Coherent-incoherent transition in a Cooper-pair-box coupled to a quantum oscillator: an equilibrium approach

TL;DR

This paper investigates how temperature affects quantum tunneling in a Cooper-pair-box coupled to a quantum oscillator, revealing a transition from coherent to thermally activated tunneling at a specific temperature.

Contribution

It provides an analytical and numerical study of the temperature-induced transition in tunneling behavior, linking it to strong coupling effects and small polaron theory.

Findings

Coherent tunneling is destroyed at high temperatures in strong coupling regimes.

A transition temperature between coherent and thermally activated tunneling is identified.

Small polaron theory explains the transition mechanism.

Abstract

Temperature effect on quantum tunneling in a Cooper-pair-box coupled to a quantum oscillator is studied by both numerical and analytical calculations. It is found that, in strong coupling regions, coherent tunneling of a Cooper-pair-box can be destroyed by its coupling to a quantum oscillator and the tunneling becomes thermally activated as the temperature rises, leading to failure of the Cooper-pair-box. The transition temperature between the coherent tunneling and thermo-activated hopping is determined and physics analysis based on small polaron theory is also provided.