Development of vertically stacked Josephson junctions based on high-temperature superconductors

Abstract

Josephson junctions (JJs) based on oxide high-temperature superconductors (HTSs) enable us to realize ultralow-power single-flux-quantum integrated circuits (SFQ-ICs) operating in the terahertz region. Towards this goal, we have been developing vertically stacked JJs suitable for SFQ-ICs, whereas the ramp-edge geometry has been widely employed up to now because of its simple structure. The performance of the vertically stacked JJs demonstrated so far is superior to that of ramp-edge JJs. In this article, we report on the recent development of HTS-JJs.