Localization and mitigation of two-level system (TLS) and non-TLS losses at interfaces of niobium superconducting quantum resonators

ORAL

Abstract

We have characterized the metal-air (MA), substrate-air (SA) and metal-substrate (MS) interfaces of niobium-on-silicon resonators with cross-sectional scanning transmission electron microscopy (STEM) and x-ray photoemission spectroscopy (XPS). These resonators have a median internal loss tangent δint of 1.07 ppm at the single-photon level, with 71% due to two-level systems (TLS). We removed the SA process oxide by selective chemical etching, and reduced δint to 0.48 ppm, now 47% TLS. Next we reduced the MA oxide thickness from 4.8 to 1.6 nm in several steps, and further reducing δint to 0.19 ppm. We found that both TLS and non-TLS losses were uniformly distributed throughout the niobium process oxide. 70% of TLS losses were associated with the SA silicon oxide, 24% with the MA niobium oxide, and 6% other locations including the MS interface. In contrast only 17% of non-TLS losses came from SA, 68% from MA, and 15% from other locations. Together, the MA and SA interfaces accounted for at least 92% of loss. Interfacial materials analysis correlated with these observations gives some insight into host materials for TLS and non-TLS losses. Post-fabrication etching improved median internal quality factors from 0.93 million to 5.26 million.

*This work was funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231 "High-Coherence Multilayer Superconducting Structures for Large Scale Qubit Integration and Photonic Transduction program (QIS-LBNL)" (resonator fabrication, BOE etching, cryogenic characterization, TEM sample prep). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. (SEM, TEM and XPS characterization and data analysis).

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Publication: Localization and reduction of superconducting quantum coherent circuit losses, arXiv:2012.07604

Presenters

  • D. Frank F Ogletree

    • Lawrence Berkeley National Laboratory

Authors

  • D. Frank F Ogletree

    • Lawrence Berkeley National Laboratory

  • Maria Virginia P Altoe

    • Lawrence Berkeley National Laboratory

  • Archan Banerjee

    • Lawrence Berkeley National Laboratory

  • Cassidy Berk

    • Lawrence Berkeley National Laboratory

  • AHMED HAJR

    • Lawrence Berkeley National Laboratory

  • Adam Schwartzberg

    • Lawrence Berkeley National Laboratory

  • Chengyu Song

    • Lawrence Berkeley National Lab

  • Michael Elowson

    • LBNL

  • John Mark Kreikebaum

    • Lawrence Berkeley National Laboratory

  • Ed K Wong

    • Lawrence Berkeley National Laboratory
    • LBNL

  • Sinead Griffin

    • LBNL
    • Materials Sciences Division and Molecular Foundry, Berkeley Lab
    • Lawrence Berkeley National Laboratory
    • Lawrence Berkeley National Lab

  • Alexander Weber-Bargioni

    • Lawrence Berkeley National Laboratory
    • LBNL

  • Andrew M Minor

    • LBNL

  • David I Santiago

    • Lawrence Berkeley National Laboratory
    • Computational Research Division, Lawrence Berkeley National Lab

  • Stefano Cabrini

    • Lawrence Berkeley National Laboratory
    • LBNL

  • Irfan Siddiqi

    • University of California, Berkeley
    • Applied Mathematics and Computational Research and Materials Sciences Divisions, LBNL
    • Lawrence Berkeley National Laboratory
    • Applied Mathematics, Computational Research and Materials Sciences Divisions, Lawrence Berkeley National Lab