A Measurement Method of Critical Current of Un-Shunted Josephson Junction

• Published in: IEEE transactions on applied superconductivity 2023-11, Vol.33 (8), p.1-6
• Main Authors: Zhou, Jian, Wang, Juan, Yao, Yewen, Wang, Yongliang, Wang, Man, Peng, Wei
• Format: Article
• Language: English
• Subjects: Analog circuits; Circuit design; critical current; Critical current (superconductivity); Current measurement; Digital electronics; Electrical resistance measurement; Electromagnetic radiation; Integrated circuits; Josephson junctions; Magnetic shielding; Measurement methods; RSFQ; Superconducting devices; Superconducting integrated circuits; Un-hunted; Uncertainty
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2023.3314855

The measurement of critical current I c , as an important parameter of un-shunted Josephson junctions (JJ), is critical for designing superconductor analog devices or digital circuits. However, precise measurement of I c from current-voltage ( I - V ) characteristic curves often faces difficulties, such as the disturbance of environmental magnetic and electromagnetic waves (EM) noise, which significantly decreases the I c value from ideal critical current I c 0 and increases the uncertainty of I c measured value (>10 %). In this article, a test procedure is proposed for measuring the I-V curve of un-shunted JJ under a magnetic shielding environment, effectively avoiding deficiencies of conventional methods such as poor uncertainty and lower I c measurement value. The uncertainty of I c is investigated based on different superconducting JJs, and the results show that the combined uncertainty of I c is less than 2% (the current step