Return current statistics in extended Josephson junctions

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In the last few years the return current, i.e., the value of the bias current where an hysteretic Josephson junction switches back to zero voltage state, has obtained interest in view of its connections with the evaluation of losses for macroscopic quantum coherence experiments and the following development of q-bit devices. Here we study carefully the problem of the return current by means of numerical simulations of associated Langevin equations in both very small and intermediate length Josephson junctions. Comparison with theoretical lifetime, fluctuations, and recent experiments are carefully carried out. The results show that the effects of finite length are important in the correct description of the return switch.