TY - JOUR

T1 - Can a future choice affect a past measurement's outcome?

AU - Aharonov, Yakir

AU - Cohen, Eliahu

AU - Elitzur, Avshalom C.

N1 - Publisher Copyright:
© 2015 Elsevier Inc.

PY - 2015/4/1

Y1 - 2015/4/1

N2 - An EPR experiment is studied where each particle within the entangled pair undergoes a few weak measurements (WMs) along some pre-set spin orientations, with the outcomes individually recorded. Then the particle undergoes one strong measurement along an orientation chosen at the last moment. Bell-inequality violation is expected between the two final measurements within each EPR pair. At the same time, statistical agreement is expected between these strong measurements and the earlier weak ones performed on that pair. A contradiction seemingly ensues: (i) Bell's theorem forbids spin values to exist prior to the choice of the orientation measured; (ii) A weak measurement is not supposed to determine the outcome of a successive strong one; and indeed (iii) Almost no disentanglement is inflicted by the WMs; and yet (iv) The outcomes of weak measurements statistically agree with those of the strong ones, suggesting the existence of pre-determined values, in contradiction with (i). Although the conflict can be solved by mere mitigation of the above restrictions, the most reasonable resolution seems to be that of the Two-State-Vector Formalism (TSVF), namely, that the choice of the experimenter has been encrypted within the weak measurement's outcomes, even before the experimenters themselves know what their choice will be.

AB - An EPR experiment is studied where each particle within the entangled pair undergoes a few weak measurements (WMs) along some pre-set spin orientations, with the outcomes individually recorded. Then the particle undergoes one strong measurement along an orientation chosen at the last moment. Bell-inequality violation is expected between the two final measurements within each EPR pair. At the same time, statistical agreement is expected between these strong measurements and the earlier weak ones performed on that pair. A contradiction seemingly ensues: (i) Bell's theorem forbids spin values to exist prior to the choice of the orientation measured; (ii) A weak measurement is not supposed to determine the outcome of a successive strong one; and indeed (iii) Almost no disentanglement is inflicted by the WMs; and yet (iv) The outcomes of weak measurements statistically agree with those of the strong ones, suggesting the existence of pre-determined values, in contradiction with (i). Although the conflict can be solved by mere mitigation of the above restrictions, the most reasonable resolution seems to be that of the Two-State-Vector Formalism (TSVF), namely, that the choice of the experimenter has been encrypted within the weak measurement's outcomes, even before the experimenters themselves know what their choice will be.

KW - Quantum nonlocality

KW - Two-State-Vector-Formalism

KW - Weak measurement

UR - http://www.scopus.com/inward/record.url?scp=84924202957&partnerID=8YFLogxK

U2 - 10.1016/j.aop.2015.02.020

DO - 10.1016/j.aop.2015.02.020

M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???

AN - SCOPUS:84924202957

SN - 0003-4916

VL - 355

SP - 258

EP - 268

JO - Annals of Physics

JF - Annals of Physics

ER -