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Hello! Ive heard of a retro causality quantum entanglement experiment that has been proposed by John G. Cramer at the University of Washington. Ive tried to look over some of the theory about it but havent been able to get my hands on too much info... What are your opinions about it? Does it seem that using quantum entanglement you may be able to create a retro causality phenomenon in the way proposed by John Cramer? Thanks for the help!
Answer 1:

I'd have to read more carefully to understand this experiment. Quantum entanglement and non-locality have been demonstrated very persuasively at this point in time. Quantum optics experiments where two polarization entangled photons are generated have demonstrated that if a measurement is performed to collapse the entangled two-photon wave function, the polarization correlation between the two photons must be preserved. In other words, measure one photon's polarization, and it's partner must have the complementary, correlated polarization.

Here it appears the idea is that one measurement is performed whose result depends on the second measurement that occurs in the future. Certainly this experiment should reflect the entangled state of two photons, but it is not clear to me why the 1st measurement does not collapse the wave function of the 2nd photon. Unfortunately, I can't offer any more help beyond this.


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