Incoherent tunneling of the cooper pairs and magnetic flux quanta in ultrasmall Josephson junctions

We have calculated the dc I-V curve and fluctuation spectrum of a Josephson junction shunted by an arbitrary frequency-dependent impedance for very small and very large Josephson coupling. The junction dynamics can be interpreted as an incoherent tunneling of the Cooper pairs (in former case) and magnetic flux quanta (in the latter case).