  The possibility of non-adiabatic electron pumping in the system of three
coupled quantum dots attached to the leads is discussed. We have found out that
periodical changing of energy level position in the middle quantum dot results
in non zero mean tunneling current appeared due to non-adiabatic
non-equilibrium processes. The same principle can be used for fabrication of a
new class of semiconductor electronic devices based on non-stationary
non-equilibrium currents. As an example we propose a nanometer quantum emitter
with non-stationary inverse level occupation achieved by electron pumping.
