Excitation of superconducting qubits from hot non-equilibrium quasiparticles

Authors:
  • JWJ. Wenner
    J. Wenner
  • YYYi Yin
    Yi Yin
  • ELErik Lucero
    Erik Lucero
  • RBR. Barends
    R. Barends
  • YCYu Chen
    Yu Chen
  • BCB. Chiaro
    B. Chiaro
  • JKJ. Kelly
    J. Kelly
  • MLM. Lenander
    M. Lenander
  • MMMatteo Mariantoni
    Matteo Mariantoni
  • AMA. Megrant
    A. Megrant
  • CNC. Neill
    C. Neill
  • POP. J. J. O'Malley
    P. J. J. O'Malley
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Abstract
Superconducting qubits probe environmental defects such as non-equilibrium quasiparticles, an important source of decoherence. We show that "hot" non-equilibrium 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-neligable increase in the qubit excited state probability P_e. By injecting hot quasiparticles into a qubit, we experimentally measure an increase of P_e in semi-quantitative agreement with the model.