Confined-atom interferometry with Bose-Einstein condensates

We devised experiments in which Bose-Einstein condensates are split by deforming the trap or waveguide potential that confines their motion. Coherent splitting and a prototypical interferometer are demonstrated: two halves of a condensate could be pulled apart by tens of microns and still keep a reproducible relative phase between them; the relative phase after a variable time evolution gave a measure of the potential difference between the locations of the two halves of the condensate. Experimental results from a variety of geometries and set-ups will be compared: atoms were trapped close to microfabricated chips by means of magnetic fields or by optical dipole force in the focus of an infrared laser. Different schemes are analyzed to read the phase of the interferometer. Some of the schemes provide clean proof-of-principle demonstrations of the dynamics of condensate splitting, the role of mechanical excitations and that of thermal atoms. Some other schemes are instead more promising for the realization of compact, portable interferometers, but are subject to technical issues that will have to be considered in building future interferometers.