Can we close the Bohr–Einstein quantum debate?

Abstract

Recent experiments allow one to conclude that Bell-type inequalities are indeed violated; thus, it is important to understand what this means and how we can explain the existence of strong correlations between outcomes of distant measurements. Do we have to announce that Einstein was wrong, Nature is non-local and non-local correlations are produced due to quantum magic and emerge, somehow, from outside space-time? Fortunately, such conclusions are unfounded because, if supplementary parameters describing measuring instruments are correctly incorporated in a theoretical model, then Bell-type inequalities may not be proved. We construct a simple probabilistic model allowing these correlations to be explained in a locally causal way. In our model, measurement outcomes are neither predetermined nor produced in an irreducibly random way. We explain why, contrary to the general belief, the introduction of setting-dependent parameters does not restrict experimenters' freedom of choice. Since the violation of Bell-type inequalities does not allow the conclusion that Nature is non-local and that quantum theory is complete, the Bohr-Einstein quantum debate may not be closed. The continuation of this debate is important not only for a better understanding of Nature but also for various practical applications of quantum phenomena.This article is part of the themed issue 'Second quantum revolution: foundational questions'.

Understanding quantum mechanics: a review and synthesis in precise language

“…More fundamentally, some of those who challenge the appropriateness of mathematical or physical assumptions (as described in Sect. 5.5 above) deny that the inequalities indicate anything significant about either locality or realism [22, § 9.3.2] [166,342,352]. Another fundamental concern is that many definitions of, or assumptions about, realism used in discussing Bell-type inequalities appear to be inconsistent with what are otherwise known to be core features of quantum theory [ .…”

“…Bell experiment results are often claimed to constrain how quantum mechanics can be understood. Many such claims appear, however, to be inappropriate, given the lack of consensus (outlined above) on the theoretical aspects of the inequalities [132,166,338,[367][368][369].…”

Quantum mechanics and modeling of physical reality

“…Nevertheless, as we mentioned in the introduction many authors still incorrectly believe that one has to abandon the locality of Nature or experimenters' freedom of choice. In a recent paper it was clearly explained why such beliefs are unfounded [52]. In the next section we recall a simple causally local contextual probabilistic model for twin photon beam SPCE which is able to reproduce predictions of QM and does not allow proving any Bell -type inequality.…”

“…There is a big difference between a position of an electron and its spin projection. A projection of electron's spin takes only discrete values and is the effect of the interaction of electron's magnetic moment with the Stern-Gerlach apparatus [52]. An electron is often considered to be a "point-like particle" thus by its definition at any moment of time it must be somewhere.…”

“…Therefore people working on the quantum computer project or trying to reconcile general relativity with QM have to be aware that rational explanations of quantum correlations do exist. They should also know that the Bohr-Einstein quantum debate about the completeness of quantum mechanics may not be closed [52].…”