Cavity optomechanics mediated by a quantum two-level system

TLDR

Coupling electromagnetic waves in a cavity to mechanical vibrations via radiation pressure is a promising platform, yet the photon‑induced effect is typically tiny, making the enhancement of interaction strength a key challenge. The authors propose a microwave cavity optomechanics design that incorporates a Josephson junction qubit to strengthen the coupling and enable rich nonlinear physics. They demonstrate a six‑order‑of‑magnitude boost in radiation‑pressure interaction, reaching the strong‑coupling regime, observe single‑photon nonlinear damping attributed to the qubit, and thereby open nonlinear cavity optomechanics as a viable tool for studying quantum properties of motion.

Abstract

Abstract Coupling electromagnetic waves in a cavity and mechanical vibrations via the radiation pressure of photons is a promising platform for investigations of quantum–mechanical properties of motion. 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. 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. 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 by six orders of magnitude, allowing to approach the strong coupling regime. We observe nonlinear phenomena at single-photon energies, such as an enhanced damping attributed to the qubit. This work opens up nonlinear cavity optomechanics as a plausible tool for the study of quantum properties of motion.