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Cited by 29Quantum Information and CryptographySuperconducting and THz Device TechnologyPhysics of Superconductivity and Magnetism

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Probing defect densities at the edges and inside Josephson junctions of superconducting qubits

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Bilmes, Alexander, Volosheniuk, Serhii, Ustinov, Alexey V., Lisenfeld, Jürgen·2022·npj Quantum Information
DOI 10.1038/s41534-022-00532-4
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Abstract

Tunneling defects in disordered materials form spurious two-level systems which are a major source of decoherence for micro-fabricated quantum devices. For superconducting qubits, defects in tunnel barriers of submicrometer-sized Josephson junctions couple strongest to the qubit, which necessitates optimization of the junction fabrication to mitigate defect formation. Here, we investigate whether defects appear predominantly at the edges or deep within the amorphous tunnel barrier of a junction. For this, we compare defect densities in differently shaped Al/AlO x /Al Josephson junctions that are part of a Transmon qubit. We observe that the number of detectable junction-defects is proportional to the junction area, and does not significantly scale with the junction’s circumference, which proposes that defects are evenly distributed inside the tunnel barrier. Moreover, we find very similar defect densities in thermally grown tunnel barriers that were formed either directly after the base electrode was deposited, or in a separate deposition step after removal of native oxide by Argon ion milling.

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  • This result is consistent with the previously observed resilience of Al to TLS defects induced by argon milling.

    “This is consistent with the previously observed resilience of Al to TLS defects induced by argon milling34,46.”

    From Advanced CMOS manufacturing of superconducting qubits on 300 mm wafers (2024) · cites this paper as [46]

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Metadata

Authors
Bilmes, A., Volosheniuk, S., Ustinov, A. V., & Lisenfeld, J.
Affiliations
  • Karlsruhe Institute of Technology (DE)
  • Delft University of Technology (NL)
Corresponding author
Bilmes, Alexander
ORCID
Venue
npj Quantum Information
Publisher
Springer Science and Business Media LLC
Published
2022-03-07
Volume
8
Issue
1
ISSN
2056-6387 (ISSN-L)
DOI
10.1038/s41534-022-00532-4
OpenAlex
W3194582893
Cited by
29
References
4
Citations by year
2026: 7 · 2025: 6 · 2024: 7 · 2023: 4 · 2022: 3
FWCI
1.64
Type
journal article
Language
en
Open access
Licence
Locations
  • npj Quantum Information (publishedVersion, cc-by)
  • Repository KITopen (Karlsruhe Institute of Technology) (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Research Repository (Delft University of Technology) (submittedVersion, cc-by)
  • Data Archiving and Networked Services (DANS) (submittedVersion, other-oa)
  • arXiv (Cornell University)
  • KITopen (cc-by)
Funders
  • Google
  • Karlsruhe Institute of Technology
  • Deutsche Forschungsgemeinschaft (LI2446-1/2, LI2446/1)
  • Bundesministerium für Bildung und Forschung
  • Russian Science Foundation (21‐72‐30026)
Topics
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Information and Cryptography
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Superconducting and THz Device Technology
  • Physical Sciences › Physics and Astronomy › Condensed Matter Physics › Physics of Superconductivity and Magnetism
Keywords
superconducting qubits, transmon qubits, Al/AlOx/Al junctions, defect density, decoherence, junction geometry, argon ion milling, native oxide removal, thermal oxide growth

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