The influence of an external test mass on the phase of the signal of an atom
interferometer is studied theoretically. Using traditional techniques in atom
optics based on the density matrix equations in the Wigner representation, we
are able to extract the various contributions to the phase of the signal
associated with the classical motion of the atoms, the quantum correction to
this motion resulting from atomic recoil that is produced when the atoms
interact with Raman field pulses, and quantum corrections to the atomic motion
that occur in the time between the Raman field pulses. By increasing the
effective wave vector associated with the Raman field pulses using modified
field parameters, we can increase the sensitivity of the signal to the point
where the quantum corrections can be measured. The expressions that are derived
can be evaluated numerically to isolate the contribution to the signal from an
external test mass. The regions of validity of the exact and approximate
expressions are determined.Comment: 23 pages, 3 figures, 2 table