The pancharatnam phase as a strictly geometric phase: A demonstration using pure projections

We describe an interferometer based on the Pancharatnam phase in which the extra phase introduced is of purely geometric origin, with no contributions from the dynamic phase. We use a cholesteric liquid crystal film as a circular analyser, and a sheet polarizer as a linear analyser, to project each polarization state on the next one. This experiment can also be viewed as a demonstration of Berry's phase arising from quantum measurements.