Fabrication and characterization of superconducting RSFQ circuits
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To meet the specification of the qubits in our laboratory, a 0.4 kA·cm−2 superconducting rapid single flux quantum (RSFQ) circuit was designed and successfully fabricated with an improved Nb-based self-aligned lift-off process. This circuit consists of a single-flux-quantum (SFQ) pulse generator, a Josephson transmission line (JTL) and a T-flip flop (TFF), and it acts as a frequency divider. The values of the inductors in this circuit were extracted using InductEX and the basic function of this circuit was confirmed using the simulation software WRspice before fabrication. After fabrication, the basic parameters of this circuit were measured at ~ 2.5 K in a Janis He-3 cryostat. This work laid the theoretical and experimental basis for the future research on the RSFQ-qubit control circuits.
KeywordsRapid single flux quantum Frequency divider WRspice InductEX
This study was financially supported by the Natural Science Foundation of China (No. 60836001), the State Key Program for Basic Research of China (No. 2011CBA00304) and the Tsinghua University Initiative Scientific Research Program (No. 20131089314). Gang Li and Hao Li would like to thank Zhejiang Tianjingsheng Foundation, China, for student assistantships.
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