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Nonlocality is the most characteristic feature of quantum mechanics. John Bell, in his seminal 1964 work, proved that local-realism imposes a bound on the correlations among the measurement statistics of distant observers. Surpassing this…

Quantum nonlocality is arguably among the most counter-intuitive phenomena predicted by quantum theory. In recent years, the development of an abstract theory of nonlocality has brought a much deeper understanding of the subject. In…

One can fix the randomness used by a randomized algorithm, but there is no analogous notion of fixing the quantumness used by a quantum algorithm. Underscoring this fundamental difference, we show that, in the black-box setting, the…

Computational Complexity · Computer Science 2024-04-26 Scott Aaronson , DeVon Ingram , William Kretschmer

Causal inequalities are bounds on correlations obtained when operations take place in a causal sequence, i.e. in which the background time or definite causal structure pre-exists such that every operation is either in the future, in the…

Quantum Physics · Physics 2015-09-22 Caslav Brukner

Given an input $x$, and a search problem $F$, local computation algorithms (LCAs) implement access to specified locations of $y$ in a legal output $y \in F(x)$, using polylogarithmic time and space. Mansour et al., (2012), had previously…

Data Structures and Algorithms · Computer Science 2014-04-23 Omer Reingold , Shai Vardi

We present a quantum algorithm which identifies with certainty a hidden subgroup of an arbitrary finite group G in only a polynomial (in log |G|) number of calls to the oracle. This is exponentially better than the best classical algorithm.…

Quantum Physics · Physics 2016-12-30 Mark Ettinger , Peter Hoyer , Emanuel Knill

Operations that are trivial in the classical world, like accessing information without introducing any change or disturbance, or like copying information, become non-trivial in the quantum world. In this note we discuss several limitations…

Quantum Physics · Physics 2016-08-10 Marco Piani

Motivated by the recent discovery of a quantum Chernoff theorem for asymptotic state discrimination, we investigate the distinguishability of two bipartite mixed states under the constraint of local operations and classical communication…

Quantum Physics · Physics 2011-03-16 William Matthews , Andreas Winter

In this paper we consider the possible correlations between two parties using local machines and shared randomness with an additional amount of classical communication. This is a continuation of the work initiated by Bacon and Toner in Ref.…

Quantum Physics · Physics 2014-05-14 Katherine Maxwell , Eric Chitambar

The nonrelativistic limit of nonlocal modifications to the Klein Gordon operator is studied, and the experimental possibilities of casting stringent constraints on the nonlocality scale via planned and/or current optomechanical experiments…

General Relativity and Quantum Cosmology · Physics 2017-02-01 Alessio Belenchia , Dionigi M. T. Benincasa , Stefano Liberati , Francesco Marin , Francesco Marino , Antonello Ortolan

We investigate (quantifier-free) spatial constraint languages with equality, contact and connectedness predicates as well as Boolean operations on regions, interpreted over low-dimensional Euclidean spaces. We show that the complexity of…

Logic in Computer Science · Computer Science 2011-04-04 Roman Kontchakov , Yavor Nenov , Ian Pratt-Hartmann , Michael Zakharyaschev

We study the question of whether parallelization in the exploration of the feasible set can be used to speed up convex optimization, in the local oracle model of computation. We show that the answer is negative for both deterministic and…

Optimization and Control · Mathematics 2019-06-21 Jelena Diakonikolas , Cristóbal Guzmán

From the premise that an observable is real after it is measured, we envisage a tomography-based protocol that allows us to propose a quantifier for the degree of indefiniteness of an observable given a quantum state. Then, we find that the…

Quantum Physics · Physics 2015-12-08 A. L. O. Bilobran , R. M. Angelo

We consider a quantum system subject to superselection rules, for which certain restrictions apply to the quantum operations that can be implemented. It is shown how the notion of quantum-nonlocality has to be redefined in the presence of…

Quantum Physics · Physics 2009-11-10 F. Verstraete , J. I. Cirac

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

We show that correlations inconsistent with any locally causal description can be a generic feature of measurements on entangled quantum states. Specifically, spatially-separated parties who perform local measurements on a…

Quantum Physics · Physics 2016-09-08 Yeong-Cherng Liang , Nicholas Harrigan , Stephen D. Bartlett , Terry Rudolph

What is the value of input information in solving linear programming? The celebrated ellipsoid algorithm tells us that the full information of input constraints is not necessary; the algorithm works as long as there exists an oracle that,…

Data Structures and Algorithms · Computer Science 2013-11-14 Xiaohui Bei , Ning Chen , Shengyu Zhang

Entanglement is an useful resource because some global operations cannot be locally implemented using classical communication. We prove a number of results about what is and is not locally possible. We focus on orthogonal states, which can…

Quantum Physics · Physics 2009-11-07 Jonathan Walgate , Lucien Hardy

The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also…

Quantum Physics · Physics 2015-05-20 D. Cavalcanti , M. L. Almeida , V. Scarani , A. Acin

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