Critical current gain in superconducting transistor quantum interference devices

A superconducting quantum interference device (SQUID) built with superconducting transistors is analyzed. The sensitivity of the critical current of the interferometer to gate charge is related to the sensitivity of the superconducting transistor critical current to gate charge by a gain parameter. For two-transistor interferometers with symmetric inductors, the gain varies from -1 to 2. An increase in critical current for either device of ΔI cannot decrease the critical current of the circuit by more than ΔI, nor can it increase it by more than 2ΔI. In special situations, the number of stored flux quanta in the circuit can be both increased and decreased by the gate charge