Quantum acoustic Fano interference of surface phonons

TL;DR

This paper demonstrates Fano interference between a surface acoustic wave resonator and a continuum of surface phonons in a quantum acoustic system, revealing complex phonon interactions relevant for quantum information processing.

Contribution

It provides the first experimental observation of Fano interference in a quantum acoustic system involving surface phonons and superconducting qubits.

Findings

Observation of Fano interference in a quantum acoustic system

Identification of additional weakly coupled mechanical modes

Impact of phononic interference on qubit-phonon interactions

Abstract

Quantum acoustic systems, which integrate surface or bulk phonons with superconducting qubits, offer a unique opportunity to investigate phononic $interference$ and $scattering$ processes in the quantum regime. In particular the interaction between a superconducting qubit and a phononic oscillator allows the qubit to sense the oscillator's excitation spectrum and underlying interference effects. Here we present measurements revealing Fano interference of a resonantly trapped piezoelectric surface acoustic wave (SAW) mode with a broad continuum of surface phonons in a system consisting of a SAW resonator coupled to a superconducting qubit. The experiments highlight the existence of additional weakly coupled mechanical modes and their influence on the qubit-phonon interaction and underscore the importance of phononic interference in quantum acoustic architectures that have been proposed for quantum information processing applications.