Ultra High Sensitive Gravi-Gradiometers – GRADUS

The GRADUS project aims at developing a novel type of gravity sensors based on atom interferometry, which will measure in a single device both the gravity acceleration and its gradient. These sensors will combine the appealing features of both absolute atom gravimeters and gravity gradiometers: accuracy and long term stability (perfectly known and stable scale factors, being tied to the wavelength of light beamsplitters), quantum noise limited sensitivity for the gradiometric measurements (thanks to the rejection of common mode vibration noise). Two such sensors will be studied and compared in the frame of this project, which will rely on different interferometer geometries. The first one is an industrial prototype sensor realized by MUQUANS, which is based on mature interferometer techniques (laser cooled free falling atoms and Raman beamsplitters) while the second one, under development at SYRTE, will explore more advanced - but less mature - interferometer methods: ultracold atoms launched in a fountain geometry as the interferometer sources on one hand, large momentum transfer (LMT) beamsplitters on the other hand.
While comparable performances are expected in terms of gravity acceleration measurements for both instruments (which are expected to be ultimately limited by ground vibration noise), the use of these new methods will allow for a drastic improvement of the gravity gradient determination. The precise assessment of their potential for high precision measurements is essential for maximizing the efficiency of the transfer of knowledge we foresee at the end of the project. We indeed anticipate that GRADUS will pave the way to the industrial development of a new generation of sensors, with decisive competitive advantages in terms of measurement capabilities, accuracy and portability.