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We experimentally demonstrate the superior discrimination of separated, unentangled two-qubit correlated states using nonlocal measurements, when compared with measurements based on local operations and classical communications. When…

Quantum Physics · Physics 2008-11-26 G. J. Pryde , J. L. O'Brien , A. G. White , Stephen D. Bartlett

The fact that quantum mechanics predicts stronger correlations than classical physics is an essential cornerstone of quantum information processing. Indeed, these quantum correlations are a valuable resource for various tasks, such as…

A shifted or misaligned feedback loop gives rise to a two-point nonlocality that is the spatial analog of a temporal delay. Important consequences of this nonlocal coupling have been found both in diffusive and in diffractive systems, and…

Pattern Formation and Solitons · Physics 2015-05-18 Roberta Zambrini , Francesco Papoff

The existence of a global causal order between events places constraints on the correlations that parties may share. Such "causal correlations" have been the focus of recent attention, driven by the realization that some extensions of…

Quantum Physics · Physics 2019-07-15 Nikolai Miklin , Alastair A. Abbott , Cyril Branciard , Rafael Chaves , Costantino Budroni

Which nonlocal correlations can be obtained, when a party has access to more than one subsystem? While traditionally nonlocality deals with spacelike separated parties, this question becomes important with quantum technologies that connect…

Quantum Physics · Physics 2023-09-04 Moisés Bermejo Morán , Alejandro Pozas-Kerstjens , Felix Huber

Although quantum mechanics is a very successful theory, its foundations are still a subject of intense debate. One of the main problems is the fact that quantum mechanics is based on abstract mathematical axioms, rather than on physical…

Quantum Physics · Physics 2010-12-17 Daniel Cavalcanti , Alejo Salles , Valerio Scarani

This review offers a comprehensive exploration and synthesis of recent advancements in the domain of quantum correlation sharing facilitated through sequential measurements. We initiate our inquiry by delving into the interpretation of the…

Quantum Physics · Physics 2024-11-18 Zinuo Cai , Changliang Ren , Tianfeng Feng , Xiaoqi Zhou , Jingling Chen

It has long been recognized as a difficult problem to determine whether the observed statistical correlation between two classical variables arise from causality or from common causes. Recent research has shown that in quantum theoretical…

Quantum Physics · Physics 2020-07-01 Chenguang Zhang , Yuexian Hou , Dawei Song

In quantum mechanics, nonlocality (a violation of a Bell inequality) is intimately linked to complementarity, by which we mean that consistently assigning values to different observables at the same time is not possible. Nonlocality can…

Quantum Physics · Physics 2012-02-02 Tobias Fritz

It is argued that quantum and relativistic correlations can be described in a unified way, in that both assume free will as an axiom, and happen without any continuous connection in space-time. This description may contribute to a coherent…

Quantum Physics · Physics 2015-10-07 Antoine Suarez

We construct a general measure for detecting the quantum speedup in both closed and open systems. The speed measure is based on the changing rate of the position of quantum states on a manifold with appropriate monotone Riemannian metrics.…

Quantum Physics · Physics 2016-07-07 Zhen-Yu Xu

Conventionally, covariances do not distinguish between spatial and temporal correlations. The same covariance matrix could equally describe temporal correlations between observations of the same system at two different times or correlations…

We consider the classical correlations that two observers can extract by measurements on a bipartite quantum state, and we discuss how they are related to the quantum mutual information of the state. We show with several examples how…

Quantum Physics · Physics 2009-09-19 Shengjun Wu , Uffe V. Poulsen , Klaus Mølmer

All physical process are subject to some laws which determine with math accurately its time-space evolution. These laws are described, in the last analysis for the principle of causality. The physical space can be homogeneous or…

General Physics · Physics 2007-05-23 Enrique Ordaz Romay

Closed timelike curves (CTCs) challenge our conception of causality by allowing information to loop back into its own past. Any consistent description of such scenarios must avoid time-travel paradoxes while respecting the no-new-physics…

Processes with indefinite causal order can arise when quantum theory is locally valid and they allow accomplishing new informational tasks. Despite recent progress, the correlations allowed in such processes have not been clearly…

Quantum Physics · Physics 2026-03-18 Zixuan Liu , Ognyan Oreshkov

Although the solution, within standard quantum physics, of the problem of outcomes has been published several times, many authors continue to treat measurement as an unsolved fundamental dilemma. The solution lies in the formation of…

Quantum Physics · Physics 2022-06-14 Art Hobson

Investigating causation in the quantum domain is crucial. Despite numerous studies of correlations in quantum many-body systems, causation, which is very distinct from correlations, has hardly been studied. We address this by demonstrating…

Quantum Physics · Physics 2025-04-24 Roopayan Ghosh , Bin Yi , Sougato Bose

It is known that "quantum non locality", leading to the violation of Bell's inequality and more generally of classical local realism, can be attributed to the conjunction of two properties, that we call here elementary locality and…

Quantum Physics · Physics 2022-01-04 Philippe Grangier

Following on from the notion of (first-order) causality, which generalises the notion of being tracepreserving from CP-maps to abstract processes, we give a characterization for the most general kind of map which sends causal processes to…

Other Computer Science · Computer Science 2017-01-04 Aleks Kissinger , Sander Uijlen