Decay of the Zero-Voltage State in Small-Area, High-Current-Density Josephson Junctions

Abstract

We have measured the distribution in current for the onset of voltage in small-area Josephson junctions for temperatures down to ∼1.6 K. The lifetime of the $〈V〉=0\mathrm{}$ state for our highest current density junctions becomes temperature independent for $k_{\mathrm{B}}T\lesssim \frac{\hslash {\omega }_0}{20}$, a $T$ much less than the WKB prediction (${\omega }_0$ is the junction resonant frequency). This is consistent with the Caldeira-Leggett theory, which includes damping effects on the quantum tunneling rate.