Crossover from weak to strong coupling regime in dispersive circuit QED

TL;DR

This paper investigates how superconducting qubits decohere when strongly coupled to a damped harmonic oscillator, revealing different dephasing behaviors beyond the weak coupling regime and applicable to various quantum systems.

Contribution

It extends the analysis of qubit decoherence into the strong coupling regime, providing new insights and a physical understanding of the mechanisms involved.

Findings

Dephasing rate behavior changes in the strong coupling regime

Identification of two distinct decoherence mechanisms

Applicability to other quantum systems like trapped ions and cavity QED

Abstract

We study the decoherence of a superconducting qubit due to the dispersive coupling to a damped harmonic oscillator. We go beyond the weak qubit-oscillator coupling, which we associate with a phase Purcell effect, and enter into a strong coupling regime, with qualitatively different behavior of the dephasing rate. We identify and give a physicaly intuitive discussion of both decoherence mechanisms. Our results can be applied, with small adaptations, to a large variety of other physical systems, e. g. trapped ions and cavity QED, boosting theoretical and experimental decoherence studies.