After more than 25 years of research, cold-atom inertial sensors based on atom interferometry have reached sensitivity and accuracy levels competing with or beating inertial sensors based on different technologies. These sensors have several applications in geophysics, inertial sensing, metrology and fundamental physics. Enlarging their range of applications requires to constantly push further their performances in terms of sensitivity, stability, accuracy, dynamic range, compactness or robustness, ease-of-use, and cost. More than 20 research groups and 4 companies worldwide are actively developing cold-atom inertial sensors for different applications, and investigating techniques to improve their performances. Regarding sensitivity improvements, the mostly studied methods involve large momentum transfer beam splitters for matter waves, long interrogation times, operations with ultra-cold atomic sources, and advanced detection or preparation methods. Other teams address specifically the concerns of simplifying the architecture of such sensors, pushing their dynamic range and/or sampling frequency for field applications, and improving their robustness. The objective of this ANR project is to pursue this research effort by studying new and generic atom interferometry techniques providing performance improvements, to characterize these techniques in a state-of-the-art instrument, and to use this instrument for precision inertial measurements. The project will proceed along 3 lines of research. First, we will pursue generic instrumental developments on a state-of-the-art cold-atom gyroscope-accelerometer located at the SYRTE laboratory. We will develop the concept of interleaved atom interferometry, which allows to benefit from both high sensitivity and high bandwidth. High bandwidth will represent a key improvement for instruments aiming at measuring signals varying on second time-scales or faster, such as in inertial navigation or gravitational wave detection. We will also study the hybridization of cold-atom sensors with optical seismometers in order to reach the quantum projection noise limit in large-area atom interferometers, which are traditionally limited by inertial noise sources. These investigations will lead to a cold-atom gyroscope with a sensitivity and a stability more than ten times better than that of current best fiber-optics gyroscopes. Second, we will use the cold-atom sensor for a test of fundamental physics. We will put at test the models of gravitational decoherence, which predict that macroscopic quantum superpositions decohere in the presence of the gravitational field generated by a local source mass. Third, we will study the performance improvement offered by using an optical resonator to interrogate the atoms. We aim at improving by one order of magnitude the interferometer scale factor with large momentum transfer beam splitters performed in a large mode, top-hat, optical resonator. These investigations will determine possible new designs for cold-atom sensors occupying a reduced volume and operating at higher sampling frequencies, two key points for field applications of quantum sensors. This project will require a multi-disciplinary approach involving expertise in metrology and instrumentation, atomic physics, precision optics, signal processing, geophysical modelling and gravitational physics. In a highly competitive landscape, this project will allow a young researcher to foster key developments in atom interferometry and thereby to strengthen the position of France and Europe in this rapidly evolving field of quantum sensors and metrology. Besides the expected impact in atomic physics, geophysics, fundamental physics and inertial guidance, the know-how acquired in this project will impact the industrial development of cold-atom inertial sensors in France, in competitive sector where the SYRTE team can establish as a leader.

The objective of the CoQuIA project is to optimize the efficiency and robustness to environmental variations of laser beamsplitters in atomic interferometers, through novel pulse shaping methods that take advantage of unconventional optics and optimal quantum control methods. The new methods and key technologies that we propose to develop within the framework of this project, as well as the intimate knowledge of their limitations in terms of performance, will allow the development of atomic sensors which will be better able to meet the expectations of users in the most demanding applications, in particular for on-board applications, such as inertial navigation.