Abstract

We demonstrate an optomechanical system with quantum cooperativity C_q = 4g²/κγ » 1 already at moderate cryogenic temperature [1]. It is realised as a membrane-in-the-middle system [2] with a high-stress silicon nitride membrane. Here, γ = k_BT/ħQ is the quantum decoherence rate of the mechanical system due to its thermal bath at temperature T~4 K, and Q~10⁷ the mechanical quality factor. In this regime, the quantum backaction of the optical measurement dominates over the thermal Langevin noise. As a consequence, optical measurements create quantum correlations between the optical and mechanical degrees of freedom, which are eventually measured as sub-vacuum noise (−2.4 dB) of the light emerging form the cavity (ponderomotive squeezing [3]). We investigate this effect in a multimode setting, in which we observe optically-induced hybridisation of mechanical modes, and the generation of squeezed light by hybrid modes [1].

© 2017 IEEE