Squeezing-enhanced feedback cooling of a microresonator

Since its inception, quantum mechanics have not ceased to fascinate the scientific world, and especially the fundamental question about the famous Schrödinger's cat being alive or dead, or both, is still far from being answered. Although superposition states have been achieved with small particles, such as photons or atoms, they have not yet been observed on large and massive objects consisting of billions of atoms.

With the advance of cavity optomechanics, the quantum behavior of massive mechanical oscillators is becoming accessible and a major key requirement in this direction is the ability to cool such oscillators into their quantum ground state. In the present work we investigate a cold damping scheme relying on the ultra-sensitive measurement of mechanical displacements, provided by a cavity-enhanced optomechanical interaction with quadrature squeezed states of light, to control strong dielectric gradient forces actuating the motion of a toroidal microresonator within a feedback loop.

We first determine theoretically the conditions and limits to squeezing-enhanced measurement sensitivity of mechanical motion in a cavity optomechanical system, and perform experimentally a proof-of-principle on our microtoroids. Secondly we model the dielectric gradient force actuation scheme and investigate its capabilities in controlling the vibrations of a microtoroid acoustic mode.