Single-crystal diamond low-dissipation cavity optomechanics

Single-crystal diamond cavity optomechanical devices are a promising example of a hybrid quantum system: by coupling mechanical resonances to both light and electron spins, they can enable new ways for photons to control solid-state qubits. However, realizing cavity optomechanical devices from high-quality diamond chips has been an outstanding challenge. Here, we demonstrate single-crystal diamond cavity optomechanical devices that can enable photon–phonon spin coupling. Cavity optomechanical coupling to 2 GHz frequency (f_m) mechanical resonances is observed. In room-temperature ambient conditions, these resonances have a record combination of low dissipation (mechanical quality factor, Q_m>9000) and high frequency, with Q_m·f_m∼1.9×10¹³, which is sufficient for room-temperature single-phonon coherence. The system exhibits high optical quality factor (Q_o>10⁴) resonances at infrared and visible wavelengths, is nearly sideband resolved, and exhibits optomechanical cooperativity C∼3. The devices’ potential for optomechanical control of diamond electron spins is demonstrated through radiation pressure excitation of mechanical self-oscillations whose 31 pm amplitude is predicted to provide 0.6 MHz coupling rates to diamond nitrogen vacancy center ground-state transitions (6 Hz/phonon) and ∼10⁵ stronger coupling rates to excited-state transitions.