Quantum acoustics with a released thickness-mode mechanical resonator

The circuit quantum acoustodynamics (cQAD) platform integrates the strong nonlinearity of superconducting Josephson elements with high-quality mechanical resonators, enabling potential applications in quantum memories, transducers, and sensors. A central challenge in this field is achieving strong electromechanical coupling between the mechanical resonator and the superconducting qubit, while preserving the resonator’s high quality factor. Strong coupling generally favors small mode volumes and often involves metallic components that introduce additional dissipation channels and fabrication complexity. Conversely, larger mode volumes reduce the coupling strength because only the portion of the resonator proximate to the qubit couples effectively. In this work, we address this trade-off by developing a released thickness-mode mechanical resonator based on an aluminum nitride (AlN)-on-silicon (Si) platform. The device is designed to achieve strong piezoelectric coupling to a superconducting qubit. The resonator, with a lateral dimension of approximately $200\times200$ μ m², is fully released from the Si substrate to minimize clamping losses. Theoretical analysis predicts coupling strengths exceeding 10 MHz between the qubit’s electric field and the resonator’s intrinsic piezoelectric mode. The design, coupling mechanism, and fabrication process of the released AlN thickness-mode resonator are presented in detail. This approach simplifies fabrication, and provides a scalable path toward hybrid quantum systems with high coherence and large electromechanical coupling strengths.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Bathala, Sharan Mourya

Contributors dc:contributor

• Fang, Kejie

• Quantum Acoustics
• Quantum Optomechanics

Statement dc:rights

• Copyright 2025 Sharan Mourya Bathala

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132710

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132710