2026/02/25 by Raquel Garcia Belles, Raquel Garcia-Belles, Alexander Anferov +15
Physics and Astronomy · Engineering · #Mechanical and Optical Resonators #Physics of Superconductivity and Magnetism #Acoustic Wave Resonator Technologies
paper · pdf · doi:10.1103/vszq-z1sh
Circuit quantum acoustodynamics (cQAD) devices have a wide range of applications in quantum science, all of which depend crucially on the quantum coherence of the mechanical subsystem. In this context, high-overtone bulk acoustic-wave resonators (HBARs) are particularly promising, since they have shown very high quality factors with negligible dephasing. However, the introduction of piezoelectric films, which are necessary for coupling to a superconducting circuit, can lead to additional loss channels, such as surface scattering and two-level systems. Here, we study the acoustic dissipation of HBAR resonators in cQAD systems and find that the defect density of the piezoelectric material and its interface with the bulk are limiting factors for the coherence. We measure acoustic modes with phonon lifetimes up to <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mn>400</a:mn> <a:mtext> </a:mtext> <a:mi mathvariant="normal">μ</a:mi> <a:mi mathvariant="normal">s</a:mi> </a:mrow> </a:math> and lifetime-limited coherence times approaching 1 ms in the quantum regime. When coupled to a superconducting qubit, this leads to a hybrid system with a large quantum coherence cooperativity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:msub> <e:mi>C</e:mi> <e:msub> <e:mi>T</e:mi> <e:mn>2</e:mn> </e:msub> </e:msub> <e:mo>=</e:mo> <e:mn>1.1</e:mn> <e:mo>×</e:mo> <e:msup> <e:mn>10</e:mn> <e:mn>5</e:mn> </e:msup> </e:math> . These results represent a new milestone for the performance of cQAD devices and offer concrete paths forward for further improvements.