A superconducting flip-flop using two interacting weak links

Experimental results are presented showing that two superconducting indium microbridges coupled via a resistor and a capacitor can exhibit bistable states under a constant current bias, with one bridge at a finite voltage while the other is at zero voltage. The voltage states of the two microbridges can be interchanged by applying an external trigger current to the circuit. Current-voltage characteristics are compared with analog simulation as well as numerical calculation and found in good agreement. The effect of bias current, coupling resistor, capacitor, bridge resistance, and critical current values on the circuit properties are investigated. Our estimate for the flip-flop switching time is in the neighborhood of 0.1 nsec.