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Bell inequalities have traditionally been used to demonstrate that quantum theory is nonlocal, in the sense that there exist correlations generated from composite quantum states that cannot be explained by means of local hidden variables.…

Bell's inequality plays an important role with respect to the Einsteinian question about the physical reality of quantum theory. While Bell's inequality is usually viewed within the geometric framework of a Hilbert space quantum model, the…

Quantum Physics · Physics 2023-04-26 Ulrich Faigle

In some key Bell experiments, including two of the well-known ones by Alain Aspect, 1981-2, it is only after the subtraction of ``accidentals'' from the coincidence counts that we get violations of Bell tests. The data adjustment, producing…

Quantum Physics · Physics 2007-05-23 Caroline H. Thompson

When separated measurements on entangled quantum systems are performed, the theory predicts correlations that cannot be explained by any classical mechanism: communication is excluded because the signal should travel faster than light;…

Quantum Physics · Physics 2011-08-11 Daniel Cavalcanti , Nicolas Brunner , Paul Skrzypczyk , Alejo Salles , Valerio Scarani

Proposals for Bell inequality tests on systems restricted by superselection rules often require operations that are difficult to implement in practice. In this paper, we derive a new Bell inequality, where pairs of states are used to…

Quantum Physics · Physics 2015-05-19 Libby Heaney , Seung-Woo Lee , Dieter Jaksch

Randomness is a ubiquitous phenomenon that is practically accompanied by physical events described by probability theory. However, probability by definition in the theory is a nonnegative scalar quantity. Here, we propose the concept of…

General Physics · Physics 2025-06-17 Sheng Feng

Quantum computational experiments exploiting Noisy Intermediate-Scale Quantum (NISQ) devices to demonstrate violation of a Bell inequality are proposed. They consist of running specified quantum algorithms on few-qubit computers. If such a…

Quantum Physics · Physics 2020-09-02 H. W. L. Naus , H. Polinder

An information-theoretic temporal Bell inequality is formulated to contrast classical and quantum computations. Any classical algorithm satisfies the inequality, while quantum ones can violate it. Therefore, the violation of the inequality…

Quantum Physics · Physics 2007-05-23 Fumiaki Morikoshi

The violation of Bell inequalities is often interpreted as showing that, if hidden variables exist, they must be contextual and non local. But they can also be explained questioning the probability space employed, or the validity of the…

Quantum Physics · Physics 2022-02-18 Aldo F. G. Solis-Labastida , Melina Gastelum , Jorge G. Hirsch

A Bell test can rule out local realistic models, and has potential applications in communications and information tasks. For example, a Bell inequality violation can certify the presence of intrinsic randomness in measurement outcomes,…

Bell inequalities are natural tools that allow one to certify the presence of nonlocality in quantum systems. The known constructions of multipartite Bell inequalities contain, however, correlation functions involving all observers, making…

Quantum Physics · Physics 2015-03-30 J. Tura , A. B. Sainz , T. Vértesi , A. Acín , M. Lewenstein , R. Augusiak

A recent experiment presented, for photons, the first violation of a Bell inequality closing the fair-sampling loophole, i.e., without having to assume that the sample of measured photons fairly represents the entire ensemble. In this note,…

Quantum Physics · Physics 2013-07-25 Johannes Kofler , Sven Ramelow , Marissa Giustina , Anton Zeilinger

In a recent paper (Phys. Rev. A 105, 042220 (2022)), Daley et al claim that some superdeterministic models are disfavoured against standard quantum mechanics, because such models overfit the statistics of a Bell-type experiment which the…

Quantum Physics · Physics 2024-02-16 Jonte R. Hance , Sabine Hossenfelder

Bell's theorem shows that local realistic theories place strong restrictions on observable correlations between different systems, giving rise to Bell's inequality which can be violated in experiments using entangled quantum states. Bell's…

In a quantum network, distant observers sharing physical resources emitted by independent sources can establish strong correlations, which defy any classical explanation in terms of local variables. We discuss the characterization of…

The temporal Bell inequalities are derived from the assumptions of realism and locality in time. It is shown that quantum mechanics violates these inequalities and thus is in conflict with the two assumptions. This can be used for…

Quantum Physics · Physics 2007-05-23 Caslav Brukner , Samuel Taylor , Sancho Cheung , Vlatko Vedral

We describe a new Bell test for two-particle entangled systems that engages an unbounded continuous variable. The continuous variable state is allowed to be arbitrary and inaccessible to direct measurements. A systematic method is…

Quantum Physics · Physics 2014-01-20 X. -F. Qian , C. J. Broadbent , J. H. Eberly

The correlations in quantum networks have attracted strong interest with new types of violations of the locality. The standard Bell inequalities cannot characterize the multipartite correlations that are generated by multiple sources. The…

Quantum Physics · Physics 2018-11-19 Ming-Xing Luo

Another Bell test "loophole" - imperfect rotational invariance - is explored, and novel realist ideas on parametric down-conversion as used in recent "quantum entanglement" experiments are presented. The usual quantum theory of entangled…

Quantum Physics · Physics 2007-05-23 Caroline H Thompson

This article is intended as a compendium and guide to the variety of Bell Inequality derivations that have appeared in the literature in recent years, classifying them into six broad categories, revealing the underlying, often hidden,…

Quantum Physics · Physics 2007-05-23 Ken Williams