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In the study of quantum nonlocality, one obstacle is that the analytical criterion for identifying the boundaries between quantum and postquantum correlations has not yet been given, even in the simplest Bell scenario. We propose a…

Quantum Physics · Physics 2018-05-23 Satoshi Ishizaka

Bell inequality violations are often taken as evidence that quantum nonlocality guarantees intrinsic randomness, effectively playing the role of a "dice" at the heart of many device-independent cryptographic protocols. We show that there…

Quantum Physics · Physics 2025-09-11 Ravishankar Ramanathan , Yuan Liu , Stefano Pironio

Self-testing is a method to certify devices from the result of a Bell test. Although examples of noise tolerant self-testing are known, it is not clear how to deal efficiently with a finite number of experimental trials to certify the…

Quantum Physics · Physics 2021-03-03 Jean-Daniel Bancal , Kai Redeker , Pavel Sekatski , Wenjamin Rosenfeld , Nicolas Sangouard

One of the most striking features of quantum theory is that it allows distant observers to share correlations that resist local hidden variable (classical) explanations, a phenomenon referred to as Bell nonlocality. Besides their…

Quantum Physics · Physics 2023-12-13 Anubhav Chaturvedi , Giuseppe Viola , Marcin Pawłowski

Quantum theory allows for nonlocality without entanglement. Notably, there exist bipartite quantum measurements consisting of only product eigenstates, yet they cannot be implemented via local quantum operations and classical communication.…

Quantum Physics · Physics 2023-07-12 Ivan Šupić , Nicolas Brunner

The future progress of semi-device independent quantum information science depends crucially on our ability to bound the strength of the nonlocal correlations achievable with finite dimensional quantum resources. In this work, we…

Quantum Physics · Physics 2014-02-05 Miguel Navascues , Gonzalo de la Torre , Tamas Vertesi

Bell inequalities reveal the fundamentally nonlocal character of quantum mechanics. In this regard, one of the interesting problems is to explore all possible Bell inequalities that demonstrate a gap between local and nonlocal quantum…

Quantum Physics · Physics 2026-02-10 Palash Pandya , Shubhayan Sarkar , Remigiusz Augusiak

We introduce a version of the chained Bell inequality for an arbitrary number of measurement outcomes, and use it to give a simple proof that the maximally entangled state of two d dimensional quantum systems has no local component. That…

Quantum Physics · Physics 2011-04-08 Jonathan Barrett , Adrian Kent , Stefano Pironio

Self testing is a device-independent technique based on non-local correlations whose aim is to certify the effective uniqueness of the quantum state and measurements needed to produce these correlations. It is known that the maximal…

Quantum Physics · Physics 2016-07-12 Ivan Šupić , Remigiusz Augusiak , Alexia Salavrakos , Antonio Acín

Scientific inquiry seeks causal explanations of observed phenomena. The Bell experiment provides a paradigmatic case, revealing correlations between spatially separated systems that no local model can reproduce. Such correlations, known as…

Quantum Physics · Physics 2026-03-03 Mark Broom , Talel Naccache , Emmanuel M. Pothos , Christoph Gallus , Pawel Blasiak

Bell's seminal paper shows that some correlations in quantum theory are not reconcilable with hidden variables and the classical notion of locality. Yet, a weaker notion of locality, known as no-signalling, survives the no-go-result. Here,…

Quantum Physics · Physics 2020-05-27 Markus Frembs , Andreas Döring

A problem in quantum information theory is to find the experimental setup that maximizes the nonlocality of correlations with respect to some suitable measure such as the violation of Bell inequalities. The latter has however some…

Quantum Physics · Physics 2016-08-30 Sacha Schwarz , Andre Stefanov , Stefan Wolf , Alberto Montina

Bell nonlocality -- the existence of quantum correlations that cannot be explained by classical means -- is certainly one of the most striking features of quantum mechanics. Its range of applications in device-independent protocols is…

Quantum Physics · Physics 2023-12-06 Rafael Santos , Debashis Saha , Flavio Baccari , Remigiusz Augusiak

Device-independent quantum key distribution allows for proving the security of a shared cryptographic key between two distant parties with potentially untrusted devices. The security proof is based on the measurement outcome statistics…

Quantum Physics · Physics 2023-10-23 Máté Farkas

We demonstrate that, in the tripartite scenario with all parties' local events being space-like separated, Hardy-type nonlocality constitutes a stronger manifestation of nonlocal correlations than those captured by Mermin-type inequalities,…

Quantum Physics · Physics 2025-04-29 Ranendu Adhikary , Souradeep Sasmal , Arup Roy

We study the faces of the set of quantum correlations, i.e., the Bell and noncontextuality inequalities without any quantum violation. First, we investigate the question whether every proper (tight) Bell inequality for two parties, other…

One of the striking properties of quantum mechanics is the occurrence of the Bell-type non-locality. They are a fundamental feature of the theory that allows two parties that share an entangled quantum system to observe correlations…

The characterization of the set of quantum correlations in Bell scenarios is a problem of paramount importance for both the foundations of quantum mechanics and quantum information processing in the device-independent scenario. However, a…

Quantum Physics · Physics 2015-09-09 Julio I. de Vicente

No-signaling theories, which can contain nonlocal correlations stronger than classical correlations but limited by the no-signaling condition, have deepened our understanding of the quantum theory. In principle, the nonlocality of these…

Quantum Physics · Physics 2016-11-01 Zhu Cao , Tianyi Peng

The goal of self-testing is to characterize an a priori unknown quantum system based solely on measurement statistics, i.e. using an uncharacterized measurement device. Here we develop self-testing methods for quantum prepare-and-measure…

Quantum Physics · Physics 2018-12-10 Armin Tavakoli , Jędrzej Kaniewski , Tamás Vértesi , Denis Rosset , Nicolas Brunner