Superconducting cavity-electromechanics on silicon-on-insulator

Abstract

Fabrication processes involving anhydrous hydrofluoric vapor etching are developed to create high-$Q$ aluminum superconducting microwave resonators on free-standing silicon membranes formed from a silicon-on-insulator wafer. Using this fabrication process, a high-impedance $8.9$GHz coil resonator is coupled capacitively with large participation ratio to a $9.7$MHz micromechanical resonator. Two-tone microwave spectroscopy and radiation pressure back-action are used to characterize the coupled system in a dilution refrigerator down to temperatures of $T_f=11$~mK, yielding a measured electromechanical vacuum coupling rate of $g_0/2\pi \approx 24.6$~Hz and a mechanical resonator $Q$-factor of $Q_m=1.7\times 10^7$. Microwave back-action cooling of the mechanical resonator is also studied, with a minimum phonon occupancy of $n_m\approx 16$ phonons being realized at an elevated fridge temperature of $T_f=211$~mK.

8 pages, 5 figures