Here's what bugs me: Those two photons aren't going to be *exactly* the same, in terms of say frequency or maybe the angle they make against the table. So how close do they have to be for the configurations to merge? Or is that a Wrong Question? Perhaps if we left the photon emmiter the same but changed the detector to one that could tell the difference in angle, then the experimental results would change? What if we use a angle-detecting photon detector but program it to dump the angle into /dev/null?