scholarly journals QUANTUM DISCORD FOR MULTIPARTITE COHERENT STATES INTERPOLATING BETWEEN WERNER AND GREENBERGER–HORNE–ZEILINGER STATES

2012 ◽  
Vol 10 (05) ◽  
pp. 1250060 ◽  
Author(s):  
M. DAOUD ◽  
R. AHL LAAMARA
Keyword(s):  
Quantum System ◽  
Ground State ◽  
Coherent States ◽  
Quantum Discord ◽  
Temporal Evolution ◽  
Conditional Entropy ◽  
Quantum Correlations ◽  
Ghz States ◽  
Werner States ◽  
Explicit Expressions

The quantum discord is used as measure of quantum correlations for two families of multipartite coherent states. The first family interpolates between generalized GHZ states and generalized Werner states. The second one is an interpolation between generalized GHZ and the ground state of the multipartite quantum system. Two inequivalent ways to split the system in a pair of qubits are introduced. The explicit expressions of quantum quantum discord in multipartite coherent states are derived. Its evaluation uses the Koashi–Winter relation in optimizing the conditional entropy. The temporal evolution of quantum correlations (quantum discord and entanglement) is also discussed.

Improvement of quantum correlations by repetitive quantum error correction

2019 ◽  
Vol 17 (05) ◽  
pp. 1950044
Author(s):  
A. El Allati ◽  
H. Amellal ◽  
A. Meslouhi
Keyword(s):  
Error Correction ◽  
Quantum Correlation ◽  
Coherent States ◽  
Quantum Discord ◽  
Error Correcting Code ◽  
Quantum Correlations ◽  
Quantum Error Correction ◽  
Optical Field ◽  
Quantum Error ◽  
Entangled Coherent States

A quantum error-correcting code is established in entangled coherent states (CSs) with Markovian and non-Markovian environments. However, the dynamic behavior of these optical states is discussed in terms of quantum correlation measurements, entanglement and discord. By using the correcting codes, these correlations can be as robust as possible against environmental effects. As the number of redundant CSs increases due to the repetitive error correction, the probabilities of success also increase significantly. Based on different optical field parameters, the discord can withstand more than an entanglement. Furthermore, the behavior of quantum discord under decoherence may exhibit sudden death and sudden birth phenomena as functions of dimensionless parameters.

scholarly journals Quantum Discord in Photon-Added Glauber Coherent States of GHZ-Type

2015 ◽  
Vol 22 (04) ◽  
pp. 1550023
Author(s):  
M. Daoud ◽  
W. Kaydi ◽  
H. El Hadfi
Keyword(s):  
Coherent States ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
Photon Excitation ◽  
Pairwise Correlations ◽  
Photon Excitations

We investigate the influence of photon excitations on quantum correlations in tripartite Glauber coherent states of Greenberger-Horne-Zeilinger type (GHZ-type). The pairwise correlations are measured by means of the entropy-based quantum discord. We also analyze the monogamy property of quantum discord in this class of tripartite states in terms of the strength of Glauber coherent states and the photon excitation order.

scholarly journals Local available quantum correlations for Bell Diagonal states and Markovian decoherence

2018 ◽  
Vol 64 (6) ◽  
pp. 662
Author(s):  
Hermann L Albrecht Q ◽  
Douglas F. Mundarain ◽  
Mario I. Caicedo S.
Keyword(s):  
Sudden Death ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
Entanglement Sudden Death ◽  
Dissipative Dynamics ◽  
Phase Damping ◽  
Werner States ◽  
Kraus Operators

Local available quantum correlations (LAQCs), as dened by Mundarain et al. [19], are analytically determined for Bell Diagonal states. Using the Kraus operators formalism [10], we analyze the dissipative dynamics of 2-qubit LAQCs under Markovian decoherence. This is done for Werner states under the depolarizing [20] and phase damping channels [21]. Since Werner states are among those that exhibit the so called entanglement sudden death [27], the results are compared with the ones obtained for Quantum Discord [22], as analyzed by Werlang et al. [24], as well as for entanglement, i.e. Concurrence[7]. The LAQCs quantier, as Quantum Discord does, only vanishes asymptotically.

scholarly journals QUANTUM DISCORD AND RELATED MEASURES OF QUANTUM CORRELATIONS IN FINITE XY CHAINS

2012 ◽  
Vol 27 (01n03) ◽  
pp. 1345033 ◽  
Author(s):  
N. CANOSA ◽  
L. CILIBERTI ◽  
R. ROSSIGNOLI
Keyword(s):  
Ground State ◽  
Quantum Discord ◽  
Nearest Neighbor ◽  
Full Range ◽  
Transverse Field ◽  
Quantum Correlations ◽  
Spin Chains ◽  
Crucial Importance ◽  
Spin Pairs ◽  
Fully Connected

We examine the quantum correlations of spin pairs in the ground state of finite XY chains in a transverse field, by evaluating the quantum discord as well as other related entropic measures of quantum correlations. A brief review of the latter, based on generalized entropic forms, is also included. It is shown that parity effects are of crucial importance for describing the behavior of these measures below the critical field. It is also shown that these measures reach full range in the immediate vicinity of the factorizing field, where they become independent of separation and coupling range. Analytical and numerical results for the quantum discord, the geometric discord and other measures in spin chains with nearest neighbor coupling and in fully connected spin arrays are also provided.

Studying quantum correlations dynamics in the phase space for continuous-variable Werner states and Bell-diagonal states

2019 ◽  
Vol 16 (07) ◽  
pp. 1950109
Author(s):  
Fatima-Zahra Siyouri ◽  
Hicham Ait Mansour ◽  
Fadoua Elbarrichi
Keyword(s):  
Wigner Function ◽  
Quantum Discord ◽  
Open Quantum Systems ◽  
Quantum Correlations ◽  
Continuous Variable ◽  
Quantum Systems ◽  
Qubit System ◽  
Classical Correlations ◽  
Werner States ◽  
System F

We investigate the ability of Wigner function to reveal and measure general quantum correlations in two-qubit open system. For this purpose, we analyze comparatively their dynamics for two different states, continuous-variable Werner states (CWS) and Bell-diagonal states (BDS), independently interacting with dephasing reservoirs. Then, we explore the effects of decreasing the degree of non-Markovianity on their behavior. We show that the presence of both quantum entanglement and quantum discord allow to have a negative Wigner function, in contrast to the result obtained for the closed two-qubit system [F. Siyouri, M. El Baz and Y. Hassouni, The negativity of Wigner function as a measure of quantum correlations, Quantum Inf. Process. 15(10) (2016) 4237–4252]. In fact, we conclude that negativity of Wigner function can be used to capture and quantify the amount of general non-classical correlations in open quantum systems.

Sudden change in the behavior of quantum discord for bipartite Gisin states

2018 ◽  
Vol 15 (03) ◽  
pp. 1850038 ◽  
Author(s):  
Fatima-Zahra Siyouri ◽  
Mustapha Ziane ◽  
Morad El Baz ◽  
Yassine Hassouni
Keyword(s):  
Quantum System ◽  
Quantum Correlation ◽  
Coherent States ◽  
Quantum Discord ◽  
Sudden Change ◽  
Classical Correlation ◽  
Mixing Parameter

In this paper, we investigate the behavior of quantum correlation for Gisin states based on the bipartite superposed coherent states (SCS). Moreover, we analyze the basis for minimizing the quantum discord (or equivalently basis maximizing the classical correlation) as function of the mixing parameter and the coherent amplitude. We found that for our quantum system, the quantum discord behavior is not smooth and could experience a sudden change (S.C).

The Dynamics of Three Different Entropic Measures of Quantum Correlations in Mixed Bipartite State Coupled with Classical Environments

2018 ◽  
Vol 17 (03) ◽  
pp. 1850023 ◽  
Author(s):  
Mahmood Shamirzaie ◽  
Salman Khan
Keyword(s):  
Quantum Discord ◽  
Conditional Entropy ◽  
Quantum Correlations ◽  
Random Telegraph Noise ◽  
Geometric Quantum Discord ◽  
Bipartite State ◽  
Telegraph Noise ◽  
Initial States ◽  
Qubit States ◽  
Static Noise

The dynamics of three different entropic measures of quantum correlations in mixed bipartite qubit states in the presence of two different classical noises, the static noise (SN) and the random telegraph noise (RTN), are investigated. The three entropic measures of quantum correlations correspond to one-way information deficit, geometric quantum discord and the cubic information. General analytic relations for each quantifier in the two configurations are obtained. In both configurations, the minimized value of each measure of quantum correlations corresponds to the conditional entropy of the same projectors. It is shown that one-way information deficit captures more correlations in highly mixed initial states. On the contrary, in both configurations the cubic information reduces to the geometric quantum discord and captures more correlations for highly pure initial states. The periodic revival of each measure of quantum correlation is more prominent in the case of RTN.

scholarly journals Simulation of Equatorial von Neumann Measurements on GHZ States Using Nonlocal Resources

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Jean-Daniel Bancal ◽  
Cyril Branciard ◽  
Nicolas Gisin
Keyword(s):  
Quantum System ◽  
Quantum State ◽  
Quantum Correlations ◽  
Communication Cost ◽  
Computational Power ◽  
Bloch Sphere ◽  
Classical Communication ◽  
Von Neumann ◽  
Ghz States ◽  
Von Neumann Measurements

Reproducing with elementary resources the correlations that arise when a quantum system is measured (quantum state simulation) allows one to get insight on the operational and computational power of quantum correlations. We propose a family of models that can simulate von Neumann measurements in thex−yplane of the Bloch sphere onn-partite GHZ states. For the tripartite and fourpartite states, the models use only bipartite nonlocal boxes; they can be translated into classical communication schemes with finite average communication cost.

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