A review of Josephson comparison results

Abstract

In March 2009, the Consultative Committee for Electricity and Magnetism (CCEM) reviewed and re-endorsed its recommendations originally proposed during its 25th meeting (April 2007) for changes in the SI electrical units (Recommendation E-1). Among its considerations, the document stated that the representation of the volt using the Josephson effect and the conventional value of the Josephson constant, K J−90 , has provided practical, accessible, reproducible, low noise and highly linear references worldwide since 1990. We summarize the measurement results of comparisons between Josephson voltage standards that help support this statement, especially concerning the accuracy and the simplicity of the Josephson relationship between voltage and frequency. We also detail a list of influence parameters and the ranges over which the Josephson relationship has been tested.

Single-electron current sources: Toward a refined definition of the ampere

“…In both cases, the experimental error rates could be quantitatively explained by a theory in an intermediate temperature range, where the majority of the errors was due to thermally activated single-junction tunneling processes. The observed low-temperature saturation of the error rates was conjectured to arise from photon-assisted tunneling and cotunneling, considered in this context theoretically, e.g., by Martinis and Nahum (1993) and White and Wagner (1993). Kautz, Keller, and Martinis (2000) explained quantitatively the error rates observed in the earlier experiments performed on pumps with N ¼ 4-7 junctions by including photonassisted processes in the model.…”

“…The ECCS experiment was first suggested by Williams, Ghosh, and Martinis (1992). A single-electron current source is used to charge a cryogenic capacitor C cryo by a known number N S of electrons.…”

Impedance measurements with Programmable Josephson Systems

“…Josephson voltage standards are widely used by national metrology institutes for the realization of the DC volt for decades and can be reproduced with an accuracy of 1 part in 10 9 or even better [1]. Based on conventional Josephson arrays these standards also have been used to measure DC resistance ratios [2].…”

A more fundamental International System of Units

“…When completed, the NIST-4 watt balance will be able to measure mass at the 1-kg level with an absolute uncertainty in the 20-μg range. figure 2) have relative uncertainties 8,9 of a few parts in 10 18 and 10 11 , respectively. Conversely, the gravitational constant G-which might seem a reasonable choice for a fundamental constant more directly linked to the traditional base mechanical units-is inherently difficult to measure (see the article by Clive Speake and Terry Quinn on page 27).…”