Ramsey interferometry with an atom laser.

We present results on a free-space atom interferometer operating on the first order magnetically insensitive |F=1,mF=0〉→|F=2,mF=0〉 ground state transition of Bose-condensed 87Rb atoms. A pulsed atom laser is output-coupled from a Bose-Einstein condensate and propagates through a sequence of two internal state beam splitters, realized via coherent Raman transitions between the two interfering states. We observe Ramsey fringes with a visibility close to 100% and determine the current and the potentially achievable interferometric phase sensitivity. This system is well suited to testing recent proposals for generating and detecting squeezed atomic states.