- #596
zonde
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No, common reference does not require FTL. Common reference is established when you set up experiment. You measure birefringence of fiber that is used to transport photons from source to measurement site. And you compensate birefringence of fiber to establish common reference.my_wan said:When you define 2 arbitrary polarizations, such as 22.5 and 30, this already requires using a common coordinate where both detectors agree on where the settings representing 22.5, 30 and all other settings, including 0 is. So even arbitrary setting requires FTL information of some sort, albeit predefined. We don't consider this FTL because space has covariant symmetries wrt various coordinate systems. Yet, in the EPR case, relative covariance is maintained, i.e., difference in detector settings, but covariance with the numerical labels we put on that coordinate system is broken. It makes our coordinate system look broken in this respect.
For example imagine that fiber is arranged so that at one site of measurement photons are received from up direction and polarizer is rotated in horizontal plane. In that case you simply establish common reference by finding out what is the angle of polarization for photons that come out of the fiber given certain angle of polarization for photons that go into the fiber at the other end.
So common reference is established by setup of experiment. Nothing like FTL.