The ampere is the standard unit of electrical current, but its definition is arbitrary. Physicists would like to redefine the ampere in terms of the motion of a small number of electrons, so that the standard is based on the unchanging charge carried by the fundamental particles.
Ville Maisi at the Centre for Metrology and Accreditation in Espoo, Finland, and his colleagues in Finland and Japan bring such a definition closer. The team uses transistors that act as electron 'turnstiles'—allowing just one of the particles through at a time. Putting ten such gates in parallel generates a measurable current that could potentially be used to define a more precise ampere, the authors say.