  Cold-atom interferometry is a powerful tool for high-precision measurements
of the quantum properties of atoms, many-body interactions and gravity. Further
enhancement of sensitivity and reduction of complexity of these devices are
crucial conditions for success of their applications. Here we introduce a
multi-path interferometric scheme that offers advances in both these aspects.
It uses coherent coupling between Bose-Einstein condensates in different Zeeman
states to generate an interferometric signal with sharp fringes. We realise
such an interferometer as a compact easy-to-use atom-chip device and thus
provide an alternative method for measurement of the light-atom and
surface-atom interactions.
