How to cool a mm-size mechanical resonator to its ground state

Resonant coupling of a Quartz nanoresonator to a superconducting qubit has provided the first observation of a macroscopic mechanical degree of freedom in its quantum ground state. However, unlike nano-oscillators, macroscopic quartz oscillators such as Bulk Acoustic Wave (BAW) oscillators offer exceptional mechanical properties including large effective masses, high frequencies, and extremely high quality factors. This makes them an attractive platform not only for the pursuit of quantum optics experiments with phonons, but also for tests of the limits of quantum mechanics itself gravitational wave detection, and tests of Lorentz symmetry. On other hand, their large geometric size makes coupling to them challenging. Most critically, large unavoidable stray capacitance between the BAW oscillator electrodes reduces the amplitude of the oscillating voltage, and the corresponding coupling strength to electrical circuits becomes impractically small. Our theoretical paper studies the scheme which can bust coupling to a such a resonator to achieve and detect the ground state of its mechanical degree of freedom. See our new preprint.