  We propose an interferometric method to probe pair correlations in a gas of
spin-1/2 fermions. The method consists of a Ramsey sequence where both spin
states of the Fermi gas are set in a superposition of a state at rest and a
state with a large recoil velocity. The two-body density matrix is extracted
via the fluctuations of the transferred fraction to the recoiled state. In the
pair-condensed phase, the off-diagonal long-range order is directly reflected
in the asymptotic behavior of the interferometric signal for long interrogation
times. The method also allows to probe the spatial structure of the condensed
pairs: the interferometric signal is an oscillating function of the
interrogation time in the Bardeen-Cooper-Schrieffer regime; it becomes an
overdamped function in the molecular Bose-Einstein condensate regime.
