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Violating Bell's inequalities (BIs) allows one to certify the preparation of entangled states from minimal assumptions -- in a device-independent manner. Finding BIs tailored to many-body correlations as prepared in present-day quantum…

Quantum Physics · Physics 2021-08-24 Guillem Müller-Rigat , Albert Aloy , Maciej Lewenstein , Irénée Frérot

We report on the experimental violation of multipartite Bell inequalities by entangled states of trapped ions. First we consider resource states for measurement-based quantum computation of between 3 and 7 ions and show that all strongly…

Quantum Physics · Physics 2014-03-19 B. P. Lanyon , M. Zwerger , P. Jurcevic , C. Hempel , W. Dür , H. J. Briegel , R. Blatt , C. F. Roos

All-photonic quantum repeaters are essential for establishing long-range quantum entanglement. Within repeater nodes, reliably performing entanglement swapping is a key component of scalable quantum communication. To tackle the challenge of…

Quantum Physics · Physics 2025-05-14 Bikun Li , Kenneth Goodenough , Filip Rozpędek , Liang Jiang

A Bell-type inequality is proposed in terms of Wigner-Yanase skew information, which is quadratic and involves only one local spin observable at each site. This inequality presents a hierarchic classification of all states of multipartite…

Quantum Physics · Physics 2010-02-20 Zeqian Chen

Theoretical considerations of Bell-inequality experiments usually assume identically prepared and independent pairs of particles. Here we consider pairs that exhibit both intra- and inter-pair entanglement. The pairs are taken from a large…

Quantum Physics · Physics 2009-12-17 S. Ashhab , Koji Maruyama , Caslav Brukner , Franco Nori

Violation of the Bell-type inequalities is necessary to confirm the existence of nonlocality in nonclassical (entangled) states. We have designed a customized operator which is made of the sum of the Pauli matrices ($\sigma_x$, $\sigma_y$,…

Quantum Physics · Physics 2025-09-30 Tomis Prajapati , Harsh Mehta , Shreya Banerjee , Prasanta K. Panigrahi , V. Narayanan

Entanglement and Bell nonlocality are used to describe quantum inseparabilities. Bell-nonlocal states form a strict subset of entangled states. A natural question arises concerning how much territory Bell nonlocality occupies entanglement…

Quantum Physics · Physics 2019-09-04 Xiao-Gang Fan , Zhi-Yong Ding , Fei Ming , Huan Yang , Dong Wang , Liu Ye

We review some counterintuitive properties of standard measures describing quantum entanglement and violation of Bell's inequality (often referred to as "nonlocality") in two-qubit systems. By comparing the nonlocality, negativity,…

Quantum Physics · Physics 2020-01-10 Adam Miranowicz , Bohdan Horst , Andrzej Koper

Self-testing constitutes one of the most powerful forms of device certification, enabling a complete and device-independent characterization of a quantum apparatus solely from the observed correlations. In recent work by the authors [23], a…

Quantum Physics · Physics 2025-12-03 Arturo Konderak , Patryk Michalski

Quantum correlations may violate the Bell inequalities. Most of the experimental schemes confirming this prediction have been realized in all-optical Bell tests suffering from the detection loophole. Experiment which closes this loophole…

Quantum Physics · Physics 2011-09-23 Magdalena Stobińska , Pavel Sekatski , Adam Buraczewski , Nicolas Gisin , Gerd Leuchs

Bell inequalities are one of the cornerstones of quantum foundations, and fundamental tools for quantum technologies. Recently, the scientific community worldwide has put a lot of effort towards them, which culminated with loophole-free…

The Pauli groups are ubiquitous in quantum information theory because of their usefulness in describing quantum states and operations and their readily understood symmetry properties. In addition, the most well-understood quantum error…

Quantum Physics · Physics 2015-01-20 Mark Howard , Eoin Brennan , Jiri Vala

Bell inequalities play a central role in the study of quantum non-locality and entanglement, with many applications in quantum information. Despite the huge literature on Bell inequalities, it is not easy to find a clear conceptual answer…

Quantum Physics · Physics 2012-06-21 Samson Abramsky , Lucien Hardy

Network Bell experiments give rise to a form of quantum nonlocality that conceptually goes beyond Bell's theorem. We investigate here the simplest network, known as the bilocality scenario. We depart from the typical use of the Bell State…

Quantum Physics · Physics 2021-06-04 Armin Tavakoli , Nicolas Gisin , Cyril Branciard

The growth of quantum technologies is attracting the interest of many students eager to learn concepts such as quantum entanglement or quantum superposition. However, the non-intuitive nature of these concepts poses a challenge to…

We show that the "practical" Bell inequalities, which use intensities as the observed variables, commonly used in quantum optics and widely accepted in the community, suffer from an inherent loophole, which severely limits the range of…

Quantum Physics · Physics 2016-10-07 Marek Zukowski , Marcin Wiesniak , Wieslaw Laskowski

We propose a scheme to test Bell's inequalities for an arbitrary number of measurement outcomes on entangled continuous variable states. The Bell correlation functions are expressible in terms of phase-space quasiprobability functions with…

Quantum Physics · Physics 2007-05-23 W. Son , C. Brukner , M. S. Kim

We present a Bell-type inequality for four-qubit systems. Using the inequality we investigate quantum nonlocality of a generic family of states $\left|G_{abcd}\right >$ [Phys. Rev. A 65, 052112 (2002)] and several canonical four-qubit…

Quantum Physics · Physics 2017-06-07 Dong Ding , Fengli Yan , Ting Gao

Quantum correlations which violate a Bell inequality are presumed to power better-than-classical protocols for solving communication complexity problems (CCPs). How general is this statement? We show that violations of correlation-type Bell…

Quantum Physics · Physics 2020-09-09 Armin Tavakoli , Marek Żukowski , Časlav Brukner

Violation of local realism via Bell inequality - a profound and counterintuitive manifestation of quantum theory that conflicts with the prediction of local realism - is viewed to be intimately linked with quantum entanglement. Experimental…