Progress report on Electrical Metrology at VSL ( 2015 – 2017 )

DC voltage and Josephson Within the JRPs “Q-wave” (finished in 2016) and its successor “QuADC” (started in 2016) VSL is working on the practical and theoretical aspects of quantum waveform metrology, including generation of arbitrary Josephson signals, the deviation problem of voltage leads at higher frequencies, a Josephson delta-sigma converter, voltage scaling and uncertainty calculations. After initial work on changing the inductance of the voltage leads, the MHz resonance was treated theoretically as a reflected wave problem [1]. A new solution is proposed and the practical details have been simulated, showing that uncertainties on the order of 10 ppm are within reach for frequencies up to 1 MHz [2]. Measurements were performed at PTB in a small cryostat to reduce the deviation significantly [3]. Further work has been performed on the electronics for a Josephson delta-sigma converter [4].