  Geometric phase has been proposed as one of the promising methodologies to
perform fault tolerant quantum computations. However, since decoherence plays a
crucial role in such studies, understanding of mixed state geometric phase has
become important. While mixed state geometric phase was first introduced
mathematically by Uhlmann, recently Sjoqvist et al. [Phys. Rev. Lett. 85(14),
2845 (2000)] have described the mixed state geometric phase in the context of
quantum interference and shown theoretically that the visibility as well as the
shift of the interference pattern are functions of geometric phase and the
purity of the mixed state. Here we report the first experimental study of the
dependence of interference visibility and shift of the interference pattern on
the mixed state geometric phase by Nuclear Magnetic Resonance.
