Atom interferometric detection of the pairing order parameter in a Fermi gas.

We propose two interferometric schemes to experimentally detect in real space the onset of pair condensation in a two-spin-component Fermi gas. Two atomic wave packets are coherently extracted from the gas at different positions and are mixed by a matter-wave beam splitter: we show that the spatial long-range order of the atomic pairs in the gas reflects in the atom counting statistics in the beam splitter output channels. The same long-range order is also shown to create a matter-wave grating in the overlapping region of the two extracted wave packets, grating that can be revealed by a light-scattering experiment.