SQUIDS in Josephson Logic Circuits

Abstract

SQUIDS (Superconducting Quantum Interference Devices) have shown considerable potential as a high-speed and low-power switching device for very fast Josephson digital circuits. Switching speeds of about 10 ps and power dissipation of a few μW per circuit in combination with superconducting transmission lines are key items for Josephson computer applications.

Basic operation principles of Josephson interferometer devices for computer logic applications will be presented with emphasis on presently most widely used latching logic circuits. Dynamic properties of interferometers such as switching delays, resetting from the voltage state into the superconducting state, etc. are discussed in terms of simple mechanical junction analogs.

The implementation of these devices into complete logic circuits is demonstrated on the example of the Current-Injection Logic and peripheral memory logic presently being developed in IBM’s Josephson program.

A brief outlook on recently proposed Josephson devices which do not rely on quantum interference will show some alternative approaches for superconducting high-speed logic circuits.