Anomalous decoherence in a dissipative two-level system

TL;DR

This paper investigates the non-Markovian decoherence dynamics of a dissipative two-level system, revealing that increased coupling can inhibit decoherence due to a quantum phase transition, offering new control strategies.

Contribution

It uncovers the counterintuitive phenomenon where stronger system-reservoir coupling inhibits decoherence via a quantum phase transition in the spin-boson model.

Findings

Decoherence is inhibited with increased coupling strength.

A quantum phase transition underlies this anomalous behavior.

The results suggest new methods to control decoherence.

Abstract

We study systematically the non-Markovian decoherence dynamics of a dissipative two-level system, i.e., the so-called spin-boson model. It is interesting to find that the decoherence tends to be inhibited with the increase of the coupling strength between the system and the reservoir, which is contrary to the common recognition that a stronger coupling always induces a severer decoherence. This is attributed to the occurrence of a quantum phase transition (QPT). The relationship between this QPT and conventional delocalized-localized QPT is also discussed. Our result suggests a useful control method to overcome the detrimental effects of the reservoir to the system.