The quantum metrological triangle experiment, which is under development at the Bureau National de Métrologie-Laboratoire Central des Industries Électriques (BNM-LCIE), consists of applying Ohm's law directly to the quantities related to the single-electron tunnelling (SET) effect, the ac Josephson effect (JE) and the quantum Hall effect (QHE). The goal of this experiment is to test, at a significant level of uncertainty of about 1 part in 108, the coherence of the constants involved in these three quantum phenomena: the Josephson constant KJ, expected to correspond to the ratio 2e/h (where e is the elementary charge and h the Planck constant); the von Klitzing constant RK, in relation to the quantum resistance h/e2; and a new constant QX, defined here as the estimate of e. Moreover, realization of the metrological triangle experiment, combined with the experiment being developed at the NIST aimed at charging a capacitor by means of a SET pump, will give information liable to be taken into account in future adjustments of the fundamental constants without requiring any hypothesis regarding the physical phenomena involved. The combination of these two experiments should yield a new value of RK in ohms of the International System of Units (SI). The broad outlines of our experimental set-up are given, along with the expected uncertainties in both the short and long terms.

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It is theoretically possible to combine several Hall bars in arrays to define new quantum standards with perfectly quantized resistance values. We have thus, for the first time, developed and fabricated novel Quantum Hall Array Resistance Standards (QHARS) made of a large number N (N=100, 50) of Hall bars placed in parallel using a triple connections technique. The Hall resistance of these quantum standards is found to be very well quantized. On the i=2 Hall plateau, the resistance of specific good arrays stays equal to R K /2N within 5 parts in 10 9 for supplying currents up to 2 mA at a temperature of 1.3 K. The mean longitudinal resistance of the Hall bars which constitute the arrays has been determined through the analysis of the array equivalent electrical circuit. This measurement shows that the carrier transport in the Hall bars is dissipationless. This work therefore demonstrates the efficiency of the multiple connections technique and consequently that QHARS are likely to extend the QHE metrological applications.

An interlaboratory comparison of small-current generation and measurement capability is presented with the ultrastable low-noise current amplifier (ULCA) acting as travelling standard. Various measurements at direct currents between 0.16 nA and 13 nA were performed to verify the degree of agreement between the three national metrology institutes involved in the study. Consistency well within one part per million (ppm) was found. Due to harsh environmental conditions during shipment, the ULCA's transfer accuracy had been limited to about ±0.4 ppm. Supplemental measurements performed at PTB indicate that further improvements in accuracy are possible. Relative uncertainties of 0.1 ppm are achieved by applying on-site calibration of the ULCA with a suitable cryogenic current comparator.