Imagine that one has a single photon of 632nm. It enters the back end of an open-ended HeNe laser tube - one with no mirrors - and along its path, causes the emission of another photon. According to the wikipedia entry on stimulated emission (https://en.wikipedia.org/wiki/Stimulated_emission), the new photon will have the same phase, frequency, polarization, and direction as the original. My question concerns the polarization. Say the original photon was in a superposition state as far as its polarization was concerned. What, then, does it mean to say that the new photon has the same polarization? Will both photons be in a superposition state, or will the original collapse into an eigenstate which will be matched by the new photon? If this is not the case and both photons are in superposition, what happens when they hit a polarizing beam splitter? If both photons are in superposition, then they should both transmit and reflect and go down both paths, but at some point, they will hit something that causes them to collapse (unless this is part of a Mach-Zehnder interferometer, but never mind that), and I'm wondering whether they will both have gone the same way. If so, this almost seems like a form of entanglement. Taken further, if the original photon causes emission of several photons, each of which causes emission of more, what is the (polarization) state of them all? They could either all be in a superposition state and later all go the same way at the PBS, or the original could collapse into an eigenstate and the rest follow. I assume that I'm stupid and don't understand at least one critical aspect of what's going on. How am I stupid?