Eliminating Surface Oxides of Superconducting Circuits with Noble Metal Encapsulation
The lifetime of superconducting qubits is limited by dielectric loss, and a major source of dielectric loss is the native oxide present at the surface of the superconducting metal. Specifically, tantalum-based superconducting qubits have been demonstrated with record lifetimes, but a major source of loss is the presence of two-level systems in the surface tantalum oxide. Here, we demonstrate a strategy for avoiding oxide formation by encapsulating the tantalum with noble metals that do not form native oxide. By depositing a few nanometers of Au or AuPd alloy before breaking vacuum, we completely suppress tantalum oxide formation. Microwave loss measurements of superconducting resonators reveal that the noble metal is proximitized, with a superconducting gap over 80% of the bare tantalum at thicknesses where the oxide is fully suppressed. Our findings suggest that losses in resonators fabricated by subtractive etching are dominated by oxides on the sidewalls, pointing to total surface encapsulation by additive fabrication as a promising strategy for eliminating surface oxide two-level system loss in superconducting qubits.
Authors
- Chenyu Zhou (ORCID: https://orcid.org/0000-0002-2749-4739)
- Y. Zhang (ORCID: https://orcid.org/0000-0003-2448-2035)
- Andrew Houck (ORCID: https://orcid.org/0000-0002-9788-5874)
- Basil M. Smitham (ORCID: https://orcid.org/0009-0005-5358-4745)
- Nathalie P. de Leon (ORCID: https://orcid.org/0000-0003-1324-1412)
- R. J. Cava (ORCID: https://orcid.org/0000-0002-3294-6867)
- Mingzhao Liu (ORCID: https://orcid.org/0000-0002-0999-5214)
- Nana Shumiya (ORCID: https://orcid.org/0000-0002-1496-579X)
- Guangming Cheng (ORCID: https://orcid.org/0000-0002-3521-5840)
- Kim Kisslinger (ORCID: https://orcid.org/0000-0002-6528-7044)
- Sarang Gopalakrishnan (ORCID: https://orcid.org/0000-0002-7493-7600)
- Russell A. McLellan (ORCID: https://orcid.org/0000-0002-8791-0220)
- Alexander C. Pakpour‐Tabrizi (ORCID: https://orcid.org/0000-0003-0875-8345)
- Faranak Bahrami (ORCID: https://orcid.org/0000-0001-5679-8355)
- Nan Yao (ORCID: https://orcid.org/0000-0002-4081-1495)
- Matthew Bland (ORCID: https://orcid.org/0000-0002-7038-1879)
- Junsik Mun (ORCID: https://orcid.org/0009-0006-2639-0280)
- Yimei Zhu (ORCID: https://orcid.org/0000-0002-1638-7217)
- Ray Chang (ORCID: https://orcid.org/0000-0002-8390-9978)
Institutions
- Brookhaven National Laboratory (US)
- Princeton University (US)
Publication Details
- Journal
- Physical Review Letters
- Published
- 2025-03-06
- DOI
- https://doi.org/10.1103/physrevlett.134.097001
- Citations
- 19
- Primary Topic
- Quantum and electron transport phenomena
- Type
- article
- Field-Weighted Citation Impact
- 23.69
Funders
- National Science Foundation
- U.S. Department of Energy
- Princeton Center for Complex Materials
- Office of Science
- Materials Research Science and Engineering Center, Harvard University
- Brookhaven National Laboratory