Dielectric losses in multi-layer Josephson junction qubits

David Gunnarsson, Juha-Matti Pirkkalainen, Jian Li, Gheorghe Sorin Paraoanu, Pertti Hakonen, Mika Sillanpää, Mika Prunnila

    Research output: Contribution to journalArticleScientificpeer-review

    18 Citations (Scopus)


    We have measured the excited state lifetimes in Josephson junction phase and transmon qubits, all of which were fabricated with the same scalable multi-layer process. We have compared the lifetimes of phase qubits before and after removal of the isolating dielectric, SiNx, and find a fourfold improvement of the relaxation time after the removal. Together with the results from the transmon qubit and measurements on coplanar waveguide resonators, these measurements indicate that the lifetimes are limited by losses from the dielectric constituents of the qubits. We have extracted the individual loss contributions from the dielectrics in the tunnel junction barrier, AlOx, the isolating dielectric, SiNx, and the substrate, Si/SiO2, by weighting the total loss with the parts of the electric field over the different dielectric materials. Our results agree well with and complement the findings from other studies, demonstrating that superconducting qubits can be used as a reliable tool for high-frequency characterization of dielectric materials. We conclude with a discussion of how changes in design and material choice could improve qubit lifetimes by up to a factor of 4.
    Original languageEnglish
    Article number085010
    JournalSuperconductor Science and Technology
    Issue number8
    Publication statusPublished - 2013
    MoE publication typeA1 Journal article-refereed


    • excited state lifetimes
    • high-frequency characterization
    • Josephson-junction
    • Josephson-Junction qubits
    • junction barrier
    • material choice
    • superconducting qubits
    • waveguide resonators


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