Single-photon cavity optomechanics mediated by a quantum two-level system

TL;DR

This paper demonstrates a significant enhancement of photon-mechanical coupling in cavity optomechanics by integrating a quantum two-level system, enabling observation of nonlinear effects at the single-photon level.

Contribution

Introducing a Josephson junction qubit into microwave cavity optomechanics to substantially increase interaction strength and observe nonlinear quantum phenomena.

Findings

Boosted radiation pressure interaction energy by six orders of magnitude

Approached the strong coupling regime with single-photon effects

Observed nonlinear phenomena such as enhanced damping due to the two-level system

Abstract

Coupling electromagnetic waves in a cavity and mechanical vibrations via the radiation pressure of the photons [1,2] is a promising platform for investigations of quantum mechanical properties of motion of macroscopic bodies and thereby the limits of quantum mechanics [3,4]. A drawback is that the effect of one photon tends to be tiny, and hence one of the pressing challenges is to substantially increase the interaction strength towards the scale of the cavity damping rate. A novel scenario is to introduce into the setup a quantum two-level system (qubit), which, besides strengthening the coupling, allows for rich physics via strongly enhanced nonlinearities [5-8]. Addressing these issues, here we present a design of cavity optomechanics in the microwave frequency regime involving a Josephson junction qubit. We demonstrate boosting of the radiation pressure interaction energy by six orders of magnitude, allowing to approach the strong coupling regime, where a single quantum of vibrations shifts the cavity frequency by more than its linewidth. We observe nonlinear phenomena at single-photon energies, such as an enhanced damping due to the two-level system. This work opens up nonlinear cavity optomechanics as a plausible tool for the study of quantum properties of motion.