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In many quantum information applications, a minimum detection efficiency must be exceeded to ensure success. Protocols depending on the violation of a Bell inequality, for instance, may be subject to the so-called detection loophole:…

Quantum Physics · Physics 2017-06-29 Jochen Szangolies , Hermann Kampermann , Dagmar Bruß

A Bell test can rule out local realistic models, and has potential applications in communications and information tasks. For example, a Bell inequality violation can certify the presence of intrinsic randomness in measurement outcomes,…

In this paper we study sharp thresholds for detecting sparse signals in $\beta$-models for potentially sparse random graphs. The results demonstrate interesting interplay between graph sparsity, signal sparsity, and signal strength. In…

Statistics Theory · Mathematics 2017-05-30 Rajarshi Mukherjee , Sumit Mukherjee , Subhabrata Sen

We consider a Bell-like inequality performed using various instances of multi-photon entangled states to demonstrate that losses occurring after the unitary transformations used in the nonlocality test can be counteracted by enhancing the…

Quantum Physics · Physics 2012-06-22 Youngrong Lim , Mauro Paternostro , Jinhyoung Lee , Minsu Kang , Hyunseok Jeong

Based on the Bell theorem, it has been believed that a theoretical computation of the Bell correlation requires explicit use of an entangled state. Such a physical superposition of light waves occurs in the downconverter sources used in…

Quantum Physics · Physics 2021-01-14 Louis Sica

The Bell inequalities in three and four correlations are re-derived in general forms showing that three and four data sets, respectively, identically satisfy them regardless of whether they are random, deterministic, measured, predicted, or…

Quantum Physics · Physics 2020-06-24 Louis Sica

Experimental tests of Bell's inequality allow to distinguish quantum mechanics from local hidden variable theories. Such tests are performed by measuring correlations of two entangled particles (e.g. polarization of photons or spins of…

The concept of self-testing (or rigidity) refers to the fact that for certain Bell inequalities the maximal violation can be achieved in an essentially unique manner. In this work we present a family of Bell inequalities which are maximally…

Quantum Physics · Physics 2020-09-22 Jędrzej Kaniewski

Certification of quantum nonlocality plays a central role in practical applications like device-independent quantum cryptography and random number generation protocols. These applications entail the challenging problem of certifying quantum…

Quantum Physics · Physics 2021-07-21 S. Gómez , D. Uzcategui , I. Machuca , E. S. Gómez , S. P. Walborn , G. Lima , D. Goyeneche

In its vast majority entanglement verification is examined either in the complete characterized or totally device independent scenario. The assumptions imposed by these extreme cases are often either too weak or strong for real experiments.…

Quantum Physics · Physics 2013-05-30 Tobias Moroder , Oleg Gittsovich

We report correlation measurements on two $^9$Be$^+$ ions that violate a chained Bell inequality obeyed by any local-realistic theory. The correlations can be modeled as derived from a mixture of a local-realistic probabilistic distribution…

Quantum Physics · Physics 2017-04-05 T. R. Tan , Y. Wan , S. Erickson , P. Bierhorst , D. Kienzler , S. Glancy , E. Knill , D. Leibfried , D. J. Wineland

Non-contextuality (NC) and Bell inequalities can be expressed as bounds $\Omega$ for positive linear combinations $S$ of probabilities of events, $S \leq \Omega$. Exclusive events in $S$ can be represented as adjacent vertices of a graph…

Recent work has extended Bell's theorem by quantifying the amount of communication required to simulate entangled quantum systems with classical information. The general scenario is that a bipartite measurement is given from a set of…

Quantum Physics · Physics 2009-11-06 Serge Massar , Dave Bacon , Nicolas Cerf , Richard Cleve

The $\boldsymbol{\beta}$-model for random graphs is commonly used for representing pairwise interactions in a network with degree heterogeneity. Going beyond pairwise interactions, Stasi et al. (2014) introduced the hypergraph…

Statistics Theory · Mathematics 2024-06-07 Sagnik Nandy , Bhaswar B. Bhattacharya

The two-particle correlation obtained from the quantum state used in the Bell inequality is sinusoidal, but the standard Bell inequality only uses two pairs of settings and not the whole sinusoidal curve. The highest to-date visibility of…

Quantum Physics · Physics 2022-03-16 Marek Zukowski , Dagomir Kaszlikowski , Adam Baturo , Jan-Åke Larsson

Graph states are an important class of entangled states that serve as a key resource for distributed information processing and communication in quantum networks. In this work, we propose a protocol that utilizes a Bell sampling subroutine…

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…

Nonlocality, manifested by the violation of Bell inequalities, indicates entanglement within a joint quantum system. A natural question is how much entanglement is required for a given nonlocal behavior. Here, we explore this question by…

Quantum Physics · Physics 2025-06-23 Yuwei Zhu , Xingjian Zhang , Xiongfeng Ma

When three or more particles are considered, quantum correlations can be stronger than the correlations generated by so-called hybrid local hidden variable models, where some of the particles are considered as a single block inside which…

Quantum Physics · Physics 2023-02-13 Fabian Bernards , Otfried Gühne

Analyzing the geometry of correlation sets constrained by general causal structures is of paramount importance for foundational and quantum technology research. Addressing this task is generally challenging, prompting the development of…