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

We have measured the distribution in current for the onset of voltage in small-area Josephson junctions for temperatures down to approx.1.6 K. The lifetime of the = 0 state for our highest current density junctions becomes temperature independent for k/sub B/T< or approx. =hw/sub 0//20, a T much less than the WKB prediction (w/sub 0/ is the junction resonant frequency). This is consistent with the Caldeira-Leggett theory, which includes damping effects on the quantum tunneling rate.