Energy/Space-Efficient Rapid Single-Flux-Quantum Circuits by Using π-Shifted Josephson Junctions

作者：Tomohiro Kamiya, Masamitsu Tanaka, Kyosuke Sano, Akira Fujimaki · 发表于：IEICE Transactions on Electronics · 年份：2018 · DOI：10.1587/transele.e101.c.385 · 被引用次数：44 · 研究领域：Physics of Superconductivity and Magnetism、Quantum and electron transport phenomena、Magnetic and transport properties of perovskites and related materials

We present a concept of an advanced rapid single-flux-quantum (RSFQ) logic circuit family using the combination of 0-shifted and π-shifted Josephson junctions. A π-shift in the current-phase relationship can be obtained in several types of Josephson junctions, such as Josephson junctions containing a ferromagnet barrier layer, depending on its thickness and temperature. We use a superconducting quantum interference devices composed of a pair of 0- and π-shifted Josephson junctions (0-π SQUIDs) as a basic circuit element. Unlike the conventional RSFQ logic, bistability is obtained by spontaneous circular currents without using a large superconductor loop, and the state can be flipped by smaller driving currents. These features lead to energy- and/or space-efficient logic gates. In this paper, we show several example circuits where we represent signals by flips of the states of a 0-π SQUID. We obtained successful operation of the circuits from numerical simulation.