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Phys. Rev. Lett. 99, 187006 (2007) [4 pages]

1/f Flux Noise in Josephson Phase Qubits

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Radoslaw C. Bialczak1, R. McDermott2, M. Ansmann1, M. Hofheinz1, N. Katz1, Erik Lucero1, Matthew Neeley1, A. D. O’Connell1, H. Wang1, A. N. Cleland1, and John M. Martinis1,*
1Department of Physics, University of California, Santa Barbara, California 93106, USA
2Department of Physics, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA

Received 11 August 2007; published 2 November 2007

We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1 Hz. A comparison of the noise taken at positive and negative bias of a phase qubit shows the dominant noise source to be flux noise and not junction critical-current noise, with a magnitude similar to that measured previously in other systems. Theoretical calculations show that the level of flux noise is not compatible with the standard model of noise from two-level state defects in the surface oxides of the films.

© 2007 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.99.187006
DOI:
10.1103/PhysRevLett.99.187006
PACS:
74.40.+k, 03.67.−a, 85.25.−j

*martinis@physics.ucsb.edu

 
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