Surface phonon interference in hybrid quantum acoustic devices*

Hybrid quantum systems based on surface acoustic wave (SAW) resonators coupled to superconducting qubits are being investigated for a variety of applications in quantum information processing. In these devices, surface phonon interference and scattering processes can alter the spectra of the mechanical modes and modify their interactions with coupled quantum systems [1]. This necessitates a more detailed investigation of phononic interference phenomenon in SAW-based hybrid systems. Here we report on the spectral analysis of a simple experimental system comprised of a SAW resonator galvanically coupled to a microwave transmission line. The entire device is fabricated on YZ-cut lithium niobate, and we are able to reveal the presence of interference effects of the surface phonon modes in the acoustic resonator over a broad range of temperature from 300K to 10mK. These measurements also allow us to extract the temperature dependent velocity for SAWs propagating on YZ-lithium niobate.

[1] Quantum acoustic Fano interference of surface phonons, J.M. Kitzman, J.R. Lane, C. Undershute, N.R. Beysengulov, C.A. Mikolas, K.W. Murch and J. Pollanen, Phys. Rev. A, 108, L010601 (2023).