Bose-Einstein condensates in dilute atomic gases have been around for almost 5 years now. The first experiments dealt with density related properties of the condensate \textendash things like internal energy, collective excitations, and density profiles. All of these aspects are well described by a non-linear Schrodinger equation, in which the non-linearity arises from repulsive potentials between 87Rb atoms that make up the condensate. While interesting in their own right, these experiments had little to do with the \textquotedblleftstrangeness\textquotedblright of a condensate as a macroscopic
quantum object.
In this work the new era of condensate physics is described. These are experiments mainly concerned with the quantum phase and coherence properties. We have constructed a robust system for creating internal-state superpositions, with the ability to image the interference between them. Our first observations show how condensates, initially created with a well-defined phase, remain coherent, unlike a sample of thermal atoms. We have devised schemes to spatially manipulate the relative phase between two condensates in unique ways which brings about very unexpected behavior. By choosing a very specific scheme we were able to create a vortex state and measure the unique 2π phase winding, making this a very simple system for utilizing quantum control.
}, year = {1999}, publisher = {University of Colorado Boulder}, }