A new cooperative regime of matter-light interactions opened up recently in research of advanced optical technologies. Optical response of strongly interacting dipolar emitters is important in systems ranging from naturally occurring photosynthesis complexes and dye molecule aggregates, to metamaterials in new solar cell and atomic clock designs. Cooperative regime offers potential for strong, collectively enhanced single-photon coupling and nonlinearities, promising new platforms for optical control at a single photon level, precision measurements and quantum simulations. However there is yet no existing methodology for understanding optical response of this complex, many-body systems. Recent progress in control of cold atom ensembles on length scales shorter than the wavelength of the field mediating interaction promises new simple and controllable platform to explore cooperative regime. This action will use unique combination of two complementary cold atom experiments in this regime. The first one achieves small, dense atomic samples; the second provides direct control and measurement of positions and states of individual atoms, together with real-time control of their external and internal degrees of freedom. The applicant will extend this two experiments to explore new control schemes and access new observables. These will be used in benchmarking of knowledge about the cooperative regime, guiding development of new theoretical methods. Applicant’s combination of experimental and theoretical experience in analysis of complex atom-light interactions will be used for high performance computing numerical simulations. During secondment this will be distilled into effective models relaying on new theoretical methodology. Through combined theoretical and experimental work, the applicant will develop and enhance independence and skills required for design and analysis of complex quantum optics experiments with atomic systems that require advanced theoretical insight.

Understanding the light-matter interaction at the quantum level is crucial for numerous applications ranging from quantum metrology to quantum computing and quantum communication. While the interaction of light with a single quantum emitter is well understood, an ensemble of many emitters coupled by a resonant probe is a complex open quantum many-body system. The collective spontaneous emission can be substantially enhanced (superradiance) or suppressed (subradiance), compared to the single emitter case. Subradiant states are particularly intriguing because they constitute an effective storage medium for light, hence for quantum information, and have been indeed proposed as useful tools for quantum communication protocols. Nevertheless, the experimental study of subradiance has been restricted to a few works, in which at most a few percent of the excitations were stored in subradiant modes, resulting in small amplitude signals. The MIDAS GOLD project aims to address the generation of subradiant states in ordered arrays of atoms, with a control at the single-atom level. The action will take place in a running, state-of-the-art experimental system producing ordered arrays of dysprosium atoms in optical tweezers. First, we will implement an original and innovative protocol to controllably generate subradiant states with 2 atoms confined in the same optical tweezer, a first proof of principle demonstration of a bottom-up approach to subradiance. Then, we will prepare arrays of many atoms with subwavelength separations by building an accordion optical lattice, and we will explore protocols to control the storage and release of excitations in subradiant modes of the array. The accomplishment of MIDAS GOLD's objectives and the key upgrades to the existing apparatus will deepen the knowledge of subradiance, paving the way for future applications, and will build up a cutting-edge experimental system for the more general problem of collective light scattering.

This proposal aims at exploring the effect of dissipation in the nascent field of quantum thermodynamics. Two related quantum many-body experiments, realized using recent advances in cold atom quantum simulation, are aimed at understanding under what conditions a quantum system thermalizes. The outgoing phase, at the University of Maryland, USA, studies intriguing quantum effects in interacting, driven-dissipative systems, whereby the collective nature of dissipation prevents the system from reaching static equilibrium, despite strong coupling to the environment. Prof. Porto leads the host team, part of the NIST/UMD group of W.D. Phillips. The return phase, at Institut d’Optique, addresses the important question of dissipation-less thermalization in closed quantum systems of interacting atoms. The team is led by Dr. Browaeys in the CNRS group headed by P. Georges. The hosts provide complementary techniques of optical trapping and cooling for neutral atoms in regular arrays, and both are experts in manipulating strongly-interacting Rydberg atoms. Novel techniques for fast single-atom manipulation derived from adaptative optics are expected to circumvent current limitations: therefore a secondment in the ETHZ team of Prof. Esslinger, Switzerland, is planned for the Experienced Researcher (ER) to learn these techniques. Fundamental questions raised by quantum thermodynamics have recently received a worldwide surge of attention from leading research groups. Along the way, this proposal will develop new methods beneficial to quantum simulation techniques and to more general applications in quantum technologies, one of the major axis supported by the EU. The ER will discover multiple techniques and a wide view of quantum many-body problems, which will strongly benefit his career. Both hosts are world-wide experts in the relevant fields, experienced in welcoming young international researchers, and possess the resources and the will to make of the project a success.

The NanoHeadTail proposes a novel and original approach combining fluorescence microscopy and nanotechnology to resolve the morphological and rheological properties of the brain extracellular space (ECS) at the nanoscale. Current methods allow to determine the local dimensions and fluidity of the ECS, but they do not allow to resolve its structural complexity and are limited to an analysis in 2D. This project proposes the simultaneous monitoring of the position, the translational and rotational diffusion of fluorescent probes over time and in 3D, allowing to determine the volumetric structure, fluidity and inner organization of the ECS locally. For that, a novel type of asymmetric probes will be designed based on the localized functionalization of single-walled carbon nanotubes with fluorescent color centers at their ends, analyzed using a custom cutting-edge fluorescence microscope and tested in live brain tissues from mice models of the Parkinson’s disease. The applicant will bring his strong expertise in the photophysics and chemistry of carbon nanotubes, critical for the preparation of the probes. In parallel, the fellow will gain a high-level hands-on training on optics assembly, super resolution microscopy and single particle tracking, imaging analysis and neurosciences. The project will be performed at the IOGS-LP2N (CNRS/Univ. Bordeaux), a leading French research institution, under the supervision of Dr. Laurent Cognet expert in the single particle tracking of nanoobjects. The proposal contains well-identified work packages which will ensure efficient science development but also project management, career development, training, technology transfer and communication. The fellow’s expertise, the hosting lab, the infrastructure, facilities and the mentoring will guarantee the successful execution of the NanoHeadTail goals and will allow the applicant to reach a high level of professional maturity and to develop his career as an independent researcher.

Volumetric imaging is crucial to perform non-invasive inspection of biological samples or industrial components. Imaging methods must have optical sectioning capabilities and collect light only from one point or plane while rejecting light from other depths. Reconstruction of the whole volume is then obtained by axially moving the sample which may be critical for biological specimens that are immersed in aqueous media and cannot remain motionless during sample scanning. This is the case for organoids, which are multi-cellular aggregates that mimic some functions of organs in vitro. In this context, Light Field Microscopy (LFM) is a promising alternative as it provides 3D imaging in a single snapshot by inserting a micro-lens array in the image plane of a microscope. Angular information is captured for each position of the sample in the focal plane and numerical processing of a 4D light-field image provides volumetric information. Yet, LFM faces two major limitations: the low imaging depth in scattering media due to the lack of optical sectioning capabilities and the trade-off between angular and spatial information as camera sensors have limited number of pixels. The objective of our project is to overcome these two limitations with an augmented version of LFM called LIght FIeld Matrix Microscopy (LIFIMM) that will allow us to perform in-depth imaging in a single snapshot. This achievement implies three specific objectives: 1/ we will increase the amount of information captured in a single LF image using remote scanning instead of specimen displacement; 2 / a matrix formalism of wave propagation will be adapted and applied to LFM to correct aberrations and multiple scattering to image deeper; 3/ we will develop a compact version of the system to be inserted inside an incubator to image organoids for extended periods of time (>15 days).