Quantum discord and its allies: a review of recent progress

Bera, Anindita; Das, Tamoghna; Sadhukhan, Debasis; Roy, Sudipto Singha; De, Aditi Sen; Sen, Ujjwal

doi:10.1088/1361-6633/aa872f

Cited by 218 publications

(167 citation statements)

References 886 publications

(1,692 reference statements)

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“…It is well known [7] that a separable state can be prepared by local operations and classical communications. Here we propose a particular way of preparing such a state in a solid state setup and explain in detail how the protocol described in the previous section works in this setup.…”

Section: Protocol In Detail For Quantum-hall Based Setupmentioning

confidence: 99%

How to observe and quantify quantum-discord states via correlations

et al. 2019

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Quantum correlations between parts of a composite system most clearly reveal themselves through entanglement. Designing, maintaining, and controlling entangled systems is very demanding, which raises the stakes for understanding the efficacy of entanglement-free, yet quantum, correlations, exemplified by quantum discord. Discord is defined via conditional mutual entropies of parts of a composite system, and its direct measurement is hardly possible even via full tomographic characterization of the system state. Here we design a simple protocol to detect and quantify quantum discord in an unentangled bipartite system. Our protocol relies on a characteristic of discord that can be extracted from repeated direct measurements of certain correlations between subsystems of the bipartite system. The proposed protocol opens a way of extending experimental studies of discord to electronic systems but can also be implemented in quantum-optical systems.

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Section: Protocol In Detail For Quantum-hall Based Setupmentioning

confidence: 99%

How to observe and quantify quantum-discord states via correlations

et al. 2019

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“…(20) From Eqs. (17) and (18) we get the expressions for the post-measurement entropy at the endpoint θ = 0, (4), and 0.8 (5) and at the second endpoint θ = π/2:…”

Section: Behavior Of Post-measurement Entropymentioning

confidence: 99%

“…Many kinds of quantum correlations have been introduced so far and now their properties are scrupulously analyzed both theoretically and experimentally. Among quantumness quantifiers beyond quantum entanglement, relevant places in the scale of importance are occupied respectively by quantum discord and quantum work (information) deficit [1,2,3,4,5].…”

Section: Introductionmentioning

confidence: 99%

On the possibility to detect quantum correlation regions with the variable optimal measurement angle

Gramegna

Yurischev

2019

Eur. Phys. J. D

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Quantum correlations described by quantum discord and one-way quantum deficit can contain ordinary regions with constant (i.e., universal) optimal measurement angle 0 or π/2 with respect to the z-axis and regions with a variable (state-dependent) angle of the optimal measurement. The latter regions which are absent in the Bell-diagonal states are very tiny for the quantum discord and cannot be observed experimentally due to various imperfections on the preparation and measurement steps of the experiment. On the contrary, for the one-way quantum deficit we succeeded in getting the special two-qubit X states which seem to allow one to reach all regions of quantum correlation exploiting available quantum optical techniques. These states give possibility to deep investigation of quantum correlations and related optimization problems at new region and its boundaries. In the paper, explicit theoretical calculations applicable to one-way deficit are reported, together with the design of the experimental setup for generating such selected family of states; moreover, there are presented numerical simulations showing that the most inaccessible region with the intermediate optimal measurement angle may be resolved experimentally.PACS. 03.67.-a Quantum information -89.70.Cf Entropy and other measures of information -42.50.Xa Optical tests of quantum theory

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“…It is easy to check that the action of this transformation on the density matrix (5) changes the sign of the off-diagonal entries, i.e., the matrix uρ AB u + is equal to the right side of Eq. (5) in which v → −v. Thus the density matrix can be brought to the form with real non-negative values for all entries (more details for the general X density matrices can be found, for example, in Refs.…”

Section: Hamiltonian Density Matrix and Pre-measurement Entropymentioning

confidence: 99%

Temperature-field phase diagrams of one-way quantum work deficit in two-qubit XXZ spin systems

Yurischev

2020

Quantum Inf Process

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The spin-1/2 XXZ chain in a uniform magnetic field at thermal equilibrium is considered. For this model, we give a complete classification of all qualitatively different phase diagrams for the one-way quantum work (information) deficit. The diagrams can contain regions (phases, fractions) with both stationary and variable (state-dependent) angles of optimal measurement. We found cases of phase diagrams in which the sizes of regions with the variable optimal measurement angle are large and perhaps such regions can be detected experimentally. We also established a relationship between the behavior of optimal measurement angles near the boundaries separated different regions and Landau's theory of phase transitions of the second and first kind.Keywords X density matrix · Quantum correlation function · Piecewisedefined function · Subdomains and phase diagram · Critical lines and boundaries between subdomaines Mathematics Subject Classification (2010) Primary 81P40 · Secondary 81Qxx 1 IntroductionQuantum correlations have foundational interest and are an essential resource for quantum information and computational technologies. There are many measures of quantum correlations. One of the most important places among them belongs to the quantum discord and one-way quantum work deficit [1,2,3,4,5]. It is significant that the concept of these correlations, as opposed to

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Quantum discord and its allies: a review of recent progress

Cited by 218 publications

References 886 publications

How to observe and quantify quantum-discord states via correlations

How to observe and quantify quantum-discord states via correlations

On the possibility to detect quantum correlation regions with the variable optimal measurement angle

Temperature-field phase diagrams of one-way quantum work deficit in two-qubit XXZ spin systems

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