Monogamy of quantum entanglement and other correlations

Koashi, Masato; Winter, Andreas

doi:10.1103/physreva.69.022309

Cited by 550 publications

(683 citation statements)

References 28 publications

Supporting

Mentioning

665

Contrasting

Unclassified

Order By: Relevance

“…We can interpret E sq (A;B) r as quantifying the minimum remnant quantum correlations between A and B after an adversary possessing the purifying system E performs a quantum operation on it with the intent of 'squashing down' the correlations that A and B share. It should also be noted that among the many entanglement measures, squashed entanglement is the only one known to satisfy all eight desirable properties that have arisen in the axiomatization of entanglement theory 22,[27][28][29] .…”

Section: Resultsmentioning

confidence: 99%

Fundamental rate-loss tradeoff for optical quantum key distribution

2014

View full text Add to dashboard Cite

Since 1984, various optical quantum key distribution (QKD) protocols have been proposed and examined. In all of them, the rate of secret key generation decays exponentially with distance. A natural and fundamental question is then whether there are yet-to-be discovered optical QKD protocols (without quantum repeaters) that could circumvent this rate-distance tradeoff. This paper provides a major step towards answering this question. Here we show that the secret key agreement capacity of a lossy and noisy optical channel assisted by unlimited two-way public classical communication is limited by an upper bound that is solely a function of the channel loss, regardless of how much optical power the protocol may use. Our result has major implications for understanding the secret key agreement capacity of optical channels-a long-standing open problem in optical quantum information theory-and strongly suggests a real need for quantum repeaters to perform QKD at high rates over long distances.

show abstract

Section: Resultsmentioning

confidence: 99%

Fundamental rate-loss tradeoff for optical quantum key distribution

2014

View full text Add to dashboard Cite

show abstract

“…For instance, it is well known that if two parties share a maximally entangled state, then any tripartite quantum state compatible with it must be such that the third party is uncorrelated to the first two. This phenomenon is known as the monogamy of entanglement [7,8] and implies that a maximally entangled state |φ + AB is incompatible with any correlated state ρ AC or ρ BC . A similar property, known as the monogamy of nonlocality, is displayed by nonlocal correlations [2].…”

Section: Introductionmentioning

confidence: 99%

Nonlocal multipartite correlations from local marginal probabilities

et al. 2012

View full text Add to dashboard Cite

Understanding what can be inferred about a multiparticle quantum system given only the knowledge of its subparts is a highly nontrivial task. Clearly, if a global system does not contain an information resource of some kind, neither do its subparts. For the case of entanglement as an information resource, it is known that the converse of this last statement is not true: Some nonentangled reduced states are only compatible with global states which are entangled. We extend this result to correlations and provide local marginal correlations that are only compatible with global genuinely tripartite nonlocal correlations. Quantum nonlocality can thus be deduced from the mere observation of local marginal correlations.

show abstract

“…Note that the purification for any discordant state is entangled across the E − (AB) splitting, which already links discord and entanglement with the environment. To further analyze the flow of correlations in a global system |ψ ABE , we apply the Koashi-Winter relation [27] …”

mentioning

confidence: 99%

Quantum nature of Gaussian discord: Experimental evidence and role of system-environment correlations

et al. 2015

View full text Add to dashboard Cite

We provide experimental evidence of quantum features in bipartite states classified as entirely classical according to a conventional criterion based on the Glauber P function but possessing nonzero Gaussian quantum discord. Their quantum nature is experimentally revealed by acting locally on one part of the discordant state. We experimentally verify and investigate the effect of discord increase under the action of local loss and link it to the entanglement with the environment. Adding an environmental system purifying the state, we unveil the flow of quantum correlations within a global pure system using the Koashi-Winter inequality. For a discordant state generated by splitting a state in which the initial squeezing is destroyed by random displacements, we demonstrate the recovery of entanglement highlighting the role of system-environment correlations. As quantum information science develops towards quantum information technology, the question of the efficient use and optimization of resources becomes a burning issue. So far, quantum information processing (QIP) has been mostly thought of as entanglement-enabled technology. Quantum cryptography is an exception, but even there the so-called effective entanglement between the parties plays a decisive role [1,2]. With the advent of new quantum computation paradigms [3] interest in more generic and even nonentangled QIP resources has emerged [4]. Unlike entanglement, the new resources, commonly dubbed as quantum correlations, reside in all states which do not diagonalize in any local product basis. Entanglement and quantum correlations are equivalent notions only for pure states. Quantumness of correlations in separable states is fundamentally related to the noncommutativity of observables, nonorthogonality of states, and properties of quantum measurements, whereas entanglement can be seen as a consequence of the quantum superposition principle. Correlated mixed states are a lucid illustration of the fact that the quantum-classical divide is actually purpose-oriented and that such states, long considered unsuitable for QIP, may become a robust and efficient quantum tool.In what follows, we will use quantum discord [5] for quantification of quantum correlations. For two systems A and B, quantum discord is defined as the difference,between quantum mutual information I(AB) = S(A) + S(B) − S(AB) encompassing all correlations present in the system, and the one-way classical correlation, which is operationally related to the amount of perfect classical correlations which can be extracted from the system [6]. Here, S is the von Neumann entropy of the respective state, H {ˆ i } (A|B) is the conditional entropy with measurement on B, and the infimum is taken over all possible measurements {ˆ i }.In this Rapid Communication, we focus on bipartite mixed Gaussian states relevant in the context of continuousvariable quantum information [7]. The respective correlation quantifier is then Gaussian quantum discord [8,9] defined by Eq. (1), where the minimization in J ← (AB) is r...

show abstract

Monogamy of quantum entanglement and other correlations

Cited by 550 publications

References 28 publications

Fundamental rate-loss tradeoff for optical quantum key distribution

Fundamental rate-loss tradeoff for optical quantum key distribution

Nonlocal multipartite correlations from local marginal probabilities

Quantum nature of Gaussian discord: Experimental evidence and role of system-environment correlations

Contact Info

Product

Resources

About