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arXiv · 0712.0838

Probing Noise in Flux Qubits via Macroscopic Resonant Tunneling

R. Harris·M. W. Johnson·S. Han·A. J. Berkley·J. Johansson·P. Bunyk·E. Ladizinsky·S. Govorkov·M. C. Thom·S. Uchaikin·B. Bumble·A. Fung·A. Kaul·A. Kleinsasser·M. H. S. Amin·D. V. Averin
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Abstract

Macroscopic resonant tunneling between the two lowest lying states of a bistable RF-SQUID is used to characterize noise in a flux qubit. Measurements of the incoherent decay rate as a function of flux bias revealed a Gaussian shaped profile that is not peaked at the resonance point, but is shifted to a bias at which the initial well is higher than the target well. The r.m.s. amplitude of the noise, which is proportional to the decoherence rate 1/T_2^*, was observed to be weakly dependent on temperature below 70 mK. Analysis of these results indicates that the dominant source of low frequency (1/f) flux noise in this device is a quantum mechanical environment in thermal equilibrium.

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R. Harris, M. W. Johnson, S. Han, A. J. Berkley, J. Johansson, P. Bunyk, E. Ladizinsky, S. Govorkov, M. C. Thom, S. Uchaikin, B. Bumble, A. Fung, A. Kaul, A. Kleinsasser, M. H. S. Amin, D. V. Averin. 2008-02-08. Probing Noise in Flux Qubits via Macroscopic Resonant Tunneling. https://doi.org/10.1103/physrevlett.101.117003

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