This project proposed by a consortium of experimental and theoretical partners, aims to tackle the few-body problem in an ultracold gas of "complex" atoms, specifically lanthanides. Due to the very large magnetic dipolar couplings present in these fluids, their properties differ starkly from those of well-known alkali metal gases. The precise adjustment of pair-wise interactions through external magnetic field scanning reveals a high density of scattering resonances whose origins are not yet fully comprehended, and whose modeling thus far relies on tools from random matrix theory. Our first objective is to experimentally characterize these resonances on a novel platform, and interpret them with a combination of precise computation of long-range interactions combined to parametric short-range interactions implemented in our in-house developed scattering code. We will start by deciphering the interplay between two-body and three-body physics for a polarized gas, and then expand our investigations to the unpolarized case, where more collision channels are available. This comprehension is vital for the integration of spin-orbit coupling in lanthanide gases. Finally, we will expand our study of the few-body problem to a mixture of dysprosium and potassium. By capitalizing on a particular confinement geometry, our objective is to predict and observe novel (stable!) Dy2K trimers, resulting from the combination of dipolar Dy–Dy interactions and the binding provided by the K atom. Such trimers can be viewed as relatives to the (short-lived!) Efimov trimers predicted in nuclear physics and observed with cold atoms. The added value of the project lies in combining high-precision measurements and state-of-the-art numerical calculations to identify the main underlying laws that govern the interactions within these gases. This research will lay the groundwork for exploring new phases of quantum matter with novel composite objects.

Information and communication technology (ICT) has revolutionized major industries, from media and entertainment to financial services, from software to pharmaceuticals. In this context, future ICTs challenges will include massive data processing, high performance computing and security. All these challenges depend critically on frequency and time standards. Accurate clocks are needed for authentication of financial transactions, for network management and synchronization of frequency references in wireless telecommunication, for fast recovery of GPS signals in dense situations, and for synchronization of radar systems. Atomic frequency references are now the best commercially available time and frequency references for timescales longer than few seconds. Future atomic clocks will rely on lasers for their operation, to improve the performances and to reduce the size and consumption. Among them, pulsed coherent population trapping (CPT) clocks, based on the use of two, frequency and phase-locked, lasers are ideal to reach the best performances. Unfortunately, this two-laser scheme limits its practical implementation, in terms of compactness and cost. In this context, the availability, in a compact form, of a single laser delivering two frequencies (a “dual-frequency laser”) would pave the way to a compact high-performance CPT clock. In this project, we propose to realize a compact and high stability pulsed CPT Cesium clock demonstrator based on the original use of a metrological dual-frequency (DF) dual-polarization (DP) laser and to assess unprecedented frequency stabilities, below 5x10-13 at 1 s and 2x10-14 at 1 h, in a volume below 2 Litres, electronic control unit being in an external 19”, 5U case. The dual-frequency dual-polarization laser will consist of a Vertical External Cavity Surface Emitting Laser (VECSEL) in an innovative architecture and will be based on an optimized semiconductor gain structure at 852 nm addressing Cesium D2 line (WP2). An in depth understanding of all limiting noise issues, critical to achieve the high-class stability of final clock demonstrator, will be theoretically and experimentally investigated in WP3. The realization of a dedicated Cesium resonator and an innovative compact and robust electro-optical bench will allow for the final demonstration of clock stability below 5x10-13 at 1 s and 2x10-14 at 1 h, in a target volume below 2 Litres (WP4). This project, led by Thales Research and Technology (TRT), gathers specific and complementary skills of six partners whose expertise are well recognized. Systèmes de Référence Temps-Espace (SYRTE) will bring its unique understanding and skills on ultra-stable atomic clocks and Thales Electron devices (TED) will bring its extensive commercial and technological expertise in the field of atomic clocks. Laser expertise will be covered by TRT for its longstanding background in the field of DF and DP lasers, and Laboratoire Charles Fabry (LCF) for its thorough expertise on optically-pumped VECSEL architecture. Laboratoire Aimé Cotton (LAC) will bring its in-depth understanding of noise and laser dynamics, and Laboratoire de Photonique et Nanostructures (LPN) its expertise on high performance ½-VCSELs design and growth. The objective of CHOCOLA answers perfectly to the societal challenge “Information and communication Society” as it will demonstrate a compact and highly precise clock, one of the key elements of future digital technologies. Innovative concepts investigated within this project will be an important step towards the development of atomic clocks with performance close to a passive hydrogen maser but in a much more compact form. At the end of CHOCOLA, the clock demonstrator will have reached a sufficiently high maturity level (TRL 3) to enter a derisking phase, which will be initiated by TED all along the project through its participation to the clock design and test, as well as its deep knowledge of atomic clock technologies and markets.

The goal of DIFOOL project is to demonstrate an ultra-low noise frequency synthesis based on coupled opto electronic oscillators (COESs) and high-frequency low-noise frequency dividers. MINOTOR project showed that passive or active optical resonators combined with an adapted laser source is a promising way to improve performances of OEOs as they allow a direct oscillation at high frequency within a significantly compact volume, especially when compared to optical-fiber-delay based OEOs. Within MINOTOR, we indeed demonstrated a COEO at 10 GHz, with performances close to that of OEwaves (best commercial product) using French- of European-only components. Quartz-based oscillators are now reaching their limits in terms of performances and availability of high-grade materials. As such, opto electronic oscillators represent a promising alternative for next generation civil or military RF systems (improvement of sensitivity for radar and electronic warfare systems, higher bandwidth for telecommunication and improved stability and precision for positioning and navigation). However, system analysis has shown that those OEOs could greatly benefit from the association with synthesis components well suited to their specificity. Within this “Astrid Maturation” project « DIFOOL », we will realize a compact high-frequency (up to 30 GHz) COEO demonstrator (TRL 4) and a low-noise high-frequency divider (TRL5), which, when combined, will allow the demonstration of a novel frequency synthesis principle with performances well above that of quartz synthesis. This project gathers all the required competencies through the following 5-partner consortium: Thales Research & Technology France (TRT - coordinator), one SME : OSAT, two academic labs (Laboratoire d’Analyse et d’Architecture des Systèmes and Laboratoire Aimé Cotton), and Thales Alenia Space. This project consists of 4 principal tasks. The first one will be devoted to the system analysis for a telecom payload application and the consequent requirements for oscillators and dividers. The 30 GHz COEO demonstrator will be designed and realized (TRL 4) within the second task, as well as, in parallel, a 10 GHz COEO, that will allow us to test different architectures. The third task is devoted to the analysis, design and realization of the high-frequency low-noise frequency divider (TFL 5). At last, the frequency division of the COEO will be demonstrated within the fourth task. Preliminary environmental tests and exploitation scheme will be conducted as well. Expected output for this project are : - Realization of 2 COEOs at 30 GHz and 10 GHz, as 2 compact breadboard at TRL4, exhibiting phase noise level of -120 to -125 dBc/H at 1kHz and -150 dBc/Hz at 100 kHz (floor) - Realization of several high-frequency low-noise frequency dividers, allowing to reach 1GHz (phase noise of 150dBc/Hz at 1 kHz, -170 dBc/Hz at 100 kHz) exhibiting TRL5 at the chip level and TRL4, when packaged in modules. - Demonstration at TRL4 of frequency synthesis combining COEOs and dividers. Those results will be exploited by OSAT -an SME which is specialized in technologies for RF synthesis for spatial applications- under the supervision of TAS -system makers in the space industry- and TRT which will bridge the gap with radar and electronic warfare applications that should benefit as well from those developments.

Wave propagation through complex media leads to signal dispersion, wavefront deformation, interference and attenuation, resulting in poor temporal and spatial focusing. More specifically, the multipath propagation distorts and lengthens the signal. In reverberating media, the distortion is so strong that the initial signal may not be recognized, limiting the efficiency or throughput of the communication. Among the many techniques addressing this issue, time reversal is a particularly powerful and universal technique since it does not require preliminary knowledge of the propagation medium: time reversal actually takes advantage of the multiple scattering that occurs during propagation. It consists in generating a short pulse from one emitter at a spatial position A and recording the detected signal amplitude on a detector at position B. This signal corresponds to the impulse response of the transmission channel between A and B. Then this signal is time-reversed and generated from an emitter placed at B. Due to the invariance of the wave propagation equation by the time-reversal transformation, the wave emitted at B propagates through the medium and refocuses both temporally and spatially at position A. A strong reverberation actually helps the quality of the refocusing. The transmission channel from B to A is now usable by pre-correcting the signal emitted from B. First proposed for acoustic waves and applied to the medical domain, time-reversal-assisted temporal and spatial focusing was later demonstrated with narrowband electromagnetic waves in a reverberating chamber. Applied to wireless communications and radar in natural or urban environments, time-reversal of electromagnetic waves is very appealing because it would greatly improve their directionality and range. However, such applications lead to four demanding performance criteria (phase fidelity, µs signal duration compatibility, GHz bandwidth and sub-ms latency), which are impossible to satisfy simultaneously with the existing state-of-the-art techniques. The ATRAP project aims at developing the first time-reversal architecture for electromagnetic signals fulfilling all the requirements for focusing wideband RF waves in non-stationary complex media. This architecture is fully analog so as to avoid the limitations due to analog-to-digital conversion. It is based on an atomic processor where optical coherent transients are implemented in a rare-earth ion-doped crystal. This project will have interesting applications and developments in electronic warfare and in wireless communications.

The ASPEN project proposes an original analog method to make the spectrum analysis of a microwave signal in a quantitative and instantaneous way. It exploits the unique luminescence properties of the NV centers in diamond in a compact operational system working at room temperature. It meets the requirement of new miniaturized components of increased reliability for hyperfrequency chaines targeting applications in radio-frequency spectrum management, in electronic war, in the field of radars or in electromagnetic characterization of components operated at high frequency. The NV center indeed possesses electronic-spin resonances, situated in the hyperfrequency domain towards 2.88 GHz, which can be detected optically from the fluorescence these color centers emit under optical excitation at the 532 nm wavelength. The application of a magnetic field allows lifting the degeneracy of the spin levels which results in a shift of the resonance frequency. This principle arouses a lot of interest of the scientific community to develop magnetometers and very sensitive nano-detectors. In this project we exploit a reciprocal principle for which a CVD synthesized diamond crystal is submitted to a magnetic field gradient and excited by a pump laser. If a microwave signal of unknown frequency is applied, it is enough to measure the position of the resonance along the axis to know the frequency. This allows reconstructing in real time the complete spectrum of a complex signal from a single image of the space distribution of the fluorescence signal emitted by the NV centers. The project involves three partners. The coordinator is an industrial research laboratory: Thales Research and Technology (TRT). The two other partners are academic: the Laboratoire Aimé Cotton (LAC) and the Laboratory of the Sciences, Materials and Processes (LSPM). These three partners established a strong collaboration for several years through common research projects on the NV centers in diamond, what has already led to numerous publications. On the basis of an already made principal demonstration, they are going to collaborate to realize a spectrum analyzer having a probability of interception of the signal close to 100 % and to optimize the performances in terms of spectral range of analysis, spectral resolution and sensitivity to the microwave signal. The structure of the project is built on these improvement directions. It consists of five tasks. The first one concerns the management of the project (TRT). Besides the management of the project itself, it will be in charge of the dissemination and the valorization of the results. The second one concerns the study of the properties of the NV center under strong magnetic field and the control of the hyperfine structure of the resonance line (LAC). The third one concerns the elaboration of isotopically purified diamond and in which the NV center is oriented (LSPM). The fourth task concerns the coupling between the hyperfrequency field and the NV centers (TRT). The fifth task involves all the partners and has for objective the integration of the elements developed in the previous tasks to end in a spectrum analyzer the expected performances of which are: spectral range of analysis 2 - 20 GHz, spectral resolution better than 500 kHz and sensitivity better than 100 µW.