CURRENT RESPONSES AND VOLTAGE FLUCTUATIONS IN JOSEPHSON-JUNCTION SYSTEMS

We consider arrays of Josephson junctions as well as single junctions in both the classical and quantum-mechanical regimes, and examine the generalized (frequency-dependent) resistance, which describes the dyna mic responses of such Josephson-junction systems to external currents. It is shown that the generalized resistance and the power spectrum of voltage fluctuations are related via the fluctuation-dissipation theo rem. Implications of the obtained relations are also discussed in vari ous experimental situations.