Chaos and noise rise in Josephson junctions

Digital computer simultations have been used to map parameters of the transition to chaos in an rf current driven Josephson junction. Our results are qualitatively like those reported by others using analog techniques, but differ quantitatively. Our calculations show that the parameters for the onset of chaos are the same as those required for high parametric gain. This leads to the conclusion that the "noise rise" in Josephson junction parametric amplifiers is due to chaos.