Integrated quantum acoustics with superconducting qubits

Quantum acoustics is a valuable choice for linear quantum computing as single phonons couple to various quantum systems and enable hybrid platforms [1]. Confined phonons, such as in one-dimensional phononic waveguides, typically exhibit longer lifetimes than surface acoustic waves and allow for on-chip routing [2]. While optomechanics has been a popular choice to date for the generation and detection of single phonons, these platforms generally suffer from low efficiencies, as the protocols are based on heralding techniques. Weak excitation energies to avoid optical heating additionally result in low scattering probabilities. In contrast, a superconducting qubit coupled to phononic structures operates as a deterministic single-phonon Fock state generator [3]. Here, we discuss the path to convert a single microwave excitation from a transmon qubit to a single mechanical excitation in a phononic waveguide via electromechanical coupling in a piezo resonator. We hybridize the mechanical modes of the piezo with the modes of the phononic waveguide, resulting in mechanical supermodes around 5 GHz and a simulated coupling strength of 2 MHz [4].



[1] Qiao, H. et al., Science 380, 1030-1033 (2023)

[2] Zivari, A. et al., Sci. Adv. 8, eadd2811 (2022)

[3] Bienfait, A. et al., Science 364, 368-371 (2019)

[4] Weaver, M. J. et al., Nat. Nanotechnol. 19, 166-172 (2024)