Nano-electronics and the metrology of the ampere

Mastery of nanofabrication techniques has enabled physicists to develop electronic devices capable of generating quantized currents. The first electron pumps were based on the single-electron tunneling effect and consisted of fixed tunnel barriers and metal islands. These devices paved the way for single-electron electronics, but can only generate very low currents of no more than 10 pA (10 ^-11 A). Over the past decade, new nanodevices have emerged. They are capable of pumping electrons at higher frequencies, are simpler to use and can be combined in parallel. They can thus become metrological tools with interesting prospects for ampere metrology. In this article, we present the electronic nanodevices that currently seem most promising for achieving this goal.

On the other hand, the world of metrology is preparing for far-reaching changes to the SI system of units. All the national metrology institutes (NMIs) are involved in a landmark project to redefine certain base units on the basis of fixed values of a limited number of fundamental constants. These constants of nature offer considerable advantages and would provide the future SI system with a solid foundation. They describe the universal properties of matter and its interactions, and are independent of any given reference system, as well as its position in space and time. In this context, the use of single-electron nanodevices would make it possible to define a quantum ampere where the unit of electric current would be directly linked to the elementary charge, e.