  We present a novel ab-initio single-electron approach to correlated electron
dynamics in strong laser fields. By writing the electronic wavefunction as a
product of a marginal one-electron wavefunction and a conditional wavefunction,
we show that the exact harmonic spectrum can be obtained from a single-electron
Schr\"odinger equation. To obtain the one-electron potential in practice, we
propose an adiabatic approximation, i.e. a potential is generated that depends
only on the position of one electron. This potential, together with the laser
interaction, is then used to obtain the dynamics of the system. For a model
Helium atom in a laser field, we show that by using our approach, the
high-order harmonic generation spectrum can be obtained to a good
approximation.
