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A correlation inequality is derived from local realism and a supplementary assumption. Unlike Clauser-Horne (CH) inequality [or Clauser-Horne-Shimony-Holt (CHSH) inequality] which is violated by quantum mechanics by a factor of $\sqrt 2$,…

Quantum Physics · Physics 2007-05-23 M. Ardehali

In contrast to the wide-spread opinion that any separable quantum state satisfies every classical probabilistic constraint, we present a simple example where a separable quantum state does not satisfy the original Bell inequality although…

Quantum Physics · Physics 2007-05-23 Elena R. Loubenets

Detection and quantification of entanglement in quantum resources are two key steps in the implementation of various quantum-information processing tasks. Here, we show that Bell-type inequalities are not only useful in verifying the…

Quantum Physics · Physics 2011-02-28 Yeong-Cherng Liang , Tamas Vertesi , Nicolas Brunner

We present a generalized Bell inequality for two entangled quNits. On one quNit the choice is between two standard von Neumann measurements, whereas for the other quNit there are $N^2$ different binary measurements. These binary…

Quantum Physics · Physics 2007-05-23 H. Bechmann-Pasquinucci , N. Gisin

Measurement incompatibility and quantum non-locality are two key features of quantum theory. Violations of Bell inequalities require quantum entanglement and incompatibility of the measurements used by the two parties involved in the…

Mathematical Physics · Physics 2023-03-30 Faedi Loulidi , Ion Nechita

We evaluate the maximal Clauser-Horne-Shimony-Holt (CHSH) violation for a generic (typically mixed) qubit-qudit state, obtaining easily computable expressions in arbitrary qudit dimension. This represents the optimal (2-2-2) Bell…

Quantum Physics · Physics 2025-10-22 Alexander Bernal , J. Alberto Casas , Jesus M. Moreno

A number of papers have suggested that it is inappropriate to combine data from different experiments when undertaking experimental tests of Bell's inequalities. It has been suggested that a correct analysis, using a single probability…

Quantum Physics · Physics 2017-01-10 C M Care

Bell nonlocality provides a robust scalable route to the efficient certification of quantum states. Here, we introduce a general framework for constructing Bell inequalities tailored to the $\mathbb{Z}_d$ toric code for odd prime local…

Quantum Physics · Physics 2025-12-02 Eloïc Vallée , Owidiusz Makuta , Patrick Emonts , Rhine Samajdar , Jordi Tura

The famous Clauser-Horne-Shimony-Holt (CHSH) inequality certifies a quantum violation, by a factor $\sqrt{2}$, of correlations predicted by the classical view of the world in the simplest possible nontrivial measurement setup (two systems…

Quantum Physics · Physics 2017-12-25 Ben Li

Many solid-state quantum platforms do not permit sharp, projective measurements but instead yield continuous voltage or field traces under weak, non-demolition readout. In such systems, standard Bell tests based on dichotomic projective…

Quantum Physics · Physics 2025-12-30 Shalender Singh , Santosh Kumar

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

Bell or Clauser-Horne-Shimony-Holt (CHSH) tests on superconducting quantum processors are commonly interpreted under the assumption that repeated circuit executions sample a single, stationary preparation ensemble. Here we show that this…

Quantum Physics · Physics 2026-01-14 Prosanta Pal , Shubhanshu Karoliya , Gargee Sharma , Ramakrishna Podila

We demonstrate an efficient experimental procedure based on entanglement swapping to determine the Bell nonlocality measure of Horodecki et al. [Phys. Lett. A 200, 340 (1995)] and the fully-entangled fraction of Bennett et al. [Phys. Rev. A…

Quantum Physics · Physics 2017-03-22 Karol Bartkiewicz , Karel Lemr , Antonín Černoch , Adam Miranowicz

The only information available about an alleged source of entangled quantum states is the amount $S$ by which the Clauser-Horne-Shimony-Holt (CHSH) inequality is violated: nothing is known about the nature of the system or the measurements…

Quantum Physics · Physics 2009-12-19 C. -E. Bardyn , T. C. H. Liew , S. Massar , M. McKague , V. Scarani

The simplest device-independent quantum key distribution protocol is based on the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality and allows two users, Alice and Bob, to generate a secret key if they observe sufficiently strong…

Quantum Physics · Physics 2021-04-27 Erik Woodhead , Antonio Acín , Stefano Pironio

The Bell inequality constrains the outcomes of measurements on pairs of distant entangled particles. The Bell contradiction states that the Bell inequality is inconsistent with the calculated outcomes of these quantum experiments. This…

Quantum Physics · Physics 2026-03-03 Kees van Hee , Kees van Berkel , Jan de Graaf

The `Schr\"odinger's cat' thought experiment highlights the counterintuitive facet of quantum theory that entanglement can exist between microscopic and macroscopic systems, producing a superposition of distinguishable states like the…

Given a Bell inequality, if its maximal quantum violation can be achieved only by a single set of measurements for each party or a single quantum state, up to local unitaries, one refers to such a phenomenon as self-testing. For instance,…

Quantum Physics · Physics 2021-09-29 Shin-Liang Chen , Huan-Yu Ku , Wenbin Zhou , Jordi Tura , Yueh-Nan Chen

We present a violation of the CHSH inequality without the fair sampling assumption with a continuously pumped photon pair source combined with two high efficiency superconducting detectors. Due to the continuous nature of the source, the…

We introduce a permutationally invariant multipartite Bell inequality for many-body three-level systems and use it to investigate a connection between Bell nonlocality and (lack of) quantum chaos. An associated Bell operator is then defined…

Quantum Physics · Physics 2026-04-08 Albert Aloy , Guillem Müller-Rigat , Maciej Lewenstein , Jordi Tura , Matteo Fadel