Superconducting Circuits without Inductors Based on Bistable Josephson Junctions

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

Automated summary

While magnetic flux quantization in superconductors poses limitations on functional density, the innovative design utilizing bistable Josephson junctions allows for the development of superconducting digital circuits without relying on magnetic flux and inductors, thus promising higher space efficiency.