Study on a high-precision current multiplier applicable to the quantum current standard

点击翻译按钮获取中文摘要

A small-current 10-time multiplier using one-dimensional arrays of small Al/Al2O3/Al Josephson junctions and based on the quantum-current-mirror effect have been fabricated and tested. It showed the expected 10-time current multiplication function. The accuracy of the multiplication, however, was not good. It was most likely due to the small coupling capacitance. In order to substantially improve the accuracy, a fabrication process of a large coupling capacitance between the arrays has been successfully installed. A 10-time current multiplier with strong coupling has been fabricated using the process. A strongly coupled quantum-current-mirror devices were also fabricated and tested, and the quantitative relationship between the strength of the coupling and accuracy of the current duplication has been obtained. In such devices current induction with 0 bias voltage on the secondary array has been observed for the first time. Moreover, novel reversal of the induced current was observed : the direction of the induced current was the same as the primary current(input current) while applied magnetic field was small and Cooper-pair tunneling was dominant, and it changed to the opposite direction when applied magnetic field was large and quasiparticle(or electron) tunneling was dominant.