Coherent manipulation of Bose-Einstein condensates with state-dependent microwave potentials on an atom chip

Entanglement-based technologies, such as quantum information processing, quantum simulations and quantum-enhanced metrology, have the potential to revolutionize our way of computing and measuring, and help clarify the puzzling concept of entanglement itself. Ultracold atoms on atom chips are attractive for their implementation, as they provide control over quantum systems in compact, robust and scalable set-ups. An important tool in this system is a potential depending on the internal atomic state. Coherent dynamics in such a potential combined with collisional interactions enables entanglement generation both for individual atoms and ensembles. Here, we demonstrate coherent manipulation of Bose-condensed atoms in a state-dependent potential, generated with microwave near-fields on an atom chip. We reversibly entangle atomic internal and motional states, realizing a trapped-atom interferometer with internal-state labelling. Our system provides control over collisions in mesoscopic condensates, paving the way to on-chip generation of many-particle entanglement and quantum-enhanced metrology with spin-squeezed states.