Dynamical Suppression of Nonlocal Decoherence in Two-State Quantum Systems

M Grigorescu

Wang Zhong-Jie, Zhang Kan

Nonlocal decoherence of two qubits due to pure phase damping has been investigated. We have proposed a scheme to keep the entanglement of two qubits from nonlocal decoherence. By applying a series of ±π pulses, nonlocal decoherence can be thoroughly suppressed.

Narayan Ganesan

Zun-Yan Nie, Zhi He, Yu Chen

Abstract The Bell nonlocality for initially general W states undergoing independent generalized amplitude damping channels are investigated. We examine in detail the effect of adding the number of qubits in the reservoir on delay of the Bell nonlocality dynamics. We show that the Bell nonlocality can be obviously enhanced in suppressing decoherence with the help of auxiliary qubits in the reservoir. In particular, the sudden death of Bell nonlocality can be perfectly bypassed, and corresponding condition has been also demonstrated for initially standard W state. We also provide two ways to produce the interesting quantum beats for the tripartite Bell nonlocality and entanglement. The obtained results may have some potential interests in the quantum decoherence field.

Ting Yu

Xiang-Ji Cai

We theoretically study the non-Markovian dynamics of qubit systems coupled to nonequilibrium environments with nonstationary and non-Markovian statistical properties. The reduced density matrix of the single qubit system satisfies a closed third-order differential equation with all the higher-order environmental correlations taken into account and the reduced density matrix of the two qubit system can be expressed as the Kraus representation in terms of the tensor products of the single qubit Kraus operators. We derive the relation between the entanglement and nonlocality of the two qubit system which are both closely associated with the decoherence function. We identify the threshold values of the decoherence function to ensure the existences of the concurrence and nonlocal quantum correlations for a given evolution time when the two qubit system is initially prepared in the composite Bell states and the extended Werner states, respectively. It is shown that the environmental nonstationary feature can suppress the decoherence and disentanglement dynamics and can reduce the coherence and entanglement revivals in non-Markovian dynamics regime. In addition, it is shown that the environmental non-Markovian feature can enhance the coherence revivals in the single decoherence dynamics and the entanglement revivals in the two qubit disentanglement dynamics, respectively. Furthermore, the environmental nonstationary and non-Markovian features can enhance the nonlocality of the two qubit system.