Exact dynamics of interacting qubits in a thermal environment: Results beyond the weak coupling limit

TL;DR

This paper presents an exact numerical approach to study the dynamics of two interacting qubits in thermal environments, revealing complex entanglement phenomena beyond the weak coupling approximation.

Contribution

It introduces an exact mapping to spin-bath problems enabling simulations beyond weak coupling, and analyzes entanglement dynamics including sudden death and revival.

Findings

Stationary entanglement can develop due to thermal environment.

Entanglement sudden death depends on initial state composition.

Analytic expressions are derived for weak coupling in the long-time limit.

Abstract

We demonstrate an exact mapping of a class of models of two interacting qubits in thermal reservoirs to two separate spin-bath problems. Based on this mapping, exact numerical simulations of the qubits dynamics can be performed, beyond the weak system-bath coupling limit. Given the time evolution of the system, we study, in a numerically exact way, the dynamics of entanglement between pair of qubits immersed in boson thermal baths, showing a rich phenomenology, including an intermediate oscillatory behavior, the entanglement sudden birth, sudden death, and revival. We find that stationary entanglement develops between the qubits due to their coupling to a thermal environment, unlike the isolated qubits case in which the entanglement oscillates. We also show that the occurrence of entanglement sudden death in this model depends on the portion of the zero and double excitation states in the subsystem initial state. In the long-time limit, analytic expressions are presented at weak system-bath coupling, for a range of relevant qubit parameters.