Dephasing of a Superconducting Flux Qubit

K. Kakuyanagi, T. Meno, S. Saito, H. Nakano, K. Semba, H. Takayanagi, F. Deppe, and A. Shnirman
Phys. Rev. Lett. 98, 047004 – Published 23 January 2007

Abstract

In order to gain a better understanding of the origin of decoherence in superconducting flux qubits, we have measured the magnetic field dependence of the characteristic energy relaxation time (T1) and echo phase relaxation time (T2echo) near the optimal operating point of a flux qubit. We have measured T2echo by means of the phase cycling method. At the optimal point, we found the relation T2echo2T1. This means that the echo decay time is limited by the energy relaxation (T1 process). Moving away from the optimal point, we observe a linear increase of the phase relaxation rate (1/T2echo) with the applied external magnetic flux. This behavior can be well explained by the influence of magnetic flux noise with a 1/f spectrum on the qubit.

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  • Received 22 August 2006

DOI:https://doi.org/10.1103/PhysRevLett.98.047004

©2007 American Physical Society

Authors & Affiliations

K. Kakuyanagi1, T. Meno2, S. Saito1, H. Nakano1, K. Semba1, H. Takayanagi3, F. Deppe4, and A. Shnirman5

  • 1NTT Basic Research Laboratories, NTT Corporation, Kanagawa, 243-0198, Japan
  • 2NTT Advanced Technology, NTT Corporation, Kanagawa, 243-0198, Japan
  • 3Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan
  • 4Walther-Meißner-Institut, Walther-Meißner-Strasse 8, D-85748 Garching, Germany
  • 5Institut für Theoretische Festkörperphysik, Universität Karlsruhe, D-76128 Karlsruhe, Germany

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Issue

Vol. 98, Iss. 4 — 26 January 2007

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