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The correlations that violate the CHSH inequality are known to have complementary contributions from signaling and local indeterminacy. This complementarity is shown to represent a strengthening of Bell's theorem, and can be used to certify…

Quantum Physics · Physics 2014-08-06 S. Aravinda , R. Srikanth

We establish a necessary and sufficient condition for the existence of a quantum state that reproduces given correlation values in the Clauser--Horne--Shimony--Holt (CHSH) setup for any fixed normalized observables. This result addresses a…

Quantum Physics · Physics 2025-06-17 Ryosuke Nogami , Jaeha Lee

From dice to modern complex circuits, there have been many attempts to build increasingly better devices to generate random numbers. Today, randomness is fundamental to security and cryptographic systems, as well as safeguarding privacy. A…

As a way of saving quantum resources, recycling of Bell nonlocality has been experimentally studied, but restricted to sequential unsharp measurements. However, it has been theoretically shown recently that projective measurements are…

Quantum Physics · Physics 2022-12-08 Ya Xiao , Yan-Xin Rong , Xin-Hong Han , Shuo Wang , Xuan Fan , Wei-Chen Li , Yong-Jian Gu

In a previous paper, we introduced a semi-device-independent scheme consisting of an untrusted source sending quantum states to an untrusted measuring device, with the sole assumption that the average energy of the states emitted by the…

Quantum Physics · Physics 2019-05-23 Thomas Van Himbeeck , Stefano Pironio

Violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality certifies genuine quantum correlations. In this work, we formalize in Lean 4 the rigidity theorem -- any strategy achieving near-optimal CHSH value must be locally isometric to…

Quantum Physics · Physics 2026-04-07 Tianrun Zhao , Nengkun Yu

It is well-known that observing nonlocal correlations allows us to draw conclusions about the quantum systems under consideration. In some cases this yields a characterisation which is essentially complete, a phenomenon known as…

Quantum Physics · Physics 2020-04-02 Tim Coopmans , Jędrzej Kaniewski , Christian Schaffner

Quantum theory introduces a cut between the observer and the observed system, but does not provide a definition of what is an observer. Based on an informational definition of observer, Grinbaum has recently predicted an upper bound on…

Quantum Physics · Physics 2015-12-31 Hou Shun Poh , Siddarth K. Joshi , Alessandro Ceré , Adán Cabello , Christian Kurtsiefer

Correlation boxes are hypothetical systems capable of producing the maximal algebraic violation of Bell inequalities, beyond the quantum bound and without superluminal signaling. The fact that these systems show stronger correlations than…

Quantum Physics · Physics 2017-03-08 A. P. Costa , Fernando Parisio

In the spirit of device-independent cryptography, we present a two-party quantum authorization primitive with non-locality as its fueling resource. Therein, users are attributed authorization levels granting them access to a private…

Quantum Physics · Physics 2021-03-03 Ricardo Faleiro , Manuel Goulão

Quantum nonlocality offers a secure way to produce random numbers: their unpredictability is intrinsic and can be certified just by observing the statistic of the measurement outcomes, without assumptions on how they are produced. To do…

Collective measurements on large quantum systems together with a majority voting strategy can lead to a violation of the CHSH Bell inequality. In presence of many entangled pairs, this violation decreases quickly with the number of pairs,…

Genuine multipartite non-locality is not only of fundamental interest but also serves as an important resource for quantum information theory. We consider the $N$-partite scenario and provide an analytical upper bound on the maximal…

Quantum Physics · Physics 2024-09-16 Youwang Xiao , Zong Wang , Wen-Na Zhao , Ming Li

The outcomes of measurements on entangled quantum systems can be nonlocally correlated. However, while it is easy to write down toy theories allowing arbitrary nonlocal correlations, those allowed in quantum mechanics are limited. Quantum…

Quantum Physics · Physics 2015-03-17 Peter Janotta , Christian Gogolin , Jonathan Barrett , Nicolas Brunner

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

We consider a range of "theories" that violate the uncertainty relation for anti-commuting observables derived in [JMP, 49, 062105 (2008)]. We first show that Tsirelson's bound for the CHSH inequality can be derived from this uncertainty…

Quantum Physics · Physics 2011-05-02 Greg Ver Steeg , Stephanie Wehner

Bell-CHSH-like inequalities have been very successful in benchmarking {\it spatial} quantum correlations. However, as this paper illustrates, they are in general not sufficient for benchmarking {\it temporal} quantum correlations. To show…

Quantum Physics · Physics 2026-04-14 Prasenjit Deb , Almut Beige , Lewis A. Clark

Device-independent protocols use nonlocality to certify that they are performing properly. This is achieved via Bell experiments on entangled quantum systems, which are kept isolated from one another during the measurements. However, with…

Quantum Physics · Physics 2013-03-26 Jonathan Silman , Stefano Pironio , Serge Massar

Quantum non-locality is an important concept in quantum physics. In this work, we study the quantum non-locality in a fermion many-body system under quasi-periodic disorders. The Clauser-Horne-Shimony-Holt (CHSH) inequality is…

Disordered Systems and Neural Networks · Physics 2024-10-08 Yoshihito Kuno

For a nonseparable bipartite quantum state violating the Clauser-Horne-Shimony-Holt (CHSH) inequality, we evaluate amounts of noise breaking the quantum character of its statistical correlations under any generalized quantum measurements of…

Quantum Physics · Physics 2007-05-23 Elena R. Loubenets
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