Synthesis of precise ac voltage with SINIS Josephson junction arrays

Based on superconductor-insulator-normal metal-insulator-superconductor (SINIS) Josephson junction arrays (JJA), an ac Josephson voltage synthesizer has been successfully developed in National Institute of Metrology (NIM), China. The root mean square (rms) value of generated ac voltage is up to 0.84 V. The frequency of synthesized voltage is up to 200 Hz and the uncertainty of synthesized voltage at 60 Hz is less than 5 parts in 10⁶. This Josephson ac waveform synthesizer mainly relies on a domestic high speed bias source which synthesizes the waveform by prompt switching of bias current for a programmable Josephson array.