Atomic phase conjugation

Abstract
We discuss the potential of nonlinear atomic optics to achieve phase conjugation of atomic de Broglie waves. We discuss specifically two examples which help illustrate the analogies and differences between the cases of conventional optics and of atomic optics. In the first case, the upper electronic level of the atoms is adiabatically eliminated, leading to a scalar theory formally identical to conventional four-wave mixing. In the second case, both electronic levels are kept, leading to a vector field for which the 'coupled-mode equations' of phase conjugation involve the coupling between the wavefunctions of the two electronic levels.