Single-flux quantum electronics

Kiyotaka Nakajima

Fujimaki Akira

Pascal Febvre

Rassul Bairamkulov, Mingfei Yu, Giovanni De Micheli

Rapid single-flux quantum (RSFQ) is one of the most advanced cryogenic superconductive electronics technologies. With orders of magnitude smaller power dissipation, RSFQ is an attractive technology for cloud computing, aerospace electronics, and high-speed interfacing with quantum computing systems. Technological challenges however greatly complicate the realization of VLSI-complexity RSFQ systems. For example, gate-level pipelining in SFQ systems incurs a significant area overhead due to the need for path balancing. This issue is particularly detrimental to SFQ systems due to the limited layout density of RSFQ systems.

Valeri Mladenov

Abstract:- In this paper we consider the Rapid Single-Flux Quantum (RSFQ) circuits with reduced Josephson current density and especially deal with one of the basic building blocks of these electronics- the DC to SFQ converter. For future promising RSFQ applications the critical current of the Josephson junctions should be reduced (by reduction of Josephson current density) to several µA, resulting into values of the interferometer’s inductance of several hundreds of pH. Such large inductances cannot be efficiently realized and we utilize an approach for substitution of inductances by arrays of classical Josephson junctions operating in nonswitching mode. We investigate the classical DC to SFQ converter and based on the utilized approach we design a new schematic with reduced Josephson current density. The circuit is optimized with respect to yield and fabrication margins of the design parameters. Key-Words:- Superconductivity, Rapid Single-Flux Quantum (RSFQ) electronics, Josephson junction, DC to SFQ converter. 1

Oleg A. Mukhanov

Key digital circuits for signal processing with tens of gigahertz speed and a few microwatts power dissipation have been recently demonstrated using a simple, 2 /spl mu/m linewidth process. These are the fastest digital circuits reported to date. These circuits use novel rapid single flux quantum (RSFQ) technology that takes advantage of the fundamental properties of superconductivity. In this technology, data and clock are picosecond-long quantized voltage pulses corresponding to the transfer of single magnetic flux quanta, /spl Phisub 0/=h/2e=2 mVps. These SFQ pulses are regenerated at each gate and are processed by circuits comprised of overdamped Josephson junctions interconnected via microstrip inductances. The inherent internal memory of all RSFQ gates (primarily flip-flops), combined with high switching speed, makes serial, bit-pipelined circuit design advantageous. This paper presents experiments in RSFQ digital circuits, including an N/spl times/8b serial multiplier, and on-chip test systems based on RSFQ shift registers and on SFQ samplers. They enable test and study of RSFQ circuits at full GHz speed while communicating with semiconductor electronics at low speed.>