Quantum Electrical Standards

Abstract

AbstractElectrical metrology entered a quantum era on 1 January 1990, the date on which the Comité International des Poids et Mesures (CIPM) recommended that the quantum Hall effect (QHE) and the Josephson effect (JE) be taken as the primary standards of resistance and voltage, respectively. These phenomena link these electrical quantities directly to the Planck constanthand the elementary chargee, through the von Klitzing constantRKand the Josephson constantKJ, which are presumably equal toh/e2and 2e/h, respectively. They insure for the corresponding units, the ohm and the volt, a high level of reproducibility and a unique representation all over the world. Moreover, with the development of electromechanical systems such as a calculable capacitor or a watt balance, the use of these quantum standards allows the determination of the key constants of the quantum mechanics, such as the fine structure constant α = μ0c/(2h/e2) and the Planck constant. Similarly, the Coulomb blockade of single‐electron tunneling could be a basis for a quantum current standard whose amplitude is equal to the product of the elementary charge and a frequency. It provides the third leg of the quantum metrological triangle and makes a direct determination of the elementary charge possible. This chapter gives an overview of the quantum Hall resistance standards and the Josephson voltage standards and the prospect of new quantum standards based on the Coulomb blockade. The experiments aimed at determining the involved fundamental constants and at checking their consistency in terms of the Planck constant and the elementary charge are described and discussed.