Probing the state of a mechanical oscillator with an ultra-strongly coupled quantum emitter

TL;DR

This paper investigates the dynamics of a mechanical oscillator coupled to a driven quantum emitter in the ultra-strong regime, revealing how emitter fluctuations influence mechanical quadratures and can be observed with current hybrid devices.

Contribution

It demonstrates the compatibility of ultra-strong coupling with semi-classical models and derives master equations describing the coupled system's behavior.

Findings

Emitter fluctuations cause asymmetric scattering of mechanical quadratures.

Back-action from the mechanical resonator leads to emitter decoupling from driving light.

Quantum-limited optical noise is detectable with existing hybrid devices.

Abstract

We study the dynamics of a mechanical resonator parametrically coupled to a driven dissipative quantum emitter in the ultra-strong coupling regime. We show that this regime is fully compatible with a semi-classical treatment, and we derive master equations for the emitter and the resonator. We show that the fluctuations of the driven emitter's population induce the non-symmetrical scattering of the mechanical quadratures. At long timescales, such scattering back-acts on the emitter, which eventually decouples from the driving light. This optical noise at the quantum limit is observable with state of the art hybrid devices.