The system we want to realize is a Mach-Zender spatial interferometer operating with trapped Bose-Einstein condensates (BECs). Phase diffusion caused by interatomic collisions are suppressed implementing BECs with tunable interactions in ultra-stable optical potentials. Entangled states can be used to improve the sensitivity of the sensor beyond the standard quantum limit to ideally reach the ultimate, Heisenberg, limit set by quantum mechanics. Our project aims at developing a sensor with unprecedented spatial resolution able to compete with, and eventually overcome, state-of-the-art interferometers with cold (non condensed) atomic waves.