Experimental observation of short-range magnetic correlations in amorphous Nb<sub>2</sub>O<sub>5</sub>and Ta<sub>2</sub>O<sub>5</sub>&nbsp;thin films.

ORAL

Abstract

Different magnetic behaviors have been observed in niobium and tantalum pentoxides. Using muon spin relaxation, we observed a magnetic response down to 2.8 K. It appeared that amorphous niobium pentoxide exhibits high-frequency magnetic fluctuations with no magnetic order. In contrast, tantalum pentoxide shows local magnetic ordering in the amorphous phase and no magnetic response when the oxide is crystalline. However, the local magnetic field in tantalum pentoxide is significant, which means that both pentoxides are detrimental to the performance of superconducting qubits. Niobium pentoxide is more lossy because it has a broad spectral range that overlaps with the operational range of superconducting qubits, and these fluctuations could likely cause flux noise. This knowledge could help improve the performance of qubits and provide a deeper understanding of sources of loss.

*This work was supported by the U.S. Department of Energy, Office of Science, National Quantum Information Science Research Centers, Superconducting Quantum Materials and Systems Center (SQMS), under Contract No. 89243024CSC000002. Fermilab is operated by Fermi Forward Discovery Group, LLC under Contract No. 89243024CSC000002 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. This work made use of the SmuS Facility of Paul Scherrer Institute. T.R., R.D. and I.M.P.  acknowledge funding from the Helmholtz Association, the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement number 847471, and the Federal Ministry of Education and Research via Project GeQCoS (FKZ: 13N15683). The authors are grateful to L. Radtke at KIT for technical support. Facilities use was supported by the KIT Nanostructure Service Laboratory (NSL) and the Karlsruhe Nano Micro Facility (KNMFi).

–

Publication: Y.V. Krasnikova et al. arXiv:2505.07957 (2025)

Presenters

  • Yulia Krasnikova

    • Fermilab, SQMS

Authors

  • Yulia Krasnikova

    • Fermilab, SQMS

  • Akshay A Murthy

    • Fermi National Accelerator Laboratory (Fermilab)

  • Daniel Bafia

    • Fermi National Accelerator Laboratory (Fermilab)

  • Francesco Crisa

    • Fermi National Accelerator Laboratory
    • Fermi National Accelerator Laboratory (Fermilab)
    • Fermi National Accelerator Laboratory (FNAL)
    • Fermilab

  • Adam C Clairmont

    • Fermilab

  • Zuhawn Sung

    • Fermi National Accelerator Laboratory (FNAL)

  • Jaeyel Lee

    • Fermi National Accelerator Laboratory (FNAL)
    • Fermi National Accelerator Laboratory

  • Maithilee Shinde

    • Illinois Institute of Technology
    • Fermi National Accelerator Laboratory (Fermilab)

  • David van Zanten

    • Fermi National Accelerator Laboratory (Fermilab)

  • Alexander Romanenko

    • Fermi National Accelerator Laboratory (Fermilab)

  • Anna Grassellino

    • Fermi National Accelerator Laboratory (Fermilab)
    • Fermi National Accelerator Laboratory, Batavia, Illinois, 60510, USA

  • Mustafa Bal

    • Fermi National Accelerator Laboratory
    • Xanadu

  • Ritika Dhundhwal

    • Karlsruhe Institute of Technology

  • Dirk Fuchs

    • Karlsruhe Institute of Technology

  • Thomas Reisinger

    • Karlsruhe Institute of Technology

  • Ioan M. Pop

    • Karlsruhe Institute of Technology

  • Andreas Suter

    • Paul Scherrer Institute

  • Thomas Prokscha

    • Paul Scherrer Institute

  • Zaher Salman

    • Paul Scherrer Institute