We love ’em short and fat

Geometrical dependence of low frequency noise in superconducting flux qubits

A general method for directly measuring the low-frequency flux noise (below 10 Hz) in compound Josephson junction superconducting flux qubits has been used to study a series of 85 devices of varying design. The variation in flux noise across sets of qubits with identical designs was observed to be small. However, the levels of flux noise systematically varied between qubit designs with strong dependence upon qubit wiring length and wiring width. Furthermore, qubits fabricated above a superconducting ground plane yielded lower noise than qubits without such a layer. These results support the hypothesis that localized magnetic impurities in the vicinity of the qubit wiring are a key source of low frequency flux noise in superconducting devices.

6 thoughts on “We love ’em short and fat

  1. i only pick mercury cause it was the 1st superconductor discovered. i’m sure it could not be the best choice now.

    qubits fabricated above a superconducting ground plane, so what are you using for the ground plane?

  2. so short and fat line equal less inductance and more capacitance. so capacitance filtering high frequency, less inductance picking up less noise. what frequency do you have to pass or is it just DC you want, a single state 1 or 0?

  3. JP: the noise measured in these experiments is low frequency noise (less than 10 Hz). The reasons for the dependence on length and width are fairly well understood I think (read the paper), has to do with current distributions and defects.

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