Optomechanical sideband cooling of a micromechanical oscillator close to the quantum ground state (original) (raw)

Cooling a mesoscopic mechanical oscillator to its quantum ground state is elementary for the preparation and control of low entropy quantum states of large scale objects. Here, we pre-cool a 70-MHz micromechanical silica oscillator to an occupancy below 200 quanta by thermalizing it with a 600-mK cold 3 He gas. Two-level system induced damping via structural defect states is shown to be strongly reduced, and simultaneously serves as novel thermometry method to independently quantify excess heating due to a cooling laser. We demonstrate that dynamical backaction sideband cooling can reduce the average occupancy to 9 ± 1 quanta, implying that the mechanical oscillator can be found (10 ± 1)% of the time in its quantum ground state.