Decoherence of a quantum two-level system by spectral diffusion

Shlomi Matityahu, Alexander Shnirman, Gerd Schön, and Moshe Schechter
Phys. Rev. B 93, 134208 – Published 18 April 2016

Abstract

We study the dephasing of an individual high-frequency tunneling two-level system (TLS) due to its interaction with an ensemble of low-frequency thermal TLSs which are described by the standard tunneling model (STM). We show that the dephasing by the bath of TLSs explains both the dependence of the Ramsey dephasing rate on an externally applied strain as well as its order of magnitude, as observed in a recent experiment [J. Lisenfeld et al., Sci. Rep. 6, 23786 (2016)]. However, the theory based on the STM predicts the Hahn-echo protocol to be much more efficient, yielding too low echo dephasing rates, as compared to the experiment. Also the strain dependence of the echo dephasing rate predicted by the STM does not agree with the measured quadratic dependence, which would fit to a high-frequency white noise environment. We suggest that few fast TLSs which are coupled much more strongly to the strain fields than the usual TLSs of the STM give rise to such a white noise. This explains the magnitude and strong fluctuations of the echo dephasing rate observed in the experiment.

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  • Received 6 February 2016
  • Revised 28 March 2016

DOI:https://doi.org/10.1103/PhysRevB.93.134208

©2016 American Physical Society

Physics Subject Headings (PhySH)

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

Authors & Affiliations

Shlomi Matityahu1, Alexander Shnirman2,3, Gerd Schön4,5, and Moshe Schechter1

  • 1Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
  • 2Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
  • 3L. D. Landau Institute for Theoretical Physics RAS, Kosygina street 2, 119334 Moscow, Russia
  • 4Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
  • 5Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany

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Issue

Vol. 93, Iss. 13 — 1 April 2016

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