Abstract

Materials developments during the past several years will facilitate the realization of promises of picosecond electronics with superconductive devices. An increasing number of groups around the world have developed the capability of making all refractory integrated circuits based on the Nb-NbO_xNb Josephson tunnel junction, which has the I-V characteristic shown in Fig. 1a. These devices have excellent and controllable electrical characteristics and are stable both in terms of shelf life and in thermal cycling. Circuits with tens of thousands of logic gates have been made and have shown remarkable electrical performance. It should be borne in mind that in complex electronic circuits with gates that switch with speeds of several picoseconds, the terminal data rates are on the nanosecond scale except in special pipelined situations, such as a shift register. It should also be kept in mind that parasitics limit switch speeds. While the niobium Josephson junctions has a theoretical limiting switching speed of 0.22 ps, the junction capacitance limits the speeds realized to date to slightly more than 1 ps.

© 1991 Optical Society of America