Decoherence of two qubits in a non-Markovian reservoir without rotating-wave approximation

TL;DR

This paper provides an exact analysis of two entangled qubits' decoherence in a non-Markovian environment, highlighting the significant impact of counter-rotating terms and questioning the validity of the rotating-wave approximation in such settings.

Contribution

It derives and solves a non-perturbative quantum master equation without using the Born-Markov or rotating-wave approximations, revealing the influence of counter-rotating terms on decoherence.

Findings

Counter-rotating terms significantly affect decoherence behavior.

Differences exist between RWA and non-RWA Hamiltonian solutions.

RWA may be inappropriate in non-Markovian reservoirs.

Abstract

The decoherence of two initially entangled qubits in a non-Markovian reservoir has been investigated exactly without Born Markovian approximation and rotating-wave approximation(RWA). The non-perturbative quantum master equation is derived and its exact solution is obtained. The decoherence behaviors of two qubits, initially entangled in Bell states, has been investigated in three different cases of parameters. The results show that the counter-rotating wave terms have great influence on the decoherence behavior, and there are differences between the exact solution of the Hamiltonian with RWA and that of the exact Hamiltonian without RWA. It might be improper to take RWA when the atom is in a non-markovian reservoir.