Thermal activation from the fluxoid and the voltage states of dc SQUIDs

The probability density of thermal fluctuations about different types of nonequilibrium steady states of a dc SQUID are evaluated by generalizing a technique used before for the fluctuations of a single Josephson junction. Probability densities obtained for both ‘‘running’’ and ‘‘beating’’ modes are used to calculate thermal activation rates as well as the various branches of the I-V characteristic. The results are compared with the experiments of Voss et al. and good agreement is found.