High-quality superconducting tantalum resonators with beta phase defects
For practical superconducting quantum processors, orders of magnitude improvement in coherence is required, motivating efforts to optimize hardware design and explore new materials. Among the latter, the coherence of superconducting transmon qubits has been shown to improve by forming the qubit capacitor pads from α-tantalum, avoiding the metastable β-phase that forms when depositing tantalum at room temperature, and has been previously identified to be a source of microwave losses. In this work, we show lumped element resonators containing β-phase tantalum in the form of inclusions near the metal–substrate interface with internal quality factors (Qi) up to 5.0 ± 2.5×106 in the single photon regime. They perform at least as good as resonators with no sign of the β-phase in x-ray diffraction and thermal quasi-particle loss. Our results indicate that small concentrations of β-phase can be beneficial, enhancing critical magnetic fields and potentially, for improving coherence in tantalum-based superconducting circuits.
Authors
- Jasmin Aghassi‐Hagmann (ORCID: https://orcid.org/0000-0003-0348-041X)
- Christian Kuebel (ORCID: https://orcid.org/0000-0001-5701-4006)
- Soroush Arabi (ORCID: https://orcid.org/0009-0008-7024-6803)
- José M. Palomo (ORCID: https://orcid.org/0000-0002-6464-1216)
- Wulf Wulfhekel
- Zaki Leghtas (ORCID: https://orcid.org/0000-0002-9172-1537)
- Alexander Welle (ORCID: https://orcid.org/0000-0002-3454-6509)
- Amir A. Haghighirad (ORCID: https://orcid.org/0000-0003-4723-4966)
- Marc Scheffler (ORCID: https://orcid.org/0000-0002-7044-7532)
- Thomas Reisinger (ORCID: https://orcid.org/0000-0001-7982-9935)
- Anil Murani
- Horst Hahn (ORCID: https://orcid.org/0000-0001-9901-3861)
- Ioan M. Pop (ORCID: https://orcid.org/0000-0002-6776-9792)
- D. Fuchs (ORCID: https://orcid.org/0000-0002-0044-7772)
- Haoran Duan (ORCID: https://orcid.org/0009-0007-0228-8705)
- Sudip Pal
- Lucas Brauch (ORCID: https://orcid.org/0009-0001-4892-0207)
- Ritika Dhundhwal (ORCID: https://orcid.org/0009-0000-2227-2523)
- Florentine Scharwaechter (ORCID: https://orcid.org/0009-0007-4755-0527)
Institutions
- University of Stuttgart (DE)
- Karlsruhe Institute of Technology (DE)
- Technische Universität Darmstadt (DE)
- HIA du Val-de-Grâce à Paris (FR)
- École Normale Supérieure (BI)
- Karlsruhe University of Education (DE)
- Laboratoire de Géologie de l’École Normale Supérieure (FR)
Publication Details
- Journal
- Applied Physics Letters
- Published
- 2025-11-24
- DOI
- https://doi.org/10.1063/5.0302324
- Citations
- 1
- Primary Topic
- Quantum and electron transport phenomena
- Type
- article
- Field-Weighted Citation Impact
- 1.25
Funders
- European Commission
- Deutsche Forschungsgemeinschaft
- Bundesministerium für Bildung und Forschung