  Theoretical approaches to the photoionization of few-electron atoms are
discussed. These include nonequilibrium Greens functions and wave function
based approaches. In particular, the Multiconfiguration Time-Dependent
Hartree-Fock method is discussed and applied to a model one-dimensional atom
with four electrons. We compute ground state energies and the time-dependent
photoionization by the field a strong laser pulse with two different
frequencies in the ultraviolet.
