New figure of merit to compare josephson balanced comparators

Abstract

The Josephson comparator, composed of two Josephson junctions in series, is the decision-making pair of the single flux quantum (SFQ) logic and also performs critical roles in superconducting analog-to-digital converter (ADC) as sampling elements. Its current resolution and speed determine the performance of these circuits. Balancing the inherent trade-off between the resolution and speed is an issue in optimizing a Josephson comparator. In this research, we propose the Normalized Speed Resolution Ratio (NSRR) to analyze the comprehensive performance of the Josephson comparator under various critical currents (Ic) and critical current densities (jc). Based on numerical simulations and results, we suggested an NSRR-based optimization criterion for the manufacturing process and design parameters of a Josephson comparator. Furthermore, a fitted value for the NSRR is determined by fitting our experimental data and the results of other research organizations. This reference value may be used to assess the complete performance of the Josephson comparator under different processes.