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(a) Measurement setup. (Insets) Optical and SEM images of a characteristic LE sample and embedded Josephson junction. (b) The spectral density of frequency fluctuations at 0.1 Hz as a function of resonator photon number, , for CPW and LE resonators. (c) The critical current noise sensitivity for CPW (red) and LE (black) embedding geometries as a function of the Josephson inductance participation ratio.
1/f frequency noise of Josephson-junction-embedded resonators. (a) The measured frequency noise of junction-embedded samples and the co-fabricated linear resonator. (b) The measured critical current noise assuming all the frequency noise is attributed to critical current fluctuations of the junction. (c) Temperature dependence of the junction-embedded resonators. (d) The spectral density of frequency noise (left axis) and equivalent critical current noise noise (right axis) for sample F at temperatures up to 250 mK.
Sample parameters. Sample A was a linear LE resonator. Sample D incorporated a single junction rather than 2 junctions in a SQUID geometry. The critical current and participation ratio were determined from the resonance frequency of the samples. The linear inductance was calculated from finite element simulations.
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