Study on Quantum Mechanical Limit of Operating Speed in Single-Flux-Quantum Circuits

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H01498
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 21060:Electron device and electronic equipment-related
• Research Institution: Nagoya University
• Principal Investigator: Tanaka Masamitsu 名古屋大学, 工学研究科, 助教 (10377864)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 単一磁束量子回路 / 超伝導デバイス / ビット誤り率 / 低消費電力 / 高エネルギ効率 / 量子ゆらぎ / 窒化ニオブ

Outline of Final Research Achievements

This research aims to pursue logic circuits operating near the quantum mechanical limit by superconductor single-flux-quantum (SFQ) circuits, by which high-speed and low-energy operations are compatible. The study on high-speed operations revealed that complex SFQ circuits could achieve 50-GHz clock frequencies by the developed precise timing design techniques and more than 100 GHz by further optimization based on the current fabrication process. Evaluations of speedup by partially removing shunt resistors, junction scaling, and niobium nitride Josephson junctions were also conducted. The detailed investigation on low-energy operation showed the relationship between energy consumption and operating speed in lowered currents and/or voltages.

Free Research Field

超伝導エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

一般に、論理回路には高速性と消費電力の間にトレードオフの関係があり、両立は困難である。SFQ回路においては、動作速度に対して配線遅延や発熱が律速要因にならないため、本研究で示したような、徹底的な動作速度の向上と低エネルギー化を同時に進めると、究極的には量子力学的不確定性が論理回路の動作速度の限界を決定するのか？という問いに行き当たると考えられる。本研究での成果は、超伝導回路の将来性を議論するために必要不可欠なだけでなく、論理回路の物理的限界の学理解明に向けた第一歩と考えられる。