Sensitivity of the balanced Josephson-junction comparator

The sensitivity of a balanced comparator composed of two overdamped Josephson junctions fed by single flux pulses is calculated, taking into account both thermal and quantum fluctuations. The results of the analysis are compared with those of recent experiments. Ultimate resolution of the balanced comparator with feasible junction parameters is estimated to be as high as approximately 50 pA/Hz/sup 1/2/ at 4 K and approximately 10 pA/Hz/sup 1/2/ at T to 0 K. Performance limits of the device are compared with those of its single-junction counterpart.