scholarly journals The freezing Rènyi quantum discord

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xiao-Yu Li ◽  
Qin-Sheng Zhu ◽  
Ming-Zheng Zhu ◽  
Hao Wu ◽  
Shao-Yi Wu ◽  
...  
Keyword(s):  
Quantum Correlation ◽  
Quantum Discord ◽  
Universal Quantum

Abstract As a universal quantum character of quantum correlation, the freezing phenomenon is researched by geometry and quantum discord methods, respectively. In this paper, the properties of Rènyi discord is studied for two independent Dimer System coupled to two correlated Fermi-spin environments under the non-Markovian condition. We further demonstrate that the freezing behaviors still exist for Rènyi discord and study the effects of different parameters on this behaviors.

The impact of resource on remote quantum correlation Preparation

2015 ◽  
Vol 15 (13&14) ◽  
pp. 1223-1232
Author(s):  
Chengjun Wu ◽  
Bin Luo ◽  
Hong Guo
Keyword(s):  
Quantum Entanglement ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Entangled States ◽  
Shared Resources ◽  
Classical Communication ◽  
Bell Measurement ◽  
Measurement Results ◽  
The Impact

When Alice and Bob share two pairs of quantum correlated states, Alice can remotely prepare quantum entanglement and quantum discord in Bob’s side by measuring the parts in her side and telling Bob the measurement results by classical communication. For remote entanglement preparation, entanglement is necessary . We find that for some shared resources having the same amount of entanglement, when Bell measurement is used, the entanglement remotely prepared can be different, and more discord in the resources actually decreases the entanglement prepared. We also find that for some resources with more entanglement, the entanglement remotely prepared may be less. Therefore, we conclude that entanglement is a necessary resource but may not be the only resource responsible for the entanglement remotely prepared, and discord does not likely to assist this process. Also, for the preparation of discord, we find that some states with no entanglement could outperform entangled states.

Measurement of quantum correlation by Frobenius norm in non-Markovian system

2018 ◽  
Vol 16 (03) ◽  
pp. 1850022 ◽  
Author(s):  
Juju Hu ◽  
Shuqin Liu ◽  
Yinghua Ji
Keyword(s):  
Density Matrix ◽  
Quantum System ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Frobenius Norm ◽  
Easy Method ◽  
Test Matrix ◽  
Research Results ◽  
Bipartite State ◽  
Markovian System

In order to measure the quantum correlation of a bipartite state quickly, an easy method is to construct a test matrix through the commutations among the blocks of its density matrix. Then, the Frobenius norm of the test matrix can be used to measure the quantum correlation. In this paper, we apply the measurement by Frobenius norm ([Formula: see text] to the dynamics evolution of the non-Markovian quantum system and compare it with the typical quantum discord ([Formula: see text] proposed by Ollivier and Zurek. The research results show that [Formula: see text] can indeed measure the quantum correlation of a bipartite state as same as [Formula: see text]. Further studies find that there are still differences between the two measurements: in some regions, when [Formula: see text] is zero, [Formula: see text] is not zero. It indicates that [Formula: see text] is more detailed than [Formula: see text] to measure quantum correlation of a bipartite state.

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.

QUANTUM CORRELATIONS IN THE ENTANGLEMENT DISTILLATION PROTOCOLS

2013 ◽  
Vol 11 (03) ◽  
pp. 1350029
Author(s):  
SHAO-XIONG WU ◽  
JUN ZHANG ◽  
CHANG-SHUI YU ◽  
HE-SHAN SONG
Keyword(s):  
Quantum Entanglement ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
The Other ◽  
Entangled States ◽  
Entanglement Distillation

We study the quantum correlations between source and target pairs in different protocols of entanglement distillation of one kind of entangled states. We find that there does not exist any quantum correlation in the standard recurrence distillation protocol, while quantum discord and even quantum entanglement are always present in the other two cases of the improved distillation protocols. In the three cases, the distillation efficiency improved with the quantum correlations enhanced.

Robustness of Quantum Correlations in Entangled Two su(2) Systems Non-mutually Interacting with su(1, 1) System under Intrinsic Decoherence

2018 ◽  
Vol 25 (03) ◽  
pp. 1850015
Author(s):  
A.-B. A. Mohamed ◽  
M. S. Abdalla ◽  
A.-S. F. Obada
Keyword(s):  
Steady State ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Bell State ◽  
Analytical Description ◽  
Quantum Correlations ◽  
Total System ◽  
Intrinsic Decoherence ◽  
Geometric Quantum Discord ◽  
Phase Decoherence

Two two-level systems generated by su(2) algebra are initially prepared in a maximum nonsymmetric Bell state and having no mutual interaction. Each su(2)-system spatially interacts with two-mode cavity field in the nondegenerate parametric amplifier type cast through operators governed by su(1, 1) Lie algebra. An analytical description for the time evolution of the final state of the total system with the effect of intrinsic decoherence is found. Therefore, the robustness of the quantum correlations between the two su(2)-system is investigated by means of geometric quantum discord, measurement-induced nonlocality and negativity. We analyze in some detail the influence of initial coherence intensities, detuning and phase decoherence parameters on the steady-state correlation. We find that the steady-state correlations can be generated and enhanced by controlling the parameters of: the initial coherence intensities, the Bargmman index and the detuning. It is shown that the phenomenon of sudden death and re-birth of entanglement, and the sudden changes of the geometric quantum correlation can be controlled by these parameters. We find that the robustness of the quantum correlation can be greatly enhanced by the Bargmman index and the resonance detuning. Negativity is the measure most susceptible to phase decoherence, while geometric quantum discord and measurement-induced nonlocality are the more robust measures.

Non-Markovian dynamics of correlations: The composite effect of two channels and robust quantum correlation preserving by detuning

2014 ◽  
Vol 29 (02) ◽  
pp. 1450249
Author(s):  
Y. H. Ji ◽  
X. D. Wan
Keyword(s):  
Quantum Information ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Quantum Information Processing ◽  
Center Frequency ◽  
Cavity Model ◽  
Classical Correlation ◽  
Composite Effect ◽  
Markovian Dynamics ◽  
Dynamics Of Correlations

We investigate the influence of the composite effect and information backflow effect in non-Markovian channel on the dynamics of quantum correlation including quantum entanglement and quantum discord. It is found that, the composite effect of independent channels is not only harmful to the maintenance of quantum correlation but also unfavorable for the maintenance of classic correlation. In a non-Markovian channel, by regulating the discord between qubit and the center frequency of cavity model, the time of quantum correlation and classical correlation of the system can be effectively prolonged. Thus, the quantum information processing can be achieved more easily under larger detuning.

QUANTUM DISCORD IN THE THERMAL STATES OF A SPIN-STAR SYSTEM

2011 ◽  
Vol 25 (30) ◽  
pp. 2289-2297 ◽  
Author(s):  
XIAO SAN MA ◽  
GUANG XING ZHAO ◽  
JIA YAN ZHANG ◽  
AN MIN WANG
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Anisotropy Parameter ◽  
Interaction Strength ◽  
The Other ◽  
Star System ◽  
Star Model ◽  
Thermal States

We investigate the quantum discord in the thermal states for a spin-star model consisting of three parties which include one central spin and the other two outer spins. Our results imply that the quantum correlation can be established between the two outer spins both of which interacting with the central spin independently. From the analysis, we find that the quantum discord and entanglement depends not only on the external magnetic field and the interaction strength but also on the anisotropy parameter and the temperature. Specially, the quantum discord is more robust than the quantum entanglement in the sense that the quantum discord lasts for higher temperatures than the entanglement does.

MONOGAMY PROPERTIES OF QUANTUM DISCORD FOR A THREE-QUBIT ENTANGLED STATE

2013 ◽  
Vol 27 (07) ◽  
pp. 1350049 ◽  
Author(s):  
XUE-KE SONG ◽  
TAO WU ◽  
LIU YE
Keyword(s):  
Relative Entropy ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
The Other ◽  
Numerical Calculations ◽  
Entangled State ◽  
Geometric Quantum Discord ◽  
The Given

In this paper, we obtain the pairwise quantum discord for a three-qubit W-class state, and investigate the monogamy property of quantum discord by two different ways (relative entropy-based distance and geometric square-norm distance). Through numerical calculations, we find that a party cannot have maximal quantum correlations with the other two parties simultaneously. For the given state, the quantum correlation between particles 1 and 3 induces limitation on the quantum correlation between them and particle 2. Moreover, the result also shows that the geometric quantum discord of the given W-class state obeys the monogamy property while the entropy quantum discord violates.

scholarly journals SUDDEN CHANGE OF QUANTUM DISCORD UNDER SINGLE QUBIT NOISE

2013 ◽  
Vol 11 (05) ◽  
pp. 1350048 ◽  
Author(s):  
LI-XING JIA ◽  
BO LI ◽  
R.-H. YUE ◽  
HENG FAN
Keyword(s):  
Quantum System ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Sudden Change ◽  
Entangled State ◽  
Noisy Environment ◽  
Noisy Environments ◽  
Single Qubit ◽  
Sudden Transition

We show that the sudden change of quantum correlation can occur even when only one part of the composite entangled state is exposed to a noisy environment. Our results are illustrated through the action of different noisy environments individually on a single qubit of quantum system. Composite noise on the whole of the quantum system is thus not the necessarily condition for the occurrence of sudden transition for quantum correlation.

Quantum discord of a three-qubit W-class state in noisy environments

2012 ◽  
Vol 12 (7&8) ◽  
pp. 677-692
Author(s):  
Hui Guo ◽  
Jin-Ming Liu ◽  
Cheng-Jie Zhang ◽  
C. H. Oh
Keyword(s):  
Numerical Analysis ◽  
Sudden Death ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Sudden Change ◽  
Noisy Environments ◽  
Classical Correlation ◽  
Entanglement Of Formation ◽  
Sudden Transition ◽  
Bit Flip

We study the dynamics of the pairwise quantum discord (QD), classical correlation (CC), and entanglement of formation (EOF) for the three-qubit W-class state |W>_{123}=\frac 12(|100>_{123}+|010>_{123}+\sqrt{2}|001>_{123}) under the influence of various Markovian noises by analytically solving the master equation in the Lindblad form. Through numerical analysis, we find that EOF decreases asymptotically to zero with time for the dephasing noise, but it undergoes sudden death for the bit-flip noise, the isotropic noise, as well as the dissipative and noisy environments. Moreover, QD decays to zero in an asymptotical way for all the noises we investigated. Thus, when the W-class state |W>_{123} is subject to the above Markovian noises, QD is more robust than EOF against decoherence excluding the phase-flip noise, implying that QD is more useful than entanglement to characterize the quantum correlation. We also find a remarkable character for the CC in the presence of the phase-flip noise, i.e., CC displays the behavior of sudden transition and then keeps constant permanently, but the corresponding QD just exhibits a very small sudden change. Furthermore, we verify the monogamic relation between the pairwise QD and EOF of the W-class state.

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