Hot Nonequilibrium Quasiparticles in Transmon Qubits

K. Serniak, M. Hays, G. de Lange, S. Diamond, S. Shankar, L. D. Burkhart, L. Frunzio, M. Houzet, and M. H. Devoret
Phys. Rev. Lett. 121, 157701 – Published 10 October 2018
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Abstract

Nonequilibrium quasiparticle excitations degrade the performance of a variety of superconducting circuits. Understanding the energy distribution of these quasiparticles will yield insight into their generation mechanisms, the limitations they impose on superconducting devices, and how to efficiently mitigate quasiparticle-induced qubit decoherence. To probe this energy distribution, we systematically correlate qubit relaxation and excitation with charge-parity switches in an offset-charge-sensitive transmon qubit, and find that quasiparticle-induced excitation events are the dominant mechanism behind the residual excited-state population in our samples. By itself, the observed quasiparticle distribution would limit T1 to 200μs, which indicates that quasiparticle loss in our devices is on equal footing with all other loss mechanisms. Furthermore, the measured rate of quasiparticle-induced excitation events is greater than that of relaxation events, which signifies that the quasiparticles are more energetic than would be predicted from a thermal distribution describing their apparent density.

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  • Received 2 April 2018
  • Revised 27 July 2018

DOI:https://doi.org/10.1103/PhysRevLett.121.157701

© 2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsQuantum Information, Science & Technology

Authors & Affiliations

K. Serniak1,*, M. Hays1, G. de Lange1,2, S. Diamond1, S. Shankar1, L. D. Burkhart1, L. Frunzio1, M. Houzet3, and M. H. Devoret1,†

  • 1Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA
  • 2QuTech and Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, Netherlands
  • 3Univ. Grenoble Alpes, CEA, INAC-Pheliqs, F-38000 Grenoble, France

  • *kyle.serniak@yale.edu
  • michel.devoret@yale.edu

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Issue

Vol. 121, Iss. 15 — 12 October 2018

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