Qubit-oscillator system under ultrastrong coupling and extreme driving

TL;DR

This paper presents a new approach to analyze a driven qubit-oscillator system in the ultrastrong coupling regime with extreme driving, revealing how coupling and driving influence qubit dynamics and spectrum.

Contribution

It introduces a method to study ultrastrong coupling and extreme driving effects on qubit-oscillator systems, highlighting control over spectrum and tunneling dynamics.

Findings

Coupling can suppress specific oscillator modes.

Extreme driving can halt qubit tunneling.

Ultrastrong coupling effects are controllable via external parameters.

Abstract

We introduce an approach to studying a driven qubit-oscillator system in the ultrastrong coupling regime, where the ratio $g/\Omega$ between coupling strength and oscillator frequency approaches unity or goes beyond, and simultaneously for driving strengths much bigger than the qubit energy splitting (extreme driving). Both qubit-oscillator coupling and external driving lead to a dressing of the qubit tunneling matrix element of different nature: the former can be used to suppress selectively certain oscillator modes in the spectrum, while the latter can bring the qubit's dynamics to a standstill at short times (coherent destruction of tunneling) even in the case of ultrastrong coupling.