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Computer

Toward Ultra-High-Speed, Ultra-Low-Power Cryogenic Superconductor Computing

Koji Inoue, Ilkwon Byun, Masamitsu Tanaka, Yosuke Ueno, Naoki Takeuchi, Satoshi Kawakami, Olivia Chen, Dongmoon Min, Teruo Tanimoto, Ono Takatsugu, Hiroshi Nakamura, Jangwoo Kim

Published Feb 1, 2026• 0 citations
Publisher

Abstract

Superconductor single-flux-quantum (SFQ) logic, which operates in a 4.2-kelvin cryogenic environment, is a promising candidate for next-generation high-performance low-power computing. This article shares our SFQ research activity, covering from circuit to architecture and from classical to quantum.
DOI
10.1109/mc.2025.3636343

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Superconductor single-flux-quantum (SFQ) logic family has been recognized as a promising technology for cryogenic applications (e.g., quantum computing, astronomy, metrology) thanks to its ultra-fast and low-energy characteristics. Therefore, recent efforts in SFQ-based computing have focused on developing fast and low-power SFQ processors for cryogenic applications. However, there still has been little progress toward a convincing SFQ processor design due to the critical performance challenges originating from its extremely deep pipeline. In this paper, we propose a super-fast and low-power in-order SFQ processor by tackling the challenges from the deep pipeline. First, we develop a minimal-depth SFQ processor pipeline with novel architecture-level ideas. Next, we conduct in-depth performance analyses and identify three real performance bottlenecks in the deeply pipelined SFQ processors (i.e., stall/flush logic, RAW stall, fetch unit). Finally, we propose SuperCore, our super-fast SFQ-based processor architecture, with three SFQ-friendly solutions that effectively resolve the identified bottlenecks. With our solutions applied, SuperCore achieves 11 times speed-up over the SFQ processor baseline. In addition, SuperCore achieves six times speed-up and consumes up to 193 times less power compared to in-order CMOS processors running at 4K.
CMOS microprocessors are limited in their capacity for clock speed improvement because of increasing computing power, i.e., they face a power-wall problem. Single-flux-quantum (SFQ) circuits offer a solution with their ultra-fast-speed and ultra-low-power natures. This paper introduces our contributions towards ultra-high-speed cryogenic SFQ computing. The first step is to design SFQ microprocessors. From qualitatively and quantitatively evaluating past-designed SFQ microprocessors, we have found that revisiting the architecture of SFQ microprocessors and on-chip caches is the first critical challenge. On the basis of cross-layer discussions and analysis, we came to the conclusion that a bit-parallel gate-level pipeline architecture is the best solution for SFQ designs. This paper summarizes our current research results targeting SFQ microprocessors and on-chip cache architectures.
The recent trend and perspectives for high-performance microprocessors based on superconductor single-fluxquantum (SFQ) logic families are described. The rapid single-flux-quantum (RSFQ) and its energy-efficient derivatives are promising as a next-generation digital circuit technology for very-large-scale integration in the post-Moore's era because of the capability of ultrahigh-frequency operation over 100 GHz and low energy consumption. Several ongoing research projects as well as results reported, including several demonstrations of SFQ-based microprocessors and their components, are reviewed.
Single flux quantum (SFQ) logic circuits, in which a single flux quantum is used for an information carrier, have a possibility to open a new digital system operated with over 100 GHz clock frequencies at extremely low power dissipations. Recently, much progress in basic technologies for designing SFQ circuits and operating circuits with high speeds has been done. By taking advancements in these designing tools, circuits including more than several thousands junctions easily operated with the clock frequency of more than several tens GHz. Applications of SFQ circuits such as high performance computers, high end router and high end servers are being developed in the world taking advantages of the high through-put nature and the low power dissipation of the SFQ logic.
Superconductor devices are promising for building large-scale quantum computing systems. This article reports the current status and issues of the superconductor classical (digital and mixed-signal) circuit technology for quantum computing applications. The single-flux-quantum-based circuits provide advanced signal processing featuring several gigahertz clock frequencies, high sensitivity, and ultra-low power operation at a millikelvin-level temperature and are helpful for control and readout of quantum bits. The superconductor cryogenic peripheral circuits are expected to be a key to breakthrough in system scalability.