2019 International Workshop: Beyond Bell’s theorem

In defense of a “single-world” interpretation of quantum mechanics

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  • #5537
    Jeffrey Bub
    Member

    https://doi.org/10.1016/j.shpsb.2018.03.002

    In a recent result, Frauchiger & Renner argue that if quantum theory accurately describes complex systems like observers who perform measurements, then “we are forced to give up the view that there is one single reality.” Following a review of the Frauchiger-Renner argument, I argue that quantum mechanics should be understood probabilistically, as a new sort of non-Boolean probability theory, rather than representationally, as a theory about the elementary constituents of the physical world and how these elements evolve dynamically over time. I show that this way of understanding quantum mechanics is not in conflict with a consistent “single-world” interpretation of the theory.

    #5588
    Mark Stuckey
    Participant

    Hi Jeff,

    On p. 7 you write, “This intrinsic randomness allows new sorts of nonlocal probabilistic correlations for ‘entangled’ quantum states of separated systems.” We offer an explanation (couched in spacetime) of this fact in our post, Mysteries of QM and SR Share a Common Origin: No Preferred Reference Frame.

    For example, in the simple case of the spin singlet state, Bob and Alice must both measure +/– 1 (in units of hbar/2) no matter their SG magnet orientation (no matter their reference frame). The fundamental constraint (explanans) at work is conservation per NPRF (angular momentum in this case, but whatever the +/– 1 outcomes represent physically). If Alice were to measure +1 and Bob measured –0.3, say, in some other reference frame (some other angle for his SG magnets), then Alice would be in the “right” frame (outcome “represents” the full value of the angular momentum) and Bob would only be measuring a component of the “right/hidden/underlying” angular momentum of his particle in this particular trial (“representationally”). There is no “intrinsic randomness” here, we can account for the outcomes of this particular trial (“how these elements evolve dynamically over time”) via a classical, dynamical mechanism (torque from magnetic interaction). But, NPRF says that Bob must also measure +/– 1, which uniquely distinguishes the quantum probability from the classical probability creating the “intrinsic randomness” (responsible for the Tsirelson bound in this case). In other words, this means conservation per NPRF can’t hold on a trial-by-trial basis (“intrinsic randomness”), but only on average (“probabilistically”).

    As viewed spatiotemporally, this becomes the origin of your view that “quantum mechanics should be understood probabilistically, as a new sort of non-Boolean probability theory, rather than representationally, as a theory about the elementary constituents of the physical world and how these elements evolve dynamically over time.” You might say that our view is “Bubism” in spacetime.

    Mark

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