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.

Optical lattice clocks (OLCs) have progressed rapidly since the initial proposal in 2002, they now outperform even the best microwave clocks realizing the current definition of the SI second, as well as single ion optical clocks, thus becoming the best frequency references. While several groups worldwide are now pushing these new clocks towards their ultimate capabilities, one of the big challenges to face is to take full advantage of the statistical resolution -- or frequency stability -- that is intrinsically possible only with OLCs. Combining the benefit of a resonance with a quality factor of 10^15 and of 10^4 atoms probed simultaneously, a fractional resolution of 10^-17 could be achieved after only one second of integration. This would correspond to an integration time reduced by 6 orders of magnitude with respect to microwave clocks. The research project presented here aims at developing strategies to reach this unprecedented level of resolution, and explore ways to possibly overcome it. Such a resolution is an enabling property for the development and applications of OLCs. The rapid integration time it yields dramatically speeds-up the characterization of systematic effects, which opens the way to characterize the systematic frequency biases with an uncertainty below 10^-18. Also, OLCs offer numerous applications in both fundamental and applied science, in particular in relativistic geodesy, that will be reachable with such a statistical resolution, in particular with the remote comparisons between European using a fiber-based all optical clock network. This project combines two devices. The first one leverages a new generation of ultra-stable Fabry-Perot cavity. The ``clock laser'', stabilized on this new generation cavity, will dramatically push down the current limitation of the frequency stability of OLCs, namely the sampling of the clock laser noise, or Dick effect. But it also opens new challenges that this project aims at addressing. Transporting such a frequency stability to the atomic cloud, at the heart of an OLC, without degradation is, as of yet, unexplored. We propose to demonstrate this stability transfer on two OLC apparatus operated with strontium atoms available at SYRTE, and, as a consequence, to report for the first time on frequency stabilities of the clock in the 10^-17 range after 1 s of integration time. To further explore the clock stability, we will explore ways to combine the two Sr clock systems to optimally sample the residual laser noise by either synchronously interrogating the clock, either by combining them into a dead-time-free clock. As a consequence, the stability of OLCs is expected to reach a fundamental limit, the quantum projection noise (QPN). We will study ways to shrink down this limit by increasing the number of atoms, while keeping under control the effect of cold collisions on the clock accuracy. The second device under study in this project is more exploratory. It aims at bringing to clock techniques that allow for statistical resolutions beyond the QPN. For this, we will make use of cavity-based non-destructive detection systems which will be implemented in the two Sr OLCs. This detection system enables to generate non-classical atomic states whose correlations enable to overcome the QPN. The possibility to use such states, yet unexplored for optical transitions, is well adapted to OLCs, in which a significant number of atoms are confined in an optical lattice. In this project, the USC to uncover the QPN in OLCs, and the cavity-assisted detection system to overcome the QPN, are combined together to demonstrate unprecedented statistical resolution in any frequency standard. This project will demonstrate the possibility to improve OLCs with fundamental physics techniques, and enable the multiple applications of OLC beyond the field of metrology.

The modern world is subject to many natural, man-made and social dangers. Many of them are global in nature, as they threaten the very existence of human civilization. Notable among them is the danger of Earth collision with space bodies of cometary and asteroid nature. At present, there is no doubt about the importance and urgency of this problem. In particular, this is evidenced by a report of the National Science and Technology Council, USA, where the importance to detect and characterize the Near-Earth Objects (NOE) population and to prevent and respond to NEO impacts on Earth is outlined. To protect our planet from the dangers of collision with small bodies, it is first of all necessary to understand from which specific of almost 1 million bodies the Earth needs to be protected. The project aims to make a system to search for possible threats to the Earth from space bodies which will be independent from the ones that are now being operated in NASA and ESA. My project NEOForCE has several objectives: 1) develop new methods for estimating of the impact probability of a small body with the Earth 2) develop methods for obtaining more reliable estimates of orbital parameters and their uncertainties 3) make a search for old observations of known objects. Several web-services at the Institut de Mécanique Céleste et de Calcul des Ephémérides, Paris observatory will be launched that will include: 1) list of potentially colliding with the Earth asteroids and comets with their impact probability values 2) list of possible close encounters of asteroids and comets with the Earth 3) list of old observations made on photographic plates many years ago (even centuries) with the identifications to the objects imaged on them.