Superconductor circuits cut component count with new retiming and amplifier designs
Duplication-Aware Retiming and Cell Interface Redesign for Superconductor Circuit Minimization
Emerging TechnologiesHardware Architecture
Summary
Building superconducting computer circuits is tricky because their designs often double parts, making them larger and more complex. The authors created a method that rearranges these circuits while considering this duplication to reduce the number of parts needed. They also designed a new type of small component that helps connect parts more efficiently. Together, these advances significantly shrink the size and improve the speed of these circuits compared to previous approaches.
What this means in practice
- •For superconductor circuit designers: Design more compact and faster superconducting circuits by applying duplication-aware retiming and improved amplifier cells to reduce component count.
- •For high-performance computing engineers: Develop energy-efficient computing systems using minimized superconductor circuits that balance speed and hardware complexity.
Authors
Panagiotis Papanikolaou, Alex Vanasse, Haoran Jin, Georgios Tzimpragos, Jennifer Volk
Abstract
Superconductor electronics have increasingly shifted away from RSFQ and its variants toward logic families that eliminate explicit gate-level clocking. While this transition enables simpler circuits and more efficient architectures, it also introduces an implicit reliance on dual-rail codes, resulting in inherent gate duplication. This work presents a duplication-aware retiming methodology for Josephson junction (JJ) count minimization, co-optimizing register placement and polarity assignment. The approach applies beyond SFQ to any monotonic circuit. We further identify cell interfaces---specifically, interconnect drivers, receivers, and fanout (FO) elements---as dominant contributors to JJ count in each cell. A new amplifier design is introduced to reduce these costs, integrated within existing SFQ cells, experimentally verified, and characterized to form a new SFQ cell library. Our results demonstrate a 63-71% JJ count reduction in single-cycle implementations and 41-66% reduction in multi-cycle implementations compared to the prior state-of-the-art. The latter establishes a new Pareto frontier, achieving both shorter critical paths and lower JJ counts than the best-to-date single-cycle implementations.