High-Q quartz mechanical resonator as quantum memory unit

Quantum memory units with lifetime longer than currently available qubits are crucial for quantum computation. Long lifetime and small size make mechanical resonators good candidates for storing quantum information. We have fabricated a suspended 1-D Z-cut quartz phononic crystal resonator presenting a mechanical mode confined in a central defect with frequency around 100MHz and high Q, which we currently measure optically. Our quartz resonator will couple parametrically to a SNAIL (Superconducting Nonlinear Asymmetric Inductive eLement) to mediate the frequency mismatch with GHz-frequency devices. Ultimately the SNAIL will couple to transmon qubits. The quartz resonator and SNAIL are fabricated on separate chips and flip-chip bonded with a few micron gap. Such a small gap will allow us to achieve a large piezoelectric coupling to the quartz resonator via non-contacting electrodes on the SNAIL chip which do not contribute extra mechanical dissipation. This modular integration architecture will improve the flexibility and scalability of the whole hybrid system.