  The edge channels of the quantum Hall effect provide one dimensional chiral
and ballistic wires along which electrons can be guided in optics like setup.
Electronic propagation can then be analyzed using concepts and tools derived
from optics. After a brief review of electron optics experiments performed
using stationary current sources which continuously emit electrons in the
conductor, this paper focuses on triggered sources, which can generate
on-demand a single particle state. It first outlines the electron optics
formalism and its analogies and differences with photon optics and then turns
to the presentation of single electron emitters and their characterization
through the measurements of the average electrical current and its
correlations. This is followed by a discussion of electron quantum optics
experiments in the Hanbury-Brown and Twiss geometry where two-particle
interferences occur. Finally, Coulomb interactions effects and their influence
on single electron states are considered.
