Here is my take on the possibility of bringing cats back to life via quantum filtering. I believe that it is indeed possible, as is pretty much anything in the quantum world, for the cat's poisoned body to suddenly realize that it doesn't "want" to be dead anymore and to revert back to a living state. The study of quantum mechanics has certainly proved that stranger things can and have happened. However, one fundamental truth that quantum mechanics also teaches is that all of existence is ruled, at least at the subatomic level, by probability which means that although theoretically possible, the outcome of a dead cat suddenly jumping back to life is so ridiculously improbable that if you lived for trillions of years you could still count yourself extremely lucky to ever see a single resurrected cat.
The thought experiment put forth by Frederik Belinfante is based on a simplified model of quantum behavior and is meant only to inspire creative thought on the subject. I say that his example is oversimplified because it assumes that we can treat the cat as a quantum object but this is not true. A cat is most certainly a classical object which is not subject to quantum weirdness like random teleportation or interference. This is because the cat has what I like to call high "quantum inertia". This means that even though the atoms which make up the cat are subject to quantum weirdness and so are governed entirely by probability, their quantum tendencies are suppressed so much by external "pressures" that they become essentially classical particles, at least as far as any human observer can tell.
What I mean by external "pressures" is that there a vast number of factors, external to any individual atom, that serve to push the atom's wave function towards a certain probability distribution. For example, there are inter-atomic forces which hold the atoms together into the shape of a cat. These forces affect the atoms' wave functions by constraining their individual positions to extremely localized points in space. The result is that any person with a sufficiently powerful microscope can look at an atom in the cat's body and see a discrete particle rather than a smeared quantum entity.
Now, going higher up in the cat's structure we come to the cells. Cells are made up of atoms and so we should expect that, in theory, they should be subject to the same rules. Well they are, except that cells are a little less quantum and a little more classical than are individual atoms. So just as the atoms which make up the cells are subject to external "pressures" so too are the cells themselves. In the case of a cat who has previously been killed via Schrodinger's Experiment, there is immense pressure on the cat's cells to remain dead. This pressure arises from the fact that the cat has already been known to be entirely dead. Its cells have died and shut down and so its body is no longer trying to maintain itself. In essence, there is no pressure on the cells to stay alive. So since there is high pressure to stay dead and no pressure to return to life, the probability distributions describing the cells' futures as living or dead entities is shifted so that death is favored almost unanimously. So to address Belinfante's suggestion that a cat could be revived, I say that even assuming the probability of any individual poisoned cell becoming alive again does not drop entirely to zero, the only way that an entire cat can come back to life is that if all of its cells miraculously arrive at the highly improbable "living" outcome simultaneously.
Also, as far as the outcome in which the cat is both living and dead simultaneously, I don't think that could ever happen. I think the pressures on the cat's cells will always strongly favor either life or death over a mixture of the two. In other words, the probability of a living/dead mixture ever happening will be muted out by the much more significant probabilities which favor either life or death. Again, this is because the living outcome and the dead outcome can be favored by external pressures whereas there is no known external factor which could favor a half-dead cat.

Hi johny_g,


I really do not think that this theory actually tells us anything about reviving a "moggey" from the grave. Like to put in my 5 cents worth here... Killing a cat or "reviving" a dead cat is not "quantum theory" but a technical process... One is more difficult than the other. All that probability theory says about this system is if you subject this "process" to a statistical mechanism then that statistical method determines the probability that the cat is dead or alive (in both cases) if cyanide gas kills cats.

Note... the gas is supposed to be highly effective in killing cats since the release of the gas is the determining factor not the lethality of the gas in this Gedanken Experiment... nobody questions if the cat will be dead or alive after the gas is released... in every case it is assumed the cat is certainly dead. That these states in quantum systems are a superposition of both and their outcome is subject to an "observation" of what the present state is... not necessarily of the cat but the vial that contains the gas.. has it been broken or not?

I have not seen the actual theory by Belinfante in an article but I think we are confusing the process with the quantum theory. The release of cyanide gas into the box with the cat is going to kill it if nothing is done to prevent it. one way to prevent this "outcome" is to suspend the cat in a cat state. Literally a quantum state in which nothing happens (no exchanges in energy or evolutionary process or event) until it is finally collapsed. It is not a statistical process as such. When this process (killing or reviving the cat) is executed is "statistically selected" and that cat state is subjected to quantum theory and collapse if and only if the "cat state" is a quantum cat state. I don't know how to put an entire cat into a cat state but the size of the cat is not the stopper to this process since macroscopic cat states are known (but not for cats). They are more difficult to sustain the bigger the system is.

On the other hand time is reversible in all quantum system. The arrow of time for almost all processes that are important to a cat is subject to possible reversal. There are a few (radioactive) processes that are not reversible but the life of a cat is really not about to depend on them in the short term. Individual quantum states can be reversed or "reset" to a previous quantum state (quantum zeno effect). This is a transactional interpretation of time not the kind of time you see in H G Wells or in some movies such as "The Sound of Thunder" or most of science fiction. The Universe may be considered as an "eventscape" in Cramers Interpretation of Wheeler-Feynman's Absorber Theory. The difference between the past and the future is related only to the "history" of all interrelated events in that the "history" of a future system will incorporate additional events along a timeline that had not occurred in the "history" of the same/similar system from some past. The differences measure time or time differences between the "before and after" systems.

In the case of the Delayed Choice Quantum Eraser Experiment from an observer point of view the state of an event in the "future" may determine the outcome of an event in the past for entangled photons. This is because photons that travel only at the speed of light undergo infinite time dilation (while moving at the speed of light the photon is "frozen in time") ... that is time does not progress while the "collapse" is undecided. Because the measurements of the properties of photon spin of entangled photon pairs are inter-related a measurement of one property will determine the other property of an entangled state even if that state was in the past and enigmatically this has been demonstrated by experiment. This is not magic because in the rest frame of the photon the instant the pair of entangled photons were created is the same instant they were both destroyed (in effect the two photons represent a single event because of entanglement). The event as outcomes for each photon separately was measured by synchronized clocks and may be separated by time in the laboratory frame but in reality in the frame of the light speed traveling photon are a single indivisible phenomenon whose mutual interdependence is very assured by theory.

If it was possible to create a single quantum state from a cat by moving the cat "without inertia" up to the speed of light... the cat would represent a single unobserved quantum event and the cat could be placed into "suspense". Infinite time dilation could be arranged to produce infinite Doppler shift in the optical frequency event making it unable to be observed as a "quantum particle" until it's collapse. The outcome either happens or it does not happen. The cat could not be considered "alive" or "dead" since at the speed of light the state which must be made to include all the cat will not change until it "collapses". If the cat is in this state while the cyanide gas is released, provided the cat (quantum) state is not permitted to collapse, the cat is unable to die... in fact the cat is unable to modify any parameter of its quantum system if it is not allowed by this state. The outcome of this state may be deferred until long after the gas has dissipated and then the cat is returned from time dilation "stasis" surviving the "certain death" of cyanide poisoning. In that way the cat state preserves the life of the cat and prevents the passage of time of the "cat system" while the experimenter decides if the cat is to live or die.

This also allows the cat to be apparently "resurrected from death" since by "definition" if the release of the gas causes death then if at a later time the cat is returned unharmed and unchanged after the gas release then this "by definition" returned the cat from death. I am being very "picky" of my reading of Schrodinger's Cat Gedanken Experiment here but you need to be very "picky" to explain what is actually happening and the separable contribution that is due to quantum mechanics and the contribution due to "process".

This does not help a lot of poor dead moggies I am afraid. Have any of you thought of storing their cats in cryogenic suspension till a time when the pussy can be returned to full health? The longer you wait after death though will have effects on the "process" used to resurrect the pussy at a later date and the longer you wait the worse things get. The other possibility (which you can technically do right now) is to clone you pussy from a few cells. It wont be the same cat but it will be biologically identical.

Cheers

Good Elf, You do realize that some of your readers aren't British? No worries, Merry Christmas!

Is your signature Quenya? It's been so long since I've read, or re-read...

Hi Sapo,