it is a circular-to-linear polarization converter.
A circular polarizer must always have the linear polarizer FIRST, and the QWP SECOND in the light path.
The difference between an LHCP and an RHCP is not whether the linear polarizer is vertical or horizontal. What you have forgotten is that the QWP has an optical axis too. The difference is the angle of the optical axis of the linear polarizer to the optical axis of the QWP.
Technically speaking, because the second polarizer is reversed, it is not a circular polarizer any more; it is a circular de-polarizer, or perhaps it would be better to say it is a circular-to-linear polarization converter.
A circular polarizer must always have the linear polarizer FIRST, and the QWP SECOND in the light path.
The difference between an LHCP and an RHCP is not whether the linear polarizer is vertical or horizontal. What you have forgotten is that the QWP has an optical axis too. The difference is the angle of the optical axis of the linear polarizer to the optical axis of the QWP.
Thanks again Schneibster.
I did not realise the length you went through in order to provide me with these explanation. I am very grateful to you for what you have done.
From your explanation, I have an uneasy feeling that Quantum Mechanics does not seem to apply to Circular Polarization.
Based on your earlier clarification, I am sure you must be aware that the explanation on light passing through two linear polarizers using particle or wave was not entirely successful. Instead, it was found that Quantum Mechanics based on cosine square of an angle (first proposed by Etienne Louis Malus) appears to provide the best answer that agrees with experimental observation. This appears to support the modulus square of the wave function rule of Quantum Mechanics that was formulated from another paradoxical Double-slits experiment of light and of electrons.
However, if one were to question what we mean by wave function, Quantum Mechanics will be nonplussed. The wave function is essentially an abstract entity incapable of any physical or logical expression. The wave function and the projection probability it seeks to predict is connected by abstract mathematical logics not one that will allow us to visualize physically whether it is based on particle or wave.
While Quantum Mechanics was successful in providing the prediction for linear polarization, the same cannot be said of circular polarization.
In the last posting, you have mentioned, “A circular polarizer must always have the linear polarizer FIRST, and the QWP SECOND in the light path”. If what you said is correct, then it must be possible to obscure the passage of a Right circularly polarized light using a Left circular polarizer as predicted by Quantum Mechanics. I have played around with some linear and circular polarizers based on your suggestion, but I was unable to obtain the result that you mentioned, however hard I tried. I hope it is not due to defect of my polarizers.
In the experiment involving a mirror, the forward path of an unpolarized light passes through a linear polarizer followed by a QWP. On the return journey, the reflected circularly polarized light will pass through the QWP followed by the linear polarizer. While the reflected image of the circular polarizer appears to be darken if one looks through the circular polarizer, it does not amount to total cancellation of light as observed for two linear polarizers placed at 90 degrees to one another.
Conversely, if we rotate the circular polarizer with the QWP placed before the linear polarizer, then the reflected image of the polarizer is not darken when it is viewed through the polarizer.
The above observation does not seem to agree with all the prediction using Quantum Mechanics.
I would appreciate it if you could comment on the above observations?
I did not realise the length you went through in order to provide me with these explanation. I am very grateful to you for what you have done.
From your explanation, I have an uneasy feeling that Quantum Mechanics does not seem to apply to Circular Polarization.
Based on your earlier clarification, I am sure you must be aware that the explanation on light passing through two linear polarizers using particle or wave was not entirely successful. Instead, it was found that Quantum Mechanics based on cosine square of an angle (first proposed by Etienne Louis Malus) appears to provide the best answer that agrees with experimental observation. This appears to support the modulus square of the wave function rule of Quantum Mechanics that was formulated from another paradoxical Double-slits experiment of light and of electrons.
However, if one were to question what we mean by wave function, Quantum Mechanics will be nonplussed. The wave function is essentially an abstract entity incapable of any physical or logical expression. The wave function and the projection probability it seeks to predict is connected by abstract mathematical logics not one that will allow us to visualize physically whether it is based on particle or wave.
While Quantum Mechanics was successful in providing the prediction for linear polarization, the same cannot be said of circular polarization.
In the last posting, you have mentioned, “A circular polarizer must always have the linear polarizer FIRST, and the QWP SECOND in the light path”. If what you said is correct, then it must be possible to obscure the passage of a Right circularly polarized light using a Left circular polarizer as predicted by Quantum Mechanics. I have played around with some linear and circular polarizers based on your suggestion, but I was unable to obtain the result that you mentioned, however hard I tried. I hope it is not due to defect of my polarizers.
In the experiment involving a mirror, the forward path of an unpolarized light passes through a linear polarizer followed by a QWP. On the return journey, the reflected circularly polarized light will pass through the QWP followed by the linear polarizer. While the reflected image of the circular polarizer appears to be darken if one looks through the circular polarizer, it does not amount to total cancellation of light as observed for two linear polarizers placed at 90 degrees to one another.
Conversely, if we rotate the circular polarizer with the QWP placed before the linear polarizer, then the reflected image of the polarizer is not darken when it is viewed through the polarizer.
The above observation does not seem to agree with all the prediction using Quantum Mechanics.
I would appreciate it if you could comment on the above observations?
First, I should be sure that you are aware that a great deal of the discussion hinges upon the fact that quanta are very different from objects in our everyday reality. The primary way in which this is true is that quanta are very, very simple- far simpler than any material object we generally interact with. Because of this simplicity, it is very easy to detect what they are doing; and when we do, what we find is that they do things that more complex objects don't.
So, although I have done my best to explain how these things work using the English language, it is in truth impossible to describe that way. The only way to describe it that we have found that works is to use mathematics. This is because human language is built upon assumptions about how things are in the world around us- but all of the things that those assumptions are based upon are composite objects, and composite objects behave differently from quanta. So when you read my explanations, you need to keep the facts about quanta- which are experimentally confirmed, with greater accuracy than any other theory of physics in history- carefully in mind, because they form the assumptions that such an explanation must be based upon.
That said, I will try to answer your questions.
So, although I have done my best to explain how these things work using the English language, it is in truth impossible to describe that way. The only way to describe it that we have found that works is to use mathematics. This is because human language is built upon assumptions about how things are in the world around us- but all of the things that those assumptions are based upon are composite objects, and composite objects behave differently from quanta. So when you read my explanations, you need to keep the facts about quanta- which are experimentally confirmed, with greater accuracy than any other theory of physics in history- carefully in mind, because they form the assumptions that such an explanation must be based upon.
That said, I will try to answer your questions.
QUOTE (hexa+)
However, if one were to question what we mean by wave function, Quantum Mechanics will be nonplussed. The wave function is essentially an abstract entity incapable of any physical or logical expression. The wave function and the projection probability it seeks to predict is connected by abstract mathematical logics not one that will allow us to visualize physically whether it is based on particle or wave.
Here you have confounded the ability to describe what it is doing in natural language, which is based upon our experience of the world, with the ability to describe what it is doing with mathematics. The mathematics works perfectly; but when we try to use natural language riddled with assumptions about how everyday objects behave, it fails. This is because quanta do not behave according to these assumptions. The logic that works for the everyday objects we find around us simply cannot work for quanta.
Now, that is not to say that natural language cannot be used in such descriptions; however, for that to be successful, you must always keep the assumptions about how quanta behave in mind. Whenever you make an assumption about how objects behave based on everyday objects, and then attempt to apply reasoning based on that assumption to quanta, you will fail to correctly describe them. Your assumption that an object must be either a particle or a wave is a perfect example. Everyday objects must be either particles or waves; but this is not true of quanta.
Now, that is not to say that natural language cannot be used in such descriptions; however, for that to be successful, you must always keep the assumptions about how quanta behave in mind. Whenever you make an assumption about how objects behave based on everyday objects, and then attempt to apply reasoning based on that assumption to quanta, you will fail to correctly describe them. Your assumption that an object must be either a particle or a wave is a perfect example. Everyday objects must be either particles or waves; but this is not true of quanta.
QUOTE (hexa+)
While Quantum Mechanics was successful in providing the prediction for linear polarization, the same cannot be said of circular polarization.
Actually, this is not true. Quantum mechanics provides the following explanation of circular polarization: if light is passed through a linear polarizer, the spin of each photon is measured in the axis defined by that linear polarizer. All photons (which are quanta) that have spin (let us say) UP are passed; all photons that have spin DOWN are absorbed. In incoherent light, the probability of each photon having spin UP or DOWN in that axis is 50%; thus, half of the photons are passed, and half absorbed.
If these polarized photons, which all have spin UP in that axis, are then sent through a QWP whose axis is at 45 degrees to the axis of the linear polarizer, then the cosine squared function will apply; a QWP also measures photons' spins, and passes photons with (let us say) spin UP without delaying them, but passes photons with spin DOWN with a delay. For one particular frequency, the QWP delays them by precisely 90 degrees, so that the spin DOWN photons are all 90 degrees out of phase with the spin UP photons. Remember, we have not measured the photons in the QWP in the same plane as in the linear polarizer; thus, we know that we have to use the cosine squared function to describe the probability that they will have spin UP or spin DOWN in this new plane. And if the angle is 45 degrees, the cosine squared function tells us that the probability is again 50%. Thus, at that particular frequency for which the QWP is precisely a QWP, 50% of the photons will be 90 degrees out of phase with the other 50%.
Two linearly polarized, monophasic, monochromatic waves precisely 90 degrees out of phase in the same space at the same time is the definition of "circular polarization." Thus, we have described a device called a "circular polarizer." But remember: that device works perfectly for only one particular frequency; for other frequencies, it is not a circular polarizer. Because the QWP is not a QWP for those other frequencies; it is an elliptical polarizer. In fact, if we choose the center frequency for the QWP in the red, at say 780nm, the very bottom of the visible spectrum, at 390nm, at the very top in the violet, it is a half-wave plate, and a half-wave plate does not convert linearly polarized light into circularly polarized light; instead, it rotates the plane of polarization by 90 degrees, but leaves the light linearly polarized.
Now generally, photographic circular polarizers are perfect circular polarizers in the middle of the visible spectrum; that is, at about 580nm, in the green. You can see that this QWP will not be a half-wave plate at any point in the visible spectrum; dividing 580nm by two gives 290nm, well up into the ultraviolet, which we cannot see. Thus, the circular polarizer will be a circular polarizer only for green light; for all other frequencies, it will be an elliptical polarizer.
And that is the best possible description of the workings of a circular polarizer in natural language.
If these polarized photons, which all have spin UP in that axis, are then sent through a QWP whose axis is at 45 degrees to the axis of the linear polarizer, then the cosine squared function will apply; a QWP also measures photons' spins, and passes photons with (let us say) spin UP without delaying them, but passes photons with spin DOWN with a delay. For one particular frequency, the QWP delays them by precisely 90 degrees, so that the spin DOWN photons are all 90 degrees out of phase with the spin UP photons. Remember, we have not measured the photons in the QWP in the same plane as in the linear polarizer; thus, we know that we have to use the cosine squared function to describe the probability that they will have spin UP or spin DOWN in this new plane. And if the angle is 45 degrees, the cosine squared function tells us that the probability is again 50%. Thus, at that particular frequency for which the QWP is precisely a QWP, 50% of the photons will be 90 degrees out of phase with the other 50%.
Two linearly polarized, monophasic, monochromatic waves precisely 90 degrees out of phase in the same space at the same time is the definition of "circular polarization." Thus, we have described a device called a "circular polarizer." But remember: that device works perfectly for only one particular frequency; for other frequencies, it is not a circular polarizer. Because the QWP is not a QWP for those other frequencies; it is an elliptical polarizer. In fact, if we choose the center frequency for the QWP in the red, at say 780nm, the very bottom of the visible spectrum, at 390nm, at the very top in the violet, it is a half-wave plate, and a half-wave plate does not convert linearly polarized light into circularly polarized light; instead, it rotates the plane of polarization by 90 degrees, but leaves the light linearly polarized.
Now generally, photographic circular polarizers are perfect circular polarizers in the middle of the visible spectrum; that is, at about 580nm, in the green. You can see that this QWP will not be a half-wave plate at any point in the visible spectrum; dividing 580nm by two gives 290nm, well up into the ultraviolet, which we cannot see. Thus, the circular polarizer will be a circular polarizer only for green light; for all other frequencies, it will be an elliptical polarizer.
And that is the best possible description of the workings of a circular polarizer in natural language.
QUOTE (hexa+)
In the last posting, you have mentioned, “A circular polarizer must always have the linear polarizer FIRST, and the QWP SECOND in the light path”. If what you said is correct, then it must be possible to obscure the passage of a Right circularly polarized light using a Left circular polarizer as predicted by Quantum Mechanics. I have played around with some linear and circular polarizers based on your suggestion, but I was unable to obtain the result that you mentioned, however hard I tried. I hope it is not due to defect of my polarizers.
First, the statement that a LHCP will completely exclude RHCP light is not exactly true; the truth is, a reversed LHCP will completely exclude RHCP light. Second, remember that the light is only precisely RHCP for one frequency, that is the frequency for which the QWP is precisely a QWP. All other frequencies are elliptically polarized, and will not be completely excluded as a result.
QUOTE (hexa+)
In the experiment involving a mirror, the forward path of an unpolarized light passes through a linear polarizer followed by a QWP. On the return journey, the reflected circularly polarized light will pass through the QWP followed by the linear polarizer. While the reflected image of the circular polarizer appears to be darken if one looks through the circular polarizer, it does not amount to total cancellation of light as observed for two linear polarizers placed at 90 degrees to one another.
This is because the light is only circularly polarized at one frequency; at other frequencies, it is elliptically polarized, and therefore is not excluded. If you used a monochromatic source that was centered on the frequency at which the QWP is precisely a QWP, all the light would be excluded.
QUOTE (hexa+)
Conversely, if we rotate the circular polarizer with the QWP placed before the linear polarizer, then the reflected image of the polarizer is not darken when it is viewed through the polarizer.
Well, I left something out of my explanation; I forgot to describe how the circularly polarized light will behave at the QWP if its optical axis is not the same as the QWP in the first circular polarizer. In this case, the spins are being measured in yet another plane, and the cosine squared function must be used; only if the planes are the same will we get the opposite result and wind up with the phases identical, and thus only if the planes are the same will the light come out of the QWP linearly polarized at 45 degrees to the plane of the QWP. And, of course, since the linear polarizer's axis is at 45 degrees, this means that only then will all the light be passed (if the circular polarizer is the same handedness as the original one) or blocked (if it is the opposite handedness).
Thinking about it, I had initially thought that the distance between the plates might also need to be taken into account; I'm still not entirely certain about that. It might not, because the circularly polarized light can be decomposed into two linear components at 90 degrees and 90 degrees out of phase. A quick experiment would show whether this is true; rotate the second, reversed circular polarizer until it is darkest, and then move it toward or away from the first, and observe whether it lightens or darkens.
Thinking about it, I had initially thought that the distance between the plates might also need to be taken into account; I'm still not entirely certain about that. It might not, because the circularly polarized light can be decomposed into two linear components at 90 degrees and 90 degrees out of phase. A quick experiment would show whether this is true; rotate the second, reversed circular polarizer until it is darkest, and then move it toward or away from the first, and observe whether it lightens or darkens.
QUOTE (hexa+)
The above observation does not seem to agree with all the prediction using Quantum Mechanics.
I disagree. I think that you have left out some considerations, such as the frequency selectivity and the angles of the axes requiring the use of the cosine squared formula. What do you think?
Hi Schneibster, thanks again for your clarification. I am not in my home country at the moment.
Please correct me if I am wrong. The way I understand Quantum Mechanics is that quantum entities or quanta are neither particles nor waves. According to Richard Feynman, “Physics has given up. We do not know how to predict what would happen in a given circumstance, and we believe now it is impossible—that the only thing that can be predicted is the probability of different events. It must be recognised that this is a retrenchment in our earlier ideal of understanding nature. It may be a backward step, but no one has seen a way to avoid it”. This predicament essentially stems from our inability to account for a few experiments based on causality that we learn from classical particles or waves in our macro-world, since one must lead to the exclusion of the other. There are four important experiments that I will discuss:
1) Double slits Experiment of light;
2) Double slits experiment of electrons.
3) Photoelectric effect, and
4) Light passing through a linear polarizer based on Malus Law.
The Double slits Experiment of light
In this experiment, we can try to explain the interference effect by assuming that light is electromagnetic wave comprising electric and magnetic field that are orthogonal to the path of propagation of light proposed by James Maxwell. Physically, waves only makes sense if light is propagated through a medium called “ether” that is similar to the propagation of water wave. Unfortunately, ether as a physical entity was proven beyond reasonable doubt that it does not exist by Michelson & Morley in the famous experiment named after them. Notwithstanding that wave is no longer a viable proposition, the idea that light is a form of wave continued to be embraced among many authors to account for many aspects of light including linear and circular polarization similar to what you have described. As you have noticed, this approach has many problems. You end up having to describe light in relation to its phase (monophasic), frequency (monochromatic) as well as spin, and how they are crucial in obtaining the prediction made in Quantum Mechanics. Strictly speaking, Quantum Mechanics essentially denies this approach. It is not concerned with any description of physical reality. In fact, it denies its existence. What it is interested is that the mathematics allows one to make prediction of its probability. In this case, it is the probability of the intensity of light passing through the apparatus that will be measured at a specific position.
Double slits experiment of electrons
I will not go into the details of this experiment, except to state that the electrons described by its founder, J.J. Thomson as particle was found to behave as wave because it also manifest the interference pattern by his son, G.P. Thomson. We have been taught all this while that interference pattern implies waves. My naďve question with regards to the Double-slits experiment is whether this experiment is considered the gold standard for anything that is “wave”, including on entities such as electrons that was proven conclusively as particles? (For reference-see Lectures on Physics by Richard Feynman, Vol. III). What if it is possible to explain the interference pattern of particles without invoking the concept of wave or the complimentary Uncertainty Principle (that forms the cornerstone of the Copenhagen Interpretation and Quantum Mechanics)? Is the particle-wave duality postulate necessary if we can prove conclusively that under special circumstances, particles can account for the interference fringe pattern including if the particles are as big as bullets fired from a machine gun?
The Photoelectric effect
While the double-slits experiment suggests that electrons may behave as wave, the photoelectric effect point towards light as particles. Einstein coined the term “photon”, to suggest that light is made of quanta or packet of energy more akin to particle than wave.
Light passing through a linear polarizer based on Malus Law
Attempt was made to account for an unpolarized light passing through two linear polarizers rotated at various angles from one another using local hidden variable models. This includes some aspect of the wave model which was used by many authors that are similar to your illustrations. You are right to caution us that this visual image may be wrong for want of a better physical model. Experimentally, the local hidden variable model was proven to depart from our physical observation. Instead, it obeys the cosine square relationship which resembles the modulus square rule that was derived from the double slits experiments. This is where Quantum Mechanics triumph over the classical wave theory that was used by many authors to explain linear and circular polarization of light.
From these experiments, Quantum Mechanics had no choice but to makes a radical postulate that the law of causality (or cause and effect) does not apply to quantum objects. This essentially overturns one of the most sacred axioms of science that was embraced since Aristotle and formalised by geniuses like Galileo, Newton, etc.
All that Quantum Mechanics does is to predict the probability of an experiment based on the mathematical rules that was borrowed heavily from the classical wave theory. Hence, the prediction of probabilities of light passing through the double-slits or through the linear polarizers was hailed as affirmation of nature’s behaviour at the quantum scale. While this appears to be expedient for linear polarization of light, the same success was not observed when it involves circular polarization. It is this failure of Quantum Mechanics that set me wondering whether there is a distinct circularly polarized state of light?
I hope you could further enlighten me on where I have gone wrong.
Cheers,
Hexa
Please correct me if I am wrong. The way I understand Quantum Mechanics is that quantum entities or quanta are neither particles nor waves. According to Richard Feynman, “Physics has given up. We do not know how to predict what would happen in a given circumstance, and we believe now it is impossible—that the only thing that can be predicted is the probability of different events. It must be recognised that this is a retrenchment in our earlier ideal of understanding nature. It may be a backward step, but no one has seen a way to avoid it”. This predicament essentially stems from our inability to account for a few experiments based on causality that we learn from classical particles or waves in our macro-world, since one must lead to the exclusion of the other. There are four important experiments that I will discuss:
1) Double slits Experiment of light;
2) Double slits experiment of electrons.
3) Photoelectric effect, and
4) Light passing through a linear polarizer based on Malus Law.
The Double slits Experiment of light
In this experiment, we can try to explain the interference effect by assuming that light is electromagnetic wave comprising electric and magnetic field that are orthogonal to the path of propagation of light proposed by James Maxwell. Physically, waves only makes sense if light is propagated through a medium called “ether” that is similar to the propagation of water wave. Unfortunately, ether as a physical entity was proven beyond reasonable doubt that it does not exist by Michelson & Morley in the famous experiment named after them. Notwithstanding that wave is no longer a viable proposition, the idea that light is a form of wave continued to be embraced among many authors to account for many aspects of light including linear and circular polarization similar to what you have described. As you have noticed, this approach has many problems. You end up having to describe light in relation to its phase (monophasic), frequency (monochromatic) as well as spin, and how they are crucial in obtaining the prediction made in Quantum Mechanics. Strictly speaking, Quantum Mechanics essentially denies this approach. It is not concerned with any description of physical reality. In fact, it denies its existence. What it is interested is that the mathematics allows one to make prediction of its probability. In this case, it is the probability of the intensity of light passing through the apparatus that will be measured at a specific position.
Double slits experiment of electrons
I will not go into the details of this experiment, except to state that the electrons described by its founder, J.J. Thomson as particle was found to behave as wave because it also manifest the interference pattern by his son, G.P. Thomson. We have been taught all this while that interference pattern implies waves. My naďve question with regards to the Double-slits experiment is whether this experiment is considered the gold standard for anything that is “wave”, including on entities such as electrons that was proven conclusively as particles? (For reference-see Lectures on Physics by Richard Feynman, Vol. III). What if it is possible to explain the interference pattern of particles without invoking the concept of wave or the complimentary Uncertainty Principle (that forms the cornerstone of the Copenhagen Interpretation and Quantum Mechanics)? Is the particle-wave duality postulate necessary if we can prove conclusively that under special circumstances, particles can account for the interference fringe pattern including if the particles are as big as bullets fired from a machine gun?
The Photoelectric effect
While the double-slits experiment suggests that electrons may behave as wave, the photoelectric effect point towards light as particles. Einstein coined the term “photon”, to suggest that light is made of quanta or packet of energy more akin to particle than wave.
Light passing through a linear polarizer based on Malus Law
Attempt was made to account for an unpolarized light passing through two linear polarizers rotated at various angles from one another using local hidden variable models. This includes some aspect of the wave model which was used by many authors that are similar to your illustrations. You are right to caution us that this visual image may be wrong for want of a better physical model. Experimentally, the local hidden variable model was proven to depart from our physical observation. Instead, it obeys the cosine square relationship which resembles the modulus square rule that was derived from the double slits experiments. This is where Quantum Mechanics triumph over the classical wave theory that was used by many authors to explain linear and circular polarization of light.
From these experiments, Quantum Mechanics had no choice but to makes a radical postulate that the law of causality (or cause and effect) does not apply to quantum objects. This essentially overturns one of the most sacred axioms of science that was embraced since Aristotle and formalised by geniuses like Galileo, Newton, etc.
All that Quantum Mechanics does is to predict the probability of an experiment based on the mathematical rules that was borrowed heavily from the classical wave theory. Hence, the prediction of probabilities of light passing through the double-slits or through the linear polarizers was hailed as affirmation of nature’s behaviour at the quantum scale. While this appears to be expedient for linear polarization of light, the same success was not observed when it involves circular polarization. It is this failure of Quantum Mechanics that set me wondering whether there is a distinct circularly polarized state of light?
I hope you could further enlighten me on where I have gone wrong.
Cheers,
Hexa
Worry not.........it's all to do with wormholes......see Spacial Vacuoles.
A very un-sober 5-doughnut......hic!
A very un-sober 5-doughnut......hic!
QUOTE (hexa+)
The way I understand Quantum Mechanics is that quantum entities or quanta are neither particles nor waves.
Basically, yes. They are quanta; they have some wavelike properties and some particle-like properties. But they are neither waves nor particles.
Because of their wavelike properties, we can use some equations that are derived conceptually from the equations we use to describe waves to describe those properties. Because of their particle-like properties, we can use some equations that are derived conceptually from the equations we use to describe particles to describe those properties. But the quanta themselves (insofar as they have any existence other than as a convenient means of referring to them using some of the concepts that we use to refer to things that we can directly observe around us) are neither wave nor particle; they are QUANTA.
Because of their wavelike properties, we can use some equations that are derived conceptually from the equations we use to describe waves to describe those properties. Because of their particle-like properties, we can use some equations that are derived conceptually from the equations we use to describe particles to describe those properties. But the quanta themselves (insofar as they have any existence other than as a convenient means of referring to them using some of the concepts that we use to refer to things that we can directly observe around us) are neither wave nor particle; they are QUANTA.
QUOTE (hexa+)
My naďve question with regards to the Double-slits experiment is whether this experiment is considered the gold standard for anything that is “wave”, including on entities such as electrons that was proven conclusively as particles?
It is the gold standard for proving that something (perhaps not an "entity" as we imagine it, but SOMETHING nevertheless, whatever it may be) has attributes that are wavelike, i.e. can be described with equations conceptually derived from the ones we use to describe waves. Whether there is "anything waving" is not merely impossible to verify, but meaningless in the absence of any other way to verify it.
QUOTE (hexa+)
What if it is possible to explain the interference pattern of particles without invoking the concept of wave or the complimentary Uncertainty Principle (that forms the cornerstone of the Copenhagen Interpretation and Quantum Mechanics)?
Various schemes to do so have been introduced, but none has been proven. In fact, the most advanced scheme (string theory) proposes that it is strings that are experiencing wavelike phenomena, far below our best ability to resolve what is physically happening.
The CI is not quantum mechanics; quantum mechanics is math. The CI is an interpretation of quantum mechanics, and there are other interpretations. No one has yet conceived an experiment to choose among these interpretations. You might want to google up Jack Cramer's Transactional Interpretation, and the Many Worlds or Everett interpretation, and you'll furthermore find that there are a couple of refined and updated CI variants as well, nor is that all the interpretations there are. There is a "Backward Causation" interpretation out there, and several others that are (as far as I can tell) also completely consistent with all our experimental and mathematical results. The most interesting of these may be the Bohm or "pilot-wave" or causal hidden-variables interpretation, and a raft of other hidden-variable interpretations that are derived from the basic idea. As I said, no one has yet conceived an experiment that can differentiate among them. This is an interesting area for speculation. But keep in mind, IT IS NOT QM. QM is a mathematical theory; these are INTERPRETATIONS of the mathematical theory into concepts that may or may not be capable of representing QM; it is entirely possible that NONE of these interpretations is correct. Or even that ALL of them are!
The CI is not quantum mechanics; quantum mechanics is math. The CI is an interpretation of quantum mechanics, and there are other interpretations. No one has yet conceived an experiment to choose among these interpretations. You might want to google up Jack Cramer's Transactional Interpretation, and the Many Worlds or Everett interpretation, and you'll furthermore find that there are a couple of refined and updated CI variants as well, nor is that all the interpretations there are. There is a "Backward Causation" interpretation out there, and several others that are (as far as I can tell) also completely consistent with all our experimental and mathematical results. The most interesting of these may be the Bohm or "pilot-wave" or causal hidden-variables interpretation, and a raft of other hidden-variable interpretations that are derived from the basic idea. As I said, no one has yet conceived an experiment that can differentiate among them. This is an interesting area for speculation. But keep in mind, IT IS NOT QM. QM is a mathematical theory; these are INTERPRETATIONS of the mathematical theory into concepts that may or may not be capable of representing QM; it is entirely possible that NONE of these interpretations is correct. Or even that ALL of them are!
QUOTE (hexa+)
Is the particle-wave duality postulate necessary if we can prove conclusively that under special circumstances, particles can account for the interference fringe pattern including if the particles are as big as bullets fired from a machine gun?
Show me such an experiment and I may offer an opinion.
QUOTE (hexa+)
From these experiments, Quantum Mechanics had no choice but to makes a radical postulate that the law of causality (or cause and effect) does not apply to quantum objects. This essentially overturns one of the most sacred axioms of science that was embraced since Aristotle and formalised by geniuses like Galileo, Newton, etc.
In fact, the Aspect realization of the Einstein-Podolsky-Rosen gedankenexperiment shows that causality as we ordinarily conceive of it cannot apply to quantum phenomena, and Scully's proposal and Kim, Kulik, Shih, and Scully's realization of the Delayed Choice Quantum Eraser, modeled after Wheeler's original suggestion but realized with more advanced optical and physics principles, make the point even more forcefully. What we define as "causation" simply does not hold in QM, and not merely in terms of the equations; in terms of the actual measurable phenomena.
Quanta do not actually have a spin in a particular direction until that spin is actually measured, and do not have any spin in different directions simultaneously; measure the spin in one direction and it is no guarantee what the spin is in another, nor can it be. And this goes for other quantum properties that are subject to uncertainty relations as well.
Quanta do not actually have a spin in a particular direction until that spin is actually measured, and do not have any spin in different directions simultaneously; measure the spin in one direction and it is no guarantee what the spin is in another, nor can it be. And this goes for other quantum properties that are subject to uncertainty relations as well.
QUOTE (hexa+)
All that Quantum Mechanics does is to predict the probability of an experiment based on the mathematical rules that was borrowed heavily from the classical wave theory. Hence, the prediction of probabilities of light passing through the double-slits or through the linear polarizers was hailed as affirmation of nature’s behaviour at the quantum scale. While this appears to be expedient for linear polarization of light, the same success was not observed when it involves circular polarization. It is this failure of Quantum Mechanics that set me wondering whether there is a distinct circularly polarized state of light?
I'm not sure why you say this, considering what I have presented. In fact, I showed precisely how the predictions of QM are fulfilled in describing circular polarization; due to the implementation of a circular polarizer in the real world, it is not as simple as how a QWP or linear polarizer works, but that's a defect in the implementation of the circular polarizer, not in the existence of circular polarization nor in the QM that describes both the state and the operation of the elements to produce that state.
Since a circular polarizer is only a circular polarizer in only one direction, it is unsurprising that it excludes opposite-handed circularly polarized light in only one direction. Which direction that might happen to be is immaterial to the overall concept, and to the realization of the description QM gives.
Perhaps if we could construct a one-step circular polarizer, it would work both ways; however, we can't do that. So we'll never know unless we manage to create one.
Hope that helps.
Since a circular polarizer is only a circular polarizer in only one direction, it is unsurprising that it excludes opposite-handed circularly polarized light in only one direction. Which direction that might happen to be is immaterial to the overall concept, and to the realization of the description QM gives.
Perhaps if we could construct a one-step circular polarizer, it would work both ways; however, we can't do that. So we'll never know unless we manage to create one.
Hope that helps.
Hi Schneibster,
Thanks again for highlighting the differences between Copenhagen Interpretation and Quantum Mechanics. You have also drawn the attention that there are other interpretations (Jack Cramer's Transactional Interpretation; Many Worlds or Everett interpretation; Backward Causation; and Bohm or "pilot-wave" or causal hidden-variables interpretation). Finally you have also state that, “it is entirely possible that NONE of these interpretations is correct”.
One question that crosses my mind is at what scale does an entity cease to be a quantum entity? According to what I was given to understand, an atom is still a quantum entity and continues to be governed by Quantum Mechanics. How and at what scale does an entity switch from obeying Quantum mechanics to one that obey the classical Newtonian mechanics?
Quantum mechanics or Wave Mechanics is essentially the mathematics used for computing wave that is applied to particles. One that is widely accepted by the mainstream science community is the Schrodinger Equation. Quantum Mechanics has no meaning unless we accept the Copenhagen Interpretation or any other interpretations. Since, Quantum Mechanics evolved out of Copenhagen Interpretation, not independently, and remain the defacto Standard Quantum Theory among the mainstream science communities, I have as such stated QM to mean QM based on CI. Anyway, thanks for highlighting the distinction.
Before we can understand Bohm’s causal hidden-variable interpretation and the Aspects experiment, I think we should start with Heisenberg Uncertainty Principle that forms the bedrock of Copenhagen Interpretation and Quantum Mechanics. Simply stated, “if we are able to determine the position of a particle with absolute certainty then we will have no information with regard to its momentum”.
Einstein did not think that the Uncertainty Principle is correct and together with Podensky and Rosen put up a thought experiment intended to demonstrate the absurdity of the Uncertainty Principle.
In 1952 David Bohm proposed a variation to the EPR experiment, and in 1964 John Bell showed how Bohm’s variation to the EPR experiment can form the basis of a real experiment. This led Alan Aspect to show that Bell’s inequality was violated. This was then hailed as confirmation of the quantum weirdness of non-locality. While there is no denying that quantum physics is weird and that existing local theory cannot effectively account for light passing through a linear polarizer or the doubleslits experiment, I do not think that the variation amount to a conclusive rebuttal of the criticism of the EPR experiment. There is nothing in this experiment to suggest that the detection of one photon in one state (say spin up) will cause its conjugate pair to appear in the opposite state (say spin down). Conversely, if it were to be detected in the spin down state, then it would cause the conjugate photon to collapse into the spin up state based on the principle of superposition of state. Nothing in the Aspect Experiment suggest that two entangle pairs of photons are involved. As such I feel that the claim has been substantially overstated that non-local action is involved (see paper by Milos V. Lokajicek Institute of Physics, AVCR, 1822 Prague 8, Czech Republic—Quantum Mechanics and EPR paradox).
In fact the defence of Quantum Mechanics was earlier supported by Von Neumann impossibility proof, but it has since been established that von Neumann impossibility proof was wrong and it cannot be used to support the validity of Quantum Mechanics.
Coming back to Circular polarization, I am more convinced after your explanation that Quantum Mechanics does not provide us the prediction that allow us to correlate with observation. I am sure you must be aware that Quantum Mechanics treat Right or Left circularly polarized state of light as two distinct states. It further provide us the following elegant predictions on the projection probabilities:
1. l <R l MR l Ψ> l^2 = 1/2
2. l <L l ML l Ψ> l^2 = 1/2
3. l <v l Mv l Ψ> l^2 = 1/2
4. l <h l Mh l Ψ> l^2 = 1/2
5. l <R l MR l R> l^2 = 1
6. l <L l ML l R> l^2 = 0
7. l <L l ML l L> l^2 = 1
8. l <R l MR l L> l^2 = 0
9. l <v l Mv l R> l^2 = 1/2
10. l <h l Mh l R> l^2 = 1/2
11. l <v l Mv l L> l^2 = 1/2
12. l <h l Mh l L> l^2 = 1/2
13. l <R l MR l v> l^2 = 1/2
14. l <L l ML l v> l^2 = 1/2
15. l <R l MR l h> l^2 = 1/2
16. l <L l ML l h> l^2 = 1/2
(Note: the 2 represent the modulus square)
Since a circular polarizer is made up of a linear polarizer followed by a quarter wave plate, I think the answer is obvious as to what we may observe when we pass light through a circular polarizer followed by a linear polarizer or vice versa. Except for 1 to 4 and 9 to 12, none of the other predictions is observed experimentally.
I am sure you would agree with me that these authors who has presented Quantum mechanics with such elegance may have overstated themselves with regards to circular polarization.
Cheers.
Thanks again for highlighting the differences between Copenhagen Interpretation and Quantum Mechanics. You have also drawn the attention that there are other interpretations (Jack Cramer's Transactional Interpretation; Many Worlds or Everett interpretation; Backward Causation; and Bohm or "pilot-wave" or causal hidden-variables interpretation). Finally you have also state that, “it is entirely possible that NONE of these interpretations is correct”.
One question that crosses my mind is at what scale does an entity cease to be a quantum entity? According to what I was given to understand, an atom is still a quantum entity and continues to be governed by Quantum Mechanics. How and at what scale does an entity switch from obeying Quantum mechanics to one that obey the classical Newtonian mechanics?
Quantum mechanics or Wave Mechanics is essentially the mathematics used for computing wave that is applied to particles. One that is widely accepted by the mainstream science community is the Schrodinger Equation. Quantum Mechanics has no meaning unless we accept the Copenhagen Interpretation or any other interpretations. Since, Quantum Mechanics evolved out of Copenhagen Interpretation, not independently, and remain the defacto Standard Quantum Theory among the mainstream science communities, I have as such stated QM to mean QM based on CI. Anyway, thanks for highlighting the distinction.
Before we can understand Bohm’s causal hidden-variable interpretation and the Aspects experiment, I think we should start with Heisenberg Uncertainty Principle that forms the bedrock of Copenhagen Interpretation and Quantum Mechanics. Simply stated, “if we are able to determine the position of a particle with absolute certainty then we will have no information with regard to its momentum”.
Einstein did not think that the Uncertainty Principle is correct and together with Podensky and Rosen put up a thought experiment intended to demonstrate the absurdity of the Uncertainty Principle.
In 1952 David Bohm proposed a variation to the EPR experiment, and in 1964 John Bell showed how Bohm’s variation to the EPR experiment can form the basis of a real experiment. This led Alan Aspect to show that Bell’s inequality was violated. This was then hailed as confirmation of the quantum weirdness of non-locality. While there is no denying that quantum physics is weird and that existing local theory cannot effectively account for light passing through a linear polarizer or the doubleslits experiment, I do not think that the variation amount to a conclusive rebuttal of the criticism of the EPR experiment. There is nothing in this experiment to suggest that the detection of one photon in one state (say spin up) will cause its conjugate pair to appear in the opposite state (say spin down). Conversely, if it were to be detected in the spin down state, then it would cause the conjugate photon to collapse into the spin up state based on the principle of superposition of state. Nothing in the Aspect Experiment suggest that two entangle pairs of photons are involved. As such I feel that the claim has been substantially overstated that non-local action is involved (see paper by Milos V. Lokajicek Institute of Physics, AVCR, 1822 Prague 8, Czech Republic—Quantum Mechanics and EPR paradox).
In fact the defence of Quantum Mechanics was earlier supported by Von Neumann impossibility proof, but it has since been established that von Neumann impossibility proof was wrong and it cannot be used to support the validity of Quantum Mechanics.
Coming back to Circular polarization, I am more convinced after your explanation that Quantum Mechanics does not provide us the prediction that allow us to correlate with observation. I am sure you must be aware that Quantum Mechanics treat Right or Left circularly polarized state of light as two distinct states. It further provide us the following elegant predictions on the projection probabilities:
1. l <R l MR l Ψ> l^2 = 1/2
2. l <L l ML l Ψ> l^2 = 1/2
3. l <v l Mv l Ψ> l^2 = 1/2
4. l <h l Mh l Ψ> l^2 = 1/2
5. l <R l MR l R> l^2 = 1
6. l <L l ML l R> l^2 = 0
7. l <L l ML l L> l^2 = 1
8. l <R l MR l L> l^2 = 0
9. l <v l Mv l R> l^2 = 1/2
10. l <h l Mh l R> l^2 = 1/2
11. l <v l Mv l L> l^2 = 1/2
12. l <h l Mh l L> l^2 = 1/2
13. l <R l MR l v> l^2 = 1/2
14. l <L l ML l v> l^2 = 1/2
15. l <R l MR l h> l^2 = 1/2
16. l <L l ML l h> l^2 = 1/2
(Note: the 2 represent the modulus square)
Since a circular polarizer is made up of a linear polarizer followed by a quarter wave plate, I think the answer is obvious as to what we may observe when we pass light through a circular polarizer followed by a linear polarizer or vice versa. Except for 1 to 4 and 9 to 12, none of the other predictions is observed experimentally.
I am sure you would agree with me that these authors who has presented Quantum mechanics with such elegance may have overstated themselves with regards to circular polarization.
Cheers.
QUOTE (hexa+)
One question that crosses my mind is at what scale does an entity cease to be a quantum entity? According to what I was given to understand, an atom is still a quantum entity and continues to be governed by Quantum Mechanics. How and at what scale does an entity switch from obeying Quantum mechanics to one that obey the classical Newtonian mechanics?
Good question.
Actually, never. However, since quantum behavior is linked to Planck's constant, it becomes unmeasurable at a certain point; that point depends on the sensitivity of your instruments and the amount of care you take in the measurement. But that does not mean it's "gone;" just that we can't measure accurately enough to show it's happening.
In fact, there was a recent experiment based upon the Fluctuation Theorem in which very small collections of molecules in liquid were shown to behave anti-entropically with a particular probability, precisely as predicted by the Theorem, and very differently from the predictions of the classically-based Second Law of Thermodynamics. The Fluctuation Theorem predicts that as the size of the sample grows smaller and smaller the probability of anti-entropic behavior increases until, in the limit, it becomes as frequent as entropic behavior. This limit appears to be somewhere around the molecular or atomic scale, and it appears to be dependent upon what sort of measurements are being made, how precisely they are made, how many times they are repeated, and several other factors. What this shows is that classical behavior merges into quantum behavior somewhere around the molecular or atomic scale; it also shows that this is a very fuzzy boundary, and one can expect to see at least some apparently classically-based behavior even below this scale, though not by much, and at least some quantum behavior above it, though again not by much.
This concept, in which classical behavior gradually becomes less and less prevalent and quantum behavior more and more, is called "decoherence." The idea is currently (AFAIK) at the status of a conjecture, and forms the basis of an interpretation of Quantum Mechanics called "Consistent Histories." Have a look.
Actually, never. However, since quantum behavior is linked to Planck's constant, it becomes unmeasurable at a certain point; that point depends on the sensitivity of your instruments and the amount of care you take in the measurement. But that does not mean it's "gone;" just that we can't measure accurately enough to show it's happening.
In fact, there was a recent experiment based upon the Fluctuation Theorem in which very small collections of molecules in liquid were shown to behave anti-entropically with a particular probability, precisely as predicted by the Theorem, and very differently from the predictions of the classically-based Second Law of Thermodynamics. The Fluctuation Theorem predicts that as the size of the sample grows smaller and smaller the probability of anti-entropic behavior increases until, in the limit, it becomes as frequent as entropic behavior. This limit appears to be somewhere around the molecular or atomic scale, and it appears to be dependent upon what sort of measurements are being made, how precisely they are made, how many times they are repeated, and several other factors. What this shows is that classical behavior merges into quantum behavior somewhere around the molecular or atomic scale; it also shows that this is a very fuzzy boundary, and one can expect to see at least some apparently classically-based behavior even below this scale, though not by much, and at least some quantum behavior above it, though again not by much.
This concept, in which classical behavior gradually becomes less and less prevalent and quantum behavior more and more, is called "decoherence." The idea is currently (AFAIK) at the status of a conjecture, and forms the basis of an interpretation of Quantum Mechanics called "Consistent Histories." Have a look.
QUOTE (hexa+)
Quantum Mechanics has no meaning unless we accept the Copenhagen Interpretation or any other interpretations.
This is not true. It has no meaning IN NATURAL LANGUAGE without such an interpretation; but saying this is basically stating what I have already told you, and what Feynman has told you: there is no explanation of quantum mechanics that is consistent with the classical physics we observe all around us, and in fact for that classical mechanics to behave as it does, the underlying quantum mechanics MUST behave in these very different ways. The Fluctuation Theorem, which is the foundation and, most physicists agree, the actual final mathematical proof of the Second Law of Thermodynamics, is based upon these peculiarities that cause very small objects not to behave the way larger ones do. So without QM, no FT, and no 2LOT. But an interpretation of QM is not required; only the math is needed, since the FT is a Theorem, that is, a formal mathematical proof.
The math of quantum mechanics IS quantum mechanics; NONE of the interpretations need be "true" for that math to work. And this is the most accurate theory in the history of science: I believe that one parameter predicted by Dirac's QED has been verified to seventeen significant figures. And THAT is some serious confirmation of its correctness.
The math of quantum mechanics IS quantum mechanics; NONE of the interpretations need be "true" for that math to work. And this is the most accurate theory in the history of science: I believe that one parameter predicted by Dirac's QED has been verified to seventeen significant figures. And THAT is some serious confirmation of its correctness.
QUOTE (hexa+)
There is nothing in this experiment to suggest that the detection of one photon in one state (say spin up) will cause its conjugate pair to appear in the opposite state (say spin down).
Nothing but conservation of angular momentum. You see, when I say it "acts like" a "real spin," I really mean it; it seems to be tied into the conservation of angular momentum, and it seems to in fact be quantized angular momentum.
Now, the conservation of angular momentum is related to the symmetry of experimental results over rotations. In other words, there is no special direction in space; in the absence of any field or matter that allows the determination of a special direction in space, there is no underlying inherent directionality in the vacuum. The relationship between this "symmetry" (for that is what physicists call any operation that you can do that leaves things unchanged) and this conservation law is something called "Noether's Theorem." This is another formally mathematically proven theorem, not just a physical theory, and it shows that for every non-discrete (that is, continuously variable) symmetry, there is a conservation law.
Please, be careful: discrete symmetries are NOT necessarily associated with conservation laws (although if they form part of a global continuously variable symmetry, they might be through that symmetry). I've told you before that spin is a discrete symmetry; that is, it can be up or down, no other value. Thus, we can see that it need not be associated with a conservation law; however, because it takes the place of angular momentum in the quantum world, and because it apparently can be interconverted with actual physical spin of a macroscopic object, which IS a continuous symmetry, and therefore IS associated with a conservation law.
Thus, for the spins to be anything BUT opposite to one another, conservation of angular momentum MUST be violated; they emerged from an interaction with zero spin, and thus, their spins must always add to zero or spin will not be conserved, and that would mean that rotational momentum would not be conserved. And in fact, any time that the two measurements in the Aspect experiment happen to be in the same plane, the opposite spin is in fact measured; this conservation is never violated.
It is when we measure the spins in DIFFERENT planes that the behavior becomes very, very odd. Because of Bell's Inequality, which (you are correct) is based on Bohm's suggestion for improvement of the EPR experiment, we can make some statements about the frequency with which we will see the same and different spins in different planes. Just as we could make statements about the percentage of photons that would have a given spin when measured along a different axis using a polarizer. The basis of the one is the basis of the other; they are the SAME THING. THIS is the underlying oddity in polarizers of all kinds.
What Bell was able to show is that the probability at a different angle depends on whether the measured particle has a spin at any other angle or not. Now, Heisenberg's Uncertainty Principle says that if we measure the spin at a particular angle at a particular time, then the particle has UNDEFINED SPIN at any other angle at that same time. But our common perception of the properties of matter is that the spin is REALLY THERE, and we JUST CAN'T MEASURE IT. What Bell showed, and he proved it mathematically in another theorem, is that just because we can't measure it directly doesn't mean it doesn't have an effect, and in fact we can DIFFERENTIATE BETWEEN the situation where the spin really DOESN'T EXIST and the situation where it EXISTS BUT WE CAN'T MEASURE IT.
Now this spin MUST exist to preserve angular momentum; and in fact, any time you measure the particle IN THE SAME AXIS as the other particle, it will ACTUALLY SHOW the opposite spin. But if you measure in a DIFFERENT AXIS, then the probability of THAT spin will NOT behave as if the other spin exists; it will in fact obey the rules of quantum mechanics with regard to its spin as if the other spin had not ever been determined (as in fact at the time of that measurement, it had not- at least not directly).
This requirement that the spins must be opposite in order to preserve a conservation law, and the fact that we have conversely conclusively shown that the measurement in different axes behaves as if there were no spin in the other's common axis, is referred to collectively as "entanglement." What it means is that although one pair of measurements (at different angles) appears to show that the particles' spins have nothing to do with one another, another pair of measurements (at the same angle) ALWAYS shows the particles with related spins.
And this is very weird, because classical particles absolutely cannot behave like this.
Now, the conservation of angular momentum is related to the symmetry of experimental results over rotations. In other words, there is no special direction in space; in the absence of any field or matter that allows the determination of a special direction in space, there is no underlying inherent directionality in the vacuum. The relationship between this "symmetry" (for that is what physicists call any operation that you can do that leaves things unchanged) and this conservation law is something called "Noether's Theorem." This is another formally mathematically proven theorem, not just a physical theory, and it shows that for every non-discrete (that is, continuously variable) symmetry, there is a conservation law.
Please, be careful: discrete symmetries are NOT necessarily associated with conservation laws (although if they form part of a global continuously variable symmetry, they might be through that symmetry). I've told you before that spin is a discrete symmetry; that is, it can be up or down, no other value. Thus, we can see that it need not be associated with a conservation law; however, because it takes the place of angular momentum in the quantum world, and because it apparently can be interconverted with actual physical spin of a macroscopic object, which IS a continuous symmetry, and therefore IS associated with a conservation law.
Thus, for the spins to be anything BUT opposite to one another, conservation of angular momentum MUST be violated; they emerged from an interaction with zero spin, and thus, their spins must always add to zero or spin will not be conserved, and that would mean that rotational momentum would not be conserved. And in fact, any time that the two measurements in the Aspect experiment happen to be in the same plane, the opposite spin is in fact measured; this conservation is never violated.
It is when we measure the spins in DIFFERENT planes that the behavior becomes very, very odd. Because of Bell's Inequality, which (you are correct) is based on Bohm's suggestion for improvement of the EPR experiment, we can make some statements about the frequency with which we will see the same and different spins in different planes. Just as we could make statements about the percentage of photons that would have a given spin when measured along a different axis using a polarizer. The basis of the one is the basis of the other; they are the SAME THING. THIS is the underlying oddity in polarizers of all kinds.
What Bell was able to show is that the probability at a different angle depends on whether the measured particle has a spin at any other angle or not. Now, Heisenberg's Uncertainty Principle says that if we measure the spin at a particular angle at a particular time, then the particle has UNDEFINED SPIN at any other angle at that same time. But our common perception of the properties of matter is that the spin is REALLY THERE, and we JUST CAN'T MEASURE IT. What Bell showed, and he proved it mathematically in another theorem, is that just because we can't measure it directly doesn't mean it doesn't have an effect, and in fact we can DIFFERENTIATE BETWEEN the situation where the spin really DOESN'T EXIST and the situation where it EXISTS BUT WE CAN'T MEASURE IT.
Now this spin MUST exist to preserve angular momentum; and in fact, any time you measure the particle IN THE SAME AXIS as the other particle, it will ACTUALLY SHOW the opposite spin. But if you measure in a DIFFERENT AXIS, then the probability of THAT spin will NOT behave as if the other spin exists; it will in fact obey the rules of quantum mechanics with regard to its spin as if the other spin had not ever been determined (as in fact at the time of that measurement, it had not- at least not directly).
This requirement that the spins must be opposite in order to preserve a conservation law, and the fact that we have conversely conclusively shown that the measurement in different axes behaves as if there were no spin in the other's common axis, is referred to collectively as "entanglement." What it means is that although one pair of measurements (at different angles) appears to show that the particles' spins have nothing to do with one another, another pair of measurements (at the same angle) ALWAYS shows the particles with related spins.
And this is very weird, because classical particles absolutely cannot behave like this.
QUOTE (hexa+)
As such I feel that the claim has been substantially overstated that non-local action is involved (see paper by Milos V. Lokajicek Institute of Physics, AVCR, 1822 Prague 8, Czech Republic—Quantum Mechanics and EPR paradox).
Again, I must disagree- the results of this experiment are currently at the nine-sigma level of confidence. This is essentially indisputable evidence. A few years back, the results had not been measured to this level of accuracy, and there was still "wriggle room." However, the experiment has now been repeated under sufficiently rigorous conditions, and with sufficiently accurate instrumentation, to remove the doubts. The use of high quantum efficiency CCD detectors and lasers to perform the experiment has improved the detection rates to a very high level (high QE CCDs were developed for astronomy, and an explosion in their power accompanied the "camera wars" going on in the consumer marketplace between Nikon, Canon, Minolta-Konica (unfortunately currently a bit behind the rest), and a few other minor players; this has lead to QE in excess of 98%), and the old objection that too many quanta were being rejected has been removed. I suggest you look into this newer work.
QUOTE (hexa+)
Coming back to Circular polarization, I am more convinced after your explanation that Quantum Mechanics does not provide us the prediction that allow us to correlate with observation.
That is unfortunate, because I have now explained it several times. I'm sorry, I don't know how to convert that explanation into bra-kets; you should speak with a professional for assistance in doing so. I'm sorry, in the face of the fact that the equations you give do not account for the two-sided nature of a circular polarizer, being in one direction a circular polarizer, but in the other merely a quarter-wave plate followed by a linear polarizer, and therefore producing only ordinary linearly polarized light, I don't believe that they are the correct equations to use to describe circular polarization.
Hi Schneibster,
Thanks again for your further explanation.
I have no disagreement with you and Feynman explanation that “there is no explanation of quantum mechanics that is consistent with the classical physics we observe all around us, and in fact for that classical mechanics to behave as it does, the underlying quantum mechanics MUST behave in these very different ways”.
The Copenhagen Interpretation or the other interpretations of Quantum Mechanics is worded not based on classical or Newtonian logic. Copenhagen Interpretation is a non classical explanation of the Double slits Experiment based on the Uncertainty Principle. Neither is the explanation of the linearly polarized light based on any classical theory including classical wave theory.
My question on Circular polarization is whether there is a distinct circularly polarized state of light similar to the linearly polarized light where we could use Quantum Mechanics to predict the outcome of its probability with the same elegance that we do for linearly polarized light.
I think we have reached the same conclusion that the equations written by some of these authors in stating the application of Quantum Mechanics to Circular polarized state of light may have been overstated.
However, I find your suggestion that we cannot even express the quantum world in any “Natural Language” even if these expressions are counter-intuitive a little bit disturbing. There are many words in our lexicon such as “ghost” or “voodoo action” that has a specific meaning. Whether they exist or are factually true is quite another thing. I will differ with you that the mathematics can be totally dissociated from where it derive its meaning-- in this case the Copenhagen Interpretation or whatever modification that has gone into it. We will not know what to make out of E=mc2 if there is no underlying Special Theory of Relativity to give meaning to it, notwithstanding the postulates used are again counterintuitive. I find it hard to accept Quantum Mechanics as the correct description of the Quantum World when it is not even supported by any interpretation irrespective of whether they are classical or not.
It is interesting that you have also brought Fluctuation Theorem into the discussion and how this Theorem shows the possibility to violate the Second Law of Thermodynamics.
At the heart of our discussion is Quantum Entanglement. You have stated that the Aspect Experiment has proven that quantum entanglement is true. You further state that “the results of this experiment are currently at the nine-sigma level of confidence. This is essentially indisputable evidence”.
On this assertion, I would like to refer you to this other view by Usenet Physics FAQ under the caption heading
“Does Bell's Inequality Principle rule out local theories of quantum mechanics?”
[Quote]:
At the time Bell's result first became known, the experimental record was reviewed to see if any known results provided evidence against locality. None did. Thus an effort began to develop tests of Bell's Inequality. A series of experiments was conducted by Aspect ending with one in which polarizer angles were changed while the photons were `in flight'. This was widely regarded at the time as being a reasonably conclusive experiment confirming the predictions of QM.
Three years later Franson published a paper showing that the timing constraints in this experiment were not adequate to confirm that locality was violated. Aspect measured the time delays between detections of photon pairs. The critical time delay is that between when a polarizer angle is changed and when this affects the statistics of detecting photon pairs. Aspect estimated this time based on the speed of a photon and the distance between the polarizers and the detectors. Quantum mechanics does not allow making assumptions about where a particle is between detections. We cannot know when a particle traverses a polarizer unless we detect the particle at the polarizer.
Experimental tests of Bell's Inequality are ongoing but none has yet fully addressed the issue raised by Franson. In addition there is an issue of detector efficiency. By postulating new laws of physics one can get the expected correlations without any nonlocal effects unless the detectors are close to 90% efficient. The importance of these issues is a matter of judgment.
The subject is alive theoretically as well. Eberhard and later Fine uncovered further subtleties in Bell's argument. Some physicists argue that there are assumptions in derivations of Bell's Inequality and that it may be possible to construct a local theory that does not respect those assumptions. The subject is not yet closed, and may yet provide more interesting insights into the subtleties of quantum mechanics.
[End Quote].
I must thank you again for providing so much insight on a simple topic of circular polarization of light.
Cheers.
Thanks again for your further explanation.
I have no disagreement with you and Feynman explanation that “there is no explanation of quantum mechanics that is consistent with the classical physics we observe all around us, and in fact for that classical mechanics to behave as it does, the underlying quantum mechanics MUST behave in these very different ways”.
The Copenhagen Interpretation or the other interpretations of Quantum Mechanics is worded not based on classical or Newtonian logic. Copenhagen Interpretation is a non classical explanation of the Double slits Experiment based on the Uncertainty Principle. Neither is the explanation of the linearly polarized light based on any classical theory including classical wave theory.
My question on Circular polarization is whether there is a distinct circularly polarized state of light similar to the linearly polarized light where we could use Quantum Mechanics to predict the outcome of its probability with the same elegance that we do for linearly polarized light.
I think we have reached the same conclusion that the equations written by some of these authors in stating the application of Quantum Mechanics to Circular polarized state of light may have been overstated.
However, I find your suggestion that we cannot even express the quantum world in any “Natural Language” even if these expressions are counter-intuitive a little bit disturbing. There are many words in our lexicon such as “ghost” or “voodoo action” that has a specific meaning. Whether they exist or are factually true is quite another thing. I will differ with you that the mathematics can be totally dissociated from where it derive its meaning-- in this case the Copenhagen Interpretation or whatever modification that has gone into it. We will not know what to make out of E=mc2 if there is no underlying Special Theory of Relativity to give meaning to it, notwithstanding the postulates used are again counterintuitive. I find it hard to accept Quantum Mechanics as the correct description of the Quantum World when it is not even supported by any interpretation irrespective of whether they are classical or not.
It is interesting that you have also brought Fluctuation Theorem into the discussion and how this Theorem shows the possibility to violate the Second Law of Thermodynamics.
At the heart of our discussion is Quantum Entanglement. You have stated that the Aspect Experiment has proven that quantum entanglement is true. You further state that “the results of this experiment are currently at the nine-sigma level of confidence. This is essentially indisputable evidence”.
On this assertion, I would like to refer you to this other view by Usenet Physics FAQ under the caption heading
“Does Bell's Inequality Principle rule out local theories of quantum mechanics?”
[Quote]:
At the time Bell's result first became known, the experimental record was reviewed to see if any known results provided evidence against locality. None did. Thus an effort began to develop tests of Bell's Inequality. A series of experiments was conducted by Aspect ending with one in which polarizer angles were changed while the photons were `in flight'. This was widely regarded at the time as being a reasonably conclusive experiment confirming the predictions of QM.
Three years later Franson published a paper showing that the timing constraints in this experiment were not adequate to confirm that locality was violated. Aspect measured the time delays between detections of photon pairs. The critical time delay is that between when a polarizer angle is changed and when this affects the statistics of detecting photon pairs. Aspect estimated this time based on the speed of a photon and the distance between the polarizers and the detectors. Quantum mechanics does not allow making assumptions about where a particle is between detections. We cannot know when a particle traverses a polarizer unless we detect the particle at the polarizer.
Experimental tests of Bell's Inequality are ongoing but none has yet fully addressed the issue raised by Franson. In addition there is an issue of detector efficiency. By postulating new laws of physics one can get the expected correlations without any nonlocal effects unless the detectors are close to 90% efficient. The importance of these issues is a matter of judgment.
The subject is alive theoretically as well. Eberhard and later Fine uncovered further subtleties in Bell's argument. Some physicists argue that there are assumptions in derivations of Bell's Inequality and that it may be possible to construct a local theory that does not respect those assumptions. The subject is not yet closed, and may yet provide more interesting insights into the subtleties of quantum mechanics.
[End Quote].
I must thank you again for providing so much insight on a simple topic of circular polarization of light.
Cheers.
QUOTE (hexa+)
The Copenhagen Interpretation or the other interpretations of Quantum Mechanics is worded not based on classical or Newtonian logic. Copenhagen Interpretation is a non classical explanation of the Double slits Experiment based on the Uncertainty Principle. Neither is the explanation of the linearly polarized light based on any classical theory including classical wave theory.
Actually, polarization is described as the interaction of the photons' spins with the electron shells of the atoms in the crystal lattice that is the polarizing medium. These interactions bend the photons' paths in different directions depending on whether the spin of the photon is UP or DOWN with respect to the orientation of the lattice. Note that this is not a case of the photon "flying by" an atom- the photon is absorbed by the electron, and another emitted, but because angular momentum is conserved, this emitted photon must have the same spin as the absorbed one; and depending on the spin, it is emitted in one of two different directions. In a linear polarizer, either two beams of orthogonal polarization (and opposite spin state) are emitted in different directions, or one beam is emitted and one absorbed, depending on the type of polarizer.
The details of uncertainty and so forth are not required to understand polarization itself, but to understand the details of the absorption and emission of the photons, and the interaction of their spin with the electron shells, and the orientation of the electron shells due to the interactions of the atoms among themselves, which is what forms the lattice and orients all the atoms in it. Once these details are understood, it will be clear with a little thought that the cosine squared relationship between spin measured at different angles accounts for the remainder of the behavior, including its orthogonally based behavior (i.e., measuring the spin of a photon at a right angle to the original direction of measurement always yields the opposite spin). If the two polarizers' optical axes are at a right angle, then the ordinary ray for the first will become the extraordinary ray for the second, and vice versa; if they are aligned or opposing (i.e. at a 180 degree angle), then the ordinary ray will remain ordinary and the extraordinary ray remain extraordinary. Since standard linear polarizing plastic film suppresses the extraordinary ray, the consequence is that orthogonally oriented films will suppress all light, and parallel oriented films will pass half at the first and all of that half at the second.
Now, it's important to understand that this explanation does not depend upon the interpretation of quantum mechanics, since it suppresses the details of the interaction which would require that interpretation to describe them, i.e. the interactions of the atoms and the interactions of the photons with the atoms.
It is also important to understand that this description does not use classical wave theory, since the photons are described as particles, not waves.
I do not know the wave-based description of polarization; I'm not sure there is one. If there is, it is extremely complex, and involves the assignment of "spin" to a field, an attribute which has no clear intuitive physical description in that context but is merely a numeric attribute.
The details of uncertainty and so forth are not required to understand polarization itself, but to understand the details of the absorption and emission of the photons, and the interaction of their spin with the electron shells, and the orientation of the electron shells due to the interactions of the atoms among themselves, which is what forms the lattice and orients all the atoms in it. Once these details are understood, it will be clear with a little thought that the cosine squared relationship between spin measured at different angles accounts for the remainder of the behavior, including its orthogonally based behavior (i.e., measuring the spin of a photon at a right angle to the original direction of measurement always yields the opposite spin). If the two polarizers' optical axes are at a right angle, then the ordinary ray for the first will become the extraordinary ray for the second, and vice versa; if they are aligned or opposing (i.e. at a 180 degree angle), then the ordinary ray will remain ordinary and the extraordinary ray remain extraordinary. Since standard linear polarizing plastic film suppresses the extraordinary ray, the consequence is that orthogonally oriented films will suppress all light, and parallel oriented films will pass half at the first and all of that half at the second.
Now, it's important to understand that this explanation does not depend upon the interpretation of quantum mechanics, since it suppresses the details of the interaction which would require that interpretation to describe them, i.e. the interactions of the atoms and the interactions of the photons with the atoms.
It is also important to understand that this description does not use classical wave theory, since the photons are described as particles, not waves.
I do not know the wave-based description of polarization; I'm not sure there is one. If there is, it is extremely complex, and involves the assignment of "spin" to a field, an attribute which has no clear intuitive physical description in that context but is merely a numeric attribute.
QUOTE (hexa+)
My question on Circular polarization is whether there is a distinct circularly polarized state of light similar to the linearly polarized light where we could use Quantum Mechanics to predict the outcome of its probability with the same elegance that we do for linearly polarized light.
The problem is not with the polarization state, but with the apparatus that creates it. If there were, and such an apparatus worked as a circular polarizer of the same handedness in both directions, then we might see similar elegance; I suspect, however, that it is more likely that even if a single-step circular polarizer exists, it is of opposite handedness in opposite directions, and I even more strongly suspect that there is no such apparatus, i.e. a circular polarizer that is a circular polarizer in both directions.
QUOTE (hexa+)
I think we have reached the same conclusion that the equations written by some of these authors in stating the application of Quantum Mechanics to Circular polarized state of light may have been overstated.
I would prefer to say "unqualified in important particulars." In fact, if left-hand circularly polarized light is sent into the back of a right-handed circular polarizer (unless I've gotten confused) it will not pass; similarly, if such light is sent into the back of a left-hand circular polarizer, it will all emerge. So the claim is not wrong, per se, it is merely unqualified by the necessary statement that the exclusion or transmission happens only if the light attempts to pass the other polarizer in the opposite direction.
QUOTE (hexa+)
However, I find your suggestion that we cannot even express the quantum world in any “Natural Language” even if these expressions are counter-intuitive a little bit disturbing. There are many words in our lexicon such as “ghost” or “voodoo action” that has a specific meaning. Whether they exist or are factually true is quite another thing. I will differ with you that the mathematics can be totally dissociated from where it derive its meaning-- in this case the Copenhagen Interpretation or whatever modification that has gone into it.
The above description is where the problem enters; above, I spoke of "photons" as if they are a realistic object with attributes of which we can gain actual physical understanding, and the idea of applying a "spin" to a wave as something that we cannot come to an understanding of; however, since we are used to thinking of "objects" as having definite position and momentum, not to mention having coordinated spin at different measuring angles, it is obvious that a photon cannot be an "object" as we ordinarily conceive of one.
This was the core of my meaning; and the only description we have that is consistent with observed reality is in fact one that assigns such counter-intuitive combinations of attributes to photons. The mere assumption that there is a "thing" that we can positively identify as a "photon" calls far to many assumptions into question for us to be entirely comfortable with it; I am by no means convinced that any such "thing" exists other than as a convenient "handle" for us to assign attributes to in our minds. Certainly the math does not directly describe any such "thing," unless we give it attributes that are inconsistent with the very idea of a "thing" as we ordinarily conceive it.
Note most carefully that we have not even approached one of the interpretations yet, and we nevertheless are engaged in conversation about the quantum world that we already KNOW is contra-factual. The problem is not the interpretations; it is the very character of the quantum world at its most basic level.
Thus, it is extremely important that you understand that the ONLY truth we know about the quantum world is the mathematics, and it is likely that it is the only truth we will EVER know. The interpretations are only interpretations, and every single one of them requires that we assign attributes to a "thing" that contravene its very "thingness." Even the very act of conceiving of the denizens of the quantum world as "things" prior to even using one of the interpretations is contrary to our deepest understanding of its actual attributes, so when we deal with these explanations, we should never take them too seriously.
OTOH, I do believe that it is possible with care to use natural language to describe events in the quantum world; it is, however, an extremely shaky basis for serious understanding, because we cannot rely on the type of logic we are used to using with the types of events natural language was developed to describe. Extreme caution is required, and relatively deep understanding as well. I am in fact attempting (although the attempt is currently at a hiatus) to develop an understanding of quantum phenomena of this sort (this sort of understanding, that is, not this sort of quantum or this sort of phenomena); whether I will ultimately be successful or not remains to be seen.
This was the core of my meaning; and the only description we have that is consistent with observed reality is in fact one that assigns such counter-intuitive combinations of attributes to photons. The mere assumption that there is a "thing" that we can positively identify as a "photon" calls far to many assumptions into question for us to be entirely comfortable with it; I am by no means convinced that any such "thing" exists other than as a convenient "handle" for us to assign attributes to in our minds. Certainly the math does not directly describe any such "thing," unless we give it attributes that are inconsistent with the very idea of a "thing" as we ordinarily conceive it.
Note most carefully that we have not even approached one of the interpretations yet, and we nevertheless are engaged in conversation about the quantum world that we already KNOW is contra-factual. The problem is not the interpretations; it is the very character of the quantum world at its most basic level.
Thus, it is extremely important that you understand that the ONLY truth we know about the quantum world is the mathematics, and it is likely that it is the only truth we will EVER know. The interpretations are only interpretations, and every single one of them requires that we assign attributes to a "thing" that contravene its very "thingness." Even the very act of conceiving of the denizens of the quantum world as "things" prior to even using one of the interpretations is contrary to our deepest understanding of its actual attributes, so when we deal with these explanations, we should never take them too seriously.
OTOH, I do believe that it is possible with care to use natural language to describe events in the quantum world; it is, however, an extremely shaky basis for serious understanding, because we cannot rely on the type of logic we are used to using with the types of events natural language was developed to describe. Extreme caution is required, and relatively deep understanding as well. I am in fact attempting (although the attempt is currently at a hiatus) to develop an understanding of quantum phenomena of this sort (this sort of understanding, that is, not this sort of quantum or this sort of phenomena); whether I will ultimately be successful or not remains to be seen.
QUOTE (hexa+)
At the heart of our discussion is Quantum Entanglement.
The details you have provided do indeed strike to the heart of the question, but what is certain is that either locality is violated, or causality is. One of the two must necessarily be, for Bell's Inequality to be so closely followed (nine sigma is impressive, to say the least). I should point out that the quantum efficiency of the detectors has now been improved to well over 90% (there are CCDs with QE over 98% available on the open market, relatively inexpensive as such things go; I myself own a CCD astrocamera that boasts QE better than 95%, and it is old enough that it has already been superceded twice by newer models!), and that this has obviated the quantum efficiency argument.
All that remains is Franson's argument, and although you have understood the part that deals with locality, you have not discussed the implications of that argument for causality; it is in fact a counter-causal argument, because in order for it to succeed and preserve locality, the photons must exceed the speed of light in a vacuum. It is in fact my position that quantum causality is very different from classical causality, and that therefore the assumptions of causality that we ordinarily assert are not followed by quantum phenomena; but that is an entirely different conversation. One which I would, in fact, be happy to have with you- but I think another thread would be appropriate. It is because of this belief of mine, in fact, that I am exploring the possibility of devising a "quantum logic" that can be used in conjunction with natural language to describe quantum phenomena; causality and locality considerations are obviously part of such a description if it is to be successful.
All that remains is Franson's argument, and although you have understood the part that deals with locality, you have not discussed the implications of that argument for causality; it is in fact a counter-causal argument, because in order for it to succeed and preserve locality, the photons must exceed the speed of light in a vacuum. It is in fact my position that quantum causality is very different from classical causality, and that therefore the assumptions of causality that we ordinarily assert are not followed by quantum phenomena; but that is an entirely different conversation. One which I would, in fact, be happy to have with you- but I think another thread would be appropriate. It is because of this belief of mine, in fact, that I am exploring the possibility of devising a "quantum logic" that can be used in conjunction with natural language to describe quantum phenomena; causality and locality considerations are obviously part of such a description if it is to be successful.
QUOTE (hexa+)
I must thank you again for providing so much insight on a simple topic of circular polarization of light.
I think that it is a very deep topic, and I'll point out that we have both learned something here (I hope you did, anyway). The research and reasoning I have used here have substantially improved my understanding of polarization phenomena, so thanks for the opportunity! 
Hi Schneibster,
I must thank you for all your posting even though we may not fully agree with one another.
I would like to share Einstein’s letter to Schrodinger of 7 June 1935, after Schrodinger has congratulated him on the publication of the EPR experiment.
[Quote]:
All physics is a description of reality; but this description can be ‘complete’ or ‘incomplete’.
To begin with, the sense of this expression is even a problem itself. I will explain with the following analogy.
In front of me stand two boxes, with lids that can be opened, and into which I can look when they are open. This looking is called ‘making an observaion’. In addition, there is a ball, which can be found in one or the other of the two boxes when an observation is made.
Now I describe the situation thus: the probability that the ball is in the first box is ˝ . Is this a complete description?
(1) NO. A complete description is: the ball is in the first box (or not). This is the way to express the characterization of the state by a complete description.
(2) YES. Before I open the box the ball is not in one of the two boxes. This existence in a definite box first occurs when I open one of the boxes. In this way arises the statistical character of the world of experience or its empirical system of laws (Gesetzlichkeit). The state before the box is opened is completely described by the number ˝.
The Talmudic philosopher doesn’t give a straw for ‘reality’, a bogy of naivete, and explains both statements as only different ways of expression.
I bring in the separation principle. The second box is independent of anything that happens to the first box. If one holds fast to the separation principle, only the Born description is possible, but now it is incomplete.[End Quote]
In addition I would also like to share Newton's distaste for non-local interaction.
[Quote]:
“That one body may act upon another at a distance through a vacuum without the mediation of anything else…. Is to me so great an absurdity, that I believe no man, who has in philosophical matters a competent faculty for thinking, can ever fall into”.
Newton was somewhat embarrassed by his own theory of gravity when he was asked, “how does the sun’s gravity managed to cross millions of miles of empty space to hold the Earth in its orbit?”
All he offered was, “Hypotheses non fingo (I frame no hypothesis)”.
[Unquote]
Fortunately, Newton’s faith in local force was vindicated by his successors, who explain gravity in terms of the field concept govern by the speed of light,c, and not something that happen instantaneously.
The fact that we are unable to state it rationally for many quantum phenomena (including the Double slits experiment, polarization of light, etc), does not mean that we should deny these fundamental axioms of science. To deny both local reality and causality is tantamount to throwing away the baby together with the bath water. This is surely not Science that is understood by two of the greatest scientists that mankind has ever produced.
I hope you can agree with me on this.
Cheers.
I must thank you for all your posting even though we may not fully agree with one another.
I would like to share Einstein’s letter to Schrodinger of 7 June 1935, after Schrodinger has congratulated him on the publication of the EPR experiment.
[Quote]:
All physics is a description of reality; but this description can be ‘complete’ or ‘incomplete’.
To begin with, the sense of this expression is even a problem itself. I will explain with the following analogy.
In front of me stand two boxes, with lids that can be opened, and into which I can look when they are open. This looking is called ‘making an observaion’. In addition, there is a ball, which can be found in one or the other of the two boxes when an observation is made.
Now I describe the situation thus: the probability that the ball is in the first box is ˝ . Is this a complete description?
(1) NO. A complete description is: the ball is in the first box (or not). This is the way to express the characterization of the state by a complete description.
(2) YES. Before I open the box the ball is not in one of the two boxes. This existence in a definite box first occurs when I open one of the boxes. In this way arises the statistical character of the world of experience or its empirical system of laws (Gesetzlichkeit). The state before the box is opened is completely described by the number ˝.
The Talmudic philosopher doesn’t give a straw for ‘reality’, a bogy of naivete, and explains both statements as only different ways of expression.
I bring in the separation principle. The second box is independent of anything that happens to the first box. If one holds fast to the separation principle, only the Born description is possible, but now it is incomplete.[End Quote]
In addition I would also like to share Newton's distaste for non-local interaction.
[Quote]:
“That one body may act upon another at a distance through a vacuum without the mediation of anything else…. Is to me so great an absurdity, that I believe no man, who has in philosophical matters a competent faculty for thinking, can ever fall into”.
Newton was somewhat embarrassed by his own theory of gravity when he was asked, “how does the sun’s gravity managed to cross millions of miles of empty space to hold the Earth in its orbit?”
All he offered was, “Hypotheses non fingo (I frame no hypothesis)”.
[Unquote]
Fortunately, Newton’s faith in local force was vindicated by his successors, who explain gravity in terms of the field concept govern by the speed of light,c, and not something that happen instantaneously.
The fact that we are unable to state it rationally for many quantum phenomena (including the Double slits experiment, polarization of light, etc), does not mean that we should deny these fundamental axioms of science. To deny both local reality and causality is tantamount to throwing away the baby together with the bath water. This is surely not Science that is understood by two of the greatest scientists that mankind has ever produced.
I hope you can agree with me on this.
Cheers.
I agree that ONE of causality or locality must be true; however, I also believe that there is sufficient proof to conclude that the OTHER is false. I believe the false one to be locality, and I believe that Aspect and other EPR/Bell based experiments show this with the certainty that it is possible to achieve in any physics experiment.
Hi Schneibster,
I would beg to differ that locality is false based on Aspect Experiment that confirm Bell’s inequality is violated. In fact there is no need to resort to Aspect experiment to show that Locality based on Bell’s argument is violated. A simple experiment using two linear polarizers clearly demonstrate that the argument based on Local Reality as we understand it now does not hold.
If we insist that non-locality represent quantum reality, then Einstein Theory of Special Relativity must me wrong. This is because SR imposes a limit uponwhich anything (particles, photons, field, etc) can move to exert an influence on another object.
When Newton was confronted with the choice to accept non-locality in order for his Gravitational Theory to make any sense, he resisted it. In fact he made a disparaging statement against anyone who even conceive such possibility (see previous post).
In this respect, I am more incline to accept Einstein proposition that our current understanding of Quantum Physics is “incomplete” rather than to accept non-locality as an integral description of the quantum world. To do so, we are in fact RELEGATING Science to accept “Voodoo action” as a possibility. This is how Nick Herbert in his book, “Quantum Reality” put it if we were to accept non-locality as a correct description of the quantum world.
Cheers.
I would beg to differ that locality is false based on Aspect Experiment that confirm Bell’s inequality is violated. In fact there is no need to resort to Aspect experiment to show that Locality based on Bell’s argument is violated. A simple experiment using two linear polarizers clearly demonstrate that the argument based on Local Reality as we understand it now does not hold.
If we insist that non-locality represent quantum reality, then Einstein Theory of Special Relativity must me wrong. This is because SR imposes a limit uponwhich anything (particles, photons, field, etc) can move to exert an influence on another object.
When Newton was confronted with the choice to accept non-locality in order for his Gravitational Theory to make any sense, he resisted it. In fact he made a disparaging statement against anyone who even conceive such possibility (see previous post).
In this respect, I am more incline to accept Einstein proposition that our current understanding of Quantum Physics is “incomplete” rather than to accept non-locality as an integral description of the quantum world. To do so, we are in fact RELEGATING Science to accept “Voodoo action” as a possibility. This is how Nick Herbert in his book, “Quantum Reality” put it if we were to accept non-locality as a correct description of the quantum world.
Cheers.
Ummmm, hexa, I think you've misunderstood what "locality" means in this context. "Locality" means only and specifically that variables that are complementary to some measured value under uncertainty HAVE SOME VALUE even though their complement has been measured to arbitrary precision, but that that value is HIDDEN and can never be measured. This is why "locality" is also known as the "assumption of hidden variables." The assumption of non-locality, on the other hand, is the assumption that such variables complementary to a measured variable DO NOT HAVE A VALUE.
Under this definition of locality, locality is violated by Aspect.
Under this definition of locality, locality is violated by Aspect.
QUOTE (hexa+)
If we insist that non-locality represent quantum reality, then Einstein Theory of Special Relativity must me wrong.
Hmmm, I don't think so. This is why I said I thought you'd misunderstood locality. If by "locality" you mean the concept that causality can only happen by direct interaction between two quanta, then you are correct; however, the above definition of locality is not the correct one. Unfortunately it seems that there are two different definitions of "locality." I wish I had a better terminology for one of them to make a distinction.
Perhaps that will help you understand what I'm asserting.
BTW, it's worth mentioning that this second type of locality is, IMO, a component of causality.
Perhaps that will help you understand what I'm asserting.
BTW, it's worth mentioning that this second type of locality is, IMO, a component of causality.
Hi Schneibster,
Thanks for pointing out the error. When I compared the linear polarizers with the Aspect experiment, I was trying to illustrate the spookiness suggested by Quantum Mechanics if we were to accept non-locality. I now realized that linear polarizer is not the right experiment to illustrate this point. The better experiment to demonstrate non-locality is still the Double-slits experiment. Similarly, I also maintain that the Aspect experiment and the other modified experiments did not refute the EPR criticism and the result cannot be used to support non-locality.
The linear polarizers essentially show that local hidden variables cannot account for the observation of the intensity of light passing through the linear polarizers. In short, there appears to be no local reality that we could use to account for light passing through the linear polarizers.
Notwithstanding the difference between Locality and Local Reality that you have pointed out to me, I still maintain that non-locality cannot form part of Science. Just as our forefathers worship the sun, the moon, the weather and anything that has an influence on their life and attribute it to some super natural spirit, I feel that non-locality will be looked upon in the same light after we could rationally account for these experiments (Double slits experiment, polarization of light, etc).
As of now, I am more incline to agree wth Einstein that our understanding of the Quantum World is incomplete.
Cheers.
Thanks for pointing out the error. When I compared the linear polarizers with the Aspect experiment, I was trying to illustrate the spookiness suggested by Quantum Mechanics if we were to accept non-locality. I now realized that linear polarizer is not the right experiment to illustrate this point. The better experiment to demonstrate non-locality is still the Double-slits experiment. Similarly, I also maintain that the Aspect experiment and the other modified experiments did not refute the EPR criticism and the result cannot be used to support non-locality.
The linear polarizers essentially show that local hidden variables cannot account for the observation of the intensity of light passing through the linear polarizers. In short, there appears to be no local reality that we could use to account for light passing through the linear polarizers.
Notwithstanding the difference between Locality and Local Reality that you have pointed out to me, I still maintain that non-locality cannot form part of Science. Just as our forefathers worship the sun, the moon, the weather and anything that has an influence on their life and attribute it to some super natural spirit, I feel that non-locality will be looked upon in the same light after we could rationally account for these experiments (Double slits experiment, polarization of light, etc).
As of now, I am more incline to agree wth Einstein that our understanding of the Quantum World is incomplete.
Cheers.
QUOTE
non-locality cannot form part of Science
I agree if by that you mean that you don't think that the spin is being sent somehow across the intervening space between the two photons. However, it is clear that something very odd is taking place; IMO, it's a causality violation, but I'm not prepared to espouse an interpretation based on it.
Hi Schneibster,
Thanks for your vote in favour of sanity for Science. I certainly agree with you that the spin cannot somehow be sent (instantly) across the intervening space between the two photons. I also agree with you that something odd is taking place. But this I believe is due to our ignorance rather than the capriciousness of Nature.
Much as I would like to believe that spin must be conserved before non-locality become an issue in the EPR experiment, it has been established that spin is not conserved. C.N.Yang and T.S.Lee had proposed the violation of Parity. This proposition was confirmed in an experiment by C.S. Wu that track the spin of electrons in beta decay of Cobalt-60. Notwithstanding the advances, I think Science does not understand enough on what constitute spin other than that the spin of a particle will interact with a magnetic field. A spin up particle will be deflected differently from a spin down particle in the presence of a strong magnetic field.
If spin is not conserved where then is the issue of non-locality in the EPR experiment? In this respect, I think Einstein’s interpretation--that the two particles that have an entangled birth are independent of one another is the only logical proposition. QM superposition principle is irrelevant in this context.
On the aforesaid reasons, I feel that the current craze on Quantum Computing--built on Quantum Entanglement (on the basis that information can be conveyed instantly based on non-locality) may have their faith totally misplaced.
Cheers.
Thanks for your vote in favour of sanity for Science. I certainly agree with you that the spin cannot somehow be sent (instantly) across the intervening space between the two photons. I also agree with you that something odd is taking place. But this I believe is due to our ignorance rather than the capriciousness of Nature.
Much as I would like to believe that spin must be conserved before non-locality become an issue in the EPR experiment, it has been established that spin is not conserved. C.N.Yang and T.S.Lee had proposed the violation of Parity. This proposition was confirmed in an experiment by C.S. Wu that track the spin of electrons in beta decay of Cobalt-60. Notwithstanding the advances, I think Science does not understand enough on what constitute spin other than that the spin of a particle will interact with a magnetic field. A spin up particle will be deflected differently from a spin down particle in the presence of a strong magnetic field.
If spin is not conserved where then is the issue of non-locality in the EPR experiment? In this respect, I think Einstein’s interpretation--that the two particles that have an entangled birth are independent of one another is the only logical proposition. QM superposition principle is irrelevant in this context.
On the aforesaid reasons, I feel that the current craze on Quantum Computing--built on Quantum Entanglement (on the basis that information can be conveyed instantly based on non-locality) may have their faith totally misplaced.
Cheers.
QUOTE (hexqa+)
Much as I would like to believe that spin must be conserved before non-locality become an issue in the EPR experiment, it has been established that spin is not conserved. C.N.Yang and T.S.Lee had proposed the violation of Parity. This proposition was confirmed in an experiment by C.S. Wu that track the spin of electrons in beta decay of Cobalt-60.
This non-conservation has only been shown for the weak interaction, and there is no weak interaction in either Aspect or the DCQE.
QUOTE (hexa+)
On the aforesaid reasons, I feel that the current craze on Quantum Computing--built on Quantum Entanglement (on the basis that information can be conveyed instantly based on non-locality) may have their faith totally misplaced.
The problem with this is, they appear to be working.
Hi Schneibster,
I fully agree with you that “there is no weak interaction in either Aspect or the DCQE”.
I am not sure about the set up of DCQE. As for the Aspect Experiment, nothing in the experiment could be interpreted as a measure of spin since a photon is not affected by a magnetic field( although quantum theory has described photon as having an integral spin). In fact, all that Aspect Experiment has proven is that Local Reality or CAUSALITY cannot be used to account for the observation based on local hidden variable model. Nothing in this Experiment can be used to support NON-LOCALITY.
Maybe we should examine Aspect Experiment in greater details. I will refer you to this website (http://roxanne.roxanne.org/epr/experiment.html).
Let me highlight the presumptions used by Aspect to interprete the experiment:
1) Because the total angular momentum at the beginning and end of the cascade is zero, the two photons emitted must each have opposite angular momentum and thus the two photons must be circularly polarized in opposite directions.
2) The filters in figure 1 only allow the transmission of one of the two colors. Thus, these filters guarantee that emitted photon pairs travel to opposite detectors such that the green photons go along path A and the blue photons go along path B.
3) Since circularly polarized light can be seen as a composition of two linear polarization states, these filters will split apart the circularly polarized light into two linear states and send them in different directions.
4) If the photon is detected as having been transmitted through the filter, it is assumed that it's polarization was parrallel to the filter and a +1 is registered at the coincidence counter. If, on the other hand, the single photon is detected at the PMT tube along the reflected path, a -1 is sent to the coincidence counter.
5) Before remarking on how the results are recorded at the coincidence counter, what do we expect to see? Recall that the two emitted photons are circularly polarized in opposite directions (i.e. one is rotating clockwise and the other is rotating counter-clockwise).
6) Notice that the detectors on the "A" side and "B" side of the experiment are facing each other. So, if A sees a photons polarization as spinning clockwise, then B will see the polarization of that same photon as spinning in the opposite direction!
7) Since we are creating photons with exactly opposite polarizations and since we are looking at these polarizations using oppositely facing filters, the two photons in this experiment should register the same polarization states and thus whichever linear component is measured on side A must also have the same value on side B.
What is being Measured?
In this experiment, the important quantity to measure is not merely the average result for one set of detector settings, but a very specific combination.1 As we discussed previously in the section which describes the experimental setup, the important quantity is S = | E(a;b) - E(a,d) | + | E(c;b) E(c,d) |.
My Inference of the Aspect Results
Look at the curve under The Aspect Results.
The curve is essentially, an explanation of Malus Law. What Aspect Experiment reestablished is CAUSALITY based on Local Hidden variables cannot be used to account for light passing through a linear polarizer. Nothing in this experiment suggest that NON-LOCALITY is involved.
Please advise where I may have erred in my interpretation of the Aspect Experiment.
Cheers.
I fully agree with you that “there is no weak interaction in either Aspect or the DCQE”.
I am not sure about the set up of DCQE. As for the Aspect Experiment, nothing in the experiment could be interpreted as a measure of spin since a photon is not affected by a magnetic field( although quantum theory has described photon as having an integral spin). In fact, all that Aspect Experiment has proven is that Local Reality or CAUSALITY cannot be used to account for the observation based on local hidden variable model. Nothing in this Experiment can be used to support NON-LOCALITY.
Maybe we should examine Aspect Experiment in greater details. I will refer you to this website (http://roxanne.roxanne.org/epr/experiment.html).
Let me highlight the presumptions used by Aspect to interprete the experiment:
1) Because the total angular momentum at the beginning and end of the cascade is zero, the two photons emitted must each have opposite angular momentum and thus the two photons must be circularly polarized in opposite directions.
2) The filters in figure 1 only allow the transmission of one of the two colors. Thus, these filters guarantee that emitted photon pairs travel to opposite detectors such that the green photons go along path A and the blue photons go along path B.
3) Since circularly polarized light can be seen as a composition of two linear polarization states, these filters will split apart the circularly polarized light into two linear states and send them in different directions.
4) If the photon is detected as having been transmitted through the filter, it is assumed that it's polarization was parrallel to the filter and a +1 is registered at the coincidence counter. If, on the other hand, the single photon is detected at the PMT tube along the reflected path, a -1 is sent to the coincidence counter.
5) Before remarking on how the results are recorded at the coincidence counter, what do we expect to see? Recall that the two emitted photons are circularly polarized in opposite directions (i.e. one is rotating clockwise and the other is rotating counter-clockwise).
6) Notice that the detectors on the "A" side and "B" side of the experiment are facing each other. So, if A sees a photons polarization as spinning clockwise, then B will see the polarization of that same photon as spinning in the opposite direction!
7) Since we are creating photons with exactly opposite polarizations and since we are looking at these polarizations using oppositely facing filters, the two photons in this experiment should register the same polarization states and thus whichever linear component is measured on side A must also have the same value on side B.
What is being Measured?
In this experiment, the important quantity to measure is not merely the average result for one set of detector settings, but a very specific combination.1 As we discussed previously in the section which describes the experimental setup, the important quantity is S = | E(a;b) - E(a,d) | + | E(c;b) E(c,d) |.
My Inference of the Aspect Results
Look at the curve under The Aspect Results.
The curve is essentially, an explanation of Malus Law. What Aspect Experiment reestablished is CAUSALITY based on Local Hidden variables cannot be used to account for light passing through a linear polarizer. Nothing in this experiment suggest that NON-LOCALITY is involved.
Please advise where I may have erred in my interpretation of the Aspect Experiment.
Cheers.
QUOTE (hexa+)
Nothing in this experiment suggest that NON-LOCALITY is involved.
I agree.
QUOTE (hexa+)
Please advise where I may have erred in my interpretation of the Aspect Experiment.
I do not believe you have.
I think that I have caused a misunderstanding by talking about this when I had not considered the matter in quite some time, having been involved in other pursuits. My use of "locality" was incorrect; I had confounded the concept with "local realism," which is definitely shown to be impossible by Aspect. I hope you'll forgive my mistake.
I think that I have caused a misunderstanding by talking about this when I had not considered the matter in quite some time, having been involved in other pursuits. My use of "locality" was incorrect; I had confounded the concept with "local realism," which is definitely shown to be impossible by Aspect. I hope you'll forgive my mistake.
Hi Schneibster,
Thanks you for agreeing that Nothing in the Aspect Experiment can be interpreted as affirming Non-Locality.
You were right to agree that Aspect Experiment reaffirmed that the local hidden variable model cannot be used to account for light passing through a linear polarizer but must use Malus Law similar to that predicted by Quantum Mechanics. In other words, it appears that Causality is violated and not Non-Locality is observed.
Unfortunately, what was claimed in Aspect Experiment is not Causality but Non-Locality. This perhap explains why you were mistaken initially.
In this website in Physorg (http://www.physorg.com/news8891.html) under the caption “Physicists Achieve Quantum Entanglement Between Remote Ensembles of Atoms”, it also claim Non-Locality and not Causality.
From our aforesaid discussion, I have an uneasy feeling that these researchers are claiming Non-Locality using experiments that only reaffirm that Local Hidden variable model cannot account for quantum phenomena. This is only a prima facie case that Causality is violated not that Causality is dead.
Look forward to your comment on the claim in the above article.
Cheers.
Thanks you for agreeing that Nothing in the Aspect Experiment can be interpreted as affirming Non-Locality.
You were right to agree that Aspect Experiment reaffirmed that the local hidden variable model cannot be used to account for light passing through a linear polarizer but must use Malus Law similar to that predicted by Quantum Mechanics. In other words, it appears that Causality is violated and not Non-Locality is observed.
Unfortunately, what was claimed in Aspect Experiment is not Causality but Non-Locality. This perhap explains why you were mistaken initially.
In this website in Physorg (http://www.physorg.com/news8891.html) under the caption “Physicists Achieve Quantum Entanglement Between Remote Ensembles of Atoms”, it also claim Non-Locality and not Causality.
From our aforesaid discussion, I have an uneasy feeling that these researchers are claiming Non-Locality using experiments that only reaffirm that Local Hidden variable model cannot account for quantum phenomena. This is only a prima facie case that Causality is violated not that Causality is dead.
Look forward to your comment on the claim in the above article.
Cheers.
Hi Schneibster,
You must have been very busy.
I do look forward to your comment on this Article found in Physorg website(http://www.physorg.com/news8891.html) under the caption “Physicists Achieve Quantum Entanglement Between Remote Ensembles of Atoms” claiming that they are using Quantum Entanglement based on Non-Locality.
I would appreciate your comment.
I would also welcome comments by other experts on this topic that strike at the heart of Quantum Mechanics.
Cheers.
You must have been very busy.
I do look forward to your comment on this Article found in Physorg website(http://www.physorg.com/news8891.html) under the caption “Physicists Achieve Quantum Entanglement Between Remote Ensembles of Atoms” claiming that they are using Quantum Entanglement based on Non-Locality.
I would appreciate your comment.
I would also welcome comments by other experts on this topic that strike at the heart of Quantum Mechanics.
Cheers.
I have been inordinately busy, and have not had time to respond until now.
First, I have to point out that spin as you are using it here and as this experiment uses it is angular momentum, and the conservation of angular momentum is a cornerstone of physics. By Noether's theorem it is related to the symmetry of experimental results over rotational orientation. This symmetry is violated by the weak interaction under certain circumstances, and the action of the EM, strong, and gravity forces can introduce a local gauge field that causes this symmetry to be broken; the breaking of this symmetry among others is in fact responsible for the actions of the non-weak forces. However, in the absence of any net force, this symmetry is manifest, and thus causality is preserved.
Entanglement happens; it is responsible for many interesting conundrums in quantum physics. Spin states are not the only states which can be entangled; any interaction that creates a distributed dependence upon a conserved quantity can result in entanglement. What entanglement means is that the value of a variable at one point in space is dependent upon the value of that variable at a point at spacelike separation from the first point. Spin is used because for quanta, spin is a discrete variable; but this does not imply that all entanglements are based on discrete variables.
The point of Aspect (and the DCQE) is not that causality is violated, and is not that locality is violated; it is that EITHER locality OR causality must be violated for us to see the results we see from these experiments. We cannot determine WHICH. It is possible to interpret the experiment whose results you posted as EITHER, and either of these interpretations makes the entanglement a useful means of implementing quantum computing; I think your bias against quantum computing ignores that EITHER of these effects makes it possible. I suggest you consider this carefully.
First, I have to point out that spin as you are using it here and as this experiment uses it is angular momentum, and the conservation of angular momentum is a cornerstone of physics. By Noether's theorem it is related to the symmetry of experimental results over rotational orientation. This symmetry is violated by the weak interaction under certain circumstances, and the action of the EM, strong, and gravity forces can introduce a local gauge field that causes this symmetry to be broken; the breaking of this symmetry among others is in fact responsible for the actions of the non-weak forces. However, in the absence of any net force, this symmetry is manifest, and thus causality is preserved.
Entanglement happens; it is responsible for many interesting conundrums in quantum physics. Spin states are not the only states which can be entangled; any interaction that creates a distributed dependence upon a conserved quantity can result in entanglement. What entanglement means is that the value of a variable at one point in space is dependent upon the value of that variable at a point at spacelike separation from the first point. Spin is used because for quanta, spin is a discrete variable; but this does not imply that all entanglements are based on discrete variables.
The point of Aspect (and the DCQE) is not that causality is violated, and is not that locality is violated; it is that EITHER locality OR causality must be violated for us to see the results we see from these experiments. We cannot determine WHICH. It is possible to interpret the experiment whose results you posted as EITHER, and either of these interpretations makes the entanglement a useful means of implementing quantum computing; I think your bias against quantum computing ignores that EITHER of these effects makes it possible. I suggest you consider this carefully.
Hi Schneibster,
Entanglement happens; it is responsible for many interesting conundrums in quantum physics. Spin states are not the only states which can be entangled; any interaction that creates a distributed dependence upon a conserved quantity can result in entanglement. What entanglement means is that the value of a variable at one point in space is dependent upon the value of that variable at a point at spacelike separation from the first point. Spin is used because for quanta, spin is a discrete variable; but this does not imply that all entanglements are based on discrete variables.
I agree with you that two or more particles may be entangled at birth, like pair production of a positron and an electron.
Two or more photons can also be emitted from the same atom.
Similarly, two electrons with opposite spin can also be emitted in weak interaction from the same nucleus of the atom.
Based on the strict definition of entanglement, two entangle particles must share the same parent or origin.
In the case of pair production of positron and electron it must originate from the same gamma particle (photon).
For two photons to be entangled to one another, it must come from the same atom and no other atom.
And finally for two electrons with opposite spin to be emitted in weak interaction, it must come from the same nucleus.
The meaning of a twin or triplets must come from the womb of the same mother otherwise they cannot be called twins or triplets and as such are not entangled in any way.
Immediately after they are borne from this entangled birth, I fail to see that whatever happen next to one particle will have immediate impact on the other. Two entangled particles may have been given an opposite spin at birth. Once separated, whatever happen to one particle will have no influence on what will happen to its twin.
Unfortunately, Quantum Mechanics need us to believe that entanglement continue even after they are separated half a Universe from one another. And that what happen to one particle in one corner of the Universe will have an immediate impact on the other twin. This is absolutely necessary, otherwise Quantum Mechanics based on Copenhagen Interpretation will fall flat on its face. To me this can only happens in Science fiction, not Science.
If we look at the setup of the Aspect Experiment, nothing in the entire set up ensure that this first condition is met.
What then follows is the passage through two linear polarizers to measure the intensity of coincidence of photons traveling in two distinct paths. This is similar to the measurement of intensity of light passing through two linear polarizers that will yield the result based on Malus Law. The result of Malus Law is non linear just as many phenomena in nature does not yield a linear result based on a straight forward rotation of the polarizing axis of two linear polarizers. This explains why the local hidden variable model failed to account for the observation based on Malus Law. This is where Quantum Mechanics happen to score, notwithstanding that the wave function it uses has no physical meaning or reality. The mathematical operation happened to mirror that which was derived based on the classical wave explanation of the double-slits experiment.
My question is—what if the observation based on Malus Law can be accounted based on some other model where it takes into consideration the interaction between the atoms forming the polarizers and the photons passing through it?
Is it possible that existing Local Hidden Variable Models did not consider certain vital presumption that led to its failure to provide a prediction consistent with the experimental observation?
If this can be done, where then is the issue of Causality or Non-Locality based on the Aspect Experiment?
I am not against quantum computing per se. I would welcome the possibility that computing speed can be increase by leaps and bounds. I just could not see the possibility of Quantum Computing based on an unproven hypothesis of Quantum Entanglement. But the bigger problem with quantum entanglement is that if Non-Locality is true, then voodoo action is also true according to Nick Herbert in his book “Quantum Reality”.
I am not against the idea that something at a distance can have an influence on us just like the sun or the moon. This can only happen if the gravitational field from the sun reaches us after traveling through empty space at the speed of light. It does not happen instantaneously. Accordingly, if the sun were to disappear this moment, its effect will be felt on earth some 8 minutes later according to the speed of light, c and not immediately. I hope you can now appreciate why I find Non-Locality abhorring just as Isaac Newton did. This is notwithstanding that Newton was slapping himself on the face when he proposed his gravitational theory then. I don’t think Non-Locality should form part of Science although it is highly desired in Science fiction.
Cheers.
QUOTE
Entanglement happens; it is responsible for many interesting conundrums in quantum physics. Spin states are not the only states which can be entangled; any interaction that creates a distributed dependence upon a conserved quantity can result in entanglement. What entanglement means is that the value of a variable at one point in space is dependent upon the value of that variable at a point at spacelike separation from the first point. Spin is used because for quanta, spin is a discrete variable; but this does not imply that all entanglements are based on discrete variables.
I agree with you that two or more particles may be entangled at birth, like pair production of a positron and an electron.
Two or more photons can also be emitted from the same atom.
Similarly, two electrons with opposite spin can also be emitted in weak interaction from the same nucleus of the atom.
Based on the strict definition of entanglement, two entangle particles must share the same parent or origin.
In the case of pair production of positron and electron it must originate from the same gamma particle (photon).
For two photons to be entangled to one another, it must come from the same atom and no other atom.
And finally for two electrons with opposite spin to be emitted in weak interaction, it must come from the same nucleus.
The meaning of a twin or triplets must come from the womb of the same mother otherwise they cannot be called twins or triplets and as such are not entangled in any way.
Immediately after they are borne from this entangled birth, I fail to see that whatever happen next to one particle will have immediate impact on the other. Two entangled particles may have been given an opposite spin at birth. Once separated, whatever happen to one particle will have no influence on what will happen to its twin.
Unfortunately, Quantum Mechanics need us to believe that entanglement continue even after they are separated half a Universe from one another. And that what happen to one particle in one corner of the Universe will have an immediate impact on the other twin. This is absolutely necessary, otherwise Quantum Mechanics based on Copenhagen Interpretation will fall flat on its face. To me this can only happens in Science fiction, not Science.
If we look at the setup of the Aspect Experiment, nothing in the entire set up ensure that this first condition is met.
What then follows is the passage through two linear polarizers to measure the intensity of coincidence of photons traveling in two distinct paths. This is similar to the measurement of intensity of light passing through two linear polarizers that will yield the result based on Malus Law. The result of Malus Law is non linear just as many phenomena in nature does not yield a linear result based on a straight forward rotation of the polarizing axis of two linear polarizers. This explains why the local hidden variable model failed to account for the observation based on Malus Law. This is where Quantum Mechanics happen to score, notwithstanding that the wave function it uses has no physical meaning or reality. The mathematical operation happened to mirror that which was derived based on the classical wave explanation of the double-slits experiment.
My question is—what if the observation based on Malus Law can be accounted based on some other model where it takes into consideration the interaction between the atoms forming the polarizers and the photons passing through it?
Is it possible that existing Local Hidden Variable Models did not consider certain vital presumption that led to its failure to provide a prediction consistent with the experimental observation?
If this can be done, where then is the issue of Causality or Non-Locality based on the Aspect Experiment?
I am not against quantum computing per se. I would welcome the possibility that computing speed can be increase by leaps and bounds. I just could not see the possibility of Quantum Computing based on an unproven hypothesis of Quantum Entanglement. But the bigger problem with quantum entanglement is that if Non-Locality is true, then voodoo action is also true according to Nick Herbert in his book “Quantum Reality”.
I am not against the idea that something at a distance can have an influence on us just like the sun or the moon. This can only happen if the gravitational field from the sun reaches us after traveling through empty space at the speed of light. It does not happen instantaneously. Accordingly, if the sun were to disappear this moment, its effect will be felt on earth some 8 minutes later according to the speed of light, c and not immediately. I hope you can now appreciate why I find Non-Locality abhorring just as Isaac Newton did. This is notwithstanding that Newton was slapping himself on the face when he proposed his gravitational theory then. I don’t think Non-Locality should form part of Science although it is highly desired in Science fiction.
Cheers.
Hmmm. Hexa, I'm going to start with the Wikipedia definition of entanglement:
"Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated."
"Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated."
QUOTE (hexa+)
Based on the strict definition of entanglement, two entangle particles must share the same parent or origin.
No, this is incorrect. The correct statement is that we don't know of any way of producing entangled particles that does not involve them sharing the same parent or origin. But that's not the definition of entanglement. The definition of entanglement is that it is a property of two or more particles which exist in quantum states that cannot be defined without reference to one another.
QUOTE (hexa+)
Immediately after they are borne from this entangled birth, I fail to see that whatever happen next to one particle will have immediate impact on the other.
This is the weirdness of QM. But it's not so weird if you think about it; for example, let's take the electron-positron pair produced by a gamma photon. If we know (for example, because we produced a whole bunch of gamma photons in a process that produces gamma photons that all have the same energy) what the energy of the photon is, and we measure the energy of one of the electron-positron pair, then we immediately know the energy of the other without measuring it. And this is because of the conservation of energy, and their entanglement. If we were to measure the energy of the other member of the pair and find that it did NOT have the expected energy, we would win a Nobel prize for an experiment that violated the conservation of energy; we don't expect this ever to happen. This conserved quantity, energy, is quantized, just as spin is. But no one ever remarks on how weird it is that we can know the energy of the partner; nevertheless, it is entanglement, just as it is for spin.
What makes it weird for spin is that we can devise an experiment in which we APPEAR to have constrained the spin, and in which if we DO measure the spin in the same axis on both partners, we always find the constrained values, but if we measure it in different axes, we find that it is NOT so constrained. The use of entangled quanta in quantum cryptography and quantum computing is based on the first effect, not the second. Specifically, it is used for key exchange; what is done is, a string of entangled quanta are divided, with one pair member going to one of the two people exchanging the key, traditionally dubbed "Alice," and the other to the other, traditionally dubbed "Bob." Bob and Alice each measure the spin of each particle on a randomly-chosen axis. When they feel that they have exchanged enough quanta to guarantee that they will get a large-enough key, they stop and each one tells the other what axis they measured each particle's spin in; they then THROW OUT all the cases where they measured in DIFFERENT axes, and keep all the cases where they measured in the SAME axis.
This works because, first, simply knowing which axis they measured in is not sufficient to know what values they got; second, knowing which measurements were the same also is not sufficient to know what values they got; and third and finally, anyone who measured the quanta before they reached Alice or Bob would disentangle them and cause their keys to not match, but would not be able to tell what they had measured without KNOWING IN ADVANCE what direction they would measure for each quantum. Thus, even if Alice immediately used her key to encrypt a secret without checking the key with Bob by sending a test message, the "eavesdropper" (traditionally dubbed "Eve") could not decrypt it, and by sending such a test message, Eve's presence would immediately be obvious. This is because Eve cannot MEASURE the quanta without CHANGING their state.
You see, it's not a matter of what HAPPENS to one particle influencing the other; it's a matter of what IS MEASURED on one particle constraining what WILL BE MEASURED on the other, should the two measurements be of entangled parameters.
What makes it weird for spin is that we can devise an experiment in which we APPEAR to have constrained the spin, and in which if we DO measure the spin in the same axis on both partners, we always find the constrained values, but if we measure it in different axes, we find that it is NOT so constrained. The use of entangled quanta in quantum cryptography and quantum computing is based on the first effect, not the second. Specifically, it is used for key exchange; what is done is, a string of entangled quanta are divided, with one pair member going to one of the two people exchanging the key, traditionally dubbed "Alice," and the other to the other, traditionally dubbed "Bob." Bob and Alice each measure the spin of each particle on a randomly-chosen axis. When they feel that they have exchanged enough quanta to guarantee that they will get a large-enough key, they stop and each one tells the other what axis they measured each particle's spin in; they then THROW OUT all the cases where they measured in DIFFERENT axes, and keep all the cases where they measured in the SAME axis.
This works because, first, simply knowing which axis they measured in is not sufficient to know what values they got; second, knowing which measurements were the same also is not sufficient to know what values they got; and third and finally, anyone who measured the quanta before they reached Alice or Bob would disentangle them and cause their keys to not match, but would not be able to tell what they had measured without KNOWING IN ADVANCE what direction they would measure for each quantum. Thus, even if Alice immediately used her key to encrypt a secret without checking the key with Bob by sending a test message, the "eavesdropper" (traditionally dubbed "Eve") could not decrypt it, and by sending such a test message, Eve's presence would immediately be obvious. This is because Eve cannot MEASURE the quanta without CHANGING their state.
You see, it's not a matter of what HAPPENS to one particle influencing the other; it's a matter of what IS MEASURED on one particle constraining what WILL BE MEASURED on the other, should the two measurements be of entangled parameters.
QUOTE (hexa+)
Unfortunately, Quantum Mechanics need us to believe that entanglement continue even after they are separated half a Universe from one another.
Sure; because entangled quantities are conserved quantities. Suppose you let those two leptons (the electron-positron pair) propagate across half the universe, shepherding all other particles out of their way before they get there so their entanglement will not be destroyed. If you then measure each one, do you contend that their energies will not add up to the energy of that original gamma? Of course you don't. THAT is the meaning of entanglement.
QUOTE (hexa+)
And that what happen to one particle in one corner of the Universe will have an immediate impact on the other twin.
No, no, not at all. Again, what is MEASURED, not what HAPPENS. And only if the two measurements happen to be of entangled parameters. For example, if spin is measured on each one, but the two measurements happen not to be in the same plane, then the parameters are NOT entangled; they are only entangled if the spins are measured in the SAME plane. For another example, if the momentum of one is measured, but the position of the other is measured, THOSE values are not entangled either. But if we measure the momenta of the two, then it will add up to the momentum of the original gamma photon, since those quantities ARE entangled.
QUOTE (hexa+)
If we look at the setup of the Aspect Experiment, nothing in the entire set up ensure that this first condition is met.
Reading your post over carefully, what I believe you are saying is that there is no guarantee that the two quanta are from the same event. But in fact there is a guarantee that the vast majority of them are: this is imposed by the requirement that the two measurements occur within a very narrow time window. To calculate the probability of the situation where the two quanta are from different events, one must use the length of the window in combination with the size of the sample from which the two quanta emerge. This is a relatively straightforward probability calculation, and it has been shown that using this probability calculation, the results of the Aspect experiment correlate to the expectations of QM to over nine sigma in recent experiments.
What would invalidate the experiment would be if there were TWO such holes in the reasoning; and in early versions, because the quantum efficiency of the detectors was low, it turns out that there WAS a second hole, because of this low quantum efficiency. However, the quantum efficiency of CCD detectors has been increased vastly, due to their use in astronomy and in cameras (where there is a great deal of money to be made, and thus a great incentive to improve the technology), and this second hole has been closed.
What would invalidate the experiment would be if there were TWO such holes in the reasoning; and in early versions, because the quantum efficiency of the detectors was low, it turns out that there WAS a second hole, because of this low quantum efficiency. However, the quantum efficiency of CCD detectors has been increased vastly, due to their use in astronomy and in cameras (where there is a great deal of money to be made, and thus a great incentive to improve the technology), and this second hole has been closed.
QUOTE (hexa+)
My question is—what if the observation based on Malus Law can be accounted based on some other model where it takes into consideration the interaction between the atoms forming the polarizers and the photons passing through it?
Is it possible that existing Local Hidden Variable Models did not consider certain vital presumption that led to its failure to provide a prediction consistent with the experimental observation?
If this can be done, where then is the issue of Causality or Non-Locality based on the Aspect Experiment?
Is it possible that existing Local Hidden Variable Models did not consider certain vital presumption that led to its failure to provide a prediction consistent with the experimental observation?
If this can be done, where then is the issue of Causality or Non-Locality based on the Aspect Experiment?
But the Malus Law does take into account such interactions- it is in fact BASED (physically speaking- yes, I know, Malus' Law was derived empirically) on them. Specifically, the cosine-squared function emerges from the QM probability of the spin in a second axis being a certain value given a prior measurement in a different axis. And this probability depends upon the very uncertainty you are having trouble with- the value would be DIFFERENT than what we measure- i.e. Malus' Law would NOT be correct- if the spins in different axes were not complementary under uncertainty!
It is in fact certain (to nine sigma) that Local Hidden Variable models didn't consider a certain vital presumption that they made- the presumption of local realism. That is, Local Hidden Variable theories (the most obvious of which is the assertion that despite the fact that it is unmeasureable due to uncertainty, a value complementary under uncertainty to a measured value has the expected, constrained value and is merely HIDDEN by uncertainty) fail; and the most obvious conclusion is that this is because there are no local hidden variables. And this is the majority interpretation of the results of the Aspect experiment, and was in fact the majority interpretation of EPR before the experiment became technically possible.
Note well that this does not violate causality in MEASURABLE parameters, but only in UNMEASURABLE parameters. The conjecture that physics always acts in such a way as to ensure that such causality violations cannot occur in measurable parameters is called the Chronology Protection Conjecture.
Nevertheless, Aspect (and EPR) show conclusively (again, to nine sigma certainty) that causality CAN be violated, but only for unmeasurable parameters.
It is in fact certain (to nine sigma) that Local Hidden Variable models didn't consider a certain vital presumption that they made- the presumption of local realism. That is, Local Hidden Variable theories (the most obvious of which is the assertion that despite the fact that it is unmeasureable due to uncertainty, a value complementary under uncertainty to a measured value has the expected, constrained value and is merely HIDDEN by uncertainty) fail; and the most obvious conclusion is that this is because there are no local hidden variables. And this is the majority interpretation of the results of the Aspect experiment, and was in fact the majority interpretation of EPR before the experiment became technically possible.
Note well that this does not violate causality in MEASURABLE parameters, but only in UNMEASURABLE parameters. The conjecture that physics always acts in such a way as to ensure that such causality violations cannot occur in measurable parameters is called the Chronology Protection Conjecture.
Nevertheless, Aspect (and EPR) show conclusively (again, to nine sigma certainty) that causality CAN be violated, but only for unmeasurable parameters.
QUOTE (hexa+)
I am not against quantum computing per se. I would welcome the possibility that computing speed can be increase by leaps and bounds. I just could not see the possibility of Quantum Computing based on an unproven hypothesis of Quantum Entanglement.
Entanglement is not an unproven hypothesis; it is supported by postdiction, prediction, conservation laws, and causality itself. Remember, entanglement is the statement that if two values are entangled, they will ALWAYS yield the constrained values if they are measured. It is Aspect and EPR that show that they are NOT constrained if one or both are NOT measured, and uncertainty that governs why this is so.
Hopefully this will serve to clear up some of your doubts about this subject.
Hopefully this will serve to clear up some of your doubts about this subject.
Hi Schneibster,
Thanks again for your clarification.
"Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated."
Thanks again for your clarification.
QUOTE
"Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated."
QUOTE (->
| QUOTE |
"Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated." QUOTE (hexa) Based on the strict definition of entanglement, two entangle particles must share the same parent or origin. No, this is incorrect. The correct statement is that we don't know of any way of producing entangled particles that does not involve them sharing the same parent or origin. But that's not the definition of entanglement. The definition of entanglement is that it is a property of two or more particles which exist in quantum states that cannot be defined without reference to one another. |
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Thank you for clarifying that two particles can be entangled yet without coming from the same parent or origin. That is precisely where I find the definition given in Wikipedia incomplete and totally evade the central criticism of the EPR Experiment. This criticism is also not addressed in other similar sites that believe Quantum Entanglement is true.
I must confess that I have difficulty to disentangle each or your argument on what is entangled and what is not. The issue of Causality and Non-Locality is hopelessly entangled that I think I will need to seek further clarification from you.
My questions are as follows:
1. Does the gamma photon with energy E1 produce a positron-electron pair where Ee1 (the energy of electron (e1)) and Ep1 (the energy of positron (p1)) are equal?
2. If the answer to the first question is positive, then it must mean that a second gamma photon with energy E2 will produce another positron-electron pair such that Ee2 = Ep2.
3. If the answers to the first and second questions are positive, then it must mean that the momentum in each case must also be identical numerically, that is: Pe1 = Pp1 and Pe2 = Pp2
4. Can we agree that the original EPR Experiment essentially state that only e1 is entangled to p1 and only e2 is entangled to p2. There is no entanglement between e1 and p2 or e2 with p1; nor is e1 with e2 or p1 with p2.
5. Can we also agree that the attack of the EPR Experiment is on the assertion of the Uncertainty Principle--that it is impossible to know both the position and momentum of a particle with absolute certainty given by dx.dP ≥ h/4π.
6. Can we also agree that it is possible to measure the position of either Xe1 or Xp1 with absolute certainty or perhaps both Xe1 and Xp1 with absolute certainty?
7. If that is possible then it must also be possible to measure both the positions of Xe2 and Xp2 with absolute certainty.
8. Alternatively we can measure either or both the momenta of Pe1 and Pp1 with absolute certainty as well as either or both the momenta of Pe2 and Pp2 with absolute certainty.
9. If the answers to 6, 7, 8 are positive, then would it be possible to measure the position of e1 but the momentum of p1 with absolute certainty?
10. If the answer to 9 is positive, coupled with the positive answer to 3, then would it not means that we can have both the position and momentum of both e1 and p1 as well as e2 and p2. If that is true, would it not be true that the Uncertainty Principle that we have stated in 5 is false?
11. Is it true that the Bell’s Theorem did not address the criticism of the EPR Experiment directly but instead address why existing Local Hidden Variable Model could not account for Malus Law when light passes through two linear polarizers?
12. Is it true, that the Aspect Experiment only verify the violation of Bell’s inequality that essentially mean one thing – Causality appears to be violated and not that Non-Locality is proved?
I would be very grateful if you could help me to resolve these questions. Thanks
Cheers.
Thank you for clarifying that two particles can be entangled yet without coming from the same parent or origin. That is precisely where I find the definition given in Wikipedia incomplete and totally evade the central criticism of the EPR Experiment. This criticism is also not addressed in other similar sites that believe Quantum Entanglement is true.
I must confess that I have difficulty to disentangle each or your argument on what is entangled and what is not. The issue of Causality and Non-Locality is hopelessly entangled that I think I will need to seek further clarification from you.
My questions are as follows:
1. Does the gamma photon with energy E1 produce a positron-electron pair where Ee1 (the energy of electron (e1)) and Ep1 (the energy of positron (p1)) are equal?
2. If the answer to the first question is positive, then it must mean that a second gamma photon with energy E2 will produce another positron-electron pair such that Ee2 = Ep2.
3. If the answers to the first and second questions are positive, then it must mean that the momentum in each case must also be identical numerically, that is: Pe1 = Pp1 and Pe2 = Pp2
4. Can we agree that the original EPR Experiment essentially state that only e1 is entangled to p1 and only e2 is entangled to p2. There is no entanglement between e1 and p2 or e2 with p1; nor is e1 with e2 or p1 with p2.
5. Can we also agree that the attack of the EPR Experiment is on the assertion of the Uncertainty Principle--that it is impossible to know both the position and momentum of a particle with absolute certainty given by dx.dP ≥ h/4π.
6. Can we also agree that it is possible to measure the position of either Xe1 or Xp1 with absolute certainty or perhaps both Xe1 and Xp1 with absolute certainty?
7. If that is possible then it must also be possible to measure both the positions of Xe2 and Xp2 with absolute certainty.
8. Alternatively we can measure either or both the momenta of Pe1 and Pp1 with absolute certainty as well as either or both the momenta of Pe2 and Pp2 with absolute certainty.
9. If the answers to 6, 7, 8 are positive, then would it be possible to measure the position of e1 but the momentum of p1 with absolute certainty?
10. If the answer to 9 is positive, coupled with the positive answer to 3, then would it not means that we can have both the position and momentum of both e1 and p1 as well as e2 and p2. If that is true, would it not be true that the Uncertainty Principle that we have stated in 5 is false?
11. Is it true that the Bell’s Theorem did not address the criticism of the EPR Experiment directly but instead address why existing Local Hidden Variable Model could not account for Malus Law when light passes through two linear polarizers?
12. Is it true, that the Aspect Experiment only verify the violation of Bell’s inequality that essentially mean one thing – Causality appears to be violated and not that Non-Locality is proved?
I would be very grateful if you could help me to resolve these questions. Thanks
Cheers.
QUOTE (hexa+)
Thank you for clarifying that two particles can be entangled yet without coming from the same parent or origin.
Nope, I didn't say that. In fact, I said precisely the opposite: we don't know of any process that creates entangled quanta without prior causal contact between the entangled particles; that is not the same as the statement that there aren't any. But my point was rather aside from this issue: my point was that the causal contact is NOT the definition of entanglement. The precise definition of entanglement is that the quantum state of one particle cannot be specified without reference to another particle or system of particles. The implication of this is that the particle in question has had an interaction with that other particle or system, and the results of that interaction have not been quantified and therefore remain probabilistic. If a measurement is made on the other particle or system of a measurable that is conserved, and the prior value of the measurable for the particle (if it had one, or existed before the interaction) and the system or other particle (again, if it existed before the interaction) was already known, then if that measurable is determined for the particle, it will have the value dictated by the conservation law; however, uncertainty tells us that if another measurable that is conjugate under uncertainty to the first one is made on the particle, then the value of the conserved measurable NEED NOT have the value dictated by the conservation law. Aspect confirms that, and shows that in SOME cases, the unmeasurable parameter in fact DOES NOT have a value that is dictated by the conservation law. We cannot measure this DIRECTLY, because if we actually measure the parameter, it will ALWAYS have the conserved value, but we can show INDIRECTLY via the Aspect experiment that if we do NOT measure it, it NEED NOT.
All of that is aside from entanglement; the entanglement is merely a property of the particles that the values of some of their parameters are subject to a conservation law combined with a prior measurement.
All of that is aside from entanglement; the entanglement is merely a property of the particles that the values of some of their parameters are subject to a conservation law combined with a prior measurement.
QUOTE (hexa+)
The issue of Causality and Non-Locality is hopelessly entangled that I think I will need to seek further clarification from you.
Precisely; and in fact I CANNOT clarify it further! NO ONE can. Either locality is violated, or local hidden variable theories are impossible; and we cannot see how to devise an experiment that will tell us which of these two is the case. We ASSUME that locality holds, and local hidden variable theories are impossible, but we cannot PROVE it, and we cannot see any way to either prove or disprove it.
QUOTE (hexa+)
1. Does the gamma photon with energy E1 produce a positron-electron pair where Ee1 (the energy of electron (e1)) and Ep1 (the energy of positron (p1)) are equal?
Not necessarily. Their mass must be equal, but their momenta need not be. However, their momenta will vector-add to the original momentum of the photon.
QUOTE (hexa+)
2. If the answer to the first question is positive, then it must mean that a second gamma photon with energy E2 will produce another positron-electron pair such that Ee2 = Ep2.
3. If the answers to the first and second questions are positive, then it must mean that the momentum in each case must also be identical numerically, that is: Pe1 = Pp1 and Pe2 = Pp2
3. If the answers to the first and second questions are positive, then it must mean that the momentum in each case must also be identical numerically, that is: Pe1 = Pp1 and Pe2 = Pp2
Since the answer to the first question is positive, neither of these is operative.
QUOTE (hexa+)
4. Can we agree that the original EPR Experiment essentially state that only e1 is entangled to p1 and only e2 is entangled to p2. There is no entanglement between e1 and p2 or e2 with p1; nor is e1 with e2 or p1 with p2.
Correct.
QUOTE (hexa+)
5. Can we also agree that the attack of the EPR Experiment is on the assertion of the Uncertainty Principle--that it is impossible to know both the position and momentum of a particle with absolute certainty given by dx.dP ≥ h/4π.
Yes- EPR says we can know the spin of the photon in one axis by measuring it, and the spin in another by measuring the spin in that axis on the other photon.
QUOTE (hexa+)
6. Can we also agree that it is possible to measure the position of either Xe1 or Xp1 with absolute certainty or perhaps both Xe1 and Xp1 with absolute certainty?
7. If that is possible then it must also be possible to measure both the positions of Xe2 and Xp2 with absolute certainty.
8. Alternatively we can measure either or both the momenta of Pe1 and Pp1 with absolute certainty as well as either or both the momenta of Pe2 and Pp2 with absolute certainty.
9. If the answers to 6, 7, 8 are positive, then would it be possible to measure the position of e1 but the momentum of p1 with absolute certainty?
7. If that is possible then it must also be possible to measure both the positions of Xe2 and Xp2 with absolute certainty.
8. Alternatively we can measure either or both the momenta of Pe1 and Pp1 with absolute certainty as well as either or both the momenta of Pe2 and Pp2 with absolute certainty.
9. If the answers to 6, 7, 8 are positive, then would it be possible to measure the position of e1 but the momentum of p1 with absolute certainty?
Yes.
QUOTE (hexa+)
10. If the answer to 9 is positive, coupled with the positive answer to 3, then would it not means that we can have both the position and momentum of both e1 and p1 as well as e2 and p2. If that is true, would it not be true that the Uncertainty Principle that we have stated in 5 is false?
But since the answer to question 1 is "not necessarily," the answer to questions 2 and 3 is "not necessarily." However, this ignores the greater fact that by measuring Xe1, we have rendered Pe1 unmeasurable, and therefore not subject to causality and conservation laws. EPR asserts local realism, that is, that Pe1 has a real value even though we cannot measure it, and secondarily that that value must correspond to the conservation law if macroscopic causality is to be preserved. Aspect shows that in fact Pe1 NEED NOT have the conserved value, and in fact in some cases DOES NOT. Similar arguments obtain for Xe2, Pe2, Xp1, Xp2, Pp1 and Pp2, relatively.
QUOTE (hexa+)
11. Is it true that the Bell’s Theorem did not address the criticism of the EPR Experiment directly but instead address why existing Local Hidden Variable Model could not account for Malus Law when light passes through two linear polarizers?
Bell's Theorem shows solely that if local realism is true, and macroscopic causality is true, then the predictions of quantum mechanics about the Aspect experiment and other experiments based on EPR must be incorrect. Actually running these experiments gives the results predicted by quantum mechanics, showing that either local realism or macroscopic causality must be false.
QUOTE (hexa+)
12. Is it true, that the Aspect Experiment only verify the violation of Bell’s inequality that essentially mean one thing – Causality appears to be violated and not that Non-Locality is proved?
Non-locality IS a violation of macroscopic causality. The violation of local realism is also a violation of causality, but it is indirect; we cannot directly measure the quantity that attains a value forbidden by causality. Most physicists choose to believe that local realism is violated rather than causality, but we don't know that- we only know that one or the other must be violated.
Hi Schneibster,
Thanks again.
I come to realize that we are generally in agreement on all the issues relating to EPR, Quantum Entanglement and Quantum Mechanics except maybe on whether Circular Polarization of Light exists as a distinct quantum state. The only difference is the extent we believe in each of these issues. For example, the violation of Bell’s inequality shown in Aspect Experiment is interpreted by you as either a violation of Causality or Non-Locality-- consistent with what is generally accepted by physicists pursuing the subject on Quantum Entanglement; whereas I will not stop at the level of definition but instead question the validity based on logic and perhaps common sense. You look upon violation of Causality and Locality as a possibility, whereas I look upon violation of either Causality or Locality as fundamentally wrong.
Without sufficient evidence and knowledge of a phenomenon, all we have are conjectures and guesses of what is involved. But that does not stop us from using a phenomenon to help us do something, just as we need not know the physics of fire before we learn to cook with it.
The use of the so call Quantum Entanglement in cryptology is a correct application of a phenomenon. All it involves is to use signals generated from the same source (not necessarily from the same atom) that is communicated to two different locations at the speed of light (not faster!). This then serve as the common key that the recipients need to use in order to decipher the message.
But, I think it is incorrect to harbour any idea that we could somehow send information to one another faster than the speed of light because we think that Non-Locality is violated. To me that is an incorrect understanding and usage of the phenomenon. The choice of their description appears to have been sensationalised.
The current Local Hidden Variable Models to account for the passage of light passing through the linear polarizers are too simplistic rendering it incapable of explaining the result predicted by Malus Law. My Question is—What if there is a better explanation to account for light passing through the linear polarizers without having to violate either Causality and Locality? If such an account is possible, is the prediction of Quantum Entanglement as violating Causality or Locality still needed?
Let us use the example of our forefathers who did not know the physics behind “Lightning and Thunder” but instead attribute it to some supernatural forces. They then spin other related phenomenon in Nature around this theory. This is the danger if we were to assert that Causality and or Non Locality is violated. It is just as absurd to state that one can die before one is even born (if Causality is violated) or that another being in another corner of the universe can be in control of our destiny (if Non-Locality is possible). To do that we are in fact giving credence to some mumbo jumbo idea such as “voodoo action” is possible as what Nick Herbert in his book “Quantum Reality” has pointed out. I don’t think this approach should be adopted if we want to pursue the Simple Truth of Nature. I am more incline to agree with Einstein when he criticized Quantum Mechanics as incomplete rather than wrong.
But unfortunately, at this point in time, what we have are partial theories of Nature. Many of these partial theories are in conflict with one another. For example, the two crucial pillars of physics, Quantum Theory is totally incompatible with Einstein’s Relativity Theories.
Thanks again for clearing up the misconception I had earlier on. I have benefited immensely from my discussion with you on this thread. I am very grateful to you for engaging me at the depth that we have gone through.
Lastly, I am curious to know, if I do have some unusual findings on the topic that we have discussed, would I be able to communicate with you outside the forum page as the materials involved are simply too voluminous to be posted in the forum page? Look forward to hearing from you. Thanks.
Cheers.
Thanks again.
I come to realize that we are generally in agreement on all the issues relating to EPR, Quantum Entanglement and Quantum Mechanics except maybe on whether Circular Polarization of Light exists as a distinct quantum state. The only difference is the extent we believe in each of these issues. For example, the violation of Bell’s inequality shown in Aspect Experiment is interpreted by you as either a violation of Causality or Non-Locality-- consistent with what is generally accepted by physicists pursuing the subject on Quantum Entanglement; whereas I will not stop at the level of definition but instead question the validity based on logic and perhaps common sense. You look upon violation of Causality and Locality as a possibility, whereas I look upon violation of either Causality or Locality as fundamentally wrong.
Without sufficient evidence and knowledge of a phenomenon, all we have are conjectures and guesses of what is involved. But that does not stop us from using a phenomenon to help us do something, just as we need not know the physics of fire before we learn to cook with it.
The use of the so call Quantum Entanglement in cryptology is a correct application of a phenomenon. All it involves is to use signals generated from the same source (not necessarily from the same atom) that is communicated to two different locations at the speed of light (not faster!). This then serve as the common key that the recipients need to use in order to decipher the message.
But, I think it is incorrect to harbour any idea that we could somehow send information to one another faster than the speed of light because we think that Non-Locality is violated. To me that is an incorrect understanding and usage of the phenomenon. The choice of their description appears to have been sensationalised.
The current Local Hidden Variable Models to account for the passage of light passing through the linear polarizers are too simplistic rendering it incapable of explaining the result predicted by Malus Law. My Question is—What if there is a better explanation to account for light passing through the linear polarizers without having to violate either Causality and Locality? If such an account is possible, is the prediction of Quantum Entanglement as violating Causality or Locality still needed?
Let us use the example of our forefathers who did not know the physics behind “Lightning and Thunder” but instead attribute it to some supernatural forces. They then spin other related phenomenon in Nature around this theory. This is the danger if we were to assert that Causality and or Non Locality is violated. It is just as absurd to state that one can die before one is even born (if Causality is violated) or that another being in another corner of the universe can be in control of our destiny (if Non-Locality is possible). To do that we are in fact giving credence to some mumbo jumbo idea such as “voodoo action” is possible as what Nick Herbert in his book “Quantum Reality” has pointed out. I don’t think this approach should be adopted if we want to pursue the Simple Truth of Nature. I am more incline to agree with Einstein when he criticized Quantum Mechanics as incomplete rather than wrong.
But unfortunately, at this point in time, what we have are partial theories of Nature. Many of these partial theories are in conflict with one another. For example, the two crucial pillars of physics, Quantum Theory is totally incompatible with Einstein’s Relativity Theories.
Thanks again for clearing up the misconception I had earlier on. I have benefited immensely from my discussion with you on this thread. I am very grateful to you for engaging me at the depth that we have gone through.
Lastly, I am curious to know, if I do have some unusual findings on the topic that we have discussed, would I be able to communicate with you outside the forum page as the materials involved are simply too voluminous to be posted in the forum page? Look forward to hearing from you. Thanks.
Cheers.
Hi Schneibster,
Please refer to my last posting.
I wonder if we could maintain an exchange of materials outside the forum in order to better understand one another position on this topic. This will help to clarify our position to our posting made in this forum.
I look forward to your response to my suggestion.
Cheers.
Please refer to my last posting.
I wonder if we could maintain an exchange of materials outside the forum in order to better understand one another position on this topic. This will help to clarify our position to our posting made in this forum.
I look forward to your response to my suggestion.
Cheers.
Sorry, hexa, I been busy recently. Lots of work and a couple of new guitars will do that to you.
QUOTE (hexa+)
I come to realize that we are generally in agreement on all the issues relating to EPR, Quantum Entanglement and Quantum Mechanics except maybe on whether Circular Polarization of Light exists as a distinct quantum state.
Hexa, dang near anything is a "quantum state." How can you maintain that linear polarization is a quantum state, or is based on a quantum state, yet maintain that continually changing linear polarization is not a quantum state? It's like saying that someone who drowned is dead, but not if you cremated the body after you hauled it out of the water.
And polarization is explicitly based on a quantum state; spin, to be precise, which is quantized. Circular polarization is merely a specification of how a particle can be in a state where measurements of spin can change over time. That's all it is, nothing more.
And polarization is explicitly based on a quantum state; spin, to be precise, which is quantized. Circular polarization is merely a specification of how a particle can be in a state where measurements of spin can change over time. That's all it is, nothing more.
QUOTE (hexa+)
The only difference is the extent we believe in each of these issues. For example, the violation of Bell’s inequality shown in Aspect Experiment is interpreted by you as either a violation of Causality or Non-Locality-- consistent with what is generally accepted by physicists pursuing the subject on Quantum Entanglement; whereas I will not stop at the level of definition but instead question the validity based on logic and perhaps common sense. You look upon violation of Causality and Locality as a possibility, whereas I look upon violation of either Causality or Locality as fundamentally wrong.
Well, then you have a basic problem, because you cannot explain the results of the dual slit experiment performed with electrons.
If each electron goes through one slit or the other, how can you explain the fact that over time the impacts of the electrons make an interference pattern? And if the electrons go through both slits, as they must in order to make the observed interference pattern, how can you call them "particles?" A "particle" is here OR there, not BOTH.
This is a basic causality violation. However, just as with Aspect, you cannot see it directly. You can only deduce its existence.
Feynman once said that you can see all of quantum mechanics in the dual slit experiment. I believe that he had good grounds for saying it. From this experiment you can deduce the existence and importance of the Shroedinger wave equation, and Heisenberg uncertainty.
You are applying logic that works in the everyday macroscopic world to quantum mechanics, where it simply does not apply. This is what you refer to as "common sense." I don't think it's sensible at all, but you have to do what you choose to do. In my opinion, the meaning of the term, "causality," is highly questionable in QM, and if it even has any meaning there, it is certainly quite different from the meaning we assign it in everyday macroscopic reality; and I don't need Aspect to tell me that, the dual slit experiment is sufficient.
If each electron goes through one slit or the other, how can you explain the fact that over time the impacts of the electrons make an interference pattern? And if the electrons go through both slits, as they must in order to make the observed interference pattern, how can you call them "particles?" A "particle" is here OR there, not BOTH.
This is a basic causality violation. However, just as with Aspect, you cannot see it directly. You can only deduce its existence.
Feynman once said that you can see all of quantum mechanics in the dual slit experiment. I believe that he had good grounds for saying it. From this experiment you can deduce the existence and importance of the Shroedinger wave equation, and Heisenberg uncertainty.
You are applying logic that works in the everyday macroscopic world to quantum mechanics, where it simply does not apply. This is what you refer to as "common sense." I don't think it's sensible at all, but you have to do what you choose to do. In my opinion, the meaning of the term, "causality," is highly questionable in QM, and if it even has any meaning there, it is certainly quite different from the meaning we assign it in everyday macroscopic reality; and I don't need Aspect to tell me that, the dual slit experiment is sufficient.
QUOTE (hexa+)
Without sufficient evidence and knowledge of a phenomenon, all we have are conjectures and guesses of what is involved.
That's what experiments are for. We have done a lot of them, and gathered a great deal of data. I realize that you are upset that the data point to conclusions you find distasteful, but the fact is that they do, and that means you're going to have to accept them, whether you like them or not.
QUOTE (hexa+)
But that does not stop us from using a phenomenon to help us do something, just as we need not know the physics of fire before we learn to cook with it.
The use of the so call Quantum Entanglement in cryptology is a correct application of a phenomenon. All it involves is to use signals generated from the same source (not necessarily from the same atom) that is communicated to two different locations at the speed of light (not faster!). This then serve as the common key that the recipients need to use in order to decipher the message.
But, I think it is incorrect to harbour any idea that we could somehow send information to one another faster than the speed of light because we think that Non-Locality is violated. To me that is an incorrect understanding and usage of the phenomenon. The choice of their description appears to have been sensationalised.
The use of the so call Quantum Entanglement in cryptology is a correct application of a phenomenon. All it involves is to use signals generated from the same source (not necessarily from the same atom) that is communicated to two different locations at the speed of light (not faster!). This then serve as the common key that the recipients need to use in order to decipher the message.
But, I think it is incorrect to harbour any idea that we could somehow send information to one another faster than the speed of light because we think that Non-Locality is violated. To me that is an incorrect understanding and usage of the phenomenon. The choice of their description appears to have been sensationalised.
In the opinions of most physicists, and in my opinion as well, it is most likely that you are correct and that there is no means by which information can be sent faster than light. Nor is sending information faster than light required for either quantum cryptography nor quantum computing. That's not what they're about.
On the other hand, using quantum cryptography is considerably more complex than cooking a meal, so I don't think your analogy is valid.
On the other hand, using quantum cryptography is considerably more complex than cooking a meal, so I don't think your analogy is valid.
QUOTE (hexa+)
The current Local Hidden Variable Models to account for the passage of light passing through the linear polarizers are too simplistic rendering it incapable of explaining the result predicted by Malus Law. My Question is—What if there is a better explanation to account for light passing through the linear polarizers without having to violate either Causality and Locality? If such an account is possible, is the prediction of Quantum Entanglement as violating Causality or Locality still needed?
You don't understand- Aspect doesn't rule out only the simplest local hidden variable theory, it rules out ALL local hidden variable theories. It does NOT rule out GLOBAL hidden variable theories, but the fact that the hidden variables in such theories are global implies a causality violation, since access to these variables (i.e. the ability to change them and observe the effects of such changes) WOULD allow FTL communication. As I have repeatedly said, Aspect implies causality violation- either direct, or indirect- by some means. It is the opinion of most physicists that this causality violation is such that it cannot be used for communication- but that is by no means certain, and no experiment that we have been able to imagine, much less conduct, can prove whether it is true or not. This also does not mean that such an experiment may or may not become imaginable in the future- but certainly it is unlikely, given how much we already know, which due to our incessant experimentation is quite a lot, actually.
QUOTE (hexa+)
Let us use the example of our forefathers who did not know the physics behind “Lightning and Thunder” but instead attribute it to some supernatural forces. They then spin other related phenomenon in Nature around this theory. This is the danger if we were to assert that Causality and or Non Locality is violated. It is just as absurd to state that one can die before one is even born (if Causality is violated) or that another being in another corner of the universe can be in control of our destiny (if Non-Locality is possible). To do that we are in fact giving credence to some mumbo jumbo idea such as “voodoo action” is possible as what Nick Herbert in his book “Quantum Reality” has pointed out. I don’t think this approach should be adopted if we want to pursue the Simple Truth of Nature. I am more incline to agree with Einstein when he criticized Quantum Mechanics as incomplete rather than wrong.
First of all, we know a heck of a lot more about how things work than people making up thunder gods. Second, I strongly prefer not to speculate about the philosophical implications of my physics knowledge until AFTER I have gained that knowledge- to do so smacks to me of deciding on acceptable conclusions and using reasoning to eliminate facts that are inconvenient to them; a highly questionable procedure commonly called "rationalizing."
Not only that, but you have drawn a false conclusion: you assume that violations of causality could result in time paradoxes (you cite a paradox derived from the famous (grandfather paradox), but in fact they need not, if there are limitations of certain types placed on what types of violations are possible.
Not only that, but you have drawn a false conclusion: you assume that violations of causality could result in time paradoxes (you cite a paradox derived from the famous (grandfather paradox), but in fact they need not, if there are limitations of certain types placed on what types of violations are possible.
QUOTE (hexa+)
Thanks again for clearing up the misconception I had earlier on. I have benefited immensely from my discussion with you on this thread. I am very grateful to you for engaging me at the depth that we have gone through.
Sure. I hope what I have said here also helps.
QUOTE (hexa+)
Lastly, I am curious to know, if I do have some unusual findings on the topic that we have discussed, would I be able to communicate with you outside the forum page as the materials involved are simply too voluminous to be posted in the forum page? Look forward to hearing from you. Thanks.
I have two reasons for saying, "no." Neither has anything to do with you, so please don't take it personally.
The first is that I am knowledgable, but by no means infallible, and I hope that there are folks here who know enough physics to step in and correct me if I step wrong. In any case, I prefer to preserve the possibility that it might happen, and if we correspond privately on these matters, it cannot.
Second, I am here to teach, not merely you, but others who might be interested- and to learn, both by being corrected or by finding errors in my reasoning, and by presenting that reasoning to others, which is rather different than working through it under guidance, and can result in detecting missing data and other interesting things. Again, if we correspond privately, no one else will benefit from it, and that is important to me as well.
I suggest that if you have something for me to take a look at, you might try posting it somewhere and PMing me a link; or perhaps even placing the material or the link in a thread here, and PMing me if you don't see a response.
I don't insist on completely public correspondence; if you have reason to proceed privately, please contact me privately and elucidate. But be aware of the two above opinions/reasons for proceeding above when you do.
The first is that I am knowledgable, but by no means infallible, and I hope that there are folks here who know enough physics to step in and correct me if I step wrong. In any case, I prefer to preserve the possibility that it might happen, and if we correspond privately on these matters, it cannot.
Second, I am here to teach, not merely you, but others who might be interested- and to learn, both by being corrected or by finding errors in my reasoning, and by presenting that reasoning to others, which is rather different than working through it under guidance, and can result in detecting missing data and other interesting things. Again, if we correspond privately, no one else will benefit from it, and that is important to me as well.
I suggest that if you have something for me to take a look at, you might try posting it somewhere and PMing me a link; or perhaps even placing the material or the link in a thread here, and PMing me if you don't see a response.
I don't insist on completely public correspondence; if you have reason to proceed privately, please contact me privately and elucidate. But be aware of the two above opinions/reasons for proceeding above when you do.
Hi Schneibster,
Thanks you for your response.
The reason I requested for communication outside the forum is because the forum is not the most appropriate vehicle to communicate huge amount of mathematics, graphics and other illustrations. It is simply too much to be posted in the forum page. Beside, you have said that the forum is a platform for general audience as well.
I am afraid that without the benefits of the same information that I am privy to, it is quite difficult to convince you on why I fervently object to the violation of Causality and Locality. To me it is fundamentally wrong. The information that I am privy to is not available in the public domain and as such I can’t provide you the link for you to access the said information.
You have cited existing literature that was build up over the last century. It is more than a century since Planck first proposed the Quantization of energy. But while Quantization of energy has led Einstein to assert that light is a particle through his account of the photoelectric effect, Einstein was unable to dissociate himself totally from the apron string of wave. He had to describe the energy of a photon as somehow intimately link to the properties of wave as it still needed wavelength (λ) and frequency (γ) in addition to the constant, h defined by Max Planck. The Quantum Theory that is currently integrated into the Standard Model, (practiced by physicists all over the world) was build on Quantum Mechanics (which is mathematics) rather than Physics. In the words of Richard Feynman, “Physics has given up” after he had described the phenomena relating to the passage of light and electrons through the Double Slits in his legendary Feynman Lectures on Physics. You are right to ask whether I could account for this:
Wrong. I could do that using a particle approach to account for all the phenomena that Richard Feynman had laboriously brought us through in his lecture.
Wrong. I could do that using a particle approach to account for all the phenomena that Richard Feynman had laboriously brought us through in his lecture.
If each electron goes through one slit or the other, how can you explain the fact that over time the impacts of the electrons make an interference pattern? And if the electrons go through both slits, as they must in order to make the observed interference pattern, how can you call them "particles?" A "particle" is here OR there, not BOTH.
I can account for the interference pattern using a particle approach not wave. I need not make a ridiculous assumption that an electron can somehow go through both slits at the same time.
Have you consider the possibility that the treatment considered by the pioneers of Quantum Theory may have overlook some fine details that led them to the enigma. Have you ever consider the possibility that many of the information on the nanoworld that we have now weren’t available or even perceived then? Never will Bohr or Heisenberg or even Feynman be able to envisage the possibility that we could physically “see” the atom in three-dimensional space using a Scanning Tunneling Microscope (STM). If we can appreciate the existence of these atoms using common sense, is there a need for us to resort to uncommon sense?
Have you consider the possibility that the treatment considered by the pioneers of Quantum Theory may have overlook some fine details that led them to the enigma. Have you ever consider the possibility that many of the information on the nanoworld that we have now weren’t available or even perceived then? Never will Bohr or Heisenberg or even Feynman be able to envisage the possibility that we could physically “see” the atom in three-dimensional space using a Scanning Tunneling Microscope (STM). If we can appreciate the existence of these atoms using common sense, is there a need for us to resort to uncommon sense?
That's what experiments are for. We have done a lot of them, and gathered a great deal of data. I realize that you are upset that the data point to conclusions you find distasteful, but the fact is that they do, and that means you're going to have to accept them, whether you like them or not.
Incorrect. I studied the claims of the Aspect Experiment very carefully and objectively based on the result that they have obtained. I have shown you that the claim was Non Locality. This is the basis for Quantum Entanglement. This is the claim that information can travel faster than light. In fact, the claim is even more preposterous. We can have instant communication not withstanding that we may be separated half a universe away. These are the claims.
What does the result of the Aspect Experiment tell us? They have obtained the intensity of the coincidence of photons based on Malus Law. It is only the existing (or according to you, All) Local Hidden Variable Models that failed to account for the result predicted by Malus Law. Period.
What if I tell you that I have a simple explanation that describe the polarizer as being made of atoms that are aligned in a certain direction and that the photons passing through the polarizers are also made of particles. And by applying these assumptions I could account for Malus Law stochastically without having to violate both Locality and Causality. My question to you is—If there is a simple common sense explanation using particles to account for Malus Law, do we still need to rely on violation of Locality and Causality to account for the Aspect Experiment?
I agree with you. It is only an opinion. And I believe they are mistaken. This is because they are unable to account logically what is involved in the phenomena of linear polarization that led to Malus Law. Since Quantum mechanics is not concerned with the Physics but only the Mathematics, would it not be a welcome relief if we now have a Physics explanation to Malus Law?
I agree with you. It is only an opinion. And I believe they are mistaken. This is because they are unable to account logically what is involved in the phenomena of linear polarization that led to Malus Law. Since Quantum mechanics is not concerned with the Physics but only the Mathematics, would it not be a welcome relief if we now have a Physics explanation to Malus Law?
Hexa, dang near anything is a "quantum state." How can you maintain that linear polarization is a quantum state, or is based on a quantum state, yet maintain that continually changing linear polarization is not a quantum state? It's like saying that someone who drowned is dead, but not if you cremated the body after you hauled it out of the water.
And polarization is explicitly based on a quantum state; spin, to be precise, which is quantized. Circular polarization is merely a specification of how a particle can be in a state where measurements of spin can change over time. That's all it is, nothing more.
I have no disagreement that light must be in one quantum state or another. The point which I was trying to make is whether it is correct to state that there is a DISTINCT Quantum State when we pass light through a Circular Polarizer. By definition and construction, a circular polarizer is made of a linear polarizer followed by a quarter-wave plate. Quantum Mechanics define the light passing through a circular polarizer as either in the Right or Left circularly polarized state. Quantum Mechanics went on to make prediction similar to the prediction it makes for a linear polarizer. This is where I disagree. The prediction made by many authors including our revered Richard Feynman in his Lectures on Physics also made the same mistake. You simply cannot get the result predicted using Quantum Mechanics. This is the reason that led me to raise this question in this forum. I must thank you that I learn a lot from you since nobody else seem interested in this topic. But in spite of your explanation I find it hard to agree with you simply because the experiment that I have done does not yield the result predicted by Quantum Mechanics. You can try it yourself to see whether it works as well. My answer is that if the quarter-wave plate is placed after the linear polarizer, then all we have is a depolarized quantum state of light. If it is the other way, then the quantum state will be described by the polarizing axis of the linear polarizer. When I did the experiment based on this assumption, all the observation that I made in the various permutations with another circular polarizer and /or another linear polarizer-- they all agree with this assumption.
Sorry to use the analogy of “Lightning and Thunder”. But I am afraid the similarity is there. Quantum Mechanics was constructed from a position of ignorance (see remarks by Richard Feynman above) and not from a position of knowledge. That is why Werner Heisenberg call it the Uncertainty Principle. I have no problem with the MEASUREMENT Uncertainty that was originally proposed by Werner Heisenberg involving the simultaneous measurement of two complementary quantities, such as: position and momentum, or energy and time. Heisenberg was chided by Bohr for thinking only along the measurement difficulty. The Uncommon sense Uncertainty that we now learn from the Copenhagen Interpretation was needed after the attack of the EPR Experiment by Einstein, Podolsky and Rosen.
The simplicity of the account of the Double slit experiment that I mentioned above amused me on why these pioneers of Quantum Physics did not consider it but instead constructed a theory that is and remain incomprehensible to the common folks. But on further investigation, I realized that one of the major problems in Physics is our inability to account for another classical theory of physics, that is Magnetism. We had to use non-abelian mathematics instead of abelian mathematics which in itself is already a bit of a problem. The currently accepted description of magnetic field is already not directly associated with the charge that gives rise to the magnetic field. You will better appreciate what I am trying to say if you try drawing the magnetic field surrounding a moving charge. This is unlike what you can do for electric field where it must originate from the charge particle. Because of our inability to give a simple common sense explanation that uses abelian mathematics to determine the magnetic forces, we end up with the possibility that there could be monopoles as well as the possibility that there could be particles moving faster than the speed of light called, tachyons. The problem is larger than just magnetism. We have two major pillars at this point in time that govern Advanced Physics. They are the Quantum Theory and Einstein’s Theories of Relativity. Unfortunately, the rules that govern Quantum Theory are incompatible with Einstein’s Relativity. There are three main implications arising from the incompatibility:
1) Either Quantum Theory is right and Einstein’s Relativity is wrong;
2) Quantum Theory is wrong and Einstein’s Relativity is right or;
3) Both are wrong or at least partially wrong.
Thank you for agreeing that it is possible for me to communicate with you outside this forum. I have noted your reservation, and I fully concur with you that we should still continue with this thread to share with the community what we know but also what we may have mistaken that we know. It is definitely useful to let other experts following this thread who are wiser to help out in our discussion. But so far no one out there seem interested to talk anything about this topic. Being relatively new, I am not sure whether the administrator in Physorg.com allows us to exchange our email without losing our privacy? I will need your advice on this as I treasure my privacy as much as you do.
Cheers.
Thanks you for your response.
The reason I requested for communication outside the forum is because the forum is not the most appropriate vehicle to communicate huge amount of mathematics, graphics and other illustrations. It is simply too much to be posted in the forum page. Beside, you have said that the forum is a platform for general audience as well.
I am afraid that without the benefits of the same information that I am privy to, it is quite difficult to convince you on why I fervently object to the violation of Causality and Locality. To me it is fundamentally wrong. The information that I am privy to is not available in the public domain and as such I can’t provide you the link for you to access the said information.
You have cited existing literature that was build up over the last century. It is more than a century since Planck first proposed the Quantization of energy. But while Quantization of energy has led Einstein to assert that light is a particle through his account of the photoelectric effect, Einstein was unable to dissociate himself totally from the apron string of wave. He had to describe the energy of a photon as somehow intimately link to the properties of wave as it still needed wavelength (λ) and frequency (γ) in addition to the constant, h defined by Max Planck. The Quantum Theory that is currently integrated into the Standard Model, (practiced by physicists all over the world) was build on Quantum Mechanics (which is mathematics) rather than Physics. In the words of Richard Feynman, “Physics has given up” after he had described the phenomena relating to the passage of light and electrons through the Double Slits in his legendary Feynman Lectures on Physics. You are right to ask whether I could account for this:
QUOTE
Well, then you have a basic problem, because you cannot explain the results of the dual slit experiment performed with electrons.
Wrong. I could do that using a particle approach to account for all the phenomena that Richard Feynman had laboriously brought us through in his lecture.
QUOTE (->
| QUOTE |
| Well, then you have a basic problem, because you cannot explain the results of the dual slit experiment performed with electrons. |
Wrong. I could do that using a particle approach to account for all the phenomena that Richard Feynman had laboriously brought us through in his lecture.
If each electron goes through one slit or the other, how can you explain the fact that over time the impacts of the electrons make an interference pattern? And if the electrons go through both slits, as they must in order to make the observed interference pattern, how can you call them "particles?" A "particle" is here OR there, not BOTH.
I can account for the interference pattern using a particle approach not wave. I need not make a ridiculous assumption that an electron can somehow go through both slits at the same time.
QUOTE
You are applying logic that works in the everyday macroscopic world to quantum mechanics, where it simply does not apply. This is what you refer to as "common sense."
Have you consider the possibility that the treatment considered by the pioneers of Quantum Theory may have overlook some fine details that led them to the enigma. Have you ever consider the possibility that many of the information on the nanoworld that we have now weren’t available or even perceived then? Never will Bohr or Heisenberg or even Feynman be able to envisage the possibility that we could physically “see” the atom in three-dimensional space using a Scanning Tunneling Microscope (STM). If we can appreciate the existence of these atoms using common sense, is there a need for us to resort to uncommon sense?
QUOTE (->
| QUOTE |
| You are applying logic that works in the everyday macroscopic world to quantum mechanics, where it simply does not apply. This is what you refer to as "common sense." |
Have you consider the possibility that the treatment considered by the pioneers of Quantum Theory may have overlook some fine details that led them to the enigma. Have you ever consider the possibility that many of the information on the nanoworld that we have now weren’t available or even perceived then? Never will Bohr or Heisenberg or even Feynman be able to envisage the possibility that we could physically “see” the atom in three-dimensional space using a Scanning Tunneling Microscope (STM). If we can appreciate the existence of these atoms using common sense, is there a need for us to resort to uncommon sense?
That's what experiments are for. We have done a lot of them, and gathered a great deal of data. I realize that you are upset that the data point to conclusions you find distasteful, but the fact is that they do, and that means you're going to have to accept them, whether you like them or not.
Incorrect. I studied the claims of the Aspect Experiment very carefully and objectively based on the result that they have obtained. I have shown you that the claim was Non Locality. This is the basis for Quantum Entanglement. This is the claim that information can travel faster than light. In fact, the claim is even more preposterous. We can have instant communication not withstanding that we may be separated half a universe away. These are the claims.
What does the result of the Aspect Experiment tell us? They have obtained the intensity of the coincidence of photons based on Malus Law. It is only the existing (or according to you, All) Local Hidden Variable Models that failed to account for the result predicted by Malus Law. Period.
What if I tell you that I have a simple explanation that describe the polarizer as being made of atoms that are aligned in a certain direction and that the photons passing through the polarizers are also made of particles. And by applying these assumptions I could account for Malus Law stochastically without having to violate both Locality and Causality. My question to you is—If there is a simple common sense explanation using particles to account for Malus Law, do we still need to rely on violation of Locality and Causality to account for the Aspect Experiment?
QUOTE
As I have repeatedly said, Aspect implies causality violation- either direct, or indirect- by some means. It is the opinion of most physicists that this causality violation is such that it cannot be used for communication- but that is by no means certain, and no experiment that we have been able to imagine, much less conduct, can prove whether it is true or not.
I agree with you. It is only an opinion. And I believe they are mistaken. This is because they are unable to account logically what is involved in the phenomena of linear polarization that led to Malus Law. Since Quantum mechanics is not concerned with the Physics but only the Mathematics, would it not be a welcome relief if we now have a Physics explanation to Malus Law?
QUOTE (->
| QUOTE |
| As I have repeatedly said, Aspect implies causality violation- either direct, or indirect- by some means. It is the opinion of most physicists that this causality violation is such that it cannot be used for communication- but that is by no means certain, and no experiment that we have been able to imagine, much less conduct, can prove whether it is true or not. |
I agree with you. It is only an opinion. And I believe they are mistaken. This is because they are unable to account logically what is involved in the phenomena of linear polarization that led to Malus Law. Since Quantum mechanics is not concerned with the Physics but only the Mathematics, would it not be a welcome relief if we now have a Physics explanation to Malus Law?
Hexa, dang near anything is a "quantum state." How can you maintain that linear polarization is a quantum state, or is based on a quantum state, yet maintain that continually changing linear polarization is not a quantum state? It's like saying that someone who drowned is dead, but not if you cremated the body after you hauled it out of the water.
And polarization is explicitly based on a quantum state; spin, to be precise, which is quantized. Circular polarization is merely a specification of how a particle can be in a state where measurements of spin can change over time. That's all it is, nothing more.
I have no disagreement that light must be in one quantum state or another. The point which I was trying to make is whether it is correct to state that there is a DISTINCT Quantum State when we pass light through a Circular Polarizer. By definition and construction, a circular polarizer is made of a linear polarizer followed by a quarter-wave plate. Quantum Mechanics define the light passing through a circular polarizer as either in the Right or Left circularly polarized state. Quantum Mechanics went on to make prediction similar to the prediction it makes for a linear polarizer. This is where I disagree. The prediction made by many authors including our revered Richard Feynman in his Lectures on Physics also made the same mistake. You simply cannot get the result predicted using Quantum Mechanics. This is the reason that led me to raise this question in this forum. I must thank you that I learn a lot from you since nobody else seem interested in this topic. But in spite of your explanation I find it hard to agree with you simply because the experiment that I have done does not yield the result predicted by Quantum Mechanics. You can try it yourself to see whether it works as well. My answer is that if the quarter-wave plate is placed after the linear polarizer, then all we have is a depolarized quantum state of light. If it is the other way, then the quantum state will be described by the polarizing axis of the linear polarizer. When I did the experiment based on this assumption, all the observation that I made in the various permutations with another circular polarizer and /or another linear polarizer-- they all agree with this assumption.
Sorry to use the analogy of “Lightning and Thunder”. But I am afraid the similarity is there. Quantum Mechanics was constructed from a position of ignorance (see remarks by Richard Feynman above) and not from a position of knowledge. That is why Werner Heisenberg call it the Uncertainty Principle. I have no problem with the MEASUREMENT Uncertainty that was originally proposed by Werner Heisenberg involving the simultaneous measurement of two complementary quantities, such as: position and momentum, or energy and time. Heisenberg was chided by Bohr for thinking only along the measurement difficulty. The Uncommon sense Uncertainty that we now learn from the Copenhagen Interpretation was needed after the attack of the EPR Experiment by Einstein, Podolsky and Rosen.
The simplicity of the account of the Double slit experiment that I mentioned above amused me on why these pioneers of Quantum Physics did not consider it but instead constructed a theory that is and remain incomprehensible to the common folks. But on further investigation, I realized that one of the major problems in Physics is our inability to account for another classical theory of physics, that is Magnetism. We had to use non-abelian mathematics instead of abelian mathematics which in itself is already a bit of a problem. The currently accepted description of magnetic field is already not directly associated with the charge that gives rise to the magnetic field. You will better appreciate what I am trying to say if you try drawing the magnetic field surrounding a moving charge. This is unlike what you can do for electric field where it must originate from the charge particle. Because of our inability to give a simple common sense explanation that uses abelian mathematics to determine the magnetic forces, we end up with the possibility that there could be monopoles as well as the possibility that there could be particles moving faster than the speed of light called, tachyons. The problem is larger than just magnetism. We have two major pillars at this point in time that govern Advanced Physics. They are the Quantum Theory and Einstein’s Theories of Relativity. Unfortunately, the rules that govern Quantum Theory are incompatible with Einstein’s Relativity. There are three main implications arising from the incompatibility:
1) Either Quantum Theory is right and Einstein’s Relativity is wrong;
2) Quantum Theory is wrong and Einstein’s Relativity is right or;
3) Both are wrong or at least partially wrong.
Thank you for agreeing that it is possible for me to communicate with you outside this forum. I have noted your reservation, and I fully concur with you that we should still continue with this thread to share with the community what we know but also what we may have mistaken that we know. It is definitely useful to let other experts following this thread who are wiser to help out in our discussion. But so far no one out there seem interested to talk anything about this topic. Being relatively new, I am not sure whether the administrator in Physorg.com allows us to exchange our email without losing our privacy? I will need your advice on this as I treasure my privacy as much as you do.
Cheers.
Hi hexa,
QUOTE (hexa+)
Thanks you for your response.
Sure.
QUOTE (hexa+)
The reason I requested for communication outside the forum is because the forum is not the most appropriate vehicle to communicate huge amount of mathematics, graphics and other illustrations. It is simply too much to be posted in the forum page. Beside, you have said that the forum is a platform for general audience as well.
I am afraid that without the benefits of the same information that I am privy to, it is quite difficult to convince you on why I fervently object to the violation of Causality and Locality. To me it is fundamentally wrong. The information that I am privy to is not available in the public domain and as such I can’t provide you the link for you to access the said information.
I am afraid that without the benefits of the same information that I am privy to, it is quite difficult to convince you on why I fervently object to the violation of Causality and Locality. To me it is fundamentally wrong. The information that I am privy to is not available in the public domain and as such I can’t provide you the link for you to access the said information.
You'll find a private message service which you can use to send me a private message if you feel the need to do so. I'll use it shortly to send you a quick message so that you'll be able to find it; look in the upper right-hand corner at the "new messages" link.
I should warn you in advance that I am quite likely to be highly skeptical of any theory of physics that has not been published in the peer-reviewed literature; this does not mean that I will not look at it fairly, but I don't want you thinking you're very likely to get an ally, and be disappointed or upset when I point out problems with it. Based on my preliminary review of the rest of your post, I see some pretty serious problems already, and I still don't think you've quite "gotten" how either polarization or interference works. I'm going to try explaining both again at appropriate points, and see if it helps; please don't take it amiss, and remember the larger audience who may be helped in understanding these phenomena by my descriptions, even if they don't help you or forward your ideas.
I should warn you in advance that I am quite likely to be highly skeptical of any theory of physics that has not been published in the peer-reviewed literature; this does not mean that I will not look at it fairly, but I don't want you thinking you're very likely to get an ally, and be disappointed or upset when I point out problems with it. Based on my preliminary review of the rest of your post, I see some pretty serious problems already, and I still don't think you've quite "gotten" how either polarization or interference works. I'm going to try explaining both again at appropriate points, and see if it helps; please don't take it amiss, and remember the larger audience who may be helped in understanding these phenomena by my descriptions, even if they don't help you or forward your ideas.
QUOTE (hexa+)
You have cited existing literature that was build up over the last century. It is more than a century since Planck first proposed the Quantization of energy. But while Quantization of energy has led Einstein to assert that light is a particle through his account of the photoelectric effect, Einstein was unable to dissociate himself totally from the apron string of wave. He had to describe the energy of a photon as somehow intimately link to the properties of wave as it still needed wavelength (λ) and frequency (γ) in addition to the constant, h defined by Max Planck.
The reason for this is because light exhibits a singularly un-particle-like behavior, the behavior of interference. Let me explain why it is that interference is un-particle-like.
Interference is a wave phenomenon. It is safe to say that anytime we observe interference, we are observing waves. The reason is because interference allows cancellation. This means that when we add two things together, we get nothing. It's not merely difficult, but impossible, to describe how one might add a photon to a photon and get no photon. It would violate conservation of energy, for starters; you'd start with some energy (two photons) and end up with no energy (no photons), and there's nowhere for the energy to go. On the other hand, adding the crest of one wave to the trough of another obviously results in cancellation, and there is no need to question where the energy went; the vector of the crest is up, the vector of the trough is down, their magnitudes are equal, and the addition of equal and opposite vectors yields zero.
So, basically, there is no known explanation for interference based solely upon the particle (photon) nature of light. All explanations for the interference of light from two sources depend upon the interference of waves. This is explicit when the wave description of light is used, but it is also implicit in the Schroedinger equation which describes the propagation of the photons, and their probability to manifest at one or another location. Consider carefully:
In the dual slit experiment, if I close one slit, I get an even distribution of photons across the screen, brightest opposite the open slit (because the screen is flat and this is the closest point to the light source, and light falls off as the square of the distance). If I close that slit and open the other, I get the same thing, except the brightest part of the screen is now opposite the newly opened slit. If I assume that light is particles, I can easily explain this; the particles pass through the slit, and spread out in all directions from there. Since they spread in all directions in 3D space, the number of particles per unit area varies as the inverse of the square of the distance from the source; thus, more particles hit the screen opposite the open slit, and the number falls off smoothly as we move away from the slit.
Now we open the second slit without closing the first. What do we expect to happen?
Even supposing that the particles can interact, bouncing off one another, we still expect two bright areas opposite the two slits, with the brightness tapering off as we move away from those areas. In other words, just the direct addition of the two original patterns. This is what we should see if light is made of particles.
So, is this what we see? No. What we see instead is a series of stripes of light and dark areas, with the brightest and darkest stripes opposite the two slits.
Our particle hypothesis has failed; its predictions do not duplicate the results of our experiment. We must therefore discard it, and try another hypothesis. Is there another credible hypothesis, which does yield predictions that duplicate the results of our experiment? Yes. The hypothesis that light is made up of waves rather than particles yields the prediction that the waves will form standing waves, and standing interference patterns, and the stripes of light and darkness are precisely what we expect to see. And because this hypothesis postdicts our experimental result, we see that light explicitly shows wave-like behavior.
This experiment was first performed by Thomas Young, the same who was the discoverer of the Young Modulus which is used to describe the elasticity of materials. Young performed this experiment at the beginning of the Nineteenth Century.
Because of the outcome of this experiment, Einstein and Planck both knew that the photons they proposed had to have some very odd properties indeed; that they could not be classical particles was immediately obvious to anyone familiar with Young's experiment, which was essentially all physicists.
Furthermore, the frequency and wavelength of light are not some abstract quantity that has no connection to real-world phenomena; in fact, the frequency and wavelength of light are easily measured, and doing so is a scientifically trivial task. Instructions for doing this are available here. You can do this for less than $20US.
Now, how can a particle have a wavelength?
Clearly, light has some very odd properties; and it is precisely these that led to the fact that, as you put it, "Einstein was unable to dissociate himself totally from the apron string of wave." This "apron string" is the outcome of physical experiment, repeatable by anyone, and leading unambiguously to the conclusion that light behaves like waves.
What Einstein and Planck showed is that light ALSO behaves like particles, under certain circumstances. For example, Planck explained the fact that blackbodies do not radiate all their energy in a flash in the far ultraviolet (a result consequent upon the wave theory of light, referred to by Lord Kelvin as the "ultraviolet catastrophe") by assuming that energy "builds up" and is radiated as individual "quanta." Physicists were reluctant to accept this explanation due to the results of Young's experiment almost a hundred years earlier, but when Einstein explained previously unaccounted-for details of the photoelectric effect using the same assumption of "quanta," the argument was essentially over. Einstein won a Nobel Prize for this.
Interference is a wave phenomenon. It is safe to say that anytime we observe interference, we are observing waves. The reason is because interference allows cancellation. This means that when we add two things together, we get nothing. It's not merely difficult, but impossible, to describe how one might add a photon to a photon and get no photon. It would violate conservation of energy, for starters; you'd start with some energy (two photons) and end up with no energy (no photons), and there's nowhere for the energy to go. On the other hand, adding the crest of one wave to the trough of another obviously results in cancellation, and there is no need to question where the energy went; the vector of the crest is up, the vector of the trough is down, their magnitudes are equal, and the addition of equal and opposite vectors yields zero.
So, basically, there is no known explanation for interference based solely upon the particle (photon) nature of light. All explanations for the interference of light from two sources depend upon the interference of waves. This is explicit when the wave description of light is used, but it is also implicit in the Schroedinger equation which describes the propagation of the photons, and their probability to manifest at one or another location. Consider carefully:
In the dual slit experiment, if I close one slit, I get an even distribution of photons across the screen, brightest opposite the open slit (because the screen is flat and this is the closest point to the light source, and light falls off as the square of the distance). If I close that slit and open the other, I get the same thing, except the brightest part of the screen is now opposite the newly opened slit. If I assume that light is particles, I can easily explain this; the particles pass through the slit, and spread out in all directions from there. Since they spread in all directions in 3D space, the number of particles per unit area varies as the inverse of the square of the distance from the source; thus, more particles hit the screen opposite the open slit, and the number falls off smoothly as we move away from the slit.
Now we open the second slit without closing the first. What do we expect to happen?
Even supposing that the particles can interact, bouncing off one another, we still expect two bright areas opposite the two slits, with the brightness tapering off as we move away from those areas. In other words, just the direct addition of the two original patterns. This is what we should see if light is made of particles.
So, is this what we see? No. What we see instead is a series of stripes of light and dark areas, with the brightest and darkest stripes opposite the two slits.
Our particle hypothesis has failed; its predictions do not duplicate the results of our experiment. We must therefore discard it, and try another hypothesis. Is there another credible hypothesis, which does yield predictions that duplicate the results of our experiment? Yes. The hypothesis that light is made up of waves rather than particles yields the prediction that the waves will form standing waves, and standing interference patterns, and the stripes of light and darkness are precisely what we expect to see. And because this hypothesis postdicts our experimental result, we see that light explicitly shows wave-like behavior.
This experiment was first performed by Thomas Young, the same who was the discoverer of the Young Modulus which is used to describe the elasticity of materials. Young performed this experiment at the beginning of the Nineteenth Century.
Because of the outcome of this experiment, Einstein and Planck both knew that the photons they proposed had to have some very odd properties indeed; that they could not be classical particles was immediately obvious to anyone familiar with Young's experiment, which was essentially all physicists.
Furthermore, the frequency and wavelength of light are not some abstract quantity that has no connection to real-world phenomena; in fact, the frequency and wavelength of light are easily measured, and doing so is a scientifically trivial task. Instructions for doing this are available here. You can do this for less than $20US.
Now, how can a particle have a wavelength?
Clearly, light has some very odd properties; and it is precisely these that led to the fact that, as you put it, "Einstein was unable to dissociate himself totally from the apron string of wave." This "apron string" is the outcome of physical experiment, repeatable by anyone, and leading unambiguously to the conclusion that light behaves like waves.
What Einstein and Planck showed is that light ALSO behaves like particles, under certain circumstances. For example, Planck explained the fact that blackbodies do not radiate all their energy in a flash in the far ultraviolet (a result consequent upon the wave theory of light, referred to by Lord Kelvin as the "ultraviolet catastrophe") by assuming that energy "builds up" and is radiated as individual "quanta." Physicists were reluctant to accept this explanation due to the results of Young's experiment almost a hundred years earlier, but when Einstein explained previously unaccounted-for details of the photoelectric effect using the same assumption of "quanta," the argument was essentially over. Einstein won a Nobel Prize for this.
QUOTE (hexa+)
QUOTE (Schneibster+)
Well, then you have a basic problem, because you cannot explain the results of the dual slit experiment performed with electrons.
Wrong. I could do that using a particle approach to account for all the phenomena that Richard Feynman had laboriously brought us through in his lecture.
To state that one can do so is one thing; to actually do it another. Please elucidate. In exhaustive detail.
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Never will Bohr or Heisenberg or even Feynman be able to envisage the possibility that we could physically “see” the atom in three-dimensional space using a Scanning Tunneling Microscope (STM). If we can appreciate the existence of these atoms using common sense, is there a need for us to resort to uncommon sense?
You can't see anything with an STM. The images are computer-generated, not direct vision or even the indirect images produced in TEMs and SEMs (a TEM generates the image by the action (or lack of it) of the electrons on a phosphor screen; an SEM is more indirect, and counts the electrons at each point of dwell, then displays a dot on a CRT whose brightness is based on the electron count at that point). In an STM, the data that are shown are a combination of the electron count and the piezoelectrically measured position of the tip of the needle over the sample. This is highly indirect, much closer to a computer representation of a measurement than anything that one might call "seeing" with any degree of accuracy. Not only that, but the very idea the STM is based on is that electrons can tunnel from one electrode to another without traversing the space between- thus, its name. This is an explicitly quantum-mechanical phenomenon, not supported by any classical particle description of the electron. And most importantly, to correctly calculate the tunneling and its effects you have to have- wait for it- the WAVELENGTH OF THE ELECTRONS. Note as well that this is also true of the SEM and TEM.
So, if electrons can have wavelengths, then what's wrong with photons having them? And again, if they have wavelengths, how can they not be wave-like?
So, if electrons can have wavelengths, then what's wrong with photons having them? And again, if they have wavelengths, how can they not be wave-like?
QUOTE (hexa+)
QUOTE (Schneibster+)
That's what experiments are for. We have done a lot of them, and gathered a great deal of data. I realize that you are upset that the data point to conclusions you find distasteful, but the fact is that they do, and that means you're going to have to accept them, whether you like them or not.
Incorrect. I studied the claims of the Aspect Experiment very carefully and objectively based on the result that they have obtained. I have shown you that the claim was Non Locality.
No, you haven't. The claim is and always was EITHER non-locality OR non-(local realism), NOT non-locality only. I cannot stress this enough. I also cannot stress enough that the majority of physicists believe that local realism is violated, not locality. To claim otherwise, on either count, is a misrepresentation of the facts.
QUOTE (hexa+)
This is the basis for Quantum Entanglement.
No, it's not. The basis for quantum entanglement is the existence of conservation laws. Entanglement is implicit in the fact that you can't directly observe a violation of a conservation law, even when the entity that originally carried the conserved quantity no longer exists. The quantities must still exist in the consequent entities, and there must be consequent entities to carry them. If there is more than one consequent entity, then those consequents are entangled until they are measured.
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This is the claim that information can travel faster than light.
No, it's not. The information is carried by the entities as parameters with conserved values. Those entities cannot travel faster than light, and therefore the information they carry in their parameter values cannot travel faster than light.
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In fact, the claim is even more preposterous. We can have instant communication not withstanding that we may be separated half a universe away. These are the claims.
No, they aren't. The claim according to the majority of physicists is that conservation laws can be violated as long as we can't directly observe it happening. This is the failure of local realism, not the failure of locality.
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What does the result of the Aspect Experiment tell us? They have obtained the intensity of the coincidence of photons based on Malus Law. It is only the existing (or according to you, All) Local Hidden Variable Models that failed to account for the result predicted by Malus Law. Period.
Correct; that is the failure of local realism. I'm sorry, I don't see how this serves as justification for anything you said above.
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What if I tell you that I have a simple explanation that describe the polarizer as being made of atoms that are aligned in a certain direction and that the photons passing through the polarizers are also made of particles. And by applying these assumptions I could account for Malus Law stochastically without having to violate both Locality and Causality.
In fact, the spin and orbital angular momenta of the photons, electrons, and atoms, and their linear momenta, account easily for the two extrema: photons interacting with atoms/electrons that have the same spin, and the opposite spin. The tricky part comes when you must account for the fact that the spin in a different axis from that of the initial polarizer is related to the angle between the axes by the cosine squared function. This is a result of the fact that we are not actually measuring the spin of a particle; what we are measuring is the component of that spin in the axis of measurement. Thus, we have to use the cosine squared to obtain the relationship between the components.
Why must it be a cosine squared function? Because that is the function that gives the relationship of angular momentum components along different axes, of course. This is just as true of spinning planets or spinning ball bearings as it is of photons. Feel free to verify that this is the equation used to calculate the vector descriptions of the angular momenta in this situation.
What we see here is that Malus' Law is postdicted by the laws governing the relationships between components of angular momentum measured on different axes. These laws are not derived from Malus' Law; they are consequences of the fact that we live in a relativistic universe. And note most carefully that the mathematics of the spinor are derived, not from Malus' Law, but from relativity. Malus' Law is empirical; but the use of the cosine squared function to calculate the possible spin angular momentum components on different axes, given a known value on one axis, is derived from the geometry of spacetime, not from Malus' Law.
Then we look into the electromagnetic field, using Maxwell's equations, which have nothing to do with Malus' Law- and we find that if we consider the alignment of the electric field vector when measured in different directions, we get exactly the same amount of extinction as predicted by Malus' Law using Maxwell's equations too.
Why must it be a cosine squared function? Because that is the function that gives the relationship of angular momentum components along different axes, of course. This is just as true of spinning planets or spinning ball bearings as it is of photons. Feel free to verify that this is the equation used to calculate the vector descriptions of the angular momenta in this situation.
What we see here is that Malus' Law is postdicted by the laws governing the relationships between components of angular momentum measured on different axes. These laws are not derived from Malus' Law; they are consequences of the fact that we live in a relativistic universe. And note most carefully that the mathematics of the spinor are derived, not from Malus' Law, but from relativity. Malus' Law is empirical; but the use of the cosine squared function to calculate the possible spin angular momentum components on different axes, given a known value on one axis, is derived from the geometry of spacetime, not from Malus' Law.
Then we look into the electromagnetic field, using Maxwell's equations, which have nothing to do with Malus' Law- and we find that if we consider the alignment of the electric field vector when measured in different directions, we get exactly the same amount of extinction as predicted by Malus' Law using Maxwell's equations too.
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My question to you is—If there is a simple common sense explanation using particles to account for Malus Law, do we still need to rely on violation of Locality and Causality to account for the Aspect Experiment?
The known explanations for Malus' Law are geometric and electrical. Neither is simple; one derives from Maxwell's equations, and the other derives from the Special Theory of Relativity. You are welcome to present your explanation, in exhaustive detail as I said above.
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This is because they are unable to account logically what is involved in the phenomena of linear polarization that led to Malus Law. Since Quantum mechanics is not concerned with the Physics but only the Mathematics, would it not be a welcome relief if we now have a Physics explanation to Malus Law?
But we have not merely one but two explanations of Malus' Law. Fully consistent with relativity, fully consistent with Maxwell's equations, and fully consistent with quantization. And unfortunately for you fully consistent with Heisenberg's uncertainty principle, as well. That the explanation cannot be simple is obvious to anyone who considers the fact that it doesn't matter if you turn the analyzer left or right- when it reaches orthogonality, extinction is total.
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I have no disagreement that light must be in one quantum state or another. The point which I was trying to make is whether it is correct to state that there is a DISTINCT Quantum State when we pass light through a Circular Polarizer.
Plain and simple, linear polarization means that as the photon moves along, it maintains a single state of polarization. Elliptical polarization (of which circular polarization is a special case) means that as the photon moves along, it changes polarization in a regular fashion. How can a state that involves a changing value not be distinct from a state that involves that same value remaining static?
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By definition and construction, a circular polarizer is made of a linear polarizer followed by a quarter-wave plate. Quantum Mechanics define the light passing through a circular polarizer as either in the Right or Left circularly polarized state. Quantum Mechanics went on to make prediction similar to the prediction it makes for a linear polarizer. This is where I disagree. The prediction made by many authors including our revered Richard Feynman in his Lectures on Physics also made the same mistake.
I own the Red Books, volumes I II and III. Please state which book, give the page, and give a quote.
Your earlier writings make me believe that you still do not understand the nature of circular polarization, and I am not clear on what you claim QM predicts circularly polarized light will do that you do not observe, nor on what basis you claim QM predicts it. Please explain precisely what you mean:
1. What do you claim QM predicts about circularly polarized light?
2. What do you observe that you believe contradicts this prediction?
3. What reference on QM did you obtain this prediction from, and what exactly did it say?
The subject of the existence or non-existence of circularly polarized light is separate from the definition of a circular polarizer. Because of the characteristics of materials, it is impossible to construct an optical one-step circular polarizer. However, you should be aware that it is possible to construct a microwave antenna that projects circularly polarized microwaves, and that for maximum sensitivity to this signal, the receiving antenna must be of the same polarization. See this page.
Something else I want you to think about: what happens to the polarization state of circularly polarized light reflected from a mirror?
I have reviewed your statements in the next paragraph, and they are not illuminating on any of these three issues.
Your earlier writings make me believe that you still do not understand the nature of circular polarization, and I am not clear on what you claim QM predicts circularly polarized light will do that you do not observe, nor on what basis you claim QM predicts it. Please explain precisely what you mean:
1. What do you claim QM predicts about circularly polarized light?
2. What do you observe that you believe contradicts this prediction?
3. What reference on QM did you obtain this prediction from, and what exactly did it say?
The subject of the existence or non-existence of circularly polarized light is separate from the definition of a circular polarizer. Because of the characteristics of materials, it is impossible to construct an optical one-step circular polarizer. However, you should be aware that it is possible to construct a microwave antenna that projects circularly polarized microwaves, and that for maximum sensitivity to this signal, the receiving antenna must be of the same polarization. See this page.
Something else I want you to think about: what happens to the polarization state of circularly polarized light reflected from a mirror?
I have reviewed your statements in the next paragraph, and they are not illuminating on any of these three issues.
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Quantum Mechanics was constructed from a position of ignorance (see remarks by Richard Feynman above) and not from a position of knowledge. That is why Werner Heisenberg call it the Uncertainty Principle.
No, to both statements. QM does not state that we are ignorant; QM states that what quanta do is essentially different from what macroscopic objects do, and as a result we cannot imagine it because there are no exemplars. The uncertainty principle is not a statement about what we know, it is a statement about what we can know.
It is logically inconsistent to claim that Aspect can behave as it does, when you claim that both locality and local reality must be maintained.
It is logically inconsistent to claim that Aspect can behave as it does, when you claim that both locality and local reality must be maintained.
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our inability to account for another classical theory of physics, that is Magnetism
There is no problem accounting for magnetism. Magnetism is the relativistic effect on the electric force. In its simplest manifestation, magnetism appears as a pseudo-field that opposes the electric field, in interacting particles moving at relativistic speeds. Consider carefully the case of a pair of particles with electric charges interacting. We represent this as the coulomb force, attractive or repulsive depending on the values of the two charges, with a magnitude of the product of the sizes of the charges and the electric force constant, divided by the square of the distance between them. However, remember that force is mass times acceleration; that means that force is also momentum divided by time. What if, instead of being stationary in our frame of reference, the two particles are initially stationary with respect to one another, but are going past us at a significant fraction of the speed of light? One of the effects of such motion is time dilation. That means that the momentum change imposed by the force will take a longer time- and THAT means that the force will appear to be less. How can we account for that lessening of the force? Simple: we propose a counter-pseudo-force that opposes the coulomb force, and that is dependent upon the velocity of the particles relative to us. This pseudo-force is magnetism, in its simplest form.
Hi Schneibster,
Thank you for agreeing that I may communicate with you outside the forum page.
I have received your short message and have given my replies by stating my private email where we can communicate more effectively with the attachment of large files that are too cumbersome to be handled by the forum page. We will continue to engage one another in this forum.
I am under no illusion that you will be my ally immediately after reading some of these private articles. All I hope is that you remain critical and objective which is the reason why I am seeking further clarification from you based on the materials that I have but you are unaware of and are simply too voluminous to be posted in the forum. I truly respect your objectivity as well as your honesty to accept and acknowledge topics that may not be familiar to you and then do the necessary research to provide a superb account of all the questions that I have raised so far. You are a true scientist and will always have my respect as such.
In your last posting, you have said:
I think your statement “Interference is a wave phenomenon” is over generalized. Is an electron or a proton a wave?
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
I think your statement “Interference is a wave phenomenon” is over generalized. Is an electron or a proton a wave?
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
The reason is because interference allows cancellation. This means that when we add two things together, we get nothing. It's not merely difficult, but impossible, to describe how one might add a photon to a photon and get no photon. It would violate conservation of energy, for starters; you'd start with some energy (two photons) and end up with no energy (no photons), and there's nowhere for the energy to go.
In a traditional wave, where a disturbance at one point is carried by a medium (water, air or whatever) to another point, then there is nothing unusual about the cancellation of one wave with another. Without the medium, no sound or water wave will be transmitted. This was what motivated Michelson & Morley to search for the existence of such a medium we call ether. Unfortunately, it was proven beyond reasonable doubt that ether does not exist. In the case of an electron or a photon, it involves a physically REAL particle that is conveyed from one point to another through empty space (or space without a medium) just like a bullet would. In other words, if we have two weighing scales: one at position-1 and another at position-2. And if an electron were to be fired from position-1 to position-2, the scale at 1 will measure less mass while at position-2 it will measure more mass. Similarly, if photons are fired from 1 to 2, the same observation will also be observed. This is where we can infer that a photon is a particle that travel at the speed of light, c. Physically it is impossible for us to measure the mass of a photon directly because we cannot measure the charge e of photon in order to infer the mass base on the relationship, e/m that a mass spectrometer uses. But from the photoelectric effect, we can measure the energy gained by an electron upon receipt of a photon.
Next, if we were to do an experiment involving the transfer of sound energy from position-1 to position-2 using air as a medium, there will be no change of mass before and after the sound energy has been conveyed from position-1 to position-2. What I have described above is to highlight the major difference between a pure particle and a pure wave.
You were right to say that:
But does it occur to you that we may get it all wrong in the way we describe what is happening at the slits when a photon or an electron strike at either of the slits? Our sheer ignorance of what is happening at the slits has led us to this ridiculous conclusion that it must pass through both slits at the same time and not one photon or one electron at any one time in order for us to observe this interference fringes.
I find the invention of the electron-wave and photon-wave mind boggling purely for the purpose to explain the interference effect. It is worst than simply admitting that we don’t know. We are in fact turning logic and commonsense on its head.
If electron or photon is a wave, then I would have a number of questions to ask:
1) How long is this wave that constitute an electron or photon pulse?
2) What is the amplitude at each ends of the wave front?
3) At what angle must the wave front interact with one another in order to cancel one another?
4) If it is wave, then according to Fourier Transform a wave at one frequency can combine to produce another wave of a different frequency—Is this possible?
5) Apart from what waves allow and don’t allow, the actual experimental observation is that each electron (as well as photon) detected on the screen is one whole electron (and one whole photon) and not half an electron (or half a photon) at any point in time. In other words there is no mistaking that the electron (or photon) behaves as a particle when detected. How do we account for this observation?
In a Double slits experiment involving electrons: if we open slit-A only, the electrons will behave as if they are particles and no interference fringes will be observed. If we open slit-B and close slit-A, the same is observed as when only slit-A is opened. Even by opening both slits, the electrons will continue to behave like particles with no interference fringes being observed (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm ). The only time we can observe any interference fringes is when we carefully control the coherency of the electrons arriving at the double slits.
What exactly does coherency do that allow us to observe the interference fringe in an electron beam?
Before we do that, we need to understand what exactly is an electron beam. The beam of electrons can be viewed upon as a stream of particles. The displacement between one preceding electron and a succeeding electron will give rise to the wavelength of the electron stream. A higher energy electron beam will have closer interval between two sequential electrons (or shorter wavelength) compared with one that has a lower energy (or longer wavelength).
A coherent electron beam is one where the intervals between any two sequential electrons in the stream are maintained. In other words, the energy of the electron beam is maintained throughout the experiment to maintain constancy in frequency and hence the wavelength. Without this important condition, the electrons would very much behave like any particles would. No interference fringes will be observed.
Geometrically, you can work this out to determine for yourselves whether what I said is true or not.
In this respect, I think it was accurate for Richard Feynman to concluded out of desperation that electron and photon is NEITHER Wave nor Particle after he had accounted for the Double Slits Experiment and conceded that
But does it occur to you that we may get it all wrong in the way we describe what is happening at the slits when a photon or an electron strike at either of the slits? Our sheer ignorance of what is happening at the slits has led us to this ridiculous conclusion that it must pass through both slits at the same time and not one photon or one electron at any one time in order for us to observe this interference fringes.
I find the invention of the electron-wave and photon-wave mind boggling purely for the purpose to explain the interference effect. It is worst than simply admitting that we don’t know. We are in fact turning logic and commonsense on its head.
If electron or photon is a wave, then I would have a number of questions to ask:
1) How long is this wave that constitute an electron or photon pulse?
2) What is the amplitude at each ends of the wave front?
3) At what angle must the wave front interact with one another in order to cancel one another?
4) If it is wave, then according to Fourier Transform a wave at one frequency can combine to produce another wave of a different frequency—Is this possible?
5) Apart from what waves allow and don’t allow, the actual experimental observation is that each electron (as well as photon) detected on the screen is one whole electron (and one whole photon) and not half an electron (or half a photon) at any point in time. In other words there is no mistaking that the electron (or photon) behaves as a particle when detected. How do we account for this observation?
In a Double slits experiment involving electrons: if we open slit-A only, the electrons will behave as if they are particles and no interference fringes will be observed. If we open slit-B and close slit-A, the same is observed as when only slit-A is opened. Even by opening both slits, the electrons will continue to behave like particles with no interference fringes being observed (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm ). The only time we can observe any interference fringes is when we carefully control the coherency of the electrons arriving at the double slits.
What exactly does coherency do that allow us to observe the interference fringe in an electron beam?
Before we do that, we need to understand what exactly is an electron beam. The beam of electrons can be viewed upon as a stream of particles. The displacement between one preceding electron and a succeeding electron will give rise to the wavelength of the electron stream. A higher energy electron beam will have closer interval between two sequential electrons (or shorter wavelength) compared with one that has a lower energy (or longer wavelength).
A coherent electron beam is one where the intervals between any two sequential electrons in the stream are maintained. In other words, the energy of the electron beam is maintained throughout the experiment to maintain constancy in frequency and hence the wavelength. Without this important condition, the electrons would very much behave like any particles would. No interference fringes will be observed.
Geometrically, you can work this out to determine for yourselves whether what I said is true or not.
In this respect, I think it was accurate for Richard Feynman to concluded out of desperation that electron and photon is NEITHER Wave nor Particle after he had accounted for the Double Slits Experiment and conceded that
“Physics has given up. We do not know how to predict what would happen in a given circumstance, and we believe now that it is impossible...... It must be recognized that this is a retrenchment in our earlier ideal of understanding nature. It may be a backward step, but no one has seen a way to avoid it”.
I will next address the issue of linear polarizer and why it obey only Malus Law and not some explanations provided by ALL existing Local Hidden Variable Models that appear to rule out any Local Reality.
Does it ever occur to you that the Local Hidden Variable Models may have overlooked some crucial variable that render it useless in their account of this phenomenon?
I will show you how-- that using a stochastic model I could obtain a prediction comparable to Malus Law without having to violate Causality, Local Reality and Locality. In fact, my Model describes a linear polarizer as comprising atoms that are aligned in a certain directions as against a non linear polarizer that are randomly arranged. Further, it describes the photons as particles with certain axial orientations that are capable of being filtered into two distinct quantum states.
I continue to maintain that the faster than light communication (including instant communication) by many research articles including the one carried by Physorg.com is based on the violation of Locality based on Quantum Entanglement (a phenomenon predicted in the Copenhagen Interpretation that underpin Quantum Mechanics). Although the experiment that they rely upon (the most important being the Aspect Experiment) only support the violation of Local Reality or more specifically Causality, what was claimed was non locality.
On the topic of Circular Polarization of Light, I find that the prediction using Quantum Mechanics is contrary to what one may observe in many experiment using Circular Polarizers.
Richard Feynman in his Lectures on Physics (see Vol. III, pg.11-9 to pg.11-12.) described the circular polarized state via equation-11.34 as similar to the linearly polarized state via equation-11.35.
Although he did not state it explicitly what are the probabilities when you pass light through a combination of circular and linear polarizers, many authors of physics text state the predictions based on the suggestion by Richard Feynman see the table in this link (http://roxanne.roxanne.org/epr/qmS.html).
I hope with this clarification, you can now better appreciate why I had raised this topic in this forum at the beginning.
I look forward to you in providing me your personal email where it is a lot easier for me to communicate these materials that are not available in the public domain.
Cheers.
Thank you for agreeing that I may communicate with you outside the forum page.
I have received your short message and have given my replies by stating my private email where we can communicate more effectively with the attachment of large files that are too cumbersome to be handled by the forum page. We will continue to engage one another in this forum.
I am under no illusion that you will be my ally immediately after reading some of these private articles. All I hope is that you remain critical and objective which is the reason why I am seeking further clarification from you based on the materials that I have but you are unaware of and are simply too voluminous to be posted in the forum. I truly respect your objectivity as well as your honesty to accept and acknowledge topics that may not be familiar to you and then do the necessary research to provide a superb account of all the questions that I have raised so far. You are a true scientist and will always have my respect as such.
In your last posting, you have said:
QUOTE
The reason for this is because light exhibits a singularly un-particle-like behavior, the behavior of interference. Let me explain why it is that interference is un-particle-like.
Interference is a wave phenomenon. It is safe to say that anytime we observe interference, we are observing waves.
Interference is a wave phenomenon. It is safe to say that anytime we observe interference, we are observing waves.
I think your statement “Interference is a wave phenomenon” is over generalized. Is an electron or a proton a wave?
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
QUOTE (->
| QUOTE |
| The reason for this is because light exhibits a singularly un-particle-like behavior, the behavior of interference. Let me explain why it is that interference is un-particle-like. Interference is a wave phenomenon. It is safe to say that anytime we observe interference, we are observing waves. |
I think your statement “Interference is a wave phenomenon” is over generalized. Is an electron or a proton a wave?
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
The reason is because interference allows cancellation. This means that when we add two things together, we get nothing. It's not merely difficult, but impossible, to describe how one might add a photon to a photon and get no photon. It would violate conservation of energy, for starters; you'd start with some energy (two photons) and end up with no energy (no photons), and there's nowhere for the energy to go.
In a traditional wave, where a disturbance at one point is carried by a medium (water, air or whatever) to another point, then there is nothing unusual about the cancellation of one wave with another. Without the medium, no sound or water wave will be transmitted. This was what motivated Michelson & Morley to search for the existence of such a medium we call ether. Unfortunately, it was proven beyond reasonable doubt that ether does not exist. In the case of an electron or a photon, it involves a physically REAL particle that is conveyed from one point to another through empty space (or space without a medium) just like a bullet would. In other words, if we have two weighing scales: one at position-1 and another at position-2. And if an electron were to be fired from position-1 to position-2, the scale at 1 will measure less mass while at position-2 it will measure more mass. Similarly, if photons are fired from 1 to 2, the same observation will also be observed. This is where we can infer that a photon is a particle that travel at the speed of light, c. Physically it is impossible for us to measure the mass of a photon directly because we cannot measure the charge e of photon in order to infer the mass base on the relationship, e/m that a mass spectrometer uses. But from the photoelectric effect, we can measure the energy gained by an electron upon receipt of a photon.
Next, if we were to do an experiment involving the transfer of sound energy from position-1 to position-2 using air as a medium, there will be no change of mass before and after the sound energy has been conveyed from position-1 to position-2. What I have described above is to highlight the major difference between a pure particle and a pure wave.
You were right to say that:
QUOTE
“how one might add a photon to a photon and get no photon”. It cannot. “It would violate conservation of energy”.
But does it occur to you that we may get it all wrong in the way we describe what is happening at the slits when a photon or an electron strike at either of the slits? Our sheer ignorance of what is happening at the slits has led us to this ridiculous conclusion that it must pass through both slits at the same time and not one photon or one electron at any one time in order for us to observe this interference fringes.
I find the invention of the electron-wave and photon-wave mind boggling purely for the purpose to explain the interference effect. It is worst than simply admitting that we don’t know. We are in fact turning logic and commonsense on its head.
If electron or photon is a wave, then I would have a number of questions to ask:
1) How long is this wave that constitute an electron or photon pulse?
2) What is the amplitude at each ends of the wave front?
3) At what angle must the wave front interact with one another in order to cancel one another?
4) If it is wave, then according to Fourier Transform a wave at one frequency can combine to produce another wave of a different frequency—Is this possible?
5) Apart from what waves allow and don’t allow, the actual experimental observation is that each electron (as well as photon) detected on the screen is one whole electron (and one whole photon) and not half an electron (or half a photon) at any point in time. In other words there is no mistaking that the electron (or photon) behaves as a particle when detected. How do we account for this observation?
In a Double slits experiment involving electrons: if we open slit-A only, the electrons will behave as if they are particles and no interference fringes will be observed. If we open slit-B and close slit-A, the same is observed as when only slit-A is opened. Even by opening both slits, the electrons will continue to behave like particles with no interference fringes being observed (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm ). The only time we can observe any interference fringes is when we carefully control the coherency of the electrons arriving at the double slits.
What exactly does coherency do that allow us to observe the interference fringe in an electron beam?
Before we do that, we need to understand what exactly is an electron beam. The beam of electrons can be viewed upon as a stream of particles. The displacement between one preceding electron and a succeeding electron will give rise to the wavelength of the electron stream. A higher energy electron beam will have closer interval between two sequential electrons (or shorter wavelength) compared with one that has a lower energy (or longer wavelength).
A coherent electron beam is one where the intervals between any two sequential electrons in the stream are maintained. In other words, the energy of the electron beam is maintained throughout the experiment to maintain constancy in frequency and hence the wavelength. Without this important condition, the electrons would very much behave like any particles would. No interference fringes will be observed.
Geometrically, you can work this out to determine for yourselves whether what I said is true or not.
In this respect, I think it was accurate for Richard Feynman to concluded out of desperation that electron and photon is NEITHER Wave nor Particle after he had accounted for the Double Slits Experiment and conceded that
QUOTE (->
| QUOTE |
| “how one might add a photon to a photon and get no photon”. It cannot. “It would violate conservation of energy”. |
But does it occur to you that we may get it all wrong in the way we describe what is happening at the slits when a photon or an electron strike at either of the slits? Our sheer ignorance of what is happening at the slits has led us to this ridiculous conclusion that it must pass through both slits at the same time and not one photon or one electron at any one time in order for us to observe this interference fringes.
I find the invention of the electron-wave and photon-wave mind boggling purely for the purpose to explain the interference effect. It is worst than simply admitting that we don’t know. We are in fact turning logic and commonsense on its head.
If electron or photon is a wave, then I would have a number of questions to ask:
1) How long is this wave that constitute an electron or photon pulse?
2) What is the amplitude at each ends of the wave front?
3) At what angle must the wave front interact with one another in order to cancel one another?
4) If it is wave, then according to Fourier Transform a wave at one frequency can combine to produce another wave of a different frequency—Is this possible?
5) Apart from what waves allow and don’t allow, the actual experimental observation is that each electron (as well as photon) detected on the screen is one whole electron (and one whole photon) and not half an electron (or half a photon) at any point in time. In other words there is no mistaking that the electron (or photon) behaves as a particle when detected. How do we account for this observation?
In a Double slits experiment involving electrons: if we open slit-A only, the electrons will behave as if they are particles and no interference fringes will be observed. If we open slit-B and close slit-A, the same is observed as when only slit-A is opened. Even by opening both slits, the electrons will continue to behave like particles with no interference fringes being observed (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm ). The only time we can observe any interference fringes is when we carefully control the coherency of the electrons arriving at the double slits.
What exactly does coherency do that allow us to observe the interference fringe in an electron beam?
Before we do that, we need to understand what exactly is an electron beam. The beam of electrons can be viewed upon as a stream of particles. The displacement between one preceding electron and a succeeding electron will give rise to the wavelength of the electron stream. A higher energy electron beam will have closer interval between two sequential electrons (or shorter wavelength) compared with one that has a lower energy (or longer wavelength).
A coherent electron beam is one where the intervals between any two sequential electrons in the stream are maintained. In other words, the energy of the electron beam is maintained throughout the experiment to maintain constancy in frequency and hence the wavelength. Without this important condition, the electrons would very much behave like any particles would. No interference fringes will be observed.
Geometrically, you can work this out to determine for yourselves whether what I said is true or not.
In this respect, I think it was accurate for Richard Feynman to concluded out of desperation that electron and photon is NEITHER Wave nor Particle after he had accounted for the Double Slits Experiment and conceded that
“Physics has given up. We do not know how to predict what would happen in a given circumstance, and we believe now that it is impossible...... It must be recognized that this is a retrenchment in our earlier ideal of understanding nature. It may be a backward step, but no one has seen a way to avoid it”.
I will next address the issue of linear polarizer and why it obey only Malus Law and not some explanations provided by ALL existing Local Hidden Variable Models that appear to rule out any Local Reality.
Does it ever occur to you that the Local Hidden Variable Models may have overlooked some crucial variable that render it useless in their account of this phenomenon?
I will show you how-- that using a stochastic model I could obtain a prediction comparable to Malus Law without having to violate Causality, Local Reality and Locality. In fact, my Model describes a linear polarizer as comprising atoms that are aligned in a certain directions as against a non linear polarizer that are randomly arranged. Further, it describes the photons as particles with certain axial orientations that are capable of being filtered into two distinct quantum states.
I continue to maintain that the faster than light communication (including instant communication) by many research articles including the one carried by Physorg.com is based on the violation of Locality based on Quantum Entanglement (a phenomenon predicted in the Copenhagen Interpretation that underpin Quantum Mechanics). Although the experiment that they rely upon (the most important being the Aspect Experiment) only support the violation of Local Reality or more specifically Causality, what was claimed was non locality.
On the topic of Circular Polarization of Light, I find that the prediction using Quantum Mechanics is contrary to what one may observe in many experiment using Circular Polarizers.
Richard Feynman in his Lectures on Physics (see Vol. III, pg.11-9 to pg.11-12.) described the circular polarized state via equation-11.34 as similar to the linearly polarized state via equation-11.35.
Although he did not state it explicitly what are the probabilities when you pass light through a combination of circular and linear polarizers, many authors of physics text state the predictions based on the suggestion by Richard Feynman see the table in this link (http://roxanne.roxanne.org/epr/qmS.html).
I hope with this clarification, you can now better appreciate why I had raised this topic in this forum at the beginning.
I look forward to you in providing me your personal email where it is a lot easier for me to communicate these materials that are not available in the public domain.
Cheers.
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Hi Schneibster,
Hi hexa.
QUOTE (hexa+)
I am under no illusion that you will be my ally immediately after reading some of these private articles. All I hope is that you remain critical and objective... I truly respect your objectivity as well as your honesty to accept and acknowledge topics that may not be familiar to you and then do the necessary research to provide a superb account of all the questions that I have raised so far. You are a true scientist and will always have my respect as such.
I truly appreciate the compliment you gave me here, but I want to be sure that you understand that I am not in fact trained as a scientist. What I am trained at is critical thinking; skepticism, if you will.
QUOTE (hexa+)
I think your statement “Interference is a wave phenomenon” is over generalized. Is an electron or a proton a wave?
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
But instead of saying we don’t know as what Richard Feynman had conceded, these giants of Science at the beginning of the 20th century invented a quantum theory to state that an electron or a proton or a photon is both a particle and a wave.
I gave the reasons why it is so quite clearly. I ask again, how does one "cancel out" a proton or electron? The simple answer is, "one doesn't." One can convert a proton and an antiproton, or an electron and an antielectron, into photons, by bringing the particle together with its antiparticle; but when a peak meets a trough, there is no conversion; neither exists any more. Wavelike behavior is essentially different from particlelike behavior in this respect, and this cancellation and its opposite- reinforcement- are responsible for interference. I'll also point out that there are no antielectrons in the Feynman version of the dual-slit experiment; how then does one add an electron to an electron to get no electrons? It's not merely counter-intuitive as uncertainty is; it's impossible.
I think that this is conclusive evidence that interference is a wavelike phenomenon, not supported by particlelike characteristics.
I think that this is conclusive evidence that interference is a wavelike phenomenon, not supported by particlelike characteristics.
QUOTE (hexa+)
In a traditional wave, where a disturbance at one point is carried by a medium (water, air or whatever) to another point, then there is nothing unusual about the cancellation of one wave with another. Without the medium, no sound or water wave will be transmitted. This was what motivated Michelson & Morley to search for the existence of such a medium we call ether. Unfortunately, it was proven beyond reasonable doubt that ether does not exist.
Essentially correct.
QUOTE (hexa+)
In the case of an electron or a photon, it involves a physically REAL particle that is conveyed from one point to another through empty space (or space without a medium) just like a bullet would.
Here is the problem: it's NOT "just like a bullet."
An essential point that you have missed is that the universe is not the same at all scales. For example, at speeds slow with respect to the speed of light, objects behave one way; at speeds fast with respect to the speed of light, objects behave in another way, and the way that fast objects behave can seem outrageous or illogical or paradoxical if all one has ever experienced is how slow objects behave. Another essential difference is in size. Objects that are big with respect to the size of an atom behave one way; objects that are small with respect to the size of an atom behave in another way, and the way that small objects behave can be seen as preposterous or illogical or incredible if all one has ever experienced is how big objects behave.
A "photon" or "electron" is an elementary object that is small, and has special characteristics that are essentially different from those of big objects, like bullets, dust motes, or planets. Some of these characteristics are wavelike, and some are particlelike. The "photon" or "electron" is indeed REAL. It shares some characteristics with a bullet, or a dust mote, or a planet, and we call these characteristics "particlelike." However, simply because it has some characteristics that are like those of a bullet, or a dust mote, or a planet, is not sufficient evidence to conclude that all of its characteristics are like those of a bullet, or a dust mote, or a planet. And in fact, in order for the universe to behave the way we see in our experiments it does, it is necessary that "photons" and "electrons" have characteristics that are distinctly un-particlelike; and specifically, that are wavelike.
You see, the thing that makes fast objects and slow objects behave differently is the nature of the spacetime they are embedded in. And this is also true of big and small objects. The most important thing to keep in mind about the difference between big and small objects is that as objects grow smaller and smaller, their characteristics grow more and more wavelike. In other words, bullets, dust motes, and planets have wavelike characteristics too; it's just that they are insignificant compared to the particlelike characteristics of these objects, due to their size. You can barely measure them for a dust mote, and by the time you're looking at something as big as a bullet, they're not measurable using our current technology; an entire planet is right out of the question. And it's no different for fast and slow objects; the laws of motion for slow objects turn out to be exactly the same as for fast objects, but we can't measure the relativistic effects of motion in slow objects, any more than we can measure the wavelike behavior of big objects.
In fact, EVERY OBJECT that is part of our ordinary, everyday experience is "big" in this sense. We simply don't encounter objects that are small enough to exhibit significant wavelike characteristics; they are too small for our senses to allow us to experience directly. As a result, the wavelike behavior of small objects is totally unfamiliar to us, and can seem paradoxical, unbelievable, or ridiculous.
But when we consider the behavior of objects like a light beam that are constituted of trillions upon trillions of small objects, photons, then we have to be able to describe that behavior in terms of the behavior of the constituents; and for such observable objects to behave the way they do, their constituents have to have these wavelike characteristics.
In truth, neither a photon nor an electron is either a wave or a particle. They are small, elementary physical objects, with real existence, but without the complete set of characteristics of either a wave or a particle. Instead, they have some characteristics of a wave, and some characteristics of a particle, but are neither a wave nor a particle. As far as we can tell, if we describe some characteristics as wavelike, some as particlelike, and some as both wavelike and particlelike, there are no characteristics left over to be explained. So the combination of the wavelike characteristics (but NOT all the characteristics of a wave, just some of them) and the particlelike characteristics (but, again, NOT all of the characteristics of a particle, just some of them) completely explains the behavior of these elementary physical objects, where neither of these descriptions is complete on its own.
Basically what you are doing here (as far as I can tell) is attempting to describe wavicles as particles, and they aren't particles. If someone were to attempt to describe wavicles as waves, they also would be incorrect. They are neither, and both. They are not waves, they are not particles; they are photons, or gluons, or weak bosons, or gravitons, or quarks, or leptons; they are wavicles, a new kind of thing that is neither a wave nor a particle but partakes of SOME of the characteristics of both. These elementary constituents of our universe must never be confused with the composite objects that we encounter in everyday life; they are essentially different, simply and solely because they are SMALL.
An essential point that you have missed is that the universe is not the same at all scales. For example, at speeds slow with respect to the speed of light, objects behave one way; at speeds fast with respect to the speed of light, objects behave in another way, and the way that fast objects behave can seem outrageous or illogical or paradoxical if all one has ever experienced is how slow objects behave. Another essential difference is in size. Objects that are big with respect to the size of an atom behave one way; objects that are small with respect to the size of an atom behave in another way, and the way that small objects behave can be seen as preposterous or illogical or incredible if all one has ever experienced is how big objects behave.
A "photon" or "electron" is an elementary object that is small, and has special characteristics that are essentially different from those of big objects, like bullets, dust motes, or planets. Some of these characteristics are wavelike, and some are particlelike. The "photon" or "electron" is indeed REAL. It shares some characteristics with a bullet, or a dust mote, or a planet, and we call these characteristics "particlelike." However, simply because it has some characteristics that are like those of a bullet, or a dust mote, or a planet, is not sufficient evidence to conclude that all of its characteristics are like those of a bullet, or a dust mote, or a planet. And in fact, in order for the universe to behave the way we see in our experiments it does, it is necessary that "photons" and "electrons" have characteristics that are distinctly un-particlelike; and specifically, that are wavelike.
You see, the thing that makes fast objects and slow objects behave differently is the nature of the spacetime they are embedded in. And this is also true of big and small objects. The most important thing to keep in mind about the difference between big and small objects is that as objects grow smaller and smaller, their characteristics grow more and more wavelike. In other words, bullets, dust motes, and planets have wavelike characteristics too; it's just that they are insignificant compared to the particlelike characteristics of these objects, due to their size. You can barely measure them for a dust mote, and by the time you're looking at something as big as a bullet, they're not measurable using our current technology; an entire planet is right out of the question. And it's no different for fast and slow objects; the laws of motion for slow objects turn out to be exactly the same as for fast objects, but we can't measure the relativistic effects of motion in slow objects, any more than we can measure the wavelike behavior of big objects.
In fact, EVERY OBJECT that is part of our ordinary, everyday experience is "big" in this sense. We simply don't encounter objects that are small enough to exhibit significant wavelike characteristics; they are too small for our senses to allow us to experience directly. As a result, the wavelike behavior of small objects is totally unfamiliar to us, and can seem paradoxical, unbelievable, or ridiculous.
But when we consider the behavior of objects like a light beam that are constituted of trillions upon trillions of small objects, photons, then we have to be able to describe that behavior in terms of the behavior of the constituents; and for such observable objects to behave the way they do, their constituents have to have these wavelike characteristics.
In truth, neither a photon nor an electron is either a wave or a particle. They are small, elementary physical objects, with real existence, but without the complete set of characteristics of either a wave or a particle. Instead, they have some characteristics of a wave, and some characteristics of a particle, but are neither a wave nor a particle. As far as we can tell, if we describe some characteristics as wavelike, some as particlelike, and some as both wavelike and particlelike, there are no characteristics left over to be explained. So the combination of the wavelike characteristics (but NOT all the characteristics of a wave, just some of them) and the particlelike characteristics (but, again, NOT all of the characteristics of a particle, just some of them) completely explains the behavior of these elementary physical objects, where neither of these descriptions is complete on its own.
Basically what you are doing here (as far as I can tell) is attempting to describe wavicles as particles, and they aren't particles. If someone were to attempt to describe wavicles as waves, they also would be incorrect. They are neither, and both. They are not waves, they are not particles; they are photons, or gluons, or weak bosons, or gravitons, or quarks, or leptons; they are wavicles, a new kind of thing that is neither a wave nor a particle but partakes of SOME of the characteristics of both. These elementary constituents of our universe must never be confused with the composite objects that we encounter in everyday life; they are essentially different, simply and solely because they are SMALL.
QUOTE (hexa+)
Next, if we were to do an experiment involving the transfer of sound energy from position-1 to position-2 using air as a medium, there will be no change of mass before and after the sound energy has been conveyed from position-1 to position-2. What I have described above is to highlight the major difference between a pure particle and a pure wave.
Ahhhhh, but here you are wrong. In fact, the object giving off the sound energy (and it is energy- kinetic energy, to be precise, added to the air that is being moved to make the longitudinal sound waves) MUST become very slightly lighter, unless the output of sound energy is balanced by an input of some other kind of energy; electricity, for example, which can make a piezoelectric crystal vibrate and make sound. Otherwise, where would the energy come from?
And the object that absorbs the sound must correspondingly become slightly heavier; in fact, what happens is that as it absorbs the sound, it gets heated up slightly, and that heat is represented as vibrations within the absorbing object; it can even be emitted as photons, when the atoms moving due to those vibrations decelerate elastically due to their connections to other atoms in the object, and due to this input of energy, the absorbing object gains some mass. Very delicate, sensitive experiments have confirmed the prediction that a hot object weighs more than that same object when it is cold, thus confirming the equivalence of mass and energy postulated in relativity, and also confirming the conservation of energy.
Thus we see that even a macroscopic wave can transmit energy from place to place. And that when energy is transmitted, so is mass.
And the object that absorbs the sound must correspondingly become slightly heavier; in fact, what happens is that as it absorbs the sound, it gets heated up slightly, and that heat is represented as vibrations within the absorbing object; it can even be emitted as photons, when the atoms moving due to those vibrations decelerate elastically due to their connections to other atoms in the object, and due to this input of energy, the absorbing object gains some mass. Very delicate, sensitive experiments have confirmed the prediction that a hot object weighs more than that same object when it is cold, thus confirming the equivalence of mass and energy postulated in relativity, and also confirming the conservation of energy.
Thus we see that even a macroscopic wave can transmit energy from place to place. And that when energy is transmitted, so is mass.
QUOTE (hexa+)
But does it occur to you that we may get it all wrong in the way we describe what is happening at the slits when a photon or an electron strike at either of the slits? Our sheer ignorance of what is happening at the slits has led us to this ridiculous conclusion that it must pass through both slits at the same time and not one photon or one electron at any one time in order for us to observe this interference fringes.
But, you see, here you are again, trying to say that a photon or electron is a particle, and it's not a particle. It's also not a wave. It's an elementary object that partakes of some but not all characteristics of each, but is neither. A wave can pass both slits without trouble; a particle cannot. A wavicle, apparently, can, as long as you don't localize it to one or the other; however, if you DO localize it, then the wavelike behavior (interference) disappears!
QUOTE (hexa+)
I find the invention of the electron-wave and photon-wave mind boggling purely for the purpose to explain the interference effect. It is worst than simply admitting that we don’t know. We are in fact turning logic and commonsense on its head.
There is no "invention" involved. It is observation: the electron and photon have some wavelike characteristics, and some particlelike characteristics. But to assert that they "must be" one or the other is simply incorrect. They are neither, but they have some characteristics of both. They are essentially different from objects in everyday life. You cannot force them into that mold; they don't fit. If you do, you leave out some of their most important characteristics; either way you try to force them.
QUOTE (hexa+)
1) How long is this wave that constitute an electron or photon pulse?
That depends upon how you try to measure it. An equally important question is, what precise frequency does it have? As it turns out, we can know the answer to one of these questions, or to the other, but not both. If you think about this "wave packet" model you are using (I am sure it is original in your mind, in other words that you haven't seen it elsewhere, but others have used similar constructs in popular science literature, for example Vincent Icke in The Force of Symmetry), then you will see that to determine the frequency with ultimate precision, you must have an infinite number of cycles; but if the wave is infinitely long, then what is its location? Similarly, to precisely locate the wave, you must have a limited number of cycles, and the convention would be that you would pick the middle-most cycle and announce that as it's "position;" note that the less cycles you have, the more precise that position is, since the actual position would go from the least first to the least last cycle. But now that you have limited the number of cycles, so that you can pick the "middle-most," you no longer precisely know the frequency; and the more precisely you can state the position, the less cycles you have, and thus the less you know about the frequency; if the wave has only one half of a cycle, it's position is precise, but how can a wave with only half a cycle be said to have a "frequency?" Its frequency is undefined; you don't have any information about it. You can know the precise position, or you can know the precise frequency, but you CAN'T KNOW BOTH AT THE SAME TIME.
Note that this is merely a demonstration of how uncertainty works; REAL uncertainty is an inherent characteristic of elementary physical constituents, and is one of their wavelike properties. Again, you should not confuse elementary physical constituents with either waves or particles; they are neither.
Note that this is merely a demonstration of how uncertainty works; REAL uncertainty is an inherent characteristic of elementary physical constituents, and is one of their wavelike properties. Again, you should not confuse elementary physical constituents with either waves or particles; they are neither.
QUOTE (hexa+)
2) What is the amplitude at each ends of the wave front?
If you insist upon this model, then the answer is, "infinitely small." In other words, the middle-most cycle has the highest amplitude, and that amplitude fades off more or less slowly depending upon exactly how you go about measuring it. If you precisely locate the wave, then no other cycle but the middle-most has an amplitude greater than zero, and you know nothing of its frequency, not having any other cycle to measure from.
QUOTE (hexa+)
3) At what angle must the wave front interact with one another in order to cancel one another?
Cancellation will occur whenever crest meets trough, whatever the angle. This is basic wave mechanics.
QUOTE (hexa+)
4) If it is wave, then according to Fourier Transform a wave at one frequency can combine to produce another wave of a different frequency—Is this possible?
Certainly, and in fact it is at the heart of spectroscopy. You must also remember that frequency is energy. And that energy is conserved, and quantized. If these combinations occur, then they must produce results that obey both quantization and conservation. A photon of incorrect energy to bring an electron to another quantized orbital from its current orbital will not be absorbed by that electron. Similarly, a photon of incorrect phase compared to the phase of the electron will not be absorbed. However, if the energy of the photon is right, and its phase is right at the moment it encounters the electron, then the electron will absorb it; the electron that was in the previous orbital will disappear, and an electron will appear in a higher orbital. The electron and photon have combined to create an electron of higher energy, just as two waves combine via the Fourier transform to create a wave of higher energy. In the Fourier transform, there is no quantization; so this combination proceeds under a different, but similar set of physical constraints.
How do we know this? Simple: Planck's calculations of the energy emitted by a blackbody sorted by frequency, and Einstein's analysis of the photoelectric effect.
How do we know this? Simple: Planck's calculations of the energy emitted by a blackbody sorted by frequency, and Einstein's analysis of the photoelectric effect.
QUOTE (hexa+)
5) Apart from what waves allow and don’t allow, the actual experimental observation is that each electron (as well as photon) detected on the screen is one whole electron (and one whole photon) and not half an electron (or half a photon) at any point in time. In other words there is no mistaking that the electron (or photon) behaves as a particle when detected. How do we account for this observation?
See above: quantization.
QUOTE (hexa+)
In a Double slits experiment involving electrons: if we open slit-A only, the electrons will behave as if they are particles and no interference fringes will be observed. If we open slit-B and close slit-A, the same is observed as when only slit-A is opened. Even by opening both slits, the electrons will continue to behave like particles with no interference fringes being observed (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm ). The only time we can observe any interference fringes is when we carefully control the coherency of the electrons arriving at the double slits.
No, not the coherency. You have misunderstood the point of the experiment. It is only when we have accumulated enough electron impacts that we can see the interference. And by either calculating the probability for different positions using the characteristics of the electron source and the characteristics of the slits and the characteristics of the detector, along with their arrangement in space, or by observing a sufficiently large number of electrons to empirically assign a probability to each point on the screen, we get the same results.
"Coherency" is a meaningless term when applied to individual electrons. It is also meaningless applied to fermions; only bosons display coherence. This is because of the laws of spin and statistics.
"Coherency" is a meaningless term when applied to individual electrons. It is also meaningless applied to fermions; only bosons display coherence. This is because of the laws of spin and statistics.
QUOTE (hexa+)
The displacement between one preceding electron and a succeeding electron will give rise to the wavelength of the electron stream.
Incorrect. Frequency and propagation speed give the wavelength of a single electron, as for all waves, and adding amplitude gives its energy. But again, you're trying to fit the wavicle peg into the particle hole, and it's not fitting.
QUOTE (hexa+)
A coherent electron beam is one where the intervals between any two sequential electrons in the stream are maintained. In other words, the energy of the electron beam is maintained throughout the experiment to maintain constancy in frequency and hence the wavelength. Without this important condition, the electrons would very much behave like any particles would. No interference fringes will be observed.
Then explain why it is that if I DON'T maintain that spacing- in other words, if I SPRAY electrons at random intervals, but all with the same energy, I STILL SEE INTERFERENCE, and (provided that everything but the spacing between the electrons is the same) I see EXACTLY the same spacing between fringes?
You have misunderstood coherence. It is not about the spacing between the entities, it is about the mono-energetic nature of the entities. Lasers, which produce coherent light, do not eject photons at regular intervals; the photons come out at random, because they come from random locations inside the lasing material, and thus take different amounts of time to reach the half-silvered end. This will be obvious when you consider that it is possible to make continuous-wave lasers, not just lasers that make a pulse.
You have misunderstood coherence. It is not about the spacing between the entities, it is about the mono-energetic nature of the entities. Lasers, which produce coherent light, do not eject photons at regular intervals; the photons come out at random, because they come from random locations inside the lasing material, and thus take different amounts of time to reach the half-silvered end. This will be obvious when you consider that it is possible to make continuous-wave lasers, not just lasers that make a pulse.
QUOTE (hexa+)
my Model describes a linear polarizer as comprising atoms that are aligned in a certain directions as against a non linear polarizer that are randomly arranged.
hexa, we have a problem here; "polarization" means that all the photons collectively represent an electric field oscillating in a single physical direction. "Random polarization" is a contradiction in terms.
QUOTE (hexa+)
I continue to maintain that the faster than light communication (including instant communication) by many research articles including the one carried by Physorg.com is based on the violation of Locality based on Quantum Entanglement (a phenomenon predicted in the Copenhagen Interpretation that underpin Quantum Mechanics). Although the experiment that they rely upon (the most important being the Aspect Experiment) only support the violation of Local Reality or more specifically Causality, what was claimed was non locality.
hexa, these are speculative articles. No FTL communication has been observed. It is impossible to rule out a GLOBAL hidden variable theory; but such a theory requires FTL transmission of information, in other words that the global hidden variable ACQUIRE the same value everywhere at the same time. And ALL FTL is a violation of causality.
QUOTE (hexa+)
On the topic of Circular Polarization of Light, I find that the prediction using Quantum Mechanics is contrary to what one may observe in many experiment using Circular Polarizers.
That is because what you call a "circular polarizer" doesn't take into account the direction in which a circular polarizer IS a circular polarizer, and the direction in which it IS NOT. You also don't take into account that because circular polarization is equivalent to linear polarization with an axis that rotates as the polarized light propagates, the interaction between circularly polarized light and a linear polarizer (technically, the first thing the light encounters is the polarizer, but the second is the analyzer, so I really should say "linear analyzer" here, but you get the idea) is dependent upon the location of the linear polarizer with respect to the phase of the circularly polarized light.
QUOTE (hexa+)
Richard Feynman in his Lectures on Physics (see Vol. III, pg.11-9 to pg.11-12.) described the circular polarized state via equation-11.34 as similar to the linearly polarized state via equation-11.35.
No, that's not what those equations show at all.
What 11.34 shows is that right- and left-handed circular polarizations can be described as combinations of x and y polarizations with their amplitudes 90 degrees out of phase; the orientations of x and y can be picked at random, provided they are orthogonal. In other words, at any point in space, the orientation of the plane of linear polarization of a right- or left-hand circularly polarized light will depend upon the phase of the two components; move forward or backward a bit, and the orientation will have rotated a bit. Which direction it changes in depends on whether it is left- or right-handed.
What 11.35 shows is that you can do the same thing backward: represent linear polarizations as combinations of right- and left-handed circular polarizations. Because both right- and left-handed circular polarizations change as the light propagates, and because they change oppositely, they will yield a constant linear polarization in terms of the |x> and |y> components.
He did not state at any point in section 11-4 (or any other section I can find) that they were similar; what he stated is the mathematical tautology (given those two sets of equations, 11.34 and 11.35) that either can be used as a basis for the complete description of polarized light (aside from elliptically polarized light; more general equations are needed for that, because the phase angle need not be 90 degrees; however, note well that although the math would be extremely complex, it would also be possible to take those more complicated equations, and show that linearly polarized light could be represented as any pair of left- and right-handed elliptically polarized states, provided they were conjugate states to one another).
Finally, note that at the end of section 11-4, on page 11-12, Feynman says, "So it is not exactly true that a circularly polarized photon looks the same for any set of axes. its phase (the phase relation of the right and left circularly polarized states keeps track of the x-direction (emphasis from the original)." This phase keeps track of the orientation of the angle of the linearly polarized equivalent at each point; as the phase changes, so does the angle.
I am not at all clear what you think Feynman was saying here, nor how that conflicts with your observations. Please be even more explicit in your statement that what he shows here is wrong.
What 11.34 shows is that right- and left-handed circular polarizations can be described as combinations of x and y polarizations with their amplitudes 90 degrees out of phase; the orientations of x and y can be picked at random, provided they are orthogonal. In other words, at any point in space, the orientation of the plane of linear polarization of a right- or left-hand circularly polarized light will depend upon the phase of the two components; move forward or backward a bit, and the orientation will have rotated a bit. Which direction it changes in depends on whether it is left- or right-handed.
What 11.35 shows is that you can do the same thing backward: represent linear polarizations as combinations of right- and left-handed circular polarizations. Because both right- and left-handed circular polarizations change as the light propagates, and because they change oppositely, they will yield a constant linear polarization in terms of the |x> and |y> components.
He did not state at any point in section 11-4 (or any other section I can find) that they were similar; what he stated is the mathematical tautology (given those two sets of equations, 11.34 and 11.35) that either can be used as a basis for the complete description of polarized light (aside from elliptically polarized light; more general equations are needed for that, because the phase angle need not be 90 degrees; however, note well that although the math would be extremely complex, it would also be possible to take those more complicated equations, and show that linearly polarized light could be represented as any pair of left- and right-handed elliptically polarized states, provided they were conjugate states to one another).
Finally, note that at the end of section 11-4, on page 11-12, Feynman says, "So it is not exactly true that a circularly polarized photon looks the same for any set of axes. its phase (the phase relation of the right and left circularly polarized states keeps track of the x-direction (emphasis from the original)." This phase keeps track of the orientation of the angle of the linearly polarized equivalent at each point; as the phase changes, so does the angle.
I am not at all clear what you think Feynman was saying here, nor how that conflicts with your observations. Please be even more explicit in your statement that what he shows here is wrong.
QUOTE (hexa+)
Although he did not state it explicitly what are the probabilities when you pass light through a combination of circular and linear polarizers, many authors of physics text state the predictions based on the suggestion by Richard Feynman see the table in this link (http://roxanne.roxanne.org/epr/qmS.html).
That page explicitly uses matrices, which in turn explicitly take phase into account. And you have not accounted for phase in your description of your observations. Describing circular (or elliptical) polarization in terms of linear polarization without taking phase into account ignores the most important differentiator between elliptical (the general case of which circular is a special case) and linear polarization, and it is no wonder that what you predict does not agree with what you observe as a result.
Hi Schneibster,
Thanks again for your comprehensive replies.
I fully appreciate your effort to try to explain these phenomena: Double slits Experiment, Linear Polarization and Circular Polarization of Light based on traditional physics text. But I have highlighted that these descriptions are based on something that according to Richard Feynman “Physics has given up… It may be a backward step, but no one has seen a way to avoid it”.
I am not holding it against contemporary physics or you. Prima facie quantum phenomena does appears to be counterintuitive as demonstrated by the Double slits Experiment. You had to use terms such as “wavicles” that I have difficulties finding this word even from a respectable Science Dictionary.
Primarily, you are correct to state that even if the electrons were to arrive at the slits one at a time, the electron will appear to “interfere” with one another to generate the interference pattern as reported in this article entitled Double Slits Experiment that appear in PhysicsWeb (http://physicsweb.org/articles/world/15/9/1) and another by Hitachi (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm).
Instead of providing you with a description on what I believe account for the Double Slits Experiment described in these sites, I will do it by asking you the following questions:
1) Does it occur to you that the electrons that are emitted do so in pairs and sequentially?
One could be in the spin up state, the other in the spin down state. It must also be stated that this is not an absolute condition (since parity can be violated) but one that is generally observed.
2) The next electron pairs in a stream of electrons can be found at the same time interval as between any two electrons in the pair or further apart that give the impression that it is random. Is this sufficient to describe the stream of electrons mentioned in the above sites that strike the Double Slits—One at a Time?
3) Does it occur to you that the electron pair if made to pass through two slits, will have a certain probability of intercepting one another?
For this to happen, the first electron passing through slit-A must be deflected towards the region where a second electron simply passes through slit-B without any deflection. The longer deflected path taken by the first electron [through slit-A] will allow the second sequential electron [through slit-B] the possibility to intercept one another. The position that the first electron intercepts the second is dependent on the displacement between the two electrons as well as the separation between the two slits.
4) Alternatively, if instead of passing the electrons pair through a double slits, we only open one slit. With one slit, is it still possible for the two electrons in the pair to ever intercept one another?
I believe the answer should be No.
5) If your answers to questions (1), (2) and (3) are positive, my next question is whether there could be a pattern showing regions where deflected electrons is most likely to be found and regions where it will not be found?
I believe your answer should be Yes, provided we can control the displacement of any electron pairs which is the de Broglie wavelength of a stream of electrons. The wavelength can be varied and is dependent on the electrical potential that is imposed on the electron source emitting the electrons.
6) If (5) is true, is it not possible that with a sufficiently large population of electrons that a pattern resembling the interference fringes be formed notwithstanding that only one electron (behaving like particle) may strike the screen one at a time?
Please provide me your comments before I even attempt to describe the Double Slits Experiment described by Richard Feynman in his Lectures on Physics.
I will also defer my discussion on Linear and Circular Polarization of Light for now.
Cheers.
Thanks again for your comprehensive replies.
I fully appreciate your effort to try to explain these phenomena: Double slits Experiment, Linear Polarization and Circular Polarization of Light based on traditional physics text. But I have highlighted that these descriptions are based on something that according to Richard Feynman “Physics has given up… It may be a backward step, but no one has seen a way to avoid it”.
I am not holding it against contemporary physics or you. Prima facie quantum phenomena does appears to be counterintuitive as demonstrated by the Double slits Experiment. You had to use terms such as “wavicles” that I have difficulties finding this word even from a respectable Science Dictionary.
Primarily, you are correct to state that even if the electrons were to arrive at the slits one at a time, the electron will appear to “interfere” with one another to generate the interference pattern as reported in this article entitled Double Slits Experiment that appear in PhysicsWeb (http://physicsweb.org/articles/world/15/9/1) and another by Hitachi (http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm).
Instead of providing you with a description on what I believe account for the Double Slits Experiment described in these sites, I will do it by asking you the following questions:
1) Does it occur to you that the electrons that are emitted do so in pairs and sequentially?
One could be in the spin up state, the other in the spin down state. It must also be stated that this is not an absolute condition (since parity can be violated) but one that is generally observed.
2) The next electron pairs in a stream of electrons can be found at the same time interval as between any two electrons in the pair or further apart that give the impression that it is random. Is this sufficient to describe the stream of electrons mentioned in the above sites that strike the Double Slits—One at a Time?
3) Does it occur to you that the electron pair if made to pass through two slits, will have a certain probability of intercepting one another?
For this to happen, the first electron passing through slit-A must be deflected towards the region where a second electron simply passes through slit-B without any deflection. The longer deflected path taken by the first electron [through slit-A] will allow the second sequential electron [through slit-B] the possibility to intercept one another. The position that the first electron intercepts the second is dependent on the displacement between the two electrons as well as the separation between the two slits.
4) Alternatively, if instead of passing the electrons pair through a double slits, we only open one slit. With one slit, is it still possible for the two electrons in the pair to ever intercept one another?
I believe the answer should be No.
5) If your answers to questions (1), (2) and (3) are positive, my next question is whether there could be a pattern showing regions where deflected electrons is most likely to be found and regions where it will not be found?
I believe your answer should be Yes, provided we can control the displacement of any electron pairs which is the de Broglie wavelength of a stream of electrons. The wavelength can be varied and is dependent on the electrical potential that is imposed on the electron source emitting the electrons.
6) If (5) is true, is it not possible that with a sufficiently large population of electrons that a pattern resembling the interference fringes be formed notwithstanding that only one electron (behaving like particle) may strike the screen one at a time?
Please provide me your comments before I even attempt to describe the Double Slits Experiment described by Richard Feynman in his Lectures on Physics.
I will also defer my discussion on Linear and Circular Polarization of Light for now.
Cheers.
Perphaps these definitions will help.
http://en.wikipedia.org/wiki/Wavicles
http://www.cosmiclight.com/ofquasarsandquanta/wavicles.htm
http://en.wikipedia.org/wiki/Wavicles
http://www.cosmiclight.com/ofquasarsandquanta/wavicles.htm
Hi hexa,
QUOTE (hexa+)
But I have highlighted that these descriptions are based on something that according to Richard Feynman “Physics has given up… It may be a backward step, but no one has seen a way to avoid it”.
Feynman is speaking of any attempt to explain elementary particles in terms of the way that we ordinarily understand "particles" to behave. What he is highlighting is the simple fact that the ONLY rational explanation we have of the behavior of things we can see and measure around us REQUIRES that elementary particles behave as I have described, in a way that is counter-intuitive based on the way that ordinary, everyday objects behave. Because this behavior is so counter-intuitive, the only reliable guide to it is the mathematics that describe it; attempting to describe it using natural language is very nearly impossible, because the assumptions about the behavior of objects that underlie all natural language are incompatible with the behavior of elementary particles.
For example, the concept of "where" an object is located assumes that each object will in fact have a precise location; however, elementary particles don't necessarily have a precise location at all times. Uncertainty tells us that the more precisely we know the momentum of an elementary particle, the less we know about its precise location, and Aspect tells us that this is not merely a matter of not being able to measure that location, but a matter of the particle not actually HAVING a precise location. In the face of this, physics indeed does "give up;" describing phenomena in natural language has no chance of succeeding at describing subatomic reality in the face of the failure of "where." But that doesn't mean physics can't describe it; it just means that we have to use a different language to describe it, and that language is mathematics. This is because the assumptions that underlie natural language are hidden, but the assumptions that underlie mathematics are explicit. It is thus far easier to describe events of this kind in mathematical language than in natural language. Clearly, it is possible to describe it in natural language, but only at the expense of logic, and only by violating the assumptions upon which natural language is built.
In fact, it is not merely necessary to the description of subatomic particles themselves that requires this violation of assumptions; it is also necessary to the description of their behavior. And if we attempt to describe that behavior in terms that do not violate those assumptions, then what we describe no longer resembles reality.
For example, the concept of "where" an object is located assumes that each object will in fact have a precise location; however, elementary particles don't necessarily have a precise location at all times. Uncertainty tells us that the more precisely we know the momentum of an elementary particle, the less we know about its precise location, and Aspect tells us that this is not merely a matter of not being able to measure that location, but a matter of the particle not actually HAVING a precise location. In the face of this, physics indeed does "give up;" describing phenomena in natural language has no chance of succeeding at describing subatomic reality in the face of the failure of "where." But that doesn't mean physics can't describe it; it just means that we have to use a different language to describe it, and that language is mathematics. This is because the assumptions that underlie natural language are hidden, but the assumptions that underlie mathematics are explicit. It is thus far easier to describe events of this kind in mathematical language than in natural language. Clearly, it is possible to describe it in natural language, but only at the expense of logic, and only by violating the assumptions upon which natural language is built.
In fact, it is not merely necessary to the description of subatomic particles themselves that requires this violation of assumptions; it is also necessary to the description of their behavior. And if we attempt to describe that behavior in terms that do not violate those assumptions, then what we describe no longer resembles reality.
QUOTE (hexa+)
1) Does it occur to you that the electrons that are emitted do so in pairs and sequentially?
a. What source do you cite that shows that this is the case not only for all electron sources that might be used in the experiment, but also for all photon sources that might be used? b. What does this have to do with the outcome of the experiment?
QUOTE (hexa+)
2) The next electron pairs in a stream of electrons can be found at the same time interval as between any two electrons in the pair or further apart that give the impression that it is random. Is this sufficient to describe the stream of electrons mentioned in the above sites that strike the Double Slits—One at a Time?
No. Whether the time between the successive emissions and passages through the slit of the electrons is truly random, or regular, the experiment works the same. Your ideas apparently do not explain that observed fact; certainly they have not so far, and you are attempting here to impose regularity on events that are known to be random, and that in fact must be random for reality to behave the way it does.
Please review the fluctuation theorem, and note that its conclusions have been supported by recent experiment. For those conclusions to be correct, the underlying reality must be truly random; any regularity in that underlying reality would impose conditions that would result in violation of the theorem's predictions about such behavior. Note that the Second Law of Thermodynamics emerges smoothly and naturally (mathematically speaking) from the fluctuation theorem, and note as well that it supports Liouville's Theorem. The evidence in favor of it being a correct description of reality is overwhelming. And since it is a theorem, it is subject to mathematical proof, and has been so proven.
Please review the fluctuation theorem, and note that its conclusions have been supported by recent experiment. For those conclusions to be correct, the underlying reality must be truly random; any regularity in that underlying reality would impose conditions that would result in violation of the theorem's predictions about such behavior. Note that the Second Law of Thermodynamics emerges smoothly and naturally (mathematically speaking) from the fluctuation theorem, and note as well that it supports Liouville's Theorem. The evidence in favor of it being a correct description of reality is overwhelming. And since it is a theorem, it is subject to mathematical proof, and has been so proven.
QUOTE (hexa+)
3) Does it occur to you that the electron pair if made to pass through two slits, will have a certain probability of intercepting one another?
What electron pair? I see conditions imposed on the experiment you have linked that prevent there from being more than one electron.
QUOTE (hexa+)
For this to happen, the first electron passing through slit-A must be deflected towards the region where a second electron simply passes through slit-B without any deflection.
How can the electron passing through slit B (assuming there is one, which as I have shown above contradicts the actual physical conditions of the experiment, but just for the sake of argument, let us suppose that it could be so) affect the electron passing through slit A without being itself affected? The very assertion of this possibility violates the known principles of electromagnetism, and also violates Newton's Third Law.
QUOTE (hexa+)
4) Alternatively, if instead of passing the electrons pair through a double slits, we only open one slit. With one slit, is it still possible for the two electrons in the pair to ever intercept one another?
I'm sorry, your argument here is unintelligible to me. Could you please try re-explaining it, preferably without violations of Newton's Laws or Maxwell's equations?
QUOTE (hexa+)
5) If your answers to questions (1), (2) and (3) are positive
They aren't.
QUOTE (hexa+)
6) If (5) is true
I don't agree that it is.
QUOTE (hexa+)
Please provide me your comments before I even attempt to describe the Double Slits Experiment described by Richard Feynman in his Lectures on Physics.
I will also defer my discussion on Linear and Circular Polarization of Light for now.
I will also defer my discussion on Linear and Circular Polarization of Light for now.
hexa, I'm having some basic problems here. The description you are hinting at violates basic principles of physics that go back four hundred some-odd years, to one of the greatest minds the human race has produced. While those laws have had to be updated as our knowledge has increased, they have never been overturned; and in fact, both relativity and quantum mechanics are required to reproduce them at ordinary everyday sizes and velocities; quite simply, because that is what we observe all around us.
Unless or until your ideas can accurately reproduce the results of known experiment, there can be no question of them being an accurate representation of reality. Denial of basic observable facts about the experiments invalidates your ideas; this is why I have repeatedly requested that you give details about precisely what you believe that quantum mechanics predicts about polarization; it is my opinion that your belief in this regard is incorrect, and I have attempted to show where previously in several posts without your ever agreeing. I have therefore elected to stop attempting to explain it until you present your argument, rather than merely referring to it. Please do so.
Unless or until your ideas can accurately reproduce the results of known experiment, there can be no question of them being an accurate representation of reality. Denial of basic observable facts about the experiments invalidates your ideas; this is why I have repeatedly requested that you give details about precisely what you believe that quantum mechanics predicts about polarization; it is my opinion that your belief in this regard is incorrect, and I have attempted to show where previously in several posts without your ever agreeing. I have therefore elected to stop attempting to explain it until you present your argument, rather than merely referring to it. Please do so.
Hi Schneibster,
Thanks again for your replies.
I think you make an excellent defence lawyer for Richard Feynman. Even an outright confession that “Physics has given up… It may be a backward step, but no one has seen a way to avoid it” is given a creative interpretation by you:
What he is highlighting is the simple fact that the ONLY rational explanation we have of the behavior of things we can see and measure around us REQUIRES that elementary particles behave as I have described, in a way that is counter-intuitive based on the way that ordinary, everyday objects behave.
I have no disagreement that a quantum particle, such as an electron or a proton is a particle that behaves differently from what a macro object would behave. A macro object will more or less obey Newton’s Laws of Motion but not an electron or a proton. A quantum particle such as an electron or proton will have an additional property call spin that is not found in most macro objects (that include a bullet to an entire planet or star). But spin can be introduced to a macro object like the spin of a billiard ball to the spin of the earth. This will make the direct application of Newtonian mechanics a little more complicated but not unsolvable. Similarly, I have no quarrel that the electron is a definite entity that has a unique mass and charge that would most probably have a shape and size. As particle, it must obey the Law of Conservation of Matter –that matter can neither be created nor destroyed. Similarly, I have no quarrel that the fastest speed that anything in Nature can travel is restricted by the speed of light, c. Similarly, I am not disagreeing that the velocity addition based on Newtonian Mechanics does not apply to particles that move at close to the speed of light.
Having described the attributes of what an electron (as a particle) would behave, we cannot then do a complete turn around that the electron must also behave as wave. If it is a wave, and we describe the electron wave as riding on some medium called ether or whatever, then it may appear to be a little more believable. No. First, the concept of ether has been proven to be irrevocably wrong by Michelson & Morley. Without the alibi of ether, we now suggest that it is possible that there is this so call Aharonov-Bohm field that pervade the universe. It acts as the vehicle to communicate information from one point in space to another instantly. This then form the basis of instant communication involving two quantum entangled entities. This is where we have difficulty trying to agree with what was claimed and what was proven by the Aspect Experiment that seek to establish the validity of this Aharonov-Bohm field.
I perceive the motivation behind the Aspect Experiment is to reestablish the validity of quantum weirdness of the Double slit experiment.
This is necessary if Quantum Mechanics that appears to be so useful in Science is to be believed as a correct theory in Science. This is something that the majority of the Science Community is not about to give up easily without a fight. You further mentioned:
I have no disagreement that a quantum particle, such as an electron or a proton is a particle that behaves differently from what a macro object would behave. A macro object will more or less obey Newton’s Laws of Motion but not an electron or a proton. A quantum particle such as an electron or proton will have an additional property call spin that is not found in most macro objects (that include a bullet to an entire planet or star). But spin can be introduced to a macro object like the spin of a billiard ball to the spin of the earth. This will make the direct application of Newtonian mechanics a little more complicated but not unsolvable. Similarly, I have no quarrel that the electron is a definite entity that has a unique mass and charge that would most probably have a shape and size. As particle, it must obey the Law of Conservation of Matter –that matter can neither be created nor destroyed. Similarly, I have no quarrel that the fastest speed that anything in Nature can travel is restricted by the speed of light, c. Similarly, I am not disagreeing that the velocity addition based on Newtonian Mechanics does not apply to particles that move at close to the speed of light.
Having described the attributes of what an electron (as a particle) would behave, we cannot then do a complete turn around that the electron must also behave as wave. If it is a wave, and we describe the electron wave as riding on some medium called ether or whatever, then it may appear to be a little more believable. No. First, the concept of ether has been proven to be irrevocably wrong by Michelson & Morley. Without the alibi of ether, we now suggest that it is possible that there is this so call Aharonov-Bohm field that pervade the universe. It acts as the vehicle to communicate information from one point in space to another instantly. This then form the basis of instant communication involving two quantum entangled entities. This is where we have difficulty trying to agree with what was claimed and what was proven by the Aspect Experiment that seek to establish the validity of this Aharonov-Bohm field.
I perceive the motivation behind the Aspect Experiment is to reestablish the validity of quantum weirdness of the Double slit experiment.
This is necessary if Quantum Mechanics that appears to be so useful in Science is to be believed as a correct theory in Science. This is something that the majority of the Science Community is not about to give up easily without a fight. You further mentioned:
the concept of "where" an object is located assumes that each object will in fact have a precise location; however, elementary particles don't necessarily have a precise location at all times. Uncertainty tells us that the more precisely we know the momentum of an elementary particle, the less we know about its precise location, and Aspect tells us that this is not merely a matter of not being able to measure that location, but a matter of the particle not actually HAVING a precise location.
If it is the difficulty arising from the physical measurement of both position and momentum, there is nothing abnormal about it since the measurement of one quantity will destroy the information that you can obtain of the other. But the type of Uncertainty that was needed after the attack of the EPR Experiment by Einstein and his colleague is something more incredible. A particle can be anywhere and everywhere in the universe at the same time. The observation of the particle in one corner of the universe will then remove the possibility of the same particle being observed any where else instantly. Such proposition to me is no better than a ridiculous jokes that one find in any science fiction.
The quantum weirdness that you are stating here as part of Science is simply based on something that we do not know as echoed by Richard Feynman which you appear to have difficulty to accept.
Instead of simply stating that we DON’T KNOW, these pioneers in Quantum Physics went ahead to describe using language that you claim:
all natural language are incompatible with the behavior of elementary particles
If so then why do we even bother to call it wave, wavicle or anything else? Don’t you think that any attempt to describe it any which way would be futile. It must fail by this definition according to you.
You went on to invoke the favorite defence of any Quantum physicists:
If so then why do we even bother to call it wave, wavicle or anything else? Don’t you think that any attempt to describe it any which way would be futile. It must fail by this definition according to you.
You went on to invoke the favorite defence of any Quantum physicists:
But that doesn't mean physics can't describe it; it just means that we have to use a different language to describe it, and that language is mathematics. This is because the assumptions that underlie natural language are hidden, but the assumptions that underlie mathematics are explicit. It is thus far easier to describe events of this kind in mathematical language than in natural language. Clearly, it is possible to describe it in natural language, but only at the expense of logic, and only by violating the assumptions upon which natural language is built.
We know that mathematics is only a tool. But by putting mathematics without resting on the foundation of Physics, don’t you think that it is like putting the cart before the horse.
Coming to the explanation for the Double Slits Experiment for electrons.
Thanks again for your replies.
I think you make an excellent defence lawyer for Richard Feynman. Even an outright confession that “Physics has given up… It may be a backward step, but no one has seen a way to avoid it” is given a creative interpretation by you:
QUOTE
What he is highlighting is the simple fact that the ONLY rational explanation we have of the behavior of things we can see and measure around us REQUIRES that elementary particles behave as I have described, in a way that is counter-intuitive based on the way that ordinary, everyday objects behave.
I have no disagreement that a quantum particle, such as an electron or a proton is a particle that behaves differently from what a macro object would behave. A macro object will more or less obey Newton’s Laws of Motion but not an electron or a proton. A quantum particle such as an electron or proton will have an additional property call spin that is not found in most macro objects (that include a bullet to an entire planet or star). But spin can be introduced to a macro object like the spin of a billiard ball to the spin of the earth. This will make the direct application of Newtonian mechanics a little more complicated but not unsolvable. Similarly, I have no quarrel that the electron is a definite entity that has a unique mass and charge that would most probably have a shape and size. As particle, it must obey the Law of Conservation of Matter –that matter can neither be created nor destroyed. Similarly, I have no quarrel that the fastest speed that anything in Nature can travel is restricted by the speed of light, c. Similarly, I am not disagreeing that the velocity addition based on Newtonian Mechanics does not apply to particles that move at close to the speed of light.
Having described the attributes of what an electron (as a particle) would behave, we cannot then do a complete turn around that the electron must also behave as wave. If it is a wave, and we describe the electron wave as riding on some medium called ether or whatever, then it may appear to be a little more believable. No. First, the concept of ether has been proven to be irrevocably wrong by Michelson & Morley. Without the alibi of ether, we now suggest that it is possible that there is this so call Aharonov-Bohm field that pervade the universe. It acts as the vehicle to communicate information from one point in space to another instantly. This then form the basis of instant communication involving two quantum entangled entities. This is where we have difficulty trying to agree with what was claimed and what was proven by the Aspect Experiment that seek to establish the validity of this Aharonov-Bohm field.
I perceive the motivation behind the Aspect Experiment is to reestablish the validity of quantum weirdness of the Double slit experiment.
This is necessary if Quantum Mechanics that appears to be so useful in Science is to be believed as a correct theory in Science. This is something that the majority of the Science Community is not about to give up easily without a fight. You further mentioned:
QUOTE (->
| QUOTE |
What he is highlighting is the simple fact that the ONLY rational explanation we have of the behavior of things we can see and measure around us REQUIRES that elementary particles behave as I have described, in a way that is counter-intuitive based on the way that ordinary, everyday objects behave. |
I have no disagreement that a quantum particle, such as an electron or a proton is a particle that behaves differently from what a macro object would behave. A macro object will more or less obey Newton’s Laws of Motion but not an electron or a proton. A quantum particle such as an electron or proton will have an additional property call spin that is not found in most macro objects (that include a bullet to an entire planet or star). But spin can be introduced to a macro object like the spin of a billiard ball to the spin of the earth. This will make the direct application of Newtonian mechanics a little more complicated but not unsolvable. Similarly, I have no quarrel that the electron is a definite entity that has a unique mass and charge that would most probably have a shape and size. As particle, it must obey the Law of Conservation of Matter –that matter can neither be created nor destroyed. Similarly, I have no quarrel that the fastest speed that anything in Nature can travel is restricted by the speed of light, c. Similarly, I am not disagreeing that the velocity addition based on Newtonian Mechanics does not apply to particles that move at close to the speed of light.
Having described the attributes of what an electron (as a particle) would behave, we cannot then do a complete turn around that the electron must also behave as wave. If it is a wave, and we describe the electron wave as riding on some medium called ether or whatever, then it may appear to be a little more believable. No. First, the concept of ether has been proven to be irrevocably wrong by Michelson & Morley. Without the alibi of ether, we now suggest that it is possible that there is this so call Aharonov-Bohm field that pervade the universe. It acts as the vehicle to communicate information from one point in space to another instantly. This then form the basis of instant communication involving two quantum entangled entities. This is where we have difficulty trying to agree with what was claimed and what was proven by the Aspect Experiment that seek to establish the validity of this Aharonov-Bohm field.
I perceive the motivation behind the Aspect Experiment is to reestablish the validity of quantum weirdness of the Double slit experiment.
This is necessary if Quantum Mechanics that appears to be so useful in Science is to be believed as a correct theory in Science. This is something that the majority of the Science Community is not about to give up easily without a fight. You further mentioned:
the concept of "where" an object is located assumes that each object will in fact have a precise location; however, elementary particles don't necessarily have a precise location at all times. Uncertainty tells us that the more precisely we know the momentum of an elementary particle, the less we know about its precise location, and Aspect tells us that this is not merely a matter of not being able to measure that location, but a matter of the particle not actually HAVING a precise location.
If it is the difficulty arising from the physical measurement of both position and momentum, there is nothing abnormal about it since the measurement of one quantity will destroy the information that you can obtain of the other. But the type of Uncertainty that was needed after the attack of the EPR Experiment by Einstein and his colleague is something more incredible. A particle can be anywhere and everywhere in the universe at the same time. The observation of the particle in one corner of the universe will then remove the possibility of the same particle being observed any where else instantly. Such proposition to me is no better than a ridiculous jokes that one find in any science fiction.
The quantum weirdness that you are stating here as part of Science is simply based on something that we do not know as echoed by Richard Feynman which you appear to have difficulty to accept.
Instead of simply stating that we DON’T KNOW, these pioneers in Quantum Physics went ahead to describe using language that you claim:
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all natural language are incompatible with the behavior of elementary particles
If so then why do we even bother to call it wave, wavicle or anything else? Don’t you think that any attempt to describe it any which way would be futile. It must fail by this definition according to you.
You went on to invoke the favorite defence of any Quantum physicists:
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all natural language are incompatible with the behavior of elementary particles |
If so then why do we even bother to call it wave, wavicle or anything else? Don’t you think that any attempt to describe it any which way would be futile. It must fail by this definition according to you.
You went on to invoke the favorite defence of any Quantum physicists:
But that doesn't mean physics can't describe it; it just means that we have to use a different language to describe it, and that language is mathematics. This is because the assumptions that underlie natural language are hidden, but the assumptions that underlie mathematics are explicit. It is thus far easier to describe events of this kind in mathematical language than in natural language. Clearly, it is possible to describe it in natural language, but only at the expense of logic, and only by violating the assumptions upon which natural language is built.
We know that mathematics is only a tool. But by putting mathematics without resting on the foundation of Physics, don’t you think that it is like putting the cart before the horse.
Coming to the explanation for the Double Slits Experiment for electrons.
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