Exact dynamics of quantum correlations of two qubits coupled to bosonic baths

TL;DR

This paper provides an exact analysis of how counter rotating-wave terms affect quantum correlations like entanglement and discord in two qubits coupled to bosonic baths, revealing significant differences from previous approximations.

Contribution

It extends the hierarchy approach to exactly solve spin boson models with Lorentzian spectra, systematically analyzing CRT effects on quantum correlations beyond the rotating-wave approximation.

Findings

CRT suppresses entanglement revival in independent baths.

Quantum discord remains finite and less affected by CRT in non-Markovian regimes.

In Markovian regimes, strong coupling enhances quantum discord.

Abstract

The counter rotating-wave term (CRT) effects from the system-bath coherence on the dynamics of quantum correlation of two qubits in two independent baths and a common bath are systematically investigated. The hierarchy approach is extended to solve the relevant spin boson models with the Lorentzian spectrum, the exact dynamics for the quantum entanglement and quantum discord (QD) are evaluated, and the comparisons with previous ones under the rotating-wave approximation are performed. For the two independent baths, beyond the weak system-bath coupling, the CRT essentially changes the evolution of both entanglement and QD. With the increase of the coupling, the revival of the entanglement is suppressed dramatically and finally disappears, and the QD becomes smaller monotonically. For the common bath, the entanglement is also suppressed by the CRT, but the QD shows quite different behaviors, if initiated from the correlated Bell states. In the non-Markovian regime, the QD is almost not influenced by the CRT and generally finite in the long time evolution at any coupling, while in the Markovian regime, it is significantly enhanced with the strong coupling.