scholarly journals Implications of Local Friendliness Violation for Quantum Causality

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 925
Author(s):  
Eric G. Cavalcanti ◽  
Howard M. Wiseman
Keyword(s):  
Quantum Mechanics ◽  
Causal Models ◽  
Bell’S Theorem ◽  
Methodological Principle ◽  
Bell's Theorem ◽  
Peaceful Coexistence ◽  
Quantum Reality ◽  
Wigner’S Friend ◽  
Relativistic Causality ◽  
New Formulation

We provide a new formulation of the Local Friendliness no-go theorem of Bong et al. [Nat. Phys. 16, 1199 (2020)] from fundamental causal principles, providing another perspective on how it puts strictly stronger bounds on quantum reality than Bell’s theorem. In particular, quantum causal models have been proposed as a way to maintain a peaceful coexistence between quantum mechanics and relativistic causality while respecting Leibniz’s methodological principle. This works for Bell’s theorem but does not work for the Local Friendliness no-go theorem, which considers an extended Wigner’s Friend scenario. More radical conceptual renewal is required; we suggest that cleaving to Leibniz’s principle requires extending relativity to events themselves.

Bell’s theorem

2018 ◽  
Author(s):  
Arthur Fine
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Experimental Tests ◽  
Bell Inequalities ◽  
Bell’S Theorem ◽  
Bell's Theorem ◽  
Bell Theorem ◽  
System Of Inequalities ◽  
Action At A Distance ◽  
High Degree

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.

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

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.

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

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 567 ◽  
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.

Bell’s theorem: Does quantum mechanics contradict relativity?

1987 ◽  
Vol 55 (8) ◽  
pp. 696-701 ◽  
Author(s):  
L. E. Ballentine ◽  
Jon P. Jarrett
Keyword(s):  
Quantum Mechanics ◽  
Bell’S Theorem ◽  
Bell's Theorem

Bell’s theorem and quantum mechanics

1994 ◽  
Vol 62 (2) ◽  
pp. 109-110 ◽  
Author(s):  
Nathan Rosen
Keyword(s):  
Quantum Mechanics ◽  
Bell’S Theorem ◽  
Bell's Theorem
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