Hello, I've been learning about Quantum Key Distribution recently, but I can't seem to find the logic in one of the steps... maybe I'm just having a brain block. So let's say Alice has sent a stream of entangled photons to Bob, and he finishes measuring them and is left with a binary code. All of the lessons I've watched tell me that Alice will tell him "right" or "wrong" once he states which detector he used for each one, but where is this communication supposed to take place? It doesn't occur in the same system through which the photons were sent, but I don't see how they could do this over any system that Eve could not access. They could meet in person, but arrangements like this would be too impractical in almost all cases. Any insight?