What, if anything, determines the amplitude of a sub-atomic particle. A specific question is do all photons have the same amplitude? I would assume that at least photons of same color do, since i can observe the destructive interference.
I guess that by amplitude you mean energy. In that case they do not have same energy. Photons are just particle/"wave impulse". Their energy is defined by process that spawned them and there are no limits (other than available energy of course).
It goes for all other particles they don't have only one well defined energy level.
In case of same colour photons you are right. Their energy is probably very similar.