Investigation of quantum frequency up-conversion process in SIS junctions and its application

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H03881
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 29:Applied condensed matter physics and related fields
• Research Institution: National Astronomical Observatory of Japan
• Principal Investigator: Uzawa Yoshinori 国立天文台, 先端技術センター, 教授 (00359093)
• Co-Investigator(Kenkyū-buntansha): 小嶋 崇文 国立天文台, 先端技術センター, 准教授 (00617417)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: SIS接合 / アップコンバージョン利得 / Nb/AlOx/Nbミキサ / マイクロ波増幅 / 低雑音 / 低消費電力 / インピーダンス整合

Outline of Final Research Achievements

We have established a simulator to theoretically calculate the frequency up-conversion characteristics of a superconductor-insulator-superconductor (SIS) junction, which predicted possible conversion gain and quantum noise performance. We measured the up-conversion characteristics of an Nb/AlOx/Nb mixer fabricated at the National Astronomical Observatory of Japan, and succeeded in experimentally observing the conversion gain for the first time in the world as far as we know. Furthermore, we tried microwave amplification by connecting the SIS up-converter and the SIS down-converter in series, which demonstrated the noise temperature of less than 10 K and the gain of more than 10 dB comparable to a typical semiconductor amplifier. The power consumption was estimated to be about 1 micro-watt which is 3-4 orders of magnitude lower than that of the amplifier.

Free Research Field

超伝導エレクトロニクス

Academic Significance and Societal Importance of the Research Achievements

これまで高感度周波数ダウンコンバータ（ヘテロダインミキサ）として広く利用されてきたSIS接合の新たな応用可能性を見出すために、理論的、実験的にアップコンバータとしての性能を世界に先駆けて明らかにし、さらに原理的に全く新しい高周波増幅器への応用に成功したことで、超伝導エレクトロニクス分野に新たな扉を開いたと言える。超低消費電力・低雑音増幅器を必要とする次世代の大規模超伝導量子コンピュータや広視野電波天文観測装置などの実現に向け、大きな貢献が期待される。