Optomechanical Quantum State Tomography

We generate and characterize heralded quantum states of a mechanical resonator with a single added phonon. Our system consists of an optomechanical crystal cavity operated at about 10 millikelvin. We perform continuous wave sideband asymmetry measurements using single photon counters to calibrate the temperature of a 4 GHz mechanical mode. Photon and phonon pairs are generated using a continuous wave laser blue detuned from the optical cavity resonance. A detected photon at the cavity resonance frequency heralds the addition of a phonon to the mechanical mode; we characterize the generated states by continuously measuring the output cavity field, and performing tomography to determine the Husimi Q function describing the state of the mechanical oscillator.