Sudden death of entanglement induced by a minimal thermal environment

TL;DR

This paper analytically investigates how a minimal thermal environment, modeled as a single mode field, affects the entanglement dynamics of two qubits, revealing phenomena like sudden death and birth of entanglement.

Contribution

It provides an exact solution for a minimal environment model and explores its impact on entanglement and coherence dynamics, highlighting new effects such as entanglement sudden death and birth.

Findings

Entanglement can abruptly vanish or reappear due to the small environment.

The dynamics depend on coupling strengths and environmental temperature.

The model offers insights into minimal environment effects on quantum systems.

Abstract

We study the dynamics of two interacting two-level systems (qubits) having one of them isolated and the other coupled to a single mode electromagnetic field in a thermal state. The field plays the role of a small environment, in contrast to the usual approach of modeling an environment via a thermal reservoir with many degrees of freedom. We find the analytical solution of the proposed model, which allows us to investigate the consequences of the coupling to the small environment on characteristic quantum features of the two-qubit system. We study the time evolution of quantum entanglement and coherence, verifying the dependence on the relevant coupling constants as well as the influence of the effective temperature of the environment. Interestingly, we find that both sudden death and sudden birth of entanglement may occur in such a simple system. We also discuss a different partition, in which the isolated qubit is considered to be coupled to a composite environment, constituted by the other qubit plus the field mode.