  In atom interferometry based on light-induced diffraction, the optical
aberrations of the laser beam splitters are a dominant source of noise and
systematic effect. In an atomic gyroscope, this effect is dramatically reduced
by the use of two atomic sources. But it remains critical while coupled to
fluctuations of atomic trajectories, and appears as a main source of noise to
the long term stability. Therefore we measure these contributions in our setup,
using cold Cesium atoms and stimulated Raman transitions.
