Quantum trajectory perspective of atom-field interaction in attosecond   time scale
  Here the ionization and high harmonic generation in Hydrogen and Helium by using quantum (hydrodynamic) trajectories is analyzed theoretically. The quantum trajectories allow a self-contained treatment of the electron exchange and correlation effects without introducing ad hoc potentials into the Schrodinger equation. Our approach predicts the correct high harmonic spectra and the attosecond pulses generated by the Helium atom beyond the single active electron approximation. It can be used to study complex multi-electron systems and their interaction with laser field of both high and low intensity. 
Ivan P. Christov