Pancharatnam phase: A tool for atom optics

The Pancharatnam phase belongs to the family of geometric Berry phases. We use this optical phase to control the phase of our atom interferometer, which involves diffraction of the atom wave by laser standing waves in the Bragg regime. The Pancharatnam phase of the reflected beam of one standing wave controls the phase imprinted on the atom wave by the diffraction process. In addition to the expected phase shift, the experimental data exhibits the signature of several defects which are described and quantified. From this analysis, we estimate that a Pancharatnam phase shifter can be reliably used to control the phase of an atom interferometer in the sub-mrad regime. Moreover, as the geometric nature of the Pancharatnam phase renders this phase achromatic, its use in multispecies atom interferometers may be of great interest.