Direct comparison of a pulse-driven Josephson arbitrary waveform synthesizer and a programmable Josephson voltage standard at 1 volt

We have performed direct ac comparisons between two types of quantum voltage standards, a pulse-driven Josephson arbitrary waveform synthesizer and a programmable Josephson voltage standard, at 1 V rms amplitude and a frequency of 100 Hz. The system architectures for these two Josephson technologies are quite different. However, in the range where their capabilities overlap, they should produce identical results. This comparison under various test conditions is a powerful method for verifying ideal performance of the systems, and exploring a number of potential systematic errors in both measurement methods and system operations.

I. Introduction

Programmable Josephson voltage standards (PJVS) are capable of generating stepwise-approximated reference waveforms with frequencies ranging from sub-hertz to a few kilohertz. Such waveforms, when combined with a sampling voltmeter and the differential sampling method, have been used to determine the root-mean-square (rms) output voltage of a commercially available high spectral-purity voltage source [1]. Recent improvements in superconductive circuit design and pulse generator electronics for the Josephson arbitrary waveform synthesizer (JAWS) have enabled 1 V rms output voltages and have extended the low end of the waveform frequency range down to 1 Hz [2]. With the JAWS and PJVS operating ranges now significantly overlapping, both indirect [3] and direct [4] comparisons between these two types of quantum voltage standards are possible.