Volume 2, Issue 2, pages 32-46
Avshalom C. Elitzur [Show Biography], Eliahu Cohen [Show Biography] and Tomer Shushi [Show Biography]
In the EPR experiment, each measurement addresses the question “What spin value has this particle along this orientation?” The outcome then proves that the spin value has been affected by the distant experimenter’s choice of spin orientation. We propose a new setting where the question is reversed: “What is the orientation along which this particle has this spin value?” It turns out that the orientation is similarly subject to nonlocal effects. To enable the reversal, each particle’s interaction with a beam-splitter at t1 leaves its spin orientation superposed. Then at t2, the experimenter selects an “up” or “down” spin value for this yet-undefined orientation. Only after the two particles undergo this procedure, the two measurements are completed, each particle having its spin value along a definite orientation. By Bell’s theorem, it is now the “choice” of orientation that must be nonlocally transmitted between the particles upon completing the measurement. This choice, however, has preceded the experimenter’s selection. This seems to lend support for the time-symmetric interpretations of QM, where retrocausality plays a significant role. We conclude with a brief comparison between these interpretations and their traditional alternatives, Copenhagen, Bohmian mechanics and the Many Worlds Interpretation.
