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Bell nonlocality is the resource that enables device-independent quantum information processing tasks. It is revealed through the violation of so-called Bell inequalities, indicating that the observed correlations cannot be reproduced by…

Quantum Physics · Physics 2024-09-25 Patrick Emonts , Mengyao Hu , Albert Aloy , Jordi Tura

Efforts to construct deeper, realistic, level of physical description, in which individual systems have, like in classical physics, preexisting properties revealed by measurements are known as hidden-variable programs. Demonstrations that a…

Quantum Physics · Physics 2009-09-15 Caslav Brukner , Marek Zukowski

The violation of Bell, CHSH and CH inequalities indicates only that the assumption of "conterfactual definiteness" and/or the probabilistic models used in proofs were incorrect. In this paper we discuss in detail an intimate relation…

Quantum Physics · Physics 2015-08-26 Marian Kupczynski

Local realistic models cannot completely describe all predictions of quantum mechanics. This is known as Bell's theorem that can be revealed either by violations of Bell inequality, or all-versus-nothing proof of nonlocality. Hardy's…

Experiments showing the violation of Bell inequalities have formed our belief that the world at its smallest is genuinely non-local. While many non-locality experiments use the first quantised picture, the physics of fields of…

Quantum Physics · Physics 2013-05-29 Libby Heaney , Janet Anders

Bell inequalities exclude a broad class of local hidden-variable explanations of quantum correlations. A recurring objection is that the usual Bell form is static, whereas real measuring devices may contain local memory, stochastic…

Quantum Physics · Physics 2026-05-26 Ming Yang

The nonlocal realistic theory might be the last cornerstone of classical physics confronting to the quantum theory, which was found mostly untenable in the bipartite system [Nature 446, 871 (2007)]. We extend the Leggett-type nonlocal…

Quantum Physics · Physics 2021-08-10 Abdul Sattar Khan , Ma-Cheng Yang , Cong-Feng Qiao

Bell tests---the experimental demonstration of a Bell inequality violation---are central to understanding the foundations of quantum mechanics, underpin quantum technologies, and are a powerful diagnostic tool for technological developments…

Entanglement swapping is a process by which two initially independent quantum systems can become entangled and generate nonlocal correlations. To characterize such correlations, we compare them to those predicted by bilocal models, where…

Quantum Physics · Physics 2012-03-23 Cyril Branciard , Denis Rosset , Nicolas Gisin , Stefano Pironio

Loophole-free violations of Bell inequalities imply that at least one of the assumptions behind local hidden-variable theories must fail. Here, we show that, if only one fails, then it has to fail completely, therefore excluding models that…

Quantum Physics · Physics 2025-05-20 Carlos Vieira , Ravishankar Ramanathan , Adán Cabello

The conflict between Quantum Mechanics (QM) and Local Realism is most noticeable in the correlations observed between distant regions of a spatially spread entangled state. It has been hypothesized that transient deviations (from the values…

Quantum Physics · Physics 2024-04-16 Alejandro Hnilo , Mónica Agüero , Marcelo Kovalsky , Myriam Nonaka

We derive two classes of multi-mode Bell inequalities under local realistic assumptions, which are violated only by the entangled states negative under partial transposition in accordance with the Peres conjecture. Remarkably, the failure…

Quantum Physics · Physics 2010-11-02 Se-Wan Ji , Jaewan Kim , Hai-Woong Lee , M. S. Zubairy , Hyunchul Nha

We derive a multipartite generalized Bell inequality which involves the entire range of settings for each of the local observers. Especially, it is applied to show non-local behavior of a six-qubit mixture of Greenberger-Horne-Zeilinger…

Quantum Physics · Physics 2009-11-13 Koji Nagata

We show that arbitrary functions of continuous variables, e.g. position and momentum, can be used to generate tests that distinguish quantum theory from local hidden variable theories. By optimising these functions, we obtain more robust…

Quantum Physics · Physics 2009-11-16 Q. Y. He , E. G. Cavalcanti , M. D. Reid , P. D. Drummond

Bell inequalities rest on three fundamental assumptions: realism, locality, and free choice, which lead to nontrivial constraints on correlations in very simple experiments. If we retain realism, then violation of the inequalities implies…

Quantum Physics · Physics 2021-05-20 Pawel Blasiak , Emmanuel M. Pothos , James M. Yearsley , Christoph Gallus , Ewa Borsuk

I impose previously neglected symmetry conditions in Leggett's non-local hidden variable theory that are required by the conditions in a recent experimental test of this theory. These conditions lead to an inequality for the polarization…

Quantum Physics · Physics 2007-10-18 Michael Nauenbeerg

Leggett-type nonlocal realist inequalities that have been derived to date are all contingent upon suitable geometrical constraints to be strictly satisfied by the spatial arrangement of the relevant measurement settings. This undesirable…

Quantum Physics · Physics 2015-03-19 Ashutosh Rai , Dipankar Home , A. S. Majumdar

Bell inequalities are mathematical constructs that demarcate the boundary between quantum and classical physics. A new class of multiplicative Bell inequalities originating from a volume maximization game (based on products of correlators…

The demonstration and use of nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detectors' inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only…

Correlations for the Bell gedankenexperiment are constructed using probabilities given by quantum mechanics, and nonlocal information. They satisfy Bell's inequality and exhibit spatial non stationarity in angle. Correlations for three…

Quantum Physics · Physics 2015-06-26 Louis Sica