  We discuss the possibility to enhance the sensitivity of optical
interferometric devices by increasing its open area using an external field
gradient that act differently on the two arms of the interfer-ometers. The use
of combined electric and magnetic field cancel non linear terms that dephases
the interferometer. This is possible using well defined (typically with n
$\sim$ 20 Rydberg) states, a magnetic field of few Tesla and an electric field
gradient of $\sim$ 10V/cm 2. However this allows only for interaction times on
the order of tens of $\mu$s leading a reachable accuracy of only 1 or 2 order
of magnitude higher than standard light-pulse atom interferometers.
Furthermore, the control of fields and states and 3D trajectories puts severe
limits to the reachable accuracy. This idea is therefore not suitable for
precision measurement but might eventually be used for gravity or neutrality in
antimatter studies.
