Detection of entanglement in asymmetric quantum networks and multipartite quantum steering

Cavalcanti, Daniel; Skrzypczyk, Paul; Aguilar, G. H.; Nery, Ranieri; Ribeiro, P. H. Souto; Walborn, S. P.

doi:10.1038/ncomms8941

Cited by 171 publications

(212 citation statements)

References 51 publications

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“…Finally, one may study the communication cost in multipartite steering experiments [29,30], where many different communication patterns can be considered. In particular, it would be interesting to investigate the effect of postquantum steering [31], which is only possible in the multipartite case.…”

Section: Discussionmentioning

confidence: 99%

Classical communication cost of quantum steering

et al. 2016

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Quantum steering is observed when performing appropriate local measurements on an entangled state. Here we discuss the possibility of simulating classically this effect, using classical communication instead of entanglement. We show that infinite communication is necessary for exactly simulating steering for any pure entangled state, as well as for a class of mixed entangled states. Moreover, we discuss the communication cost of steering for general entangled states, as well as approximate simulation. Our findings reveal striking differences between Bell nonlocality and steering, and provide a natural way of measuring the strength of the latter.Comment: 7 pages, 1 figure. See also arXiv:1603.xxxxx for related work by S. Nagy and T. V\'ertes

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Section: Discussionmentioning

confidence: 99%

Classical communication cost of quantum steering

et al. 2016

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“…[14] to construct multipartite semi-device independent entanglement witnesses. The intuition is the following.…”

Section: Entanglement Detectionmentioning

confidence: 99%

“…This is an asymmetric situation in the sense * Corresponding author. alejandro.mattar@icfo.es that only some of the parties in the network use trusted devices while others do not [14]. Once more, trust should be understood in terms of full knowledge or characterisation of the devices used.…”

Section: Introductionmentioning

confidence: 99%

Experimental multipartite entanglement and randomness certification of the W state in the quantum steering scenario

Máttar¹,

Skrzypczyk²,

Aguilar³

et al. 2017

Quantum Sci. Technol.

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Recently [Cavalcanti et al. Nat Commun 6, 7941 (2015)] proposed a method to certify the presence of entanglement in asymmetric networks, where some users do not have control over the measurements they are performing. Such asymmetry naturally emerges in realistic situtations, such as in cryptographic protocols over quantum networks. Here we implement such "semi-device independent" techniques to experimentally witness all types of entanglement on a three-qubit photonic W state. Furthermore we analise the amount of genuine randomness that can be certified in this scenario from any bipartition of the three-qubit W state.

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“…Since quantum steering can be formulated as a quantum-information task where the classical measurements simulate an untrusted device, it has been extended to a multipartite scenario useful for semi-deviceindependent entanglement certification in quantum networks [20]. Our generalization of MUBs will enable developments in the young field of quantum random access codes by allowing for more involved and optimal scenarios than those discussed until now [21].…”

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confidence: 99%

Quantum steering inequality with tolerance for measurement-setting-errors: experimentally feasible signature of unbounded violation

Stobińska¹

2017

Quantum Information and Measurement (QIM) 2017

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Quantum steering is a relatively simple test for quantumness of correlations, proving that the values of quantum-mechanical measurement outcomes come into being only in the act of measurement. By exploiting quantum correlations Alice can influence -steer -Bob's physical system in a way inaccessible in classical world, leading to violation of some inequalities. Demonstrating this and similar quantum effects for systems of increasing size, approaching even the classical limit, is a long-standing challenging problem. Here we provide experimentally feasible signature of unbounded violation of a steering inequality. We derive its universal form where tolerance for measurement-setting-errors is explicitly build-in by means of the Deutsch-Maassen-Uffink uncertainty relation. Then, generalizing the mutual unbiasedness, we apply the inequality to the multi-singlet and multi-particle bipartite Bell-state. However, the method is general and opens the possibility of employing multi-particle bipartite steering for randomness certification and development of quantum technologies, e.g. random access codes.In their famous paper, Einstein, Podolsky and Rosen (EPR) highlighted the phenomenon of entanglement [1]: it is possible to see perfect correlations between measurement outcomes obtained by two observers, Alice and Bob, at distant locations, while for each observer his/her outcomes appear to be statistically random. These are the EPR correlations. Validation of entanglement requires designing a specific experimental scenario where measurements on a quantum state give outcomes which violate a classical inequality. The inequality can be constructed, for example, on the basis of probability distribution satisfying the Kolmogorov axioms. Its unbounded violation is equivalent to observation of the EPR correlations which become more and more pronounced when size of a system increases, reaching even classical limit of macroscopic population. This is very challenging to accomplish in the paradigm of Bell-nonlocality testing: if specific observables with (2 log 2 d ) d settings and d possible outcomes are used, bipartite quantum states with local Hilbert space dimension d can violate a Bell inequality by a factor of O[2], later improved to [3][4][5]. Thus, an unbounded violation of a Bell inequality requires exponentially many observables (or equivalently, settings). According to the monogamy relation [6], this scaling can be improved only up to the linear one (see the Supplementary Information). How- * fizar@ug.edu.pl † aburacze@gmail.com ‡ pawel@mif.pg.gda.pl § magdalena.stobinska@gmail.com; Corresponding author ever, the present results are still far from this limit and this makes them purely academic as far as the experimental perspective is concerned [7]. In case of quantum steering, the task has been found to be less difficult: violation of a steering inequality by a factor of O √ d requires d + 1 observables in the form of mutually unbiased bases (MUBs) [8]. However, this scenario necessitates the complementarity relation among...

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Detection of entanglement in asymmetric quantum networks and multipartite quantum steering

Cited by 171 publications

References 51 publications

Classical communication cost of quantum steering

Classical communication cost of quantum steering

Experimental multipartite entanglement and randomness certification of the W state in the quantum steering scenario

Quantum steering inequality with tolerance for measurement-setting-errors: experimentally feasible signature of unbounded violation

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