Exploring High-Order Shapiro Steps for Staircase-Approximated Josephson Waves with a Dry-Cooled SNIS Programmable Array

An alternating programmable Josephson voltage standard (AC-PJVS) configured as a multibit digital-to-analog converter has been developed to explore the staircase-approximated waveforms synthesis at frequencies up to the acoustic range. The AC-PJVS setup is based on state-of-the-art modular electronics able to bias individually the subsections of a binary-divided array consisting of 8192 intrinsically shunted SNIS junctions. High order Shapiro steps have been employed for waveform synthesis having amplitude beyond 1 V by finely trimming the SNIS temperature using a two stage cryocooler. Alongside the experiments on the synthesis, the experimental setup was improved for direct comparisons between quantum staircase waves and conventional sine waves based on the use of a room temperature-operating phase sensitive detector and on a differential precision sampling system. Both methods maximize the accuracy obtained from the AC-PJVS synthesizer, allowing, in principle, its use for primary LF AC voltage metrology.