Quantum voltage standards based on ac Josephson effect are in use in metrology since just a few years after the discovery of the physical effect. The role of quantum standards is now crucial following the SI redefinition in 2019: electrical units are now defined in function of the fundamental constants e (elementary charge) and h (Planck’s constant). The extremely low uncertainty in dc measurements, that can be below 1 nV/V at 10 V, is stimulating research to extend application to ac and signals arbitrarily changing with time. Approaching the dc accuracy is challenging, however. The two main technologies used for the generation of non-steady voltage signals are programmable and pulsed Josephson junction arrays. In the following we discuss the main advancements obtained with both technologies and the most recent developments, in particular the advantages of He-free device cooling techniques.

Direct comparison of quantum Hall resistance in the same or different materials requires demanding experimental resources, such as two separate cryostats or a specially designed dual-socket probe operating far below the temperature of liquid helium. Here we experimentally demonstrate an efficient direct comparison of quantum Hall resistance in graphene and gallium arsenide/aluminium gallium arsenide heterostructure in liquid helium at 4.2 K with a standard probe from the practical point of view. To perform the direct comparison with one probe, we stacked two Hall devices with a printed circuit board and mating pins and employed a gallium arsenide Hall device with a high electron density. The direct comparison shows that the relative difference in quantized Hall resistance between the two materials in liquid helium is as small as 5 nΩ/Ω.

Nowadays, digital solutions are dominant in almost all industry related activities and applications, especially in the metrology domain. Digital Calibration Certificates (DCCs) will soon replace both paper and electronic calibration certificates. This is due to the fact that electronic files can be communicated instantly and securely to the customer and are machine readable. However, DCCs require a digital security and software infrastructure to fulfill the current ‘analogue’ processes of authentication and validation that secures traceability of the measurements. In this work, we present the efforts at SASO-NMCC of Saudi Arabia towards modifying its work processes for replacing analog calibration certificates with the modern DCCs. A smart e-infrastructure for issuing DCCs is proposed. The system communicates with customers and national standards communities via metrology clouds (e.g. SASO Cloud and GULFMET cloud). Our proposed system is also able to be compatible with recent artificial intelligence applications, the Internet of Things (IoT) and future completely digital metrology.

Digital transformation is challenging and changing the basic pillars of the quality infrastructure – metrology, standardization, accreditation, conformity assessment and market surveillance. The individual organizations are thus preparing and implementing digital transformation strategies to address the novel challenges and to make use of the new opportunities and possibilities. However, most of these developments still have a human- centric, document-based point of view. In this contribution we outline how the individual developments can be interconnected in the future and what a document-less digital quality infrastructure may look like.

The DCC enables an updatable and thus improvable uncertainty budget. A direct benefit of the updatable DCC (UDCC) for the device under test (DUT) and thus for the end users would be the transfer of improvements with respect to the uncertainties of the primary standards. An illustrative application example is the new realization of the Pascal via quantum-based methods, such as primary standards using Fabry-Perot (FP) refractometry. This novel realization is based on traceability by means of frequency measurements and it is expected that the uncertainties of the relevant fundamental quantities, such as the polarizability and virial coefficients of the gases used, will improve noticeably on a regular basis over the next years. The resulting reduction in the uncertainties of all corresponding primary standards can be passed on directly to the end user due to the advantages of the machine-readable (and potentially machine-interpretable) digital calibration certificate which makes it well updatable.