Uncertainty in annihilation?

Good evening /sci/, I'm currently still in school with the intention of studying Theoretical physics next year, hopefully at Imperial College London. In our physics class this morning, we were covering the creation and annihilation of particle-antiparticle pairs, and one of my peers raised an interesting question. Take for example the annihilation of an electron-positron pair. Upon annihilation two gamma photons are released.The question raised was that if the position of a photon is an event which will be determined probabilistically, how is it that we know that the outcome of this annihilation is indeed two gamma photons travelling opposite directions?

Like 4tran said, conservation of momentum. You've discovered nothing new, so don't try to act like it. Kids like you who spew this crap really get on my nerve, especially with your added arrogance comments like "hopefully at ICL". So fucking what? I don't go running my mouth off about peterhouse. Learn some modesty you retard fuck.