Quantum Signatures of the Optomechanical Instability

TL;DR

This paper demonstrates that strong optomechanical coupling can produce non-classical mechanical states with negative Wigner density and unique photon correlation signatures near the instability threshold, observable via optical tomography.

Contribution

It reveals the emergence of non-classical mechanical states and distinct photon correlations in optomechanical systems at the onset of instability, highlighting new quantum signatures.

Findings

Non-classical, negative Wigner density states can form at high single-photon coupling.

Distinct photon-photon correlation oscillations occur, lasting longer than mechanical decay.

Robust signatures are detectable near the self-induced oscillation threshold.

Abstract

In the past few years, coupling strengths between light and mechanical motion in optomechanical setups have improved by orders of magnitude. Here we show that, in the standard setup under continuous laser illumination, the steady state of the mechanical oscillator can develop a non-classical, strongly negative Wigner density if the optomechanical coupling is large at the single-photon level. Because of its robustness, such a Wigner density can be mapped using optical homodyne tomography. These features are observed near the onset of the instability towards self-induced oscillations. We show that there are also distinct signatures in the photon-photon correlation function $g^{(2)}(t)$ in that regime, including oscillations decaying on a time scale not only much longer than the optical cavity decay time, but even longer than the \emph{mechanical} decay time.