  We experimentally realize Rydberg excitations in Bose-Einstein condensates of
rubidium atoms loaded into quasi one-dimensional traps and in optical lattices.
Our results for condensates expanded to different sizes in the one-dimensional
trap agree well with the intuitive picture of a chain of Rydberg excitations.
We also find that the Rydberg excitations in the optical lattice do not destroy
the phase coherence of the condensate, and our results in that system agree
with the picture of localized collective Rydberg excitations including
nearest-neighbour blockade.

Quantum Gases;Quantum Physics