High-speed switching and logic circuits using Josephson devices

We have investigated the use of Josephson devices as switching components for computer circuits. One part of this work is a study of the switching properties of the superconductor-semiconductor-superconductor junction. The switching speeds of a single junction and a basic memory cell, computed by numerical methods, are comparable with the corresponding values for oxide-barrier junctions. Having a much lower Q than the conventional oxide-barrier junction, it should not have the previously experienced difficulties caused by junction resonances. The damping of plasma oscillations in the semiconductor junction is also more effective, leading to a shorter switching time. A new type of logic gate employing Josephson devices has been investigated. This circuit would automatically unlatch after each operation, thus requiring no external means for resetting. Numerical analysis predicts subnanosecond switch-reset operation for appropraite parameter choices. The qualitative behavior of the circuit has also been shown with a mechanical analog.