SFQ Technology Developments in NEDO Next-Generation High-Efficiency Network Device project

Mitsuo Hidaka

Shinichi Yorozu, Y. Kameda, Shuichi Tahara

S. Hasuo

In recent years, the development of superconducting digital electronics has been making rapid progress. A variety of digital circuits based on Single-Flux Quantum (SFQ) device technology such as high-speed switching circuits for router systems and high-speed sampling oscilloscope systems have been demonstrated. These achievements have been mainly based on the NEDO project, “Development of Low-power Superconducting Network Devices”. This paper describes these recent progress and future prospects of superconducting digital electronics.

Shinichi Yorozu, 義男 亀田, Shuichi Tahara

K. Tanabe, M. Hidaka

Recent progress in single flux quantum (SFQ) device technologies in Japan is described, mainly focusing on those developed in the NEDO "Superconductors Network Device Project" which includes developments of both LTS and HTS devices. The advanced Nb process which consists of a planarized structure with nine Nb layers and 10 kA/cm2Josephson junctions (JJs) has been developed. This enables fabrication of chips including 100,000 JJs and operating frequency up to 80 GHz. We have also developed the CAD tool by which one can generate SFQ circuit layouts including about 400,000 JJs from logic descriptions. For demonstration of a small-scale switch system, a 4 times 4 switch chip, a 117 Gbps multi-chip-module (MCM) technology, and a packaging technology with 32-ch 10 Gbps I/Os to an MCM have been developed. By using the multilayer process with three HTS epitaxial layers and interface-engineered ramp-edge JJs, we demonstrated operation of SFQ circuits with up to 200 JJs. A variety of elementary SFQ circuits such as a T-FF and a 1:2 switch required for an A/D converter front-end circuit have been designed based on a new layout method, and their operation at 30-50 K has been confirmed. A prototype sampler system is being developed for demonstration of bandwidth over 100 GHz for optical input signals.

P. Bunyk, Konstantin K. Likharev, Dmitry Y. Zinoviev