Quantum acoustics with a released thickness-mode resonator, part 2

The circuit quantum acoustodynamics (cQAD) system offers a promising platform for storing quantum information with high coherence and compact size. It combines the strong nonlinearity of the Josephson element with small scale, high-quality factor mechanical element. Currently, the coupling between superconducting circuits and mechanical mode are in the range of hundreds of kHz to tens of MHz, which is significantly lower than that typically achieved in circuit quantum electrodynamics (cQED) systems. The limited coupling strength limits the application of established cQED techniques to mechanical systems and can restrict performance. Here we aim to address this issue by coupling a superconducting qubit to a released thickness-mode resonator based on AlN. The mechanical mode couples with the qubit's electric field through the piezoelectric properties of AlN. The released structure reduces the mass of the mechanical mode compared to usual bulk acoustic mode, enhancing the coupling strength. In this talk, we will present the design and fabrication of this system and share preliminary data demonstrating strong coupling between the quantum circuit and the mechanical mode.