  By fixing two fundamental constants from quantum mechanics, the Planck
constant $h$ and the elementary charge $e$, the revised Syst\`eme International
(SI) of units endorses explicitly quantum mechanics. This evolution also
highlights the importance of this theory which underpins the most accurate
realization of the units. From 20 May 2019, the new definitions of the kilogram
and of the ampere, based on fixed values of $h$ and $e$ respectively, will
particularly impact the electrical metrology. The Josephson effect (JE) and the
quantum Hall effect (QHE), used to maintain voltage and resistance standards
with unprecedented reproducibility since 1990, will henceforth provide
realizations of the volt and the ohm without the uncertainties inherited from
the older electromechanical definitions. More broadly, the revised SI will
sustain the exploitation of quantum effects to realize electrical units, to the
benefit of end-users. Here, we review the state-of-the-art of these standards
and discuss further applications and perspectives.
