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Non-local boxes are hypothetical ``machines'' that give rise to superstrong non-local correlations, leading to a stronger violation of Bell/CHSH inequalities than is possible within the framework of quantum mechanics. We show how non-local…

Quantum Physics · Physics 2007-05-23 Harry Buhrman , Matthias Christandl , Falk Unger , Stephanie Wehner , Andreas Winter

Bell inequalities are central tools for studying nonlocal correlations and their applications in quantum information processing. Identifying inequalities for many particles or measurements is, however, difficult due to the computational…

Quantum Physics · Physics 2020-11-17 Fabian Bernards , Otfried Gühne

We prove that every conceivable hidden variable model reproducing the quantum mechanical predictions of almost any entangled state must necessarily violate Bell's locality condition. The proof does not involve the consideration of any Bell…

Quantum Physics · Physics 2007-05-23 GianCarlo Ghirardi , Luca Marinatto

In this paper we consider the description by a general Bell-type non-local hidden variable theory (NLHVT) of bipartite quantum states with two observables per sub-system. We derive Bell inequalities of the…

Quantum Physics · Physics 2024-04-19 Bryan J Dalton

The investigation of Bell nonlocality traditionally relies on joint probabilities of observing certain measurement outcomes. In this work we explore a possibilistic approach, where only patterns of possible outcomes matter, and apply it to…

Quantum Physics · Physics 2022-09-21 Antoine Restivo , Nicolas Brunner , Denis Rosset

We present bipartite Bell-type inequalities which allow the two partners to use some non-local resource. Such inequality can only be violated if the parties use a resource which is more non-local than the one permitted by the inequality. We…

Quantum Physics · Physics 2015-06-26 Nicolas Brunner , Valerio Scarani , Nicolas Gisin

We give a set of necessary conditions for locality in bipartite systems, which include and generalize known Bell's inequalities. Each condition corresponds to a specific order of the expansion of random variables defined on graphs, in terms…

Correlations in quantum networks with independent sources exhibit a completely novel form of nonclassicality in the sense that the nonlocality of such correlations can be demonstrated in fixed local input scenarios. Before the pioneering…

Quantum Physics · Physics 2023-03-16 Kaushiki Mukherjee

It is widely accepted that the violation of Bell inequalities excludes local theories of the quantum realm. This paper presents a new derivation of the inequalities from non-trivial non-local theories and formulates a stronger Bell argument…

Quantum Physics · Physics 2018-07-06 Paul M. Näger

The exploration of entanglement and Bell non-locality among multi-particle quantum systems offers a profound avenue for testing and understanding the limits of quantum mechanics and local real hidden variable theories. In this work, we…

Quantum Physics · Physics 2025-10-23 Paweł Horodecki , Kazuki Sakurai , Abhyoudai S. Shaleena , Michael Spannowsky

Nonlocal correlations created in networks with multiple independent sources enable surprising phenomena in quantum information and quantum foundations. The presence of independent sources, however, makes the analysis of network nonlocality…

Quantum Physics · Physics 2026-04-21 José Mário da Silva , Alejandro Pozas-Kerstjens , Fernando Parisio

If Nature allowed nonlocal correlations other than those predicted by quantum mechanics, would that contradict some physical principle? Various approaches have been put forward in the past two decades in an attempt to single out quantum…

Quantum Physics · Physics 2019-04-19 Avishy Carmi , Eliahu Cohen

Topological systems, such as fractional quantum Hall liquids, promise to successfully combat environmental decoherence while performing quantum computation. These highly correlated systems can support non-Abelian anyonic quasiparticles that…

Quantum Physics · Physics 2009-10-12 G. K. Brennen , S. Iblisdir , J. K. Pachos , J. K. Slingerland

The apparent nonlocality of quantum theory has been a persistent concern. Einstein et. al. (1935) and Bell (1964) emphasized the apparent nonlocality arising from entanglement correlations. While some interpretations embrace this…

Quantum Physics · Physics 2020-03-10 Mordecai Waegell , Kelvin J. McQueen

Bell non-locality is a fundamental feature of quantum mechanics whereby measurements performed on "spatially separated" quantum systems can exhibit correlations that cannot be understood as revealing predetermined values. This is a special…

Quantum Physics · Physics 2024-11-05 Atul Singh Arora , Kishor Bharti , Alexandru Cojocaru , Andrea Coladangelo

Entanglement allows for the nonlocality of quantum theory, which is the resource behind device-independent quantum information protocols. However, not all entangled quantum states display nonlocality, and a central question is to determine…

Quantum Physics · Physics 2016-11-09 Daniel Cavalcanti , Leonardo Guerini , Rafael Rabelo , Paul Skrzypczyk

The use of Bell's theorem in any application or experiment relies on the assumption of free choice or, more precisely, measurement independence, meaning that the measurements can be chosen freely. Here, we prove that even in the simplest…

Quantum Physics · Physics 2016-11-25 Gilles Pütz , Denis Rosset , Tomer Jack Barnea , Yeong-Cherng Liang , Nicolas Gisin

We consider relations between communication complexity problems and detecting correlations (violating local realism) with no local hidden variable model. We show first universal equivalence between characteristics of protocols used in that…

Quantum Physics · Physics 2015-10-16 L. Czekaj , A. Grudka , M. Horodecki , P. Horodecki , M. Markiewicz

We present a simple hidden variable model for the singlet state of a pair of qubits, characterized by two kinds, hierarchically ordered, of hidden variables. We prove that, averaging over both types of variables, one reproduces all the…

Quantum Physics · Physics 2015-06-04 GianCarlo Ghirardi , Raffaele Romano

Non-locality without inequality is an elegant argument introduced by L. Hardy for two qubit systems, and later generalised to $n$ qubits, to establish contradiction of quantum theory with local realism. Interestingly, for $n=2$ this…

Quantum Physics · Physics 2015-05-19 Sibasish Ghosh , Shasanka Mohan Roy