Probing noise in flux qubits via macroscopic resonant tunneling.
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 rms amplitude of the noise, which is proportional to the dephasing rate 1/tauphi, was observed to be weakly dependent on temperature below 70 mK. Analysis of these results indicates that the dominant source of low energy flux noise in this device is a quantum mechanical environment in thermal equilibrium.
Harris
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D-Wave Systems Inc., 100-4401 Still Creek Drive, Burnaby, BC V5C 6G9, Canada. rharris@dwavesys.com
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Berkley
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Johansson
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Bunyk
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Ladizinsky
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Govorkov
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Thom
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Uchaikin
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Bumble
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Kleinsasser
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Amin
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Averin
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