Locality, Bell's theorem, and quantum mechanics

Bell’s theorem is concerned with the outcomes of a special type of ‘correlation experiment’ in quantum mechanics. It shows that under certain conditions these outcomes would be restricted by a system of inequalities (the ‘Bell inequalities’) that contradict the predictions of quantum mechanics. Various experimental tests confirm the quantum predictions to a high degree and hence violate the Bell inequalities. Although these tests contain loopholes due to experimental inefficiencies, they do suggest that the assumptions behind the Bell inequalities are incompatible not only with quantum theory but also with nature. A central assumption used to derive the Bell inequalities is a species of no-action-at-a-distance, called ‘locality’: roughly, that the outcomes in one wing of the experiment cannot immediately be affected by measurements performed in another wing (spatially distant from the first). For this reason the Bell theorem is sometimes cited as showing that locality is incompatible with the quantum theory, and the experimental tests as demonstrating that nature is nonlocal. These claims have been contested.

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Bell's Theorem Refuted: Real Physics and Philosophy for Quantum Mechanics

Physics Essays ◽

10.4006/1.3025319 ◽

1998 ◽

Vol 11 (3) ◽

pp. 413-421 ◽

Cited By ~ 1

Author(s):

Gordon Watson

Keyword(s):

Quantum Mechanics ◽

Bell’S Theorem ◽

Bell's Theorem

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Bell’s theorem and its tests: Proof that nature is superdeterministic—Not random

Physics Essays ◽

10.4006/0836-1398-33.2.216 ◽

2020 ◽

Vol 33 (2) ◽

pp. 216-218

Author(s):

Johan Hansson

Keyword(s):

Quantum Mechanics ◽

Reference Frames ◽

Space Time ◽

Bell’S Theorem ◽

Quantum Mechanical ◽

Bell's Theorem ◽

Fundamental Level ◽

Global Space ◽

Mechanical Measurements

By analyzing the same Bell experiment in different reference frames, we show that nature at its fundamental level is superdeterministic, not random, in contrast to what is indicated by orthodox quantum mechanics. Events—including the results of quantum mechanical measurements—in global space-time are fixed prior to measurement.

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Nonlocality in Bell’s Theorem, in Bohm’s Theory, and in Many Interacting Worlds Theorising

Entropy ◽

10.3390/e20080567 ◽

2018 ◽

Vol 20 (8) ◽

pp. 567 ◽

Cited By ~ 2

Author(s):

Mojtaba Ghadimi ◽

Michael Hall ◽

Howard Wiseman

Keyword(s):

Quantum Mechanics ◽

Quantum Theory ◽

Bohmian Mechanics ◽

Bell’S Theorem ◽

Bell's Theorem ◽

Significant Progress ◽

Technical Problems ◽

New Approach ◽

Weak Notion ◽

Bohm’S Theory

“Locality” is a fraught word, even within the restricted context of Bell’s theorem. As one of us has argued elsewhere, that is partly because Bell himself used the word with different meanings at different stages in his career. The original, weaker, meaning for locality was in his 1964 theorem: that the choice of setting by one party could never affect the outcome of a measurement performed by a distant second party. The epitome of a quantum theory violating this weak notion of locality (and hence exhibiting a strong form of nonlocality) is Bohmian mechanics. Recently, a new approach to quantum mechanics, inspired by Bohmian mechanics, has been proposed: Many Interacting Worlds. While it is conceptually clear how the interaction between worlds can enable this strong nonlocality, technical problems in the theory have thus far prevented a proof by simulation. Here we report significant progress in tackling one of the most basic difficulties that needs to be overcome: correctly modelling wavefunctions with nodes.

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