Non-Markovian qubit dynamics in nonequilibrium environments

TL;DR

This paper investigates how nonstationary and non-Markovian environments influence qubit dynamics, revealing that such environments can suppress decoherence and enhance quantum correlations like entanglement and nonlocality.

Contribution

It provides a theoretical framework for understanding non-Markovian and nonstationary effects on qubit systems, including explicit relations between decoherence, entanglement, and nonlocality.

Findings

Nonstationary environments can suppress decoherence and disentanglement.

Non-Markovian features can enhance coherence and entanglement revivals.

Environmental nonstationarity and non-Markovianity can boost nonlocal quantum correlations.

Abstract

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.