Excitation of superconducting qubits from hot non-equilibrium quasiparticles

  1. J. Wenner,
  2. Yi Yin,
  3. Erik Lucero,
  4. R. Barends,
  5. Yu Chen,
  6. B. Chiaro,
  7. J. Kelly,
  8. M. Lenander,
  9. Matteo Mariantoni,
  10. A. Megrant,
  11. C. Neill,
  12. P. J. J. O'Malley,
  13. D. Sank,
  14. A. Vainsencher,
  15. H. Wang,
  16. T. C. White,
  17. A. N. Cleland,
  18. and John M. Martinis
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.
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