  We describe here the realization of a single electron source similar to
single photon sources in optics. On-demand single electron injection is
obtained using a quantum dot connected to the conductor via a tunnel barrier of
variable transmission (quantum point contact). Electron emission is triggered
by a sudden change of the dot potential which brings a single energy level
above the Fermi energy in the conductor. A single charge is emitted on an
average time ranging from 100 ps to 10 ns ultimately determined by the barrier
transparency and the dot charging energy. The average single electron emission
process is recorded with a 0.5 ns time resolution using a real-time fast
acquisition card. Single electron signals are compared tosimulation based on
scattering theory approach adapted for finite excitation energies.
