Inductance-compensated Josephson current-injection device

A current-injection device (CID) can be used to perform the AND function in Josephson technology. The sensitivity of the CID operating margins to variations in the critical currents of the Josephson junctions is examined. Further, we present here a novel Compensated Current-Injection Device (CCID) in which Josephson junctions are used not only as switches, but also as inductors. This significantly increases the tolerance of the CCID to systematic variations in Josephson junction critical currents, by maintaining the effective LIoproduct invariant. Monte Carlo analyses of the threshold curves of the CID and the CCID under identical sets of assumed process variations show roughly a factor of two improvement for the CCID in the signal current operating window and also in the standard deviation of the device threshold, for cases with an arbitrarily assumed ± 20% chip-to-chip systematic variations in critical currents. The relative improvement is less if the systematic variation is smaller.