Description
Superconducting qubits are highly susceptible to quasiparticle generation from background ionizing radiation, which produces energetic phonons capable of breaking Cooper pairs and inducing correlated errors. Following the observation of cosmic-ray–induced error bursts in large-scale superconducting qubit arrays [1], recent efforts have explored reducing the impact of ionizing radiation through gap engineering, phonon downconversion, material optimization, and underground operation [2,3,4]. However, scalable on-chip suppression of phonon-mediated quasiparticles remains an open challenge.
In this work, we present the design and fabrication of transmon qubits on a silicon-on-insulator (SOI) platform incorporating suspended membranes that act as acoustic low-pass filters. This architecture enables systematic investigation of phonon transport and its role in radiation-induced decoherence. We report successful fabrication and characterization of SOI-based transmons with parity-switching rate approaching 0.1 Hz. These results demonstrate the compatibility of membrane-supported architectures with standard superconducting qubit fabrication processes. The proposed architecture can be implemented alongside other mitigation strategies to further reduce the impact of ionizing radiation. Future work will focus on comparative surface and underground measurements to quantify radiation-induced decoherence and validate the proposed phonon-isolation approach.
[1]: McEwen, M., Faoro, L., Arya, K. et al. Resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits. Nat. Phys. 18, 107–111 (2022).
[2]: T. Yamamoto, Y. Nakamura, Yu. A. Pashkin, O. Astafiev, and J. S. Tsai, "Parity effect in superconducting aluminum single electron transistors with spatial gap profile controlled by film thickness," Appl. Phys. Lett. 88, 212509 (2006).
[3]: Loer, B., et al. Abatement of ionizing radiation for superconducting quantum devices. Nat. Commun. 15, (2024).
[4]: Bargerbos, A., et al. Mitigation of quasiparticle loss in superconducting qubits by phonon scattering. Phys. Rev. Lett. 131, (2023).
| I am the presenting author | Yes |
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