Interferometers are fundamental tools for the study of nature laws and for the precise measurement and control of the physical world. In the last century, the scientific and technological progress has proceeded in parallel with a constant improvement of interferometric performances. For this reason, the challenge of conceiving and realizing new generations of interferometers with broader ranges of operation and with higher sensitivities is always open and actual.Despite the introduction of laser devices has deeply improved the way of developing and performing interferometric measurements with light, the atomic matter wave analogous, i.e. the Bose-Einstein condensate (BEC), has not yet triggered any revolution in precision interferometry. However, thanks to recent improvements on the control of the quantum properties of ultra-cold atomic gases, and new original ideas on the creation and manipulation of quantum entangled particles, the field of atom interferometry is now mature to experience a big step forward.The system I want to realize is a Mach-Zehnder spatial interferometer operating with trapped BECs. Undesired decoherence sources will be suppressed by implementing BECs with tunable interactions in ultra-stable optical potentials. Entangled states will 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. The resulting apparatus will show unprecedented spatial resolution and will overcome state-of-the-art interferometers with cold (non condensed) atomic gases.A successful completion of this project will lead to a new generation of interferometers for the immediate application to local inertial measurements with unprecedented resolution. In addition, we expect to develop experimental capabilities which might find application well beyond quantum interferometry and crucially contribute to the broader emerging field of quantum-enhanced technologies.