Two-level systems in superconducting quantum devices due to trapped quasiparticles
Journal article, 2020
A major issue for the implementation of large-scale superconducting quantum circuits is the interaction with interfacial two-level system (TLS) defects that lead to qubit parameter fluctuations and relaxation. Another major challenge comes from nonequilibrium quasiparticles (QPs) that result in qubit relaxation and dephasing. Here, we reveal a previously unexplored decoherence mechanism in the form of a new type of TLS originating from trapped QPs, which can induce qubit relaxation. Using spectral, temporal, thermal, and magnetic field mapping of TLS-induced fluctuations in frequency tunable resonators, we identify a highly coherent subset of the general TLS population with a low reconfiguration temperature similar to 300 mK and a nonuniform density of states. These properties can be understood if the TLS are formed by QPs trapped in shallow subgap states formed by spatial fluctutations of the superconducting order parameter. This implies that even very rare QP bursts will affect coherence over exponentially long time scales.
Author
S. E. de Graaf
National Physical Laboratory (NPL)
L. Faoro
Sorbonne University
University of Wisconsin Madison
L. B. Ioffe
Google Inc.
University of Wisconsin Madison
Sumedh Mahashabde
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics
J. J. Burnett
National Physical Laboratory (NPL)
T. Lindstrom
National Physical Laboratory (NPL)
Sergey Kubatkin
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics
Andrey Danilov
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics
A. Ya Tzalenchuk
Royal Holloway University of London
National Physical Laboratory (NPL)
Science advances
2375-2548 (eISSN)
Vol. 6 51 eabc5055Subject Categories
Atom and Molecular Physics and Optics
Other Physics Topics
Condensed Matter Physics
DOI
10.1126/sciadv.abc5055
PubMed
33355127