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Bell's theorem states that, to simulate the correlations created by measurement on pure entangled quantum states, shared randomness is not enough: some "non-local" resources are required. It has been demonstrated recently that all…

Quantum Physics · Physics 2009-11-10 Nicolas Brunner , Nicolas Gisin , Valerio Scarani

To date, most efforts to demonstrate quantum nonlocality have concentrated on systems of two (or very few) particles. It is however difficult in many experiments to address individual particles, making it hard to highlight the presence of…

We consider multiple entanglement swappings performed on a chain of bipartite states. Each state does not violate CHSH inequality. We show that before some critical number of entanglement swappings is achieved the output state does not…

Quantum Physics · Physics 2012-08-06 Waldemar Kłobus , Wiesław Laskowski , Marcin Markiewicz , Andrzej Grudka

Bell inequalities have traditionally been used to demonstrate that quantum theory is nonlocal, in the sense that there exist correlations generated from composite quantum states that cannot be explained by means of local hidden variables.…

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

In contrast to the wide-spread opinion that any separable quantum state satisfies every classical probabilistic constraint, we present a simple example where a separable quantum state does not satisfy the original Bell inequality although…

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

Device-independent quantum key distribution is a secure quantum cryptographic paradigm that allows two honest users to establish a secret key, while putting minimal trust in their devices. Most of the existing protocols have the following…

Device-independent certification, also known as self-testing, aims at guaranteeing the proper functioning of untrusted and uncharacterized devices. For example, the quality of an unknown source expected to produce two-qubit maximally…

Quantum Physics · Physics 2022-04-08 Xavier Valcarce , Julian Zivy , Nicolas Sangouard , Pavel Sekatski

Quantum nonlocality is usually associated with entangled states by their violations of Bell-type inequalities. However, even unentangled systems, whose parts may have been prepared separately, can show nonlocal properties. In particular, a…

Quantum Physics · Physics 2019-02-06 Saronath Halder , Manik Banik , Sristy Agrawal , Somshubhro Bandyopadhyay

Bell nonlocality is a fundamental phenomenon of quantum physics as well as an essential resource for various tasks in quantum information processing. It is known that for the observation of nonlocality the measurements on a quantum system…

Quantum Physics · Physics 2025-07-16 Martin Plávala , Otfried Gühne , Marco Túlio Quintino

The assumption of source independence was used to reveal nonlocal (apart from standard Bell-CHSH scenario) nature of correlations generated in entanglement swapping experiments. In this work, we have derived a set of sufficient criteria,…

Quantum Physics · Physics 2023-07-12 Kaushiki Mukherjee , Biswajit Paul , Debasis Sarkar

The majority of recent works investigating the link between non-locality and randomness, e.g. in the context of device-independent cryptography, do so with respect to some specific Bell inequality, usually the CHSH inequality. However, the…

Quantum Physics · Physics 2014-01-23 O. Nieto-Silleras , S. Pironio , J. Silman

Non-local correlations are not only a fascinating feature of quantum theory, but an interesting resource for information processing, for instance in communication-complexity theory or cryptography. An important question in this context is…

Quantum Physics · Physics 2008-10-17 Dejan D. Dukaric , Stefan Wolf

Unsharp measurements are widely seen as the key resource for recycling the nonlocality of an entangled state shared between several sequential observers. Contrasting this, we here show that nonlocality can be recycled using only standard…

Quantum Physics · Physics 2024-03-04 Anna Steffinlongo , Armin Tavakoli

Device-independent randomness generation and quantum key distribution protocols rely on a fundamental relation between the non-locality of quantum theory and its random character. This relation is usually expressed in terms of a trade-off…

Quantum Physics · Physics 2018-03-20 Olmo Nieto-Silleras , Cédric Bamps , Jonathan Silman , Stefano Pironio

In quantum information and computation, the generation of entanglement through unitary gates remains a significant and active area of research. However, there are states termed as absolutely separable, from which entanglement cannot be…

Quantum Physics · Physics 2026-02-13 Bivas Mallick , Saheli Mukherjee , Nirman Ganguly , A. S. Majumdar

A standard approach to quantifying resources is to determine which operations on the resources are freely available, and to deduce the partial order over resources that is induced by the relation of convertibility under the free operations.…

Understanding the relation between the different forms of inseparability in quantum mechanics is a longstanding problem in the foundations of quantum theory and has implications for quantum information processing. Here we make progress in…

Quantum Physics · Physics 2013-04-09 Daniel Cavalcanti , Antonio Acin , Nicolas Brunner , Tamas Vertesi

Spatial separation restricts the set of locally implementable quantum operations on distributed multipartite quantum systems. We propose that indefinite causal structure arising due to quantum superposition of different space-time…

Quantum Physics · Physics 2023-02-21 Pratik Ghosal , Arkaprabha Ghosal , Debarshi Das , Ananda G. Maity

A set of orthogonal product states of a composite Hilbert space is genuinely nonlocal if the states are locally indistinguishable across any bipartition. In this work, we construct a minimal set of party asymmetry genuine nonlocal set in…

Quantum Physics · Physics 2025-08-21 Atanu Bhunia , Indrani Chattopadhyay , Debasis Sarkar