05-02-12, 03:11 PM #41
Specifically: if you work in this retrocausal "picture" of the experiment, then an important detail is that when Victor performs an entangling measurement, he effectively retroactively projects the state shared by Alice and Bob randomly onto one of four different entangled states, only one of which Alice and Bob are actually interested in. So to see correlations they need to know which of the photons they receive are in the entangled state they're interested in, and they can only get that information from Victor.
This kind of detail is clear if you're already familiar with the theory behind this sort of experiment, but it is also stated in a few places in the paper. For instance, near the beginning of page 4:
When used for a BSM, our BiSA can project onto two of the four Bell states, namely onto (both detectors in b'' firing or both detectors in c'' firing) and (one photon in b'' and one in c'' with the same polarization).
For each pair of photons 1&4, we record the chosen measurement configurations and the 4-fold coincidence detection events. All raw data are sorted into four subensembles in real time according to Victor’s choice and measurement results. After all the data had been taken, we calculated the polarization correlation function of photons 1 and 4. It is derived from their coincidence counts of photons 1 and 4 conditional on projecting photons 2 and 3 to when the Bell-state measurement was performed, and to or when the separable state measurement was performed.
Let me ask it another way, putting Victor's choice ahead of Alice and Bob's measurements: if Victor produces a stream of entangled photon pairs and sends one each to Alice and Bob, you agree that they should be able to measure them, compare their results, and after sufficient iterations determine whether or not the stream is correlated WITHOUT asking Victor, yes?
That's the whole point of Bell's experiment!
Last edited by przyk; 05-02-12 at 03:27 PM.
05-02-12, 04:54 PM #42
Last edited by brucep; 05-02-12 at 05:07 PM.
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