Quantum discord for Gaussian states with non-Gaussian measurements

Giorda, Paolo; Allegra, Michele; Paris, Matteo G. A.

doi:10.1103/physreva.86.052328

Cited by 25 publications

(14 citation statements)

References 50 publications

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“…It is important to note that Gaussian discord D is an upper bound to the actual discord, even if they are conjectured to coincide [60,61]. Correspondingly, the measure for classical correlations which is here considered C = I − D represents a lower bound to the actual amount of classical correlations.…”

Section: Symmetric and Asymmetric Noise Correlationsmentioning

confidence: 96%

Entanglement reactivation in separable environments

Pirandola

2013

New J. Phys.

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Combining two entanglement-breaking channels into a correlatednoise environment restores the distribution of entanglement. Surprisingly, this reactivation can be induced by the injection of separable correlations from the composite environment. In any dimension (finite or infinite), we can construct classically correlated 'twirling' environments which are entanglement-breaking in the transmission of single systems but entanglement-preserving when two systems are transmitted. Here entanglement is simply preserved by the existence of decoherence-free subspaces. Remarkably, even when such subspaces do not exist, a fraction of the input entanglement can still be distributed. This is found in separable Gaussian environments, where distillable entanglement is able to survive the two-mode transmission, despite being broken in any single-mode transmission by the strong thermal noise. In the Gaussian setting, entanglement restoration is a threshold process, occurring only after a critical amount of correlations has been injected. Such findings suggest new perspectives for distributing entanglement in realistic environments with extreme decoherence, identifying separable correlations and classical memory effects as physical resources for 'breaking entanglement-breaking'.

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Section: Symmetric and Asymmetric Noise Correlationsmentioning

confidence: 96%

Entanglement reactivation in separable environments

Pirandola

2013

New J. Phys.

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“…See also [106]. Giorda et al [107] asked whether non-Gaussian measurements can be optimal for obtaining QD for Gaussian states. To address this query, two-mode squeezed thermal states and mixed thermal states have been studied by considering a range of experimentally feasible non-Gaussian measurements.…”

Section: Gaussian Quantum Discordmentioning

confidence: 99%

Quantum discord and its allies: a review of recent progress

Bera¹,

Das²,

Sadhukhan³

et al. 2017

Rep. Prog. Phys.

218

162

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“…( 27) are always separable, and the STS of Eq. ( 28) are separable when k 2 (x − y ) ≥ 1, both classes of states always contain more general forms of quantum correlations such as quantum discord and have in general a nonzero GIP [61,62,73,74], as soon as they are not completely uncorrelated (i.e., as soon as y, y 0). Since the resource ensuring a precision in blackbox interferometry is indeed associated with discord-type correlations, as quantified by the GIP, and not with entanglement, and since we are exploiting this figure of merit to investigate non-Markovianity, both classes of states (as well as any other non-product Gaussian state) are in principle able to provide a useful witness of non-Markovianity in generic local Gaussian channels.…”

Section: Non-markovianity Witness Beyond Entangled Probesmentioning

confidence: 99%

Gaussian interferometric power as a measure of continuous-variable non-Markovianity

et al. 2015

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We investigate the non-Markovianity of continuous-variable Gaussian quantum channels through the evolution of an operational metrological quantifier, namely, the Gaussian interferometric power, which captures the minimal precision that can be achieved using bipartite Gaussian probes in a black-box phase estimation setup, where the phase shift generator is a priori unknown. We observe that the monotonicity of the Gaussian interferometric power under the action of local Gaussian quantum channels on the ancillary arm of the bipartite probes is a natural indicator of Markovian dynamics; consequently, its breakdown for specific maps can be used to construct a witness and an effective quantifier of non-Markovianity. In our work, we consider two paradigmatic Gaussian models, the damping master equation and the quantum Brownian motion, and identify analytically and numerically the parameter regimes that give rise to non-Markovian dynamics. We then quantify the degree of non-Markovianity of the channels in terms of Gaussian interferometric power, showing, in particular, that even nonentangled probes can be useful to witness non-Markovianity. This establishes an interesting link between the dynamics of bipartite continuous-variable open systems and their potential for optical interferometry. The results are an important supplement to the recent research on characterization of non-Markovianity in continuous-variable systems.

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Quantum discord for Gaussian states with non-Gaussian measurements

Cited by 25 publications

References 50 publications

Entanglement reactivation in separable environments

Entanglement reactivation in separable environments

Quantum discord and its allies: a review of recent progress

Gaussian interferometric power as a measure of continuous-variable non-Markovianity

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