title: Excitation of superconducting qubits from hot nonequilibrium quasiparticles.
abstract: Superconducting qubits probe environmental defects such as nonequilibrium quasiparticles, an important source of decoherence. We show that "hot" nonequilibrium quasiparticles, with energies above the superconducting gap, affect qubits differently from quasiparticles at the gap, implying qubits can probe the dynamic quasiparticle energy distribution. For hot quasiparticles, we predict a non-negligible increase in the qubit excited state probability Pe. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of Pe in semiquantitative agreement with the model and rule out the typically assumed thermal distribution.
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wenner
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Lucero
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: R
authors.initials: R
authors.lastname: Barends
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: B
authors.initials: B
authors.lastname: Chiaro
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kelly
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: M
authors.initials: M
authors.lastname: Lenander
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA and California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA.
authors.forename: Matteo
authors.initials: M
authors.lastname: Mariantoni
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA and Department of Materials, University of California, Santa Barbara, California 93106, USA.
authors.forename: A
authors.initials: A
authors.lastname: Megrant
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: C
authors.initials: C
authors.lastname: Neill
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: P J J
authors.initials: PJ
authors.lastname: O'Malley
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: D
authors.initials: D
authors.lastname: Sank
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: A
authors.initials: A
authors.lastname: Vainsencher
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA and Department of Physics, Zhejiang University, Hangzhou 310027, China.
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: White
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA and California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Cleland
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA and California NanoSystems Institute, University of California, Santa Barbara, California 93106, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Martinis