Rapid single-flux-quantum balanced comparator based on high-<i>T</i> <i>c</i> bicrystal Josephson junctions

Abstract

A balanced current comparator based on high-Tc bicrystal Josephson junctions has been designed, fabricated, and experimentally tested. The operation of the balanced comparator has been demonstrated in the temperature range from 4.2 to 70 K. The correct sequence of switching of the Josephson junctions has been determined by dc measurements for different values of operating frequency and signal current Ix. The threshold uncertainty ΔIx of the balanced comparator, measured at 40 K, was 60 μA at 40 GHz and 300 μA at 240 GHz.