Is there are conflict between the time-symmetry of some elementary processes and the evolution of the wave functions for those processes? For instance, the emission of a photon from atom A subsequently absorbed by atom B should AFAIK be time symmetric such that it could be viewed as an emission from B followed by an absorption at A going backwards in time. But the wave function for the photon emitted (or to be emitted) from A spreads out through space until it collapses when absorbed by B. Similarly, when time-reversed, the wave function of the photon following an emission by B should spread out until it collapses when absorbed by A. These two functions will look different. How does this get resolved? I have read a view that the wave function for photon emission should not be viewed as the wave function for the photon itself but for the emitter. This makes some sense to me, since the wave function is based on not knowing when the photon will be emitted; that is, it cannot be the wave function for the photon since it probably doesn't exist yet. But this, as it seems to me, would not support the entirely indeterministic picture of quantum transfers. It would be a case of not being able to know, rather than an intrinsic uncertainty of where the photon's wavefunction will collapse following an emission event. Sorry, this is a very elementary question. I just haven't read anything that treats it exactly yet. Thanks, El Hombre.