- #1
phonon44145
- 53
- 0
I've been reading about this two-photon interference experiment
http://en.wikipedia.org/wiki/Hong–Ou–Mandel_effect
But the wikipedia article does not explain the origin of the "-" sign before states 3 and 4. Just because one photon reflecting off the bottom side changes its phase, how does it follow that states 2 and 3 cancel each other? The transmitted photon in state 2 still has the same phase as the photon reflected off the upper side in state 3, so why would the states cancel completely? And why does it take only one photon from the pair changing its phase for the "-" sign to appear in front of the entire 2-photon state?
(As a side note, isn't it true that if the number of photons is known, 2 photons in this case, then phase is indeterminate anyway?)
http://en.wikipedia.org/wiki/Hong–Ou–Mandel_effect
But the wikipedia article does not explain the origin of the "-" sign before states 3 and 4. Just because one photon reflecting off the bottom side changes its phase, how does it follow that states 2 and 3 cancel each other? The transmitted photon in state 2 still has the same phase as the photon reflected off the upper side in state 3, so why would the states cancel completely? And why does it take only one photon from the pair changing its phase for the "-" sign to appear in front of the entire 2-photon state?
(As a side note, isn't it true that if the number of photons is known, 2 photons in this case, then phase is indeterminate anyway?)