AQP Seminar: Coupling acoustic resonators to transmon qubits
Piezoelectric resonators are electroacoustic harmonic oscillators that are integrable into electrical circuits. They are compact in size and are known to exhibit high quality factors - therefore being a strong candidate to accompany superconducting transmon qubits in a fault-tolerant quantum computer . Offering a high spectral density of modes in a small mode volume and a feasible means of on-chip integration with promising scaling aspects, we consider high-overtone bulk acoustic resonators (HBARs) as the perfect candidate for prototyping quantum applications in a coupled hybrid system, such as a quantum random access memory (QRAM) [2,3]. With the recent development in epitaxially grown HBAR devices demonstrating phonon lifetimes up to 500 us , the challenges are turning from parameter optimization to implementational ones.
In this talk, I will cover circuit quantum acoustodynamics (cQAD) in the context of an HBAR coupled to a transmon qubit, discuss parameters design of an HBAR from a practical point of view and reveal some of the rich physics found in a multimodal HBAR-qubit hybrid system. The topics include the modelling of a multimode system under flux modulation and multiphonon transitions at increased drive amplitude.
 C. Chamberland et. al K. Noh and P. Arrangoiz-Arriola and E. T. Campbell and C. T. Hann and J. Iverson and H. Putterman and T. C. Bohdanowicz and S. T. Flammia and A. Keller and G. Refael and J. Preskill and L. Jiang and A. H. Safavi-Naeini and O. Painter and F. G. S. L. Brandão "Building a fault-tolerant quantum computer using concatenated cat codes". arXiv 2012.04108 (2020)
 V. Giovannetti, S. Lloyd, and L. Maccone, "Architectures for a quantum random access memory". Phys. Rev. A 78, 052310 (2008).
 Hann, Connor T. and Zou, Chang-Ling and Zhang, Yaxing and Chu, Yiwen and Schoelkopf, Robert J. and Girvin, S. M. and Jiang, Liang "Hardware-Efficient Quantum Random Access Memory with Hybrid Quantum Acoustic Systems". PRL 123, 250501 (2019)
 Gokhale, V.J., Downey, B.P., Katzer, D.S. et al. "Epitaxial bulk acoustic wave resonators as highly coherent multi-phonon sources for quantum acoustodynamics". Nat Commun 11, 2314 (2020).