  Cavity optomechanics is a tool to study the interaction between light and
micromechanical motion. Here we observe near-quantum limited optomechanical
physics in a truly macroscopic oscillator. As the mechanical system, we use a
mm-sized piezoelectric quartz disk oscillator. Its motion is coupled to a
charge qubit which translates the piezo-induced charge into an effective
radiation-pressure interaction between the disk and a microwave cavity. We
measure the thermal motion of the lowest mechanical shear mode at 7MHz down to
35 mK, corresponding to roughly 100 quanta in a 20mg oscillator. The work opens
up opportunities for macroscopic quantum experiments.
