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A device-independent randomness expansion protocol aims to take an initial random string and generate a longer one, where the security of the protocol does not rely on knowing the inner workings of the devices used to run it. In order to do…

Quantum Physics · Physics 2026-01-06 Rutvij Bhavsar , Sammy Ragy , Roger Colbeck

Free will (or randomness) has been studied to achieve loophole-free Bell's inequality test and to provide device-independent quantum key distribution security proofs. The required randomness such that a local hidden variable model (LHVM)…

Quantum Physics · Physics 2017-03-29 Yifeng Teng , Shenghao Yang , Siwei Wang , Mingfei Zhao

Measurements on entangled quantum systems necessarily yield outcomes that are intrinsically unpredictable if they violate a Bell inequality. This property can be used to generate certified randomness in a device-independent way, i.e.,…

Quantum Physics · Physics 2013-01-31 Stefano Pironio , Serge Massar

In any Bell test, loopholes can cause issues in the interpretation of the results, since an apparent violation of the inequality may not correspond to a violation of local realism. An important example is the coincidence-time loophole that…

Quantum Physics · Physics 2017-08-16 Jonathan Jogenfors , Jan-Åke Larsson

A direct analysis of the protocol of randomness amplification using Bell inequality violation is performed in terms of the convex combination of no-signaling boxes required to simulate quantum violation of the inequality. The probability…

We investigate the Bell inequalities derived from the graph states with violations detectable even with the presence of noises, which generalizes the idea of error-correcting Bell inequalities [Phys. Rev. Lett. 101, 080501 (2008)]. Firstly…

Quantum Physics · Physics 2009-03-20 Qing Chen , Sixia Yu , C. H. Oh

The violation of a Bell inequality implies the existence of nonlocality, making device-independent randomness certification possible. This paper derives a tight upper bound for the maximal quantum violation of Gisin's elegant Bell…

Quantum Physics · Physics 2025-02-14 Dan-Dan Hu , Meng-Yan Li , Fen-Zhuo Guo , Yu-Kun Wang , Hai-Feng Dong , Fei Gao

Recently it has been found that there exist maximally nonlocal quantum correlations that fail to certify randomness for any fixed input pair, rendering them useless for device-independent spot-checking randomness expansion schemes. Here we…

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

Nonlocal games with synchronous correlations are a natural generalization of functions between two finite sets. In this work we examine analogues of Bell's inequalities for such correlations, and derive a synchronous device-independent…

Quantum Physics · Physics 2020-04-20 Nishant Rodrigues , Brad Lackey

Different variants of a Bell inequality, such as CHSH and CH, are known to be equivalent when evaluated on nonsignaling outcome probability distributions. However, in experimental setups, the outcome probability distributions are estimated…

Quantum Physics · Physics 2022-02-15 Marc-Olivier Renou , Denis Rosset , Anthony Martin , Nicolas Gisin

In the last decade research of quantum nonlocality has moved beyond the regime of standard Bell nonlocality to consider network-based experimental set-ups involving multiple independent sources. Notion of full network nonlocality has…

Quantum Physics · Physics 2026-03-23 Kaushiki Mukherjee

The Bell inequality constrains the outcomes of measurements on pairs of distant entangled particles. The Bell contradiction states that the Bell inequality is inconsistent with the calculated outcomes of these quantum experiments. This…

Quantum Physics · Physics 2026-03-03 Kees van Hee , Kees van Berkel , Jan de Graaf

The simplest device-independent quantum key distribution protocol is based on the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality and allows two users, Alice and Bob, to generate a secret key if they observe sufficiently strong…

Quantum Physics · Physics 2021-04-27 Erik Woodhead , Antonio Acín , Stefano Pironio

The nonlocal behavior of quantum mechanics can be used to generate guaranteed fresh randomness from an untrusted device that consists of two nonsignalling components; since the generation process requires some initial fresh randomness to…

Quantum Physics · Physics 2013-02-26 Serge Fehr , Ran Gelles , Christian Schaffner

Nonlocality is a fascinating and counterintuitive aspect of Nature, revealed by the violation of a Bell inequality. The standard and easiest configuration in which Bell inequalities can be measured has been proposed by…

Quantum Physics · Physics 2015-03-17 Enrico Pomarico , Jean-Daniel Bancal , Bruno Sanguinetti , Anas Rochdi , Nicolas Gisin

Non-local correlations that obey the no-signalling principle contain intrinsic randomness. In particular, for a specific Bell experiment, one can derive relations between the amount of randomness produced, as quantified by the min-entropy…

Quantum Physics · Physics 2019-05-07 Boris Bourdoncle , Pei-Sheng Lin , Denis Rosset , Antonio Acín , Yeong-Cherng Liang

Randomness is a vital resource for modern day information processing, especially for cryptography. A wide range of applications critically rely on abundant, high quality random numbers generated securely. Here we show how to expand a random…

Quantum Physics · Physics 2016-11-02 Carl A. Miller , Yaoyun Shi

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

The generation of certifiable randomness is the most fundamental information-theoretic task that meaningfully separates quantum devices from their classical counterparts. We propose a protocol for exponential certified randomness expansion…

Quantum Physics · Physics 2019-01-14 Matthew Coudron , Jalex Stark , Thomas Vidick

Bell inequalities are an important tool in device-independent quantum information processing because their violation can serve as a certificate of relevant quantum properties. Probably the best known example of a Bell inequality is due to…