arXiv:2004.14570 · Frontiers in Physics

Is the Moon There If Nobody Looks: Bell Inequalities and Physical Reality

Marian Kupczyński

Published Sep 23, 2020• 42 citations

Abstract

Bell-CHSH inequalities are trivial algebraic properties satisfied by each line of Nx4 spreadsheets containing ±1 entries, thus it is surprising that their violation in some experiments allows to speculate about the existence of nonlocal influences in nature and casts doubt on the existence of external physical reality. Such speculations are rooted in incorrect interpretations of quantum mechanics and in a failure of local realistic hidden variable models to reproduce quantum predictions for spin polarisation correlation experiments (SPCE). In these models, one uses a counterfactual joint probability distribution of only pairwise measurable random variables (A, A’, B, B’) to prove Bell-CHSH inequalities. In SPCE Alice and Bob, using 4 incompatible pairs of experimental settings, estimate imperfect correlations between clicks registered by their detectors. Clicks announce detection of photons and are coded by ±1. Expectations of corresponding random variables: E (AB), E (AB’), E (A’B) and E (A’B’) are estimated and compared with quantum predictions. These estimates significantly violate CHSH inequalities. Since variables (A, A’) as well as (B, B’) cannot be measured jointly, neither Nx4 spreadsheets nor a joint probability distribution of (A, A’, B, B’) exist, thus Bell-CHSH inequalities may not be derived. Nevertheless, imperfect correlations between clicks in SPCE may be explained in a locally causal way, if contextual setting-dependent parameters describing measuring instruments are correctly included in the description. The violation of Bell-CHSH inequalities may not therefore justify the existence of a spooky action at the distance, super-determinism or speculations that an electron can be here and a meter away at the same time. In this paper we review and rephrase several arguments proving that such conclusions are unfounded. Entangled photon pairs cannot be described as pairs of socks nor as pairs of fair dice producing in each trial perfectly correlated outcomes. Thus the violation of inequalities confirms only that the measurement outcomes and `the fate of photons ` are not predetermined before the experiment is done. It does not allow for doubt regarding the objective existence of atoms, electrons and other invisible elementary particles which are the building blocks of the visible world around us including ourselves.

DOI: 10.3389/fphy.2020.00273

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