10 V programmable Josephson voltage standard circuits using NbN/TiN_x/NbN/TiN_x/NbN double-junction stacks

摘要

Using NbN/TiN_x/NbN/TiN_x/NbN double-junction stack technology we have demonstrated a programmable Josephson voltage standard chip that operates up to 10.16 V output voltage cooled with a two-stage Gifford-McMahon cryocooler. The circuit uses double-junction stacks, where two junctions are fabricated in each stack, in order to integrate 327 680 junctions into a 15.3 mm X 15.3 mm chip. A 1-to-32 microwave distribution circuit is also integrated on the chip. The chip is divided into 22 cells, which perform as an 11-bit digital-to-analog converter. The 21 working cells include 307 200 junctions biased with 16 GHz microwaves at 10.2 K that generated flat voltage steps with current margins greater than 1 mA, which indicates good uniformity of the stacked junctions.