- #211
ShayanJ
Gold Member
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What you describe doesn't need collapse only if we make the assumption that the quantum state is subjective, so after A measures her photon, she assigns a pure state to the B's photon but B himself assigns a mixed state to his photon. Otherwise if you want to assume that the quantum state is objective, your own description leads to collapse.vanhees71 said:Also note that there's no collapse of the state as a whole via the measurement of either A or B. It's only such that if A finds H, she knows that B's photon will be found to have polarization B, but for Bob that doesn't change anything, i.e., the only thing he knows is that he will find with probability 50% either H or V. Also A finds with 50% probability H. So everything is consistent, and there is no spooky action at a distance, which is implied by the assumption of a collapse, but as you see, we don't need the collapse to understand the correlations. Further according to QT you cannot say more about the outcome of these measurements than the said probabilities, and the understanding is that the polarization of the single photons is really maximally indetermined.