If you answer yes or no, provide a reason of why or how for your answer. If you'd like.

It's called classical superposition and is in Maxwell's equations.

If A is a solution to Maxwell's equations in vacuum, and B is a solution to Maxwell's equation in vacuum, then any mixture: aA + bB where a and b are scalars is also a solution.

Specifically, if A is a bunch of light, 2 A is a double-big bunch.

Secondly, in space there are natural cases of stimulated emission of radiation, and this is the definition of photons form two sources sharing the same state of motion.

How do you get photon A on the same superposition space as photon B? without source B interfering with photon A?

Stimulated emission:

A certain atom is excited and falls into a metastable state.

Photon A hits the atom, causing it (with some probability) to fall to the ground state, releasing photon B.

If photon A and photon B have the same energy, they are in phase, and so constructively interfere.

If you get a lot of excited atoms (a population inversion) this process is called lasing.

I agree with rpenner. The whole mode of operation of a laser is to stimulate new photons to join the herd of photons which are already traveling through the tube. When a new photon joins, it is identical to the existing ones (i.e. it is in precisely the same state). Since the new photons are the result of separate emission events compared to the older photons, they qualify as coming from a different source. Simply aim a pocket laser at the night sky, and the beam will travel for years, retaining most of its photons, so yes, you will have photons from different sources persisting in the same state for years.

--Stuart Anderson