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The degree of experimentally attainable nonlocality, as gauged by the loophole-free or effective violation of Bell inequalities, remains severely limited due to inefficient detectors. We address an experimentally motivated question: Which…

Optical hybrid entanglement can be created between two qubits, one encoded in a single photon and another one in coherent states with opposite phases. It opens the path to a variety of quantum technologies, such as heterogeneous quantum…

The CHSH inequality is an inequality used to test locality in quantum theory and is recognized as one of Bell's inequalities. In contrast, the KCBS inequality is employed to test noncontextuality in quantum theory. While certain quantum…

Quantum Physics · Physics 2025-07-10 Yuichiro Kitajima

We establish a necessary and sufficient condition for the existence of a quantum state that reproduces given correlation values in the Clauser--Horne--Shimony--Holt (CHSH) setup for any fixed normalized observables. This result addresses a…

Quantum Physics · Physics 2025-06-17 Ryosuke Nogami , Jaeha Lee

Nonlocality is an essential concept that distinguishes quantum from classical models and has been extensively studied in systems of qubits. For higher-dimensional systems, certain results for their two-level counterpart, like Bell…

Quantum Physics · Physics 2025-08-25 Uta Isabella Meyer , Ivan Šupić , Damian Markham , Frédéric Grosshans

Violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality certifies genuine quantum correlations. In this work, we formalize in Lean 4 the rigidity theorem -- any strategy achieving near-optimal CHSH value must be locally isometric to…

Quantum Physics · Physics 2026-04-07 Tianrun Zhao , Nengkun Yu

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 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

We propose a new method for detecting entanglement of two qubits and discuss its relation with the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality. Without the need for full quantum tomography for the density matrix we can experimentally…

Quantum Physics · Physics 2007-05-23 Kai Chen , Ling-An Wu

The Hardy test of nonlocality can be seen as a particular case of the Bell tests based on the Clauser-Horne (CH) inequality. Here we stress this connection when we analyze the relation between the CH-inequality violation, its threshold…

Quantum Physics · Physics 2015-06-03 G. Lima , E. B. Inostroza , R. O. Vianna , J. -Å. Larsson , C. Saavedra

We prove, modulo a conjecture on quantum steering ellipsoids being true, the existence of the phenomenon of locally inaccessible hidden quantum correlations. That is, the existence of two-particle states whose hidden quantum correlations…

Quantum Physics · Physics 2024-12-23 Andrés F. Ducuara , Cristian E. Susa , Paul Skrzypczyk

Motivated by very recent experiments, we consider a scenario "\`a la Bell" in which two protagonists test the Clauser-Horne-Shimony-Holt (CHSH) inequality using a photon-pair source based on spontaneous parametric down conversion and…

The Bell-CHSH (Clauser-Horne-Shimony-Holt) inequality in the vacuum state of a relativistic scalar quantum field is analyzed. Using Weyl operators built with smeared fields localized in the Rindler wedges, the Bell-CHSH inequality is…

High Energy Physics - Theory · Physics 2024-09-16 Philipe De Fabritiis , Marcelo S. Guimaraes , Itzhak Roditi , Silvio P. Sorella

Quantum correlations resulting in violations of Bell inequalities have generated a lot of interest in quantum information science and fundamental physics. In this paper, we address some questions that become relevant in Bell-type tests…

Quantum Physics · Physics 2016-01-11 Adetunmise C. Dada , Erika Andersson

We show that a pair of massive relativistic spin-1/2 particles prepared in a maximally entangled spin state in general is not capable of maximally violating the Clauser-Horne-Shimony-Holt (CHSH) version of Bell's inequalities without a…

Quantum Physics · Physics 2012-06-12 Pablo L. Saldanha , Vlatko Vedral

A quantum state can be characterized from the violation of a Bell inequality. The well-known CHSH inequality for example can be used to quantify the fidelity (up to local isometries) of the measured state with respect to the singlet state.…

We generalize the correlation functions of the Clauser-Horne-Shimony-Holt (CHSH) inequality to arbitrarily high-dimensional systems. Based on this generalization, we construct the general CHSH inequality for bipartite quantum systems of…

Quantum Physics · Physics 2007-05-23 Li-Bin Fu

We investigate quantum nonlocality of a single-photon entangled state under feasible measurement techniques consisting of on-off and homodyne detections along with unitary operations of displacement and squeezing. We test for a potential…

Quantum Physics · Physics 2017-01-30 Su-Yong Lee , Jiyong Park , Jaewan Kim , Changsuk Noh

Self-testing refers to the phenomenon that certain extremal quantum correlations (almost) uniquely identify the quantum system under consideration. For instance observing the maximal violation of the CHSH inequality certifies that the two…

Quantum Physics · Physics 2016-08-12 Jędrzej Kaniewski

This Master's thesis has two central subjects: the simulation of correlations generated by local measurements on entangled quantum states by local hidden-variables models and the revelation of hidden nonlocality. We present and detail the…

Quantum Physics · Physics 2014-07-23 Leonardo Guerini