Probing spin-phonon interactions in silicon vacancy centers via surface acoustic waves

Phonons in solid-state quantum systems hold intriguing advantages for encoding chip-scale itinerant qubits. Phononic devices are compact: gigahertz-range phonons have wavelengths of microns, which is 10^5 times smaller than the wavelength of a photon at the same frequency. Phonons can also couple to many systems, including superconducting qubits, optical photons, and solid-state defects. Of these, the negatively charged silicon-vacancy center (SiV) in diamond has a remarkably high strain susceptibility, and its spin levels can be coherently driven by resonant surface acoustic waves (SAW). Due to the coherent nature of this coupling we expect that when the SiV spin relaxes, it can emit a coherent phonon into the diamond lattice. Channeling these phonons into specific mechanical modes is necessary to create phononic quantum network architecture. We attempt to enhance the emission rate of phonons from an SiV into measurable mechanical modes by engineering the local phononic density of states around the SiV. Existing SAW technology allows us to electrically probe certain mechanical modes via the piezoelectric coupling between the motion of the modes and an interdigital transducer. We also discuss potential devices that could exploit the SiV spin as a source of single coherent phonons.