* Astronomy

Title: Can a Future Choice Affect a Past Measurement's Outcome?
Authors: Yakir Aharonov, Eliahu Cohen, Doron Grossman, Avshalom C. Elitzur

An EPR experiment is studied where each particle undergoes a few weak measurements of different spin-orientations, whose outcomes are individually recorded. Then the particle undergoes a strong measurement along a spin orientation freely chosen at the last moment. Bell-inequality violation is expected between the two strong measurements. At the same time, agreement is expected between all same-spin measurements, whether weak or strong. A contradiction thereby ensues: i) A weak measurement cannot determine the outcome of a successive strong one; ii) Bell's theorem forbids spin values to exist prior to the final choice of the spin-orientation to be measured; and iii) Indeed no disentanglement is inflicted by the weak measurements; yet iv) The weak measurements' outcome agrees with those of the strong ones. The only reasonable resolution seems to be that of the Two-State-Vector Formalism, namely that the weak measurement's outcomes anticipate the experimenter's future choice, even before the experimenter themselves knows what their choice is going to be. Causal loops are avoided by this anticipation remaining encrypted until the final outcomes enable to decipher it.

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