Lyapunov Exponent Analyses of Chaotic Oscillations in rf-biased Josephson Junctions

We have been studying chaos in Josephson junctions for the purpose of applying it to physical random number generators. In this paper, parameter maps, under which chaotic oscillation occurred, were evaluated with RCSJ simulations. Lyapunov exponents were calculated to judge whether their dynamics were chaotic or not. The mapping of chaos occurrence with different system parameters were reported by calculating the exponent for each system parameters. The conditions to generate chaos in Josephson junction toward the random number generator were discussed.