Lithium niobate HBARs with Q > 1 million compatible with superconducting qubits

There has been recent interest in high overtone bulk acoustic resonators (HBARs) for their use in quantum computing [1,2], as well as for novel sensing applications [3]. HBARs are advantageous for their large internal quality factors, ease of design, and gigahertz operating frequencies. However, a significant challenge, particularly for the integration of HBARs into superconducting qubit systems, is increasing the coupling to the acoustic modes while maintaining the internal Q’s of both the HBAR modes and the qubits. One approach to achieve this, which can be readily integrated into existing qubit-HBAR device geometries, is to utilize materials with stronger piezoelectric coupling strengths. In our work, we focus on the use of lithium niobate (LiNbO­₃). We show classical measurements at both room and cryogenic temperatures of both bulk and film LiNbO₃ HBAR devices and demonstrate that internal quality factors above one million can be achieved. Further, we explore the capability for this material stack and device geometry to be integrated into superconducting qubit architectures.

[1] Y. Chu, et al., Science 358, 199-202 (2017)

[2] C. A. Potts, et al., Nat. Comm. 16, 6096 (2024)

[3] R. Linehan, et al., arXiv:2410.17308 (2024)