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A continuous-variable Bell inequality, valid for an arbitrary number of observers measuring observables with an arbitrary number of outcomes, was recently introduced in [Cavalcanti \emph{et al.}, Phys. Rev. Lett. {\bf 99}, 210405 (2007)].…

Quantum Physics · Physics 2008-07-25 Alejo Salles , Daniel Cavalcanti , Antonio Acín

The violation of J. Bell's inequality with two entangled and spatially separated quantum two- level systems (TLS) is often considered as the most prominent demonstration that nature does not obey ?local realism?. Under different but related…

The correspondence principle suggests that quantum systems grow classical when large. Classical systems cannot violate Bell inequalities. Yet agents given substantial control can violate Bell inequalities proven for large-scale systems. We…

Quantum Physics · Physics 2021-02-10 Adam Bene Watts , Nicole Yunger Halpern , Aram Harrow

The demonstration and use of nonlocality, as defined by Bell's theorem, rely strongly on dealing with non-detection events due to losses and detector inefficiencies. Otherwise, the so-called detection loophole could be exploited. The only…

Quantum Physics · Physics 2016-01-20 Gilles Pütz , Nicolas Gisin

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

We prove that for every Bell's inequality and for a broad class of protocols, there always exists a multi-party communication complexity problem, for which the protocol assisted by states which violate the inequality is more efficient than…

Quantum Physics · Physics 2009-11-07 Caslav Brukner , Marek Zukowski , Jian-Wei Pan , Anton Zeilinger

If $Q$ is a real, symmetric and positive definite $n\times n$ matrix, and $B$ a real $n\times n$ matrix whose eigenvalues have negative real parts, we consider the Ornstein--Uhlenbeck semigroup on $\mathbb{R}^n$ with covariance $Q$ and…

Functional Analysis · Mathematics 2023-02-15 Valentina Casarino , Paolo Ciatti , Peter Sjögren

Bell inequalities are an important tool for studying non-locality, however quickly become computationally intractable as the system size grows. We consider a novel method for finding an upper bound for the quantum violation of such…

Quantum Physics · Physics 2025-06-16 Luke Mortimer

Unitary operators are employed to investigate the violation of the Bell-CHSH inequality. The ensuing modifications affecting both classical and quantum bounds are elucidated. The relevance of a particular class of unitary operators whose…

Quantum Physics · Physics 2024-10-15 M. S. Guimaraes , I. Roditi , S. P. Sorella

In this article, we present some new general forms of numerical radius inequalities for Hilbert space operators. The significance of these inequalities follow from the way they extend and refine some known results in this field. Among other…

Functional Analysis · Mathematics 2019-06-21 Mohammad Sababheh , Hamid Reza Moradi

Quantum nonlocality is a counterintuitive phenomenon that lies beyond the purview of causal influences. Recently, Bell inequalities have been generalized to the case of quantum inputs, leading to a powerful family of semi-quantum Bell…

Quantum Physics · Physics 2016-08-12 Charles Ci Wen Lim

We present a novel tight bound on the quantum violations of the CGLMP inequality in the case of infinitely many outcomes. Like in the case of Tsirelson's inequality the proof of our new inequality does not require any assumptions on the…

Quantum Physics · Physics 2010-05-04 S. Zohren , P. Reska , R. D. Gill , W. Westra

We derive a new class of correlation Bell-type inequalities. The inequalities are valid for any number of outcomes of two observables per each of n parties, including continuous and unbounded observables. We show that there are no…

Quantum Physics · Physics 2007-11-24 E. G. Cavalcanti , C. J. Foster , M. D. Reid , P. D. Drummond

We derive a multipartite generalized Bell inequality which involves the entire range of settings for each of the local observers. Especially, it is applied to show non-local behavior of a six-qubit mixture of Greenberger-Horne-Zeilinger…

Quantum Physics · Physics 2009-11-13 Koji Nagata

Non-locality can be quantified by the violation of a Bell inequality. Since this violation may be amplified by local operations an alternative measure has been proposed - distillable non-locality. The alternative measure is difficult to…

Quantum Physics · Physics 2011-06-21 Manuel Forster

Recently a new Bell inequality has been introduced (CGLMP,KKCZO) that is strongly resistant to noise for maximally entangled states of two $d$-dimensional quantum systems. We prove that a larger violation, or equivalently a stronger…

Quantum Physics · Physics 2009-11-07 A. Acin , T. Durt , N. Gisin , J. I. Latorre

Witnessing continuous-variable Bell nonlocality is a challenging endeavor, but Bell himself showed how one might demonstrate this nonlocality. Though Bell nearly showed a violation using the CHSH inequality with sign-binned…

Quantum Physics · Physics 2016-01-20 James Schneeloch , Samuel H. Knarr , Daniel J. Lum , John C. Howell

We give a partial list of 26 tight Bell inequalities for the case where Alice and Bob choose among four two-outcome measurements. All tight Bell inequalities with less settings are reviewed as well. For each inequality we compute…

Quantum Physics · Physics 2009-11-13 Nicolas Brunner , Nicolas Gisin

I derive separability inequalities for Bell correlations of observables in arbitrary pure or mixed $N$ Qudit states in $D^N$-dimensional state space. I find states (a continuum of states if $D>3$) including maximally entangled states which…

Quantum Physics · Physics 2020-02-03 S. M. Roy

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