Microscopic Model of Critical Current Noise in Josephson Junctions

Abstract

We present a simple microscopic model to show how fluctuating two-level systems in a Josephson junction tunnel barrier of thickness $L$ can modify the potential energy of the barrier and produce critical current noise spectra. We find low frequency $1/f$ noise that goes as $L^5$. Our values are in good agreement with recent experimental measurements of critical current noise in $\mathrm{Al}/{\mathrm{AlO}}_x/\mathrm{Al}$ Josephson junctions. We also investigate the sensitivity of the noise on the nonuniformity of the tunnel barrier.