EPR paradox, quantum nonlocality and physical reality

M Kupczynski

doi:10.1088/1742-6596/701/1/012021

Abstract

Eighty years ago Einstein, Podolsky and Rosen demonstrated that instantaneous reduction of wave function, believed to describe completely a pair of entangled physical systems, led to EPR paradox. The paradox disappears in statistical interpretation of quantum mechanics (QM) according to which a wave function describes only an ensemble of identically prepared physical systems. QM predicts strong correlations between outcomes of measurements performed on different members of EPR pairs in far-away locations. Searching for an intuitive explanation of these correlations John Bell analysed so called local realistic hidden variable models and proved that correlations consistent with these models satisfy Bell inequalities which are violated by some predictions of QM and by experimental data. Several different local models were constructed and inequalities proven. Some eminent physicists concluded that Nature is definitely nonlocal and that it is acting according to a law of nonlocal randomness. According to these law perfectly random, but strongly correlated events, can be produced at the same time in far away locations and a local and causal explanation of their occurrence cannot be given. We strongly disagree with this conclusion and we prove the contrary by analysing in detail some influential finite sample proofs of Bell and CHSH inequalities and so called Quantum Randi Challenges. We also show how one can win so called Bell's game without violating locality of Nature. Nonlocal randomness is inconsistent with local quantum field theory, with standard model in elementary particle physics and with causal laws and adaptive dynamics prevailing in the surrounding us world. The experimental violation of Bell-type inequalities does not prove the nonlocality of Nature but it only confirms a contextual character of quantum observables and gives a strong argument against counterfactual definiteness and against a point of view according to which experimental outcomes are produced in irreducible random way.

Highlights

Eighty years ago Einstein, Podolsky and Rosen (EPR) [1] demonstrated that an instantaneous reduction of a wave function describing a couple of entangled physical systems led to so called EPR paradox
Fifty years ago John Bell [6,7], trying to explain strong correlations between spin polarization projections of two physical systems prepared in spin singlet state, analyzed a large class of so called local realistic hidden variable models (LRHV) and found that correlations predicted by these models obeyed Bell inequalities (BI) which were violated by some correlations predicted by quantum mechanics (QM)
A statistical contextual interpretation of QM reconciles the ideas of Bohr and Einstein and is free of paradoxes

Summary

Introduction

Eighty years ago Einstein, Podolsky and Rosen (EPR) [1] demonstrated that an instantaneous reduction of a wave function describing a couple of entangled physical systems led to so called EPR paradox. Alice and Bob randomly choose setting for measurements of their respective electrons They obtain their measurement outcomes and Juanita performs a joint measurement of the photons sent by Alice and Bob. If Juanita registers undistinguishable photons it means that the electrons in distant locations were prepared in particular physical states in which the outcomes of the measurement of their spin polarisation projections are correlated. If Juanita registers undistinguishable photons it means that the electrons in distant locations were prepared in particular physical states in which the outcomes of the measurement of their spin polarisation projections are correlated In this experiment the cause of the correlations is not a partial memory of a common past or instantaneous communication from Juanita but similar physical conditions created in far-away locations when successful measurements were performed.

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Findings

Conclusions