Josephson Computer Technology

I. Kurosawa, Hiroshi Nakagawa, Masahiro Aoyagi +1 more

理化学研究所, 英一 後藤, 嵩 相馬 +2 more

Jie Han, Pieter P. Jonker

A superconducting qubit (or quantum bit), which consists of a micrometer-sized loop with three Josephson junctions, has two persistent currents of opposite direction as its two states. The states of the qubit can be brought into quantum coherence to perform quantum computing. Classical bits can also be obtained from these superconducting loops, making it possible to base a classical computer architecture. We study a novel computing structure based on these Josephson Persistent Current (PC) Bits, starting from elementary logic gates to a Random Access Memory (RAM). The investigation shows that the Josephson PC Bit technology would not surpass semiconductor technology in term of the device density, while it is a promising candidate for unltra-fast memory, which can be integrated with other technologies. The classical computer might also serve as pre and post processor for the quantum computing performed in the heart of the array. The Josephson PC circuits, therefore, seems a good vehicle for the study of the quantum computer paradigm.

Hisao Hayakawa, Seigo Kotani

Juri Matisoo

This paper serves as an introduction to the other logic and memory papers in this issue. Basic concepts of superconductivity and electron tunneling underlying the operation of Josephson devices are outlined and an overview of the literature on the subject is presented, with emphasis on work performed at the IBM research laboratories since the beginnings of the Josephson computer technology program in 1965.

M. B. Ketchen

It is suggested that the possibility now exists of highly leveraging existing semiconductor technology to explore submicron Josephson technology. Some of the opportunities and challenges of such an undertaking are discussed in the context of superconducting quantum interference devices (SQUIDs) and digital applications. In the area of digital Josephson technology, a 50-100-ps cycle-time 64-b RISC (reduced instruction set computer) microprocessor is proposed as a long-term goal. While it is unlikely that one will see a sub-100-ps system like this in the near term, research results supporting its feasibility may ultimately help build the case for the resources needed to produce it. Fabrication has been and will probably continue to be an impediment to the exploration of submicron and deep submicron Josephson technology. Coupling to existing semiconductor fabrication capability should help considerably in this area and should help to lay the groundwork for eventual manufacturing of submicron Josephson products.>