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Impact of time-ordered measurements of the two states in a niobium superconducting qubit structure

K. Segall, D. Crankshaw, D. Nakada, T. P. Orlando, L. S. Levitov, S. Lloyd, N. Markovic, S. O. Valenzuela, M. Tinkham, and K. K. Berggren
Phys. Rev. B 67, 220506(R) – Published 27 June 2003
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Measurements of thermal activation are made in a superconducting, niobium persistent-current qubit structure, which has two stable classical states of equal and opposite circulating current. The magnetization signal is read out by ramping the bias current of a dc superconducting quantum interference device. This ramping causes time-ordered measurements of the two states, where measurement of one state occurs before the other. This time ordering results in effective measurement time, which can be used to probe the thermal activation rate between the two states. Fitting the magnetization signal as a function of temperature and ramp time allows one to estimate a quality factor of 3×105 for our devices, a value favorable for the observation of long quantum coherence times at lower temperatures.

  • Received 28 January 2003


©2003 American Physical Society

Authors & Affiliations

K. Segall, D. Crankshaw, D. Nakada, T. P. Orlando, L. S. Levitov, and S. Lloyd

  • Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

N. Markovic, S. O. Valenzuela, and M. Tinkham

  • Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

K. K. Berggren

  • MIT Lincoln Laboratory, Lexington, Massachusetts 02421, USA

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Vol. 67, Iss. 22 — 1 June 2003

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