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Direct DC 10 V comparison between two Programmable Josephson Voltage Standards made of Niobium Nitride (NbN)-based and amorphous niobium silicon (NbxSi1-x)-based Josephson Junctions



Alain Rufenacht, Stephane Solve, M Maruyama, Chiharu Urano, Nobu Kaneko


For the first time, the BIPM’s new transportable programmable Josephson voltage standard (PJVS) has been used for an on-site comparison at the National Metrology Institute of Japan (NMIJ), the National Institute of Advanced Industrial Science and Technology (AIST) (NMIJ/AIST, hereafter, called just NMIJ unless otherwise noted). This was also the first time that an array of amorphous niobium silicon NbxSi1x Josephson junctions, developed by the National Institute of Standards and Technology (NIST), was directly compared to an array of niobium nitride (NbN)-based junctions (developed by the NMIJ in collaboration with the Nanoelectronics Research Institute (NeRI), AIST). The results showed that nominally identical voltages produced by both systems agreed within 5 parts in 1012 (0.05 nV at the level of 10 V) with a combined relative uncertainty of 7.9  10−11 (0.79 nV). The low side of the NMIJ apparatus is, by construction, referred to the ground potential. An analysis of the systematic errors due to the leakage current to ground, when using this configuration, was conducted. The influence of a multi-stage low-pass filter installed at the output measurement leads of the NMIJ primary standard was also investigated. The number of capacitances in parallel in the filter and their insulation resistance has a direct impact on the amplitude of a systematic voltage error introduced by the leakage current even if the current does not necessarily return to ground. The filtering of the output of the voltage leads of the PJVS has the positive consequence of protecting the array from external sources of noise. Current noise when coupled to the array reduces the width of the quantized voltage steps. In the present work, the voltage error induced by the leakage current in the filter is one order of magnitude larger than the evaluated voltage error due to a loss of quantization in the absence of all filtering.


Josephson arrays, Voltage measurement, Standards, Superconductor-normal-superconductor devices, Superconducting devices, Superconducting integrated circuits


Rufenacht, A. , Solve, S. , Maruyama, M. , Urano, C. and Kaneko, N. (2018), Direct DC 10 V comparison between two Programmable Josephson Voltage Standards made of Niobium Nitride (NbN)-based and amorphous niobium silicon (NbxSi1-x)-based Josephson Junctions, Metrologia, [online], (Accessed June 18, 2024)


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Created March 15, 2018, Updated November 10, 2018