Cryogenic microwave loss in epitaxial Al/GaAs/Al trilayers for superconducting circuits
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Abstract
Epitaxially grown superconductor/dielectric/superconductor trilayers have the potential to form high-performance superconducting quantum devices and may even allow scalable superconducting quantum computing with low-surface-area qubits such as the merged-element transmon. In this work, we measure the power-independent loss and two-level-state (TLS) loss of epitaxial, wafer-bonded, and substrate-removed Al/GaAs/Al trilayers by measuring lumped element superconducting microwave resonators at millikelvin temperatures and down to single-photon powers. The power-independent loss of the device is ( 4.8 ± 0.1 ) × 10 − 5, and the resonator-induced intrinsic TLS loss is ( 6.4 ± 0.2 ) × 10 − 5. Dielectric loss extraction is used to determine a lower bound of the intrinsic TLS loss of the trilayer of 7.2 × 10 − 5. The unusually high power-independent loss is attributed to GaAs’s intrinsic piezoelectricity.