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 con tributions from the dynamic phase. We use a cholesteric liquid crystal film as a circular analyser, and a sheet polarizer as a linear analys er, to project each polarization state on the next one. This experimen t can also be viewed as a demonstration of Berry's phase arising from quantum measurements.