Development of a 1 V pulse-driven Josephson voltage standard

We are developing a pulse-driven Josephson voltage standard with an 1 V_rms output voltage. On our way to the 1 V level we have already reached 307 mV_rms by combining five Josephson arrays with 27,000 junctions in total. Spectrally pure sine waves are achieved for voltages up to 132 mV_rms. At higher voltage we observe harmonics due to interference of compensation signals and non-linearity of the sampler. An excellent direct on-chip comparison at 22 mV_rms demonstrates that perfect quantization is possible with a relative uncertainty of (1.8 ± 2.0) × 10^·8 (k = 2).