Superconducting circuits without inductors based on bistable Josephson junctions

TL;DR

This paper proposes a novel superconducting digital circuit design that eliminates inductors by using bistable Josephson junctions to represent information in Josephson energy, enabling more scalable and space-efficient superconducting logic.

Contribution

Introduction of all-Josephson junction circuits utilizing bistable Josephson junctions for flux-free, scalable superconducting digital logic design.

Findings

Design methodology for all-JJ circuits demonstrated

Analysis of simple logic cells and 8-bit adder

Potential for reduced JJ count and space efficiency

Abstract

Magnetic flux quantization in superconductors allows the implementation of fast and energy-efficient digital superconducting circuits. However, the information representation in magnetic flux severely limits their functional density presenting a long-standing problem. Here we introduce a concept of superconducting digital circuits that do not utilize magnetic flux and have no inductors. We argue that neither the use of geometrical nor kinetic inductance is promising for the deep scaling of superconducting circuits. The key idea of our approach is the utilization of bistable Josephson junctions allowing the representation of information in their Josephson energy. Since the proposed circuits are composed of Josephson junctions only, they can be called all-Josephson junction (all-JJ) circuits. We present a methodology for the design of the circuits consisting of conventional and bistable junctions. We analyze the principles of the circuit functioning, ranging from simple logic cells and ending with an 8-bit parallel adder. The utilization of bistable junctions in the all-JJ circuits is promising in the aspects of simplification of schematics and the decrease of the JJ count leading to space-efficiency.