Mutual validation of PTB’s Josephson and INRIM-POLITO’s electronic impedance bridges for the realization of the farad from graphene quantum standards

In the International System of Units, the impedance units can be realized from the quantum Hall effect, a macroscopic quantum phenomenon producing quantized resistance values. Established experiments employ individual GaAs devices [1], but novel materials such as graphene can be exploited to realize the units with relaxed experimental conditions. Furthermore, simple traceability chains can be implemented with novel digital impedance bridges. By combining novel digital impedance bridges and graphene quantum standards, an easy-to-operate and affordable impedance standard has been developed in the framework of the European EMPIR project 18SIB07 GIQS (Graphene Impedance Quantum Standards). An onsite comparison of an electronic and a Josephson impedance bridge developed at INRIM (Istituto Nazionale di Ricerca Metrologica, Italy) together with POLITO (Politecnico di Torino, Italy) and at PTB (Physikalisch-Technische Bundesanstalt, Germany), respectively, were organized for their mutual validation in the realization of the farad from graphene quantum standards. The result of the comparison and the last progresses of the GIQS project are here presented.