Abstract—Recently, superconducting digital circuits have emerged as a promising technology in the post-Moore’s law paradigm. Utilizing Josephson junctions as the active switching element, superconducting digital circuits rely on the quantization of magnetic flux (fluxons) to encode binary information. Reciprocal Quantum Logic (RQL) is a leading superconducting logic family that has demonstrated fast, ultralow power operation with wide operating margins. Furthermore, it has shown promising scaling properties producing some of largest, most complex superconducting digital circuits to date.
While previous demonstrations of scaling have relied on custom design and physical layout of circuits, further scaling of superconducting digital circuits have been hindered by the lack of electronic design automation (EDA) tools. EDA tools have been essential to the realization and maturation of very-large scale integration (VLSI) of CMOS circuits. However, superconducting digital circuits introduce novel challenges which make off-the-shelf use of standard EDA tools incompatible for superconducting designs.
This paper introduces digital design using RQL and explores some of the difficulties encountered during synthesis, timing, and place & routing of RQL circuits. It also describes how these issues have led to novel solutions and features within the Cadence suite of EDA tools to realize digital superconducting circuits. With these advances in EDA tools, RQL technology is poised to achieve