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Probing hundreds of individual two-level defects in polycrystalline and amorphous alumina.

ORAL

Abstract

Quantum two-level systems (TLSs) appear in the dielectrics of superconducting qubits and parasitically limit the qubit coherence time. The Josephson junction barrier, amorphous alumina, is known to host TLSs similar to other amorphous films, but TLSs are not microscopically understood in atomic composition. In this study we extend the quantitative data available on TLSs by using a superconducting resonator to characterize two alumina film types: polycrystalline and amorphous. We find a clear difference between the structure types when analyzing TLSs. A large sample of ~ 400 individual TLSs is analyzed from polycrystalline films. Their dipole moments directed vertically have a mean value of 2.6(0) Debye and a standard deviation of 1.6(5) Debye. They fit well to a single Gaussian distribution indicating a single defect type. In contrast, the amorphous film contains TLSs with the larger dipole moments but only few are observed due to larger frequency noise.

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Presenters

  • Chih-Chiao Hung

    Laboratory for Physical Sciences, University of Maryland, College Park

Authors

  • Chih-Chiao Hung

    Laboratory for Physical Sciences, University of Maryland, College Park

  • Neda Forouzani

    Laboratory for Physical Sciences, Laboratory for Physical Sciences, University of Maryland University College, University of Maryland, College Park

  • Liuqi Yu

    Department of Physics, University of Basel, University of Basel, LPS at the University of Maryland, College Park, University of Maryland, College Park

  • Stefan Fritz

    Physics, Karlsruhe Institute of Technology

  • Dagmar Gerthsen

    Physics, Karlsruhe Institute of Technology

  • Kevin Daniel Osborn

    Laboratory for Physical Sciences, Laboratory for Physical Sciences, University of Maryland University College, LPS at the University of Maryland, College Park, University of Maryland, College Park