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Density matrices are the most general descriptions of quantum states, covering both pure and mixed states. Positive semidefiniteness is a physical requirement of density matrices, imposing nonnegative probabilities of measuring physical…

Quantum Physics · Physics 2024-09-11 Colm Kelleher

Nonlocality captures one of the counterintuitive features of nature that defies classical intuition. Recent investigations reveal that our physical world's nonlocality is at least tripartite; i.e., genuinely tripartite nonlocal correlations…

For the Bell scenario with two parties and two binary observables per party, it is known that the no-signaling polytope is the polyhedral dual (polar) of the Bell polytope. Computational evidence suggests that this duality also holds for…

Quantum Physics · Physics 2012-07-17 Tobias Fritz

In this letter, a nonlocal effect for a bipartite system which is induced by a local cyclic evolution of one of its subsystem is suggested. This effect vanishes when the system is at a disentangled pure state but can be observed for some…

Quantum Physics · Physics 2009-11-10 Li-Bin Fu

Any bipartite quantum state has quasi-probability representations in terms of separable states. For entangled states these quasi-probabilities necessarily exhibit negativities. Based on the general structure of composite quantum states, one…

Quantum Physics · Physics 2015-05-13 J. Sperling , W. Vogel

We examine the possible states of subsystems of a system of bits or qubits. In the classical case (bits), this means the possible marginal distributions of a probability distribution on a finite number of binary variables; we give necessary…

Quantum Physics · Physics 2015-06-26 Paul Butterley , Anthony Sudbery , Jason Szulc

We explore correlation polytopes to derive a set of all Boole-Bell type conditions of possible classical experience which are both maximal and complete. These are compared with the respective quantum expressions for the…

Quantum Physics · Physics 2007-05-23 Itamar Pitowsky , Karl Svozil

A bipartite quantum channel represents the interaction between systems, generally allowing for exchange of information. A special class of bipartite channels are the no-signaling ones, which do not allow communication. In Ref. [1] it has…

Quantum Physics · Physics 2011-01-28 Giacomo Mauro D'Ariano , Stefano Facchini , Paolo Perinotti

Non-signalling quantum channels -- relevant in, e.g., the study of Bell and Einstein-Podolsky-Rosen scenarios -- may be simulated via affine combinations of local operations in bipartite scenarios. Moreover, when these channels correspond…

Quantum Physics · Physics 2022-10-05 Paulo J. Cavalcanti , John H. Selby , Jamie Sikora , Ana Belén Sainz

Genuine multipartite nonlocality is a salient feature of quantum systems, empowering the security of multi-party device independent cryptographic protocols. Given a correlation, characterizing and detecting genuineness have been subjected…

Quantum Physics · Physics 2015-07-28 Some Sankar Bhattacharya , Arup Roy , Amit Mukherjee , Ramij Rahaman

We have studied the possibility of post-quantum theories more nonlocal than the (standard) quantum theory using the modification of the quantum probability rule under the no-signaling condition. For this purpose we have considered the…

Quantum Physics · Physics 2012-08-15 Yeong Deok Han , Taeseung Choi

Super-selection rules severely restrict the possible operations one can perform on an entangled state. Their effect on the observation of non-locality through the Bell inequalities is only partially understood in the bipartite case. In this…

Quantum Physics · Physics 2011-08-09 Sebastian Meznaric , Libby Heaney , Dieter Jaksch

Quantum systems that have never interacted can become nonlocally correlated through a process called entanglement swapping. To characterize nonlocality in this context, we introduce local models where quantum systems that are initially…

Quantum Physics · Physics 2010-04-27 Cyril Branciard , Nicolas Gisin , Stefano Pironio

We give a set of necessary conditions for locality in bipartite systems, which include and generalize known Bell's inequalities. Each condition corresponds to a specific order of the expansion of random variables defined on graphs, in terms…

We propose a flexible and identifiable version of the two-groups model, motivated by hierarchical Bayes considerations, that features an empirical null and a semiparametric mixture model for the non-null cases. We use a computationally…

Methodology · Statistics 2012-06-26 Ryan Martin , Surya T. Tokdar

It has recently been shown that by broadcasting the subsystems of a bipartite quantum state, one can activate Bell nonlocality and significantly improve noise tolerance bounds for device-independent entanglement certification. In this work…

We specify for a general correlation scenario a particular type of a local quasi hidden variable (LqHV) model [J. Math. Phys. 53 (2012), 022201] -- a deterministic LqHV model, where all joint probability distributions of a correlation…

Quantum Physics · Physics 2012-04-27 Elena R. Loubenets

Recent advancements in network nonlocality have led to the concept of local operations and shared randomness-based genuine multipartite nonlocality (LOSR-GMNL). In this paper, we consider two recent experimental demonstrations of LOSR-GMNL,…

Quantum Physics · Physics 2024-12-10 Soumyadip Patra , Peter Bierhorst

We consider Bell tests involving bipartite states shared between three parties. We show that the simple inclusion of a third part may greatly simplify the measurement scenario (in terms of the number of measurement settings per part) and…

Quantum Physics · Physics 2012-01-26 Daniel Cavalcanti , Rafael Rabelo , Valerio Scarani

From an operational criterion of physical reality, a quantifier of realism-based nonlocality was recently introduced for two-part quantum states. This measure has shown to capture aspects that are rather different from Bell nonlocality.…

Quantum Physics · Physics 2019-12-11 D. M. Fucci , R. M. Angelo