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Ji Y.-H.,Jiangxi Normal University | Ji Y.-H.,Key Laboratory of Photoelectronics and Telecommunication of Jiangxi Province
Chinese Physics B | Year: 2015

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. © 2015 Chinese Physical Society and IOP Publishing Ltd. Source


Ji Y.,Jiangxi Normal University | Ji Y.,Key Laboratory of Photoelectronics and Telecommunication of Jiangxi Province
Optik | Year: 2013

Utilizing the concurrence and the Bell inequality, we investigated in detail the evolution of entangled decoherence of two superconductor qubits in non-Markovian process. The results show that the evolution of entanglement dynamics can cause entanglement sudden death (ESD) and entanglement sudden birth (ESB) because of the interaction between the environment and the quantum qubits. The concurrence of a quantum system is not only related with the environmental dissipation effects, the interaction between the qubits, and the initial quantum state, but also strongly related with the coupling symmetry between qubit-environment. Under certain initial states, the effect of environmental dissipation can be avoided completely by controlling the coupling model between qubits and environments. The interaction between qubits can prolong the survival time of the entanglement, and it is the dynamic for reviving the entanglement of quantum system. The further research results indicate that, the non-Markovian memory effects of the environment are helpful to prolong the survival time of the entanglement or to prevent the outbreak of ESD. © 2012 Elsevier GmbH. Source


Hu J.-J.,Jiangxi Normal University | Li S.,Key Laboratory of Photoelectronics and Telecommunication of Jiangxi Province
Communications in Theoretical Physics | Year: 2014

The dynamics of entanglement between two qubits in the local damping two-sided channel and single-sided channel are compared through non-Markovian process and Markovian process. The entanglement between two qubits is found to be longer in the single-sided channel case due to the weakening of the dissipative effects. In the two-sided channel, influenced by the entanglement between qubits, the previous independent dissipative channels incline to the composite effect of the Markovian process. This composite effect results in the dissipative effect of one channel affecting the qubits in the other channel, especially inhibiting the backflow effect in the non-Markovian channel, which is disadvantageous to the entanglement maintenance between qubits. In the Markovian channel, the composite effect of the damping two-sided channels is more obvious since there is no backflow effect, thus more disadvantageous to the entanglement maintenance. © 2014 Chinese Physical Society and IOP Publishing Ltd. Source


Ji Y.-H.,Jiangxi Normal University | Ji Y.-H.,Key Laboratory of Photoelectronics and Telecommunication of Jiangxi Province | Liu Y.-M.,Jiangxi Normal University
International Journal of Theoretical Physics | Year: 2013

We investigate the dynamic evolution behaviors of entanglement and geometric quantum discord (GQD) of hybrid qubits in a circuit QED system. Under certain initial conditions, interactions between qubits and that between the qubit and the cavity can suppress the decay of entanglement and GQD of qubits. Under the initial condition {pipe}ψ Q(0)〉I=sinα{pipe}↓↑〉+cosα{pipe}↑↓〉, such decay was avoided by increasing the coupling strength ratio between qubits and that between the qubit and the cavity. Under the aforementioned condition, the survival time of entanglement and GQD was prolonged by decreasing the coupling strength ratio between qubits and that between the qubit and the cavity. © 2013 Springer Science+Business Media New York. Source


Ji Y.-H.,Jiangxi Normal University | Ji Y.-H.,Key Laboratory of Photoelectronics and Telecommunication of Jiangxi Province | Liu Y.-M.,Jiangxi Normal University
Chinese Physics B | Year: 2013

In this paper, we investigate the quantum correlation of coupled qubits which are initially in maximally entangled mixed states in a squeezed vacuum reservoir. We compare and analyze the effects of squeezed parameters on quantum discord and quantum concurrence. The results show that in a squeezed vacuum reservoir, the quantum discord and quantum concurrence perform with completely opposite behaviors with the change of squeezed parameters. Quantum discord survives longer with the increase of squeezed amplitude parameter, but entanglement death is faster on the contrary. The results also indicate that the classical correlation of the system is smaller than quantum discord in a vacuum reservoir, while it is bigger than quantum discord in a squeezed vacuum reservoir. The quantum discord and classical correlation are more robust than quantum concurrence in the two reservoir environments, which indicates that the entanglement actually is easily affected by decoherence and quantum discord has a stronger ability to avoid decoherence in a squeezed vacuum reservoir. © 2013 Chinese Physical Society and IOP Publishing Ltd. Source

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