Design and test of component circuits of an integrated quantum voltage noise source for Johnson noise thermometry

• We demonstrated RSFQ digital components of a new quantum voltage noise source.
• A pseudo-random number generator and variable pulse number multiplier are designed.
• Fabrication process is based on four Nb wiring layers and Nb/AlOx/Nb junctions.
• The circuits successfully operated with wide dc bias current margins, 80–120%.

We present design and testing of a pseudo-random number generator (PRNG) and a variable pulse number multiplier (VPNM) which are digital circuit subsystems in an integrated quantum voltage noise source for Jonson noise thermometry. Well-defined, calculable pseudo-random patterns of single flux quantum pulses are synthesized with the PRNG and multiplied digitally with the VPNM. The circuit implementation on rapid single flux quantum technology required practical circuit scales and bias currents, 279 junctions and 33 mA for the PRNG, and 1677 junctions and 218 mA for the VPNM. We confirmed the circuit operation with sufficiently wide margins, 80–120%, with respect to the designed bias currents.