ABSTRACT
Josephson integrated circuits have attracted considerable interest because of their high-speed operation with very low power dissipation as compared with conventional semiconductor circuits (McDonald et al 1980). Recently, many Josephson large-scale integrated (LSI) circuits have been fabricated by using integration technology based on the superconducting materials of Nb and NbN (Nakagawa et al 1991). The operation modes of these LSI circuits fall into two broad categories: voltage and phase. The first category has a close relation with the hysteretic current-voltage (I-V) characteristics of a Josephson junction. The second category is related to quantum mechanical quantization of magnetic flux. The flux quantization(h/2e) is a basic characteristic of superconductors and is represented in terms of the phase of a macroscopic quantum mechanical wavefunction. Let us discuss the fundamentals of single-flux quantum electronics starting from Josephson junction behaviours caused by the nonlinear relation between the current and phase difference across the junction.
