Resumen:

The diffraction of atomic and molecular beams is typically described by non-trivial solutions of the stationary Schroedinger equation. This has been done traditionally in the absence of external fields. In this talk, the techniques that incorporate a moderate gravitational field are presented. A derivation of the corresponding propagator is provided without approximations, identifying the propagation coordinate with a pseudo-time. Implications on quantum tests of the equivalence principle are briefly reviewed in this light, showing that modified probability densities arise when small corrections of the mass ratio are introduced.