Circuit quantum acoustodynamics systems have emerged as a promising platform for quantum information by coupling superconducting qubits to mechanical resonators, with their long-lived mechanical modes serving as quantum memories. We demonstrate suspended quartz phononic crystal resonators at 100 MHz with millisecond lifetimes at 8 K. With a contactless electrode geometry suppressing both two-level system losses and other electrode-induced energy dissipation, we evaluate the piezoelectric coupling rate between the mechanical modes and fluxonium qubits (resonant coupling) and transmon qubits (parametric coupling mediated by a Josephon-junction-based three-wave mixer). We further discuss multi-period defect geometries for enhancing these coupling rates.
@article{arxiv.2509.07900,
title = {Quartz phononic crystal resonators for hybrid acoustic quantum memories},
author = {Yang Hu and Angad Gupta and Jacob Repicky and Michael Hatridge and Thomas P. Purdy},
journal= {arXiv preprint arXiv:2509.07900},
year = {2025}
}