C. D. Nugroho, V. Orlyanchik, D. J. Van Harlingen
We present low-temperature measurements of the low-frequency $1/f$ noise arising from an ensemble of two-level fluctuators in the oxide barrier of Al/AlO$_{x}$/Al Josephson junctions. Both the critical-current noise ($S_{I_{c}}/I_{c}^{2}$) and normal-state resistance noise ($S_{R_{n}}/R_{n}^{2}$) scale linearly in temperature with the same noise magnitude, implying an equivalence between the two. Combining our noise results with those from other laboratories and junction architectures, we deduce the scaling $\frac{S_{R_{n}}}{R_{n}^{2}}\equiv\frac{S_{I_{c}}}{I_{c}^{2}}\approx\frac{1}{A/\mu m^{2}}(\frac{T}{1 \textrm{K}})\times 10^{-13} \textrm{Hz}^{-1}$. We find that the density of two-level fluctuators in the junction barrier is similar to the typical value in glassy systems. We discuss the implications and consistency with recent qubit experiments.
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http://arxiv.org/abs/1302.6175
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