This seems relevant to what Sabine was saying at Backreaction recently about free will and the quantum world, although (of course) I am not sure exactly sure what retrocausality means for free will. The abstract:
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.
No comments:
Post a Comment