Basic standards and fundamental constants

Abstract

These introductory remarks to the panel discussion on Basic Standards and Fundamental Constants at the 1988 Conference on Precision Electromagnetic Measurements (CPEM) touch upon two topics: the importance of precision electromagnetic measnrements to the fundamental constants and vice versa; and the idea that recent advances in the determination of a number of constants may have made future least squares adjustments of the constants unnecessary.

The quantum Hall effect as an electrical resistance standard

“…It was the task of the Comité Consultatif d'Électricité (CCE) to recommend such values based on the data available. All the values for R K and K J available by June 1988 in units of the SI were analyzed and the following conventional values were proposed [52]:…”

“…Relative uncertainties with respect to the SI of 2×10 −7 and 4×10 −7 respectively were assigned to the two values. The conventional values were accepted by all member states of the Metre Convention and came into effect as of January 1, 1990. In the case of R K-90 , the chosen value is essentially the mean of the most accurate direct measurements of R K based on the calculable capacitor and the value from the calculation of the fine-structure constant based on the anomalous magnetic moment of the electron [52]. In the most recent least-square adjustment of fundamental constants carried out by the CODATA Task Group on Fundamental Constants [50], R K = 25812.807572 Ω with a relative uncertainty of 3.7 parts in 10 9 was evaluated.…”

Redefinition of the kilogram: a decision whose time has come

“…Ways of redefining the kilogram along the lines discussed in this paper have already appeared in a number of publications [4,[11][12][13][14][15][16][17][18][19][20][21][22], including suggested words for a revised definition. Some possible phrasings for a new definition are presented below, first for a definition that fixes h and then for a definition that fixes N A .…”

Substantially enhanced robustness of quantum Hall effect in graphene on LaAlO3/SrTiO3 heterostructure

“…he quantum Hall effect (QHE), which is the quantization of the Hall conductance to integer multiples of e 2 /h in a two-dimensional electron gas (2DEG) system when subjected to a perpendicular magnetic field, has drawn considerable attention ever since its discovery in the 1980s. 1) As the quantized Hall resistance depends exclusively on fundamental constants and is unaffected by impurities or sample geometry, it has become a new metrological standard with high precision and repeatability for the SI unit ohm, 2) as well as an excellent model system for exhibiting basic physical principles. Furthermore, the non-dissipative nature of quantum Hall edge channels is extremely attractive for applications in low-power and high-speed electronic devices.…”