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Quantum discord and its dynamics for multipartite systems
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作者 罗嘉欣 郭琼 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第6期168-175,共8页
Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit q... Quantum discord, one of the famous quantum correlations, has been recently generalized to multipartite systems by Radhakrishnan et al. Here we give analytical solutions of the quantum discord for a family of N-qubit quantum states. For the bipartite system, we derive a zero quantum discord which will remain unchanged under the phase damping channel. For multiparitite systems, it is found that the quantum discord can be classified into three categories and the quantum discord for odd-partite systems can exhibit freezing under the phase damping channel, while the freezing does not exist in the even-partite systems. 展开更多
关键词 quantum discord multipartite systems decoherence channels frozen discord
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Symmetric quantum discord for a two-qubit state 被引量:1
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作者 王仲宵 王波波 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第7期274-278,共5页
We discuss the symmetric quantum discord (SQD) for an arbitrary two-qubit state consisting of subsystems A and B and give the analysis formula of the symmetric quantum discord for the arbitrary two-qubit state. We a... We discuss the symmetric quantum discord (SQD) for an arbitrary two-qubit state consisting of subsystems A and B and give the analysis formula of the symmetric quantum discord for the arbitrary two-qubit state. We also give the optimization process of the symmetric quantum discord for some states and obtain the symmetric quantum discord. We compare the quantum discord (QD) with the symmetric quantum discord, and find that the symmetric quantum discord is greater than the quantum discord. We also find that the symmetric quantum discord can be unequal to the quantum discord when the right quantum discord (measure on subsystem B) is equal to the left quantum discord (measure on subsystem A). 展开更多
关键词 quantum discord symmetric quantum discord optimization process
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Controlling quantum discord dynamics in cavity QED systems by applying a classical driving field with phase decoherence 被引量:3
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作者 钱懿 许晶波 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第3期56-62,共7页
We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of t... We investigate a two=level atom interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence and find that a stationary quantum discord can arise in the interaction of the atom and cavity field as the time turns to infinity. We also find that the stationary quantum discord can be increased by applying a classical driving field. Furthermore, we explore the quantum discord dynamics of two identical non=interacting two-level atoms independently interacting with a quantized cavity field and a classical driving field in the presence of phase decoherence. Results show that the quantum discord between two atoms is more robust than entanglement under phase decoherence and the classical driving field can help to improve the amount of quantum discord of the two atoms. 展开更多
关键词 stationary quantum discord classical driving field phase decoherence
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Thermal quantum discord in Heisenberg models with Dzyaloshinski-Moriya interaction 被引量:2
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作者 王林成 闫俊彦 衣学喜 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第4期53-58,共6页
We study the quantum discord of the bipartite Heisenberg model with the Dzyaloshinski-Moriya (DM) interaction in thermal equilibrium state and discuss the effect of the DM interaction on the quantum discord. The qua... We study the quantum discord of the bipartite Heisenberg model with the Dzyaloshinski-Moriya (DM) interaction in thermal equilibrium state and discuss the effect of the DM interaction on the quantum discord. The quantum entanglement of the system is also discussed and compared with quantum discord. Our results show that the quantum discord may reveal more properties of the system than quantum entanglement and the DM interaction may play an important role in the Heisenberg model. 展开更多
关键词 quantum discord thermal equilibrium state Heisenberg model Dzyaloshinski-Moriya interaction
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Thermal Quantum Discord in Anisotropic Heisenberg XXZ Model with Dzyaloshinskii-Moriya Interaction 被引量:3
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作者 陈一新 尹志 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第7期60-66,共7页
The thermal quantum discord (QD) is studied in a two-qubit Heisenberg XXZ system with DzyaloshinskiiMoriya (DM) interaction. We compare the thermal QD with thermal entanglement in this system and find remarkable d... The thermal quantum discord (QD) is studied in a two-qubit Heisenberg XXZ system with DzyaloshinskiiMoriya (DM) interaction. We compare the thermal QD with thermal entanglement in this system and find remarkable differences between them. For instance, we show situations where QD decreases asymptotically to zero with temperature T while entanglement decreases to zero at the point of critical temperature, situations where QD decreases with certain tunable parameters such as Dx and Dx when entanglement increases. We find that the characteristic of QD is exotic in this system and this possibly offers a potential solution to enhance entanglement of a system. We also show that tunable parameter Dx is more efficient than parameter Dz in most regions for controlling the QD. 展开更多
关键词 thermal quantum discord Heisenberg XXZ model Dzyaloshinskii-Moriya interaction
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Continuous-Variable Quantum Network Coding Based on Quantum Discord 被引量:2
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作者 Tao Shang Ran Liu +1 位作者 Jianwei Liu Yafei Hou 《Computers, Materials & Continua》 SCIE EI 2020年第9期1629-1645,共17页
Establishing entanglement is an essential task of quantum communication technology.Beyond entanglement,quantum discord,as a measure of quantum correlation,is a necessary prerequisite to the success of entanglement dis... Establishing entanglement is an essential task of quantum communication technology.Beyond entanglement,quantum discord,as a measure of quantum correlation,is a necessary prerequisite to the success of entanglement distribution.To realize efficient quantum communication based on quantum discord,in this paper,we consider the practical advantages of continuous variables and propose a feasible continuous-variable quantum network coding scheme based on quantum discord.By means of entanglement distribution by separable states,it can achieve quantum entanglement distribution from sources to targets in a butterfly network.Compared with the representative discrete-variable quantum network coding schemes,the proposed continuous-variable quantum network coding scheme has a higher probability of entanglement distribution and defends against eavesdropping and forgery attacks.Particularly,the deduced relationship indicates that the increase in entanglement is less than or equal to quantum discord. 展开更多
关键词 Continuous variable quantum network coding quantum discord entanglement distribution Gaussian cloning
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Phase effect on dynamics of quantum discord modulated by interaction between qubits 被引量:1
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作者 王国友 郭有能 曾浩生 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第9期101-105,共5页
We study the effects of the interaction strength and the initial phase on the dynamics of quantum discord in a twoqubit system under both spontaneous emission and dephasing noisy channels. It is shown that the time ev... We study the effects of the interaction strength and the initial phase on the dynamics of quantum discord in a twoqubit system under both spontaneous emission and dephasing noisy channels. It is shown that the time evolution of quantum discord displays quicker oscillations with increasing inter-qubit interaction strength but the effect of the initial phase closely depends on the interaction between the qubits. Only for non-zero inter-qubit interaction cases, the evolution of quantum discord is affected by the initial phase and its oscillating amplitude increases with increasing initial phase. A comparison between evolutions of quantum discord and entanglement is also made. 展开更多
关键词 quantum discord spontaneous emission DEPHASING
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Conservation issue of pairwise quantum discord and entanglement of two coupled qubits in a two-mode vacuum cavity 被引量:1
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作者 陈秋英 方卯发 +1 位作者 肖兴 周湘峰 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第5期44-48,共5页
The conservation issues of pairwise quantum discord and entanglement of two qubits coupled to a two-mode vacuum cavity are investigated by considering the dipole^tipole interaction between two qubits. It is found that... The conservation issues of pairwise quantum discord and entanglement of two qubits coupled to a two-mode vacuum cavity are investigated by considering the dipole^tipole interaction between two qubits. It is found that the sum of the square of the pairwise quantum discords and the sum of the square of the pairwise concurrences are both conserved in the strong dipole-dipole interaction limit. However, in the middle dipole-dipole and weak dipole-dipole interaction limits, the sum of the square of the pairwise concurrences is still conserved while the sum of the square of the pairwise discords is not. The crucial reason for this is that the quantum discords are not equivalent if the measurements are performed on different subsystems in a general situation. So it is very important for quantum computation depending on the quantum discord to select the target performed by the measurements. 展开更多
关键词 quantum discord quantum entanglement dipole-lipole (DD) interaction
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Robustness of quantum discord to sudden death in nuclear magnetic resonance
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作者 胥建卫 陈起辉 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第4期60-66,共7页
We investigate the dynamics of the entanglement and quantum discord of two qubits in liquid state homonuclear nuclear magnetic resonance. Applying a phenomenological description for nuclear magnetic resonance under a ... We investigate the dynamics of the entanglement and quantum discord of two qubits in liquid state homonuclear nuclear magnetic resonance. Applying a phenomenological description for nuclear magnetic resonance under a relaxation process, and taking a group of typical parameters of nuclear magnetic resonance, we show that when a zero initial state experiences a relaxation process, its entanglement disappears completely after a sequence of so-called sudden deaths and revivals, while the quantum discord retains remarkable values after a sequence of oscillations. That is to say, the quantum discord is more robust than entanglement. 展开更多
关键词 quantum discord nuclear magnetic resonance CONCURRENCE sudden death
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Quantum discord of two-qutrit system under quantum-jump-based feedback control
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作者 Chang Wang Mao-Fa Fang 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第12期75-81,共7页
This paper studies quantum discord of two qutrits coupled to their own environments independently and coupled to the same environment simultaneously under quantum-jump-based feedback control. Our results show that spo... This paper studies quantum discord of two qutrits coupled to their own environments independently and coupled to the same environment simultaneously under quantum-jump-based feedback control. Our results show that spontaneous emission, quantum feedback parameters, classical driving, initial state, and detection efficiency all affect the evolution of quantum discord in a two-qutrit system. We find that under the condition of designing proper quantum-jump-based feedback parameters, quantum discord can be protected and prepared. In the case where two qutrits are independently coupled to their own environments, classical driving, spontaneous emission, and low detection efficiency have negative effect on the protection of quantum discord. For different initial states, it is found that the evolution of quantum discord under the control of appropriate parameters is similar. In the case where two qutrits are simultaneously coupled to the same environment,the classical driving plays a positive role in the generation of quantum discord, but spontaneous emission and low detection efficiency have negative impact on the generation of quantum discord. Most importantly, we find that the steady discord depends on feedback parameters, classical driving, and detection efficiency, but not on the initial state. 展开更多
关键词 QUTRIT quantum-jump-based feedback quantum discord
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Characterizing the dynamics of quantum discord under phase damping with POVM measurements
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作者 蒋峰建 叶剑锋 +1 位作者 闫新虎 吕海江 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第10期53-58,共6页
In the analysis of quantum discord, the minimization of average entropy traditionally involved over orthogonal projective measurements may be attained at more optimal decompositions by using the positive-operator-valu... In the analysis of quantum discord, the minimization of average entropy traditionally involved over orthogonal projective measurements may be attained at more optimal decompositions by using the positive-operator-valued measure(POVM)measurements. Taking advantage of the quantum steering ellipsoid in combination with three-element POVM optimization,we show that, for a family of two-qubit X states locally interacting with Markovian non-dissipative environments, the decay rates of quantum discord show smooth dynamical evolutions without any sudden change. This is in contrast to two-element orthogonal projective measurements, in which case the sudden change of the decay rates of quantum and classical decoherences may be a common phenomenon. Notwithstanding this, we find that a subset of X states(including the Bell diagonal states) involving POVM optimization can still preserve the sudden change character as usual. 展开更多
关键词 quantum steering ellipsoid quantum discord DECOHERENCE
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Dynamics of quantum discord in a two-qubit system under classical noise
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作者 郭有能 方卯发 +1 位作者 刘翔 杨百元 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第3期274-277,共4页
We study the quantum discord dynamics of two noninteracting qubits that are, respectively, subject to classical noise. The results show that the dynamics of quantum discord are dependent on both the coupling between t... We study the quantum discord dynamics of two noninteracting qubits that are, respectively, subject to classical noise. The results show that the dynamics of quantum discord are dependent on both the coupling between the qubits and classical noise, and the average switching rate of the classical noise. In the weak-coupling Markovian region, quantum discord exhibits exponent decay without revival, and can be well protected by increasing the average classical noise switching rate. While in the strong-coupling non-Markovian region, quantum discord reveals slowly decayed oscillations with quick revival by decreasing the average switching rate of the classical noise. Thus, our results provide a new method of protecting quantum discord in a two-qubit system by controlling the coupling between the qubits and classical noise, and the average switching rate of the classical noise. 展开更多
关键词 quantum discord non-Markovian region classical noise
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Geometric quantum discord and Berry phase between two charge qubits coupled by a quantum transmission line
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作者 朱汉杰 张国锋 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第12期55-58,共4页
Geometric quantum discord(GQD) and Berry phase between two charge qubits coupled by a quantum transmission line are investigated. We show how GQDs evolve and investigate their dependencies on the parameters of the s... Geometric quantum discord(GQD) and Berry phase between two charge qubits coupled by a quantum transmission line are investigated. We show how GQDs evolve and investigate their dependencies on the parameters of the system.We also calculate the energy and the Berry phase and compare them with GQD, finding that there are close connections between them. 展开更多
关键词 geometric quantum discord(GQD) Berry phase charge qubits
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Controlling the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environments
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作者 Rong-Yu Wu Mao-Fa Fang 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第3期441-446,共6页
The uncertainty principle is a crucial aspect of quantum mechanics.It has been shown that the uncertainty principle can be tightened by quantum discord and classical correlation in the presence of quantum memory.We in... The uncertainty principle is a crucial aspect of quantum mechanics.It has been shown that the uncertainty principle can be tightened by quantum discord and classical correlation in the presence of quantum memory.We investigate the control of the entropic uncertainty and quantum discord in two two-level systems by an ancilla in dissipative environment.Our results show that the entropic uncertainty of an observed system can be reduced and the quantum discord between the observed system and the quantum memory system can be enhanced in the steady state of the system by adding an dissipative ancilla.Particularly,via preparing the state of the system to the highest excited state with hight fidelity,the entropic uncertainty can be reduced markedly and the quantum discord can be enhanced obviously.We explain these results using the definition of state fidelity.Furthermore,we present an effective strategy to further reduce the the entropic uncertainty and to enhance the the quantum discord via quantum-jump-based feedback control.Therefore,our results may be of importance in the context of quantum information technologies. 展开更多
关键词 entropic uncertainty quantum discord dissipative environment ancilla
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Dynamics of Quantum Discord in Asymmetric and Local Non-Markovian Environments
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作者 郝翔 潘涛 +1 位作者 沙金巧 朱士群 《Communications in Theoretical Physics》 SCIE CAS CSCD 2011年第1期41-45,共5页
The non-Markovian decoherence of quantum and classical correlations is analytically obtained when two qubits are asymmetrically subjected to the bit flip channel and phase flip channel. For one class of initial mixed ... The non-Markovian decoherence of quantum and classical correlations is analytically obtained when two qubits are asymmetrically subjected to the bit flip channel and phase flip channel. For one class of initial mixed states, quantum correlations quantified by quantum discord decay synchronously with classical correlations. The discovery that the decaying rates of quantum and classical correlations suddenly change at the characteristic time is physically interpreted by the distance from quantum state to the closest classical states. In a large time interval, quantum correlations are greater than classical correlations. The quantum and classical correlations can be preserved over a longer period of time via the kernel characterizing the environment memory effects. 展开更多
关键词 DECOHERENCE quantum discord non-Markovian environments interaction
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Protecting geometric quantum discord via partially collapsing measurements of two qubits in multiple bosonic reservoirs
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作者 Xue-Yun Bai Su-Ying Zhang 《Chinese Physics B》 SCIE EI CAS CSCD 2022年第4期163-169,共7页
We study the dynamics of geometric quantum discord(GQD) between two qubits,each qubit interacting at the same time with K independent multiple bosonic reservoirs at zero temperature.In both weak and strong qubit-reser... We study the dynamics of geometric quantum discord(GQD) between two qubits,each qubit interacting at the same time with K independent multiple bosonic reservoirs at zero temperature.In both weak and strong qubit-reservoirs coupling regimes,we find that the increase of the number K of reservoirs can induce the damped oscillation of GQD,and enhance the memory effects of the overall environment.And the Hilbert-Schmidt norm GQD(two-norm GQD) is always smaller than the trace norm geometric quantum discord(one-norm GQD).Therefore,the one-norm GQD is a better way to measure the quantum correlation.Finally,we propose an effective strategy to improve GQD by using partially collapsing measurements,and we find that the protection effect is better with the increase of the weak measurement strength. 展开更多
关键词 geometric quantum discord(GQD) the Hilbert-Schmidt norm GQD the trace norm GQD partially collapsing measurements
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Geometric global quantum discord of two-qubit states
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作者 肖运龙 李陶 +3 位作者 费少明 景乃桓 王志玺 李先清 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第3期60-64,共5页
We consider the geometric global quantum discord (GGQD) of two-qubit systems. By analyzing the symmetry of geometric global quantum discord we give an approach for deriving analytical formulae of the extremum proble... We consider the geometric global quantum discord (GGQD) of two-qubit systems. By analyzing the symmetry of geometric global quantum discord we give an approach for deriving analytical formulae of the extremum problem which lies at the core of computing the GGQD for arbitrary two-qubit states. Furthermore, formulae of GGQD of arbitrary two-qubit states and some concrete examples are presented. 展开更多
关键词 geometric global quantum discord two-qubit state
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Dynamics of super-quantum discord and direct control with weak measurement in open quantum system
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作者 嵇英华 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第12期209-214,共6页
Super-quantum discord(SQD) with weak measurement is regarded as a kind of quantum correlation in quantum information processing. We compare and analyze the dynamical evolutions of SQD, quantum discord(QD), and qua... Super-quantum discord(SQD) with weak measurement is regarded as a kind of quantum correlation in quantum information processing. We compare and analyze the dynamical evolutions of SQD, quantum discord(QD), and quantum entanglement(QE) between two qubits in the correlated dephasing environmental model. The results indicate that(i) owing to the much smaller influence of weak measurement on the coherence of the system than that of von Neumann projection measurement, SQD with weak measurement is larger than QD, and(ii) dynamical evolution of QD or QE monotonically goes to zero with time, while SQD monotonically tends to a stable value and a freezing phenomenon occurs. The stable value after freezing mainly depends on the measurement strength and the purity of the initial quantum state. 展开更多
关键词 super-quantum discord(SQD) weak measurement CONTROL
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Tuning Quantum Discord in Josephson Charge Qubits System
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作者 SHANG Boxing ZHANG Weiwei +1 位作者 GUO Yucui XI Xiaoqiang 《China Communications》 SCIE CSCD 2014年第A01期187-194,共8页
A type of two qubits Josephson charge system is constructed, and properties of the quantum discord (QD) as well as the differences between thermal QD and thermal entanglement are investigated. A detailed calculation... A type of two qubits Josephson charge system is constructed, and properties of the quantum discord (QD) as well as the differences between thermal QD and thermal entanglement are investigated. A detailed calculation shows that the magnetic flux is more efficient than the voltage in tuning QD. By choosing proper system parameter the maximum QD can be realized in our two qubits Josephson charge system. 展开更多
关键词 quantum discord Josephson charge qubits
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A Comparison of the Concurrence and the Quantum Discord in a Two-Qubit System
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作者 杨国晖 王荣 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第2期5-9,共5页
The quantum correlation dynamics in an anisotropic Heisenberg XY Z model under decoherence are investigated with the use of concurrence C and quantum discord (QD). There is a remarkable difference between the time e... The quantum correlation dynamics in an anisotropic Heisenberg XY Z model under decoherence are investigated with the use of concurrence C and quantum discord (QD). There is a remarkable difference between the time evolution behaviors of these two correlation measures: there is a entanglement-sudden-death phenomenon in the concurrence while there is none in QD, which is valid for all of the initial states of this system, and the interval time of the entanglement death is found to be strongly dependent on the initial states and the parameters B and △. With the long-time limit the steady entanglement (SC) and steady quantum discord (SO, D) can be obtained. The magnitudes of SC and SQD are closely related to the parameters B and △, while the strength of the Dzyaloshinskii-Moriya interaction, D, has no influence. In addition, the effects of the parameters B and △ on SC and SQD display such different and complicated features that one cannot obtain a uniform law about them, thus we give an analytical explanation of this phenomenon. Lastly, it can be noted that the value of SC is not always larger than SQD, which is strongly dependent on the parameters B and △. 展开更多
关键词 A Comparison of the Concurrence and the quantum discord in a Two-Qubit System
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