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Energy/Space-Efficient Rapid Single-Flux-Quantum Circuits by Using π-Shifted Josephson Junctions
Tomohiro KAMIYA Masamitsu TANAKA Kyosuke SANO Akira FUJIMAKI
IEICE TRANSACTIONS on Electronics
Publication Date: 2018/05/01
Online ISSN: 1745-1353
Type of Manuscript: Special Section PAPER (Special Section on Innovative Superconducting Devices Based on New Physical Phenomena)
energy-efficient circuit, π-shifted Josephson junctions, rapid single-flux-quantum, superconducting spintronics,
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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.