Laser cooling of a micromechanical membrane to the quantum backaction limit

TL;DR

This paper demonstrates cooling a micromechanical membrane to the quantum backaction limit using optomechanical sideband cooling, with direct observation of thermal equilibrium achieved through monitoring optical sidebands.

Contribution

It achieves quantum backaction limited cooling of a micromechanical membrane by combining pre-cooling in a dilution refrigerator with sideband cooling techniques.

Findings

Cooling to the quantum backaction limit verified by optical sideband monitoring

Mechanical object reaches thermal equilibrium with optical bath

Demonstrates fundamental quantum limits in mechanical cooling

Abstract

The radiation pressure of light can act to damp and cool the vibrational motion of a mechanical resonator. In understanding the quantum limits of this cooling, one must consider the effect of shot noise fluctuations on the final thermal occupation. In optomechanical sideband cooling in a cavity, the finite Stokes Raman scattering defined by the cavity linewidth combined with shot noise fluctuations dictates a quantum backaction limit, analogous to the Doppler limit of atomic laser cooling. In our work we sideband cool to the quantum backaction limit by using a micromechanical membrane precooled in a dilution refrigerator. Monitoring the optical sidebands allows us to directly observe the mechanical object come to thermal equilibrium with the optical bath.