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We have determined numerically the maximum quantum violation of over 100 tight bipartite Bell inequalities with two-outcome measurements by each party on systems of up to four dimensional Hilbert spaces. We have found several cases,…

Quantum Physics · Physics 2009-11-13 K. F. Pál , T. Vértesi

Bell nonlocality between distant quantum systems---i.e., joint correlations which violate a Bell inequality---can be verified without trusting the measurement devices used, nor those performing the measurements. This leads to…

Quantum Physics · Physics 2015-01-16 Sacha Kocsis , Michael J. W. Hall , Adam J. Bennet , Dylan J. Saunders , G. J. Pryde

Bell's theorem prompts us with a fundamental inquiry: what is the simplest scenario leading to the incompatibility between quantum correlations and the classical theory of causality? Here we demonstrate that quantum non-classicality is…

Quantum Physics · Physics 2025-12-23 Pedro Lauand , Davide Poderini , Rafael Rabelo , Rafael Chaves

Complex numbers play a crucial role in quantum mechanics. However, their necessity remains debated: whether they are fundamental or merely convenient. Recently, it was claimed that quantum mechanics based on real numbers can be…

We consider retarded settings in the context of a Bell-type experiment. The retarded setting is defined as the value the setting would have taken were it not for some external intervention (for example, by a human). We derive retarded Bell…

Quantum Physics · Physics 2015-08-28 Lucien Hardy

Bell inequalities follow from a set of seemingly natural assumptions about how to provide a causal model of a Bell experiment. In the face of their violation, two types of causal models that modify some of these assumptions have been…

Quantum Physics · Physics 2022-05-11 Patrick J. Daley , Kevin J. Resch , Robert W. Spekkens

Quantum nonlocality in networks featuring multiple independent sources underpins large-scale quantum communication and poses fundamental challenges for its characterization. In this work, we construct a family of explicit nonlinear Bell…

Quantum Physics · Physics 2025-09-08 Yao Xiao , Fenzhuo Guo , Haifeng Dong , Fei Gao

The entangled quantum states play a key role in quantum information. The association of the quantum state vector with each individual physical system in an attributive way is a source of many false paradoxes and inconsistencies. The…

Quantum Physics · Physics 2007-10-15 M. Kupczynski

We provide an analytical tripartite-study from the generalized $R$-matrix. It provides the upper bound of the maximum violation of Mermin's inequality. For a generic 2-qubit pure state, the concurrence or $R$-matrix characterizes the…

Quantum Physics · Physics 2023-01-11 Xingyu Guo , Chen-Te Ma

Quantum networks are the center of many of the recent advances in quantum science, not only leading to the discovery of new properties in the foundations of quantum theory but also allowing for novel communication and cryptography…

The interpretation of the meaning of Quantum Mechanics has faced controversy since its inception. Bell's inequalities are a touchstone in this controversy. Their observed violation demonstrates that at least one of the hypotheses involved…

Quantum Physics · Physics 2026-03-27 Mónica Agüero , Juliana Bordieu , Alejandro Hnilo , Marcelo Kovalsky , Myriam Nonaka

Quantum hypothesis testing is a central task in the entire field of quantum information theory. Understanding its ultimate limits will give insight into a wide range of quantum protocols and applications, from sensing to communication.…

Quantum Physics · Physics 2020-11-18 Quntao Zhuang , Stefano Pirandola

It is now a well-known fact that the correlations arising from local dichotomic measurements on an entangled quantum state may exhibit intrinsically non-classical features. In this paper we delve into a comprehensive study of random…

We propose two semi-device-independent approaches that are able to quantify unknown multipartite quantum entanglement experimentally, where the only information that has to be known beforehand is quantum dimension, and the concept that…

Quantum Physics · Physics 2022-01-05 Lijinzhi Lin , Zhaohui Wei

Bell's test, initially devised to distinguish quantum theory from local hidden variable models through {violations of local bounds}, is also a common tool for detecting entanglement. For this purpose, one can assume the quantum description…

Quantum Physics · Physics 2026-04-21 Liang-Liang Sun , Yong-Shun Song , Sixia Yu

Combining recent advances in superconducting quantum hardware, we explore quantum correlations in a previously inaccessible regime by observing \emph{simultaneously} high-dimensional and many-body Bell non-locality. We report a…

Quantum Physics · Physics 2026-04-28 Yousef Mafi , Ali G. Moghaddam , Teemu Ojanen

In standard quantum mechanics, complex numbers are used to describe the wavefunction. Although complex numbers have proven sufficient to predict the results of existing experiments, there is no apparent theoretical reason to choose them…

We obtain a general connection between a quantum advantage in communication complexity and non-locality. We show that given any protocol offering a (sufficiently large) quantum advantage in communication complexity, there exists a way of…

A logical approach to Bell's Inequalities of quantum mechanics has been introduced by Abramsky and Hardy [2]. We point out that the logical Bell's Inequalities of [2] are provable in the probability logic of Fagin, Halpern and Megiddo [4].…

Logic · Mathematics 2016-03-10 Tapani Hyttinen , Gianluca Paolini , Jouko Väänänen

In this paper I demonstrate that the quantum correlations of polarization (or spin) observables used in Bell's argument against local realism have to be interpreted as {\it conditional} quantum correlations. By taking into account…

Quantum Physics · Physics 2018-07-18 Andrei Khrennikov