HAL Portal IOGS (nstitut d'Optique Graduate School)
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Cold Rydberg atoms for electromagnetic field sensing
No full textInternational audienceRydberg atoms, where one valence electron is promoted to an orbit far away from the nucleus, have very large dipole moments, making them good candidates to be used as very sensitive probes of electromagnetic fields (Fancher et al., IEEE Transactions on Quantum Engineering, 2, 1–13, 2021). Compared to classical antennae, they can be made dielectric, their size is independent of the wavelength to be measured, and they offer the potential to perform self-calibrated measurements, referenced on the properties of the atoms themselves. So far, most of the research in this field has focused on sensing electromagnetic fields with room-temperature (or hotter) Rydberg atoms, where the absorption of a probe laser beam can be made dependent of the microwave field to be measured via the phenomenon of electromagnetically - induced transparency
Experimental Demonstration of a Versatile and Scalable Scheme for Iterative Generation of Non-Gaussian States of Light
No full textInternational audienceNon-Gaussian states of light, such as GKP states, are essential resources for optical continuous-variable quantum computing. The ability to efficiently produce these states would open up tremendous prospects for quantum technologies in general and fault-tolerant quantum computing in particular. This letter demonstrates a versatile method using a quantum memory cavity to overcome the probabilistic nature of the breeding protocols and generate non-Gaussian states at high rates with scalability perspectives. The performances of our experimental setup are illustrated with the generation of Schrödinger cat states of amplitude α=1.63 with a fidelity of more than 60% at a generation rate in the kHz range, which is higher than the state of the art for such states
POSTER: Compact Linked Data for Constrained Web of Things Using CBOR-LD
No full textInternational audienceAbstract—Web of Things (WoT) brings web technologies and knowledge graphs to Internet of Things. JSON-LD, with its popularity in representing and exchanging structured data onthe web, can be a suitable data format for WoT. However, its verbose nature can pose challenges for constrained IoT devices with limited bandwidth, and memory. In this paper, we study CBOR-LD scheme for encoding JSON-LD to a lightweight binary format CBOR (Compact Binary Object Representation). We also study possible optimisations such as using a custom dictionary. We provide a C library and evaluate it on several examples. Results demonstrate that our approach provides savings up to 94% in terms of network overhead for IoT devices
Design of an αZ Wide-field and High Angular Resolution Imaging System in the Visible Spectrum
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Very High Dose Rate Proton Dosimetry with Radioluminescent Silica-based Optical Fibers
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System Description: A Theorem-Prover for Subregular Systems: The Language Toolkit and Its Interpreter, Plebby
No full textInternational audienceWe introduce here a domain-specific language, PLEB. The Piecewise-Local Expression Builder interpreter (plebby) is an interactive system for defining, manipulating, and classifying regular formal languages. The interactive theorem-proving environment provides a generalization of regular expressions with which one can intuitively construct languages via constraints. These constraints retain their semantics upon extension to larger alphabets. The system allows one to decide implications and equalities, either at the language level (with a specified alphabet) or at the logical level (across all possible alphabets). Additionally, one can decide membership in a number of predefined classes, or arbitrary algebraic varieties. With several views of a language, including multiple algebraic structures, the system provides ample opportunity to explore and understand properties of languages
Statistiques du nombre et corrélations en impulsion dans des gaz de Bose interagissants
No full textThis thesis work is dedicated to the study of number statistics and momentum correlations in interacting lattice Bose gases. The Bose-Hubbard model is simulated by loading Bose-Einstein condensates (BECs) of metastable Helium-4 atoms into a three-dimensional (3D) optical lattice. This model exhibits a quantum phase transition from a superfluid to a Mott insulator that is driven by interaction-induced quantum fluctuations. The objective of this work is to comprehend the role of these quantum fluctuations by analyzing their signatures in momentum space. The original detection scheme employed towards this aim provides the single-particle resolved momentum distribution of the atoms in 3D. From such datasets made up of thousands of individual atoms, the number statistics of occupation of different sub-volumes of momentum space yield information about correlation or coherence properties of the interacting Bose gas. At close-by momenta these occupation probabilities permit the identification of underlying pure-state statistics in the case of textbook many-body states such as lattice superfluids and Mott insulators. In the weakly-interacting regime, well-established correlations between pairs of atoms at opposite momenta are observed. Furthermore, these pair correlations are found to decrease in favor of more intricate correlations between more than two particles as interactions are increased. A direct observation of non-Gaussian correlations encapsulates the complex statistical nature of strongly-interacting superfluids well before the Mott insulator phase transition. Finally, at the phase transition, fluctuations of the occupation number of the BEC mode are found to be enhanced, constituting a direct signature of the quantum fluctuations driving the transition. System-size independent quantities such as the Binder cumulant are shown to exhibit distinctive sharp features even in a finite-size system, and hold promise for constituting suitable observables for determining universal behavior when measured in a homogeneous system.Ce travail de thèse est dédié à l'étude des statistiques du nombre et corrélations en impulsion dans des gaz de Bose sur réseaux interagissants. Le modèle de Bose-Hubbard est simulé en chargeant des condensats de Bose-Einstein (BEC) d'atomes d'Hélium-4 métastables dans un réseau optique tridimensionnel (3D). Ce modèle présente une transition de phase quantique d'un superfluide à un isolant de Mott induite par des fluctuations quantiques provoquées par l'interaction. L'objectif de ce travail est de comprendre le rôle de ces fluctuations quantiques en analysant leurs signatures dans l'espace des impulsions. Le schéma de détection original utilisé à cette fin fournit la distribution d'impulsion résolue à l'échelle de l'atome unique en 3D. À partir de ces jeux de données composés de milliers d'atomes individuels, les statistiques du nombre d'occupation de différents sous-volumes de l'espace des impulsions fournissent des informations sur les propriétés de corrélation ou de cohérence du gaz de Bose interagissant. À impulsions proches, ces probabilités d'occupation permettent l'identification de statistiques d'état pur sous-jacentes dans le cas d'états many-body classiques tels que les superfluides en réseau et les isolants de Mott. Dans le régime faiblement interagissant, des corrélations bien établies entre les paires d'atomes à impulsions opposées sont observées. De plus, on constate que ces corrélations entre paires diminuent en faveur de corrélations plus complexes entre plus de deux particules lorsque les interactions sont augmentées. Une observation directe de corrélations non-Gaussiennes encapsule la nature statistique complexe des superfluides fortement interagissants bien en amont de la transition de phase vers l'isolant de Mott. Enfin, lors de la transition de phase, on constate une augmentation des fluctuations du nombre d'occupation du mode du BEC, constituant une signature directe des fluctuations quantiques induisant la transition. Des quantités indépendantes de la taille du système, telles que le cumulant de Binder, présentent des variations abruptes même dans un système de taille finie et semblent prometteuses pour constituer des observables appropriés permettant de déterminer le comportement universel lorsqu'elles sont mesurées dans un système homogène
Quand l’imagerie accompagne la restauration d’œuvres picturales : le cas Soulages
No full textInternational audienceEnregistrer l’apparence des oeuvres d’art moderne est un enjeu majeur car celle-ci évolue dans le temps, et un défi qui exige le développement de nouveaux principes d’imagerie ou d’adapter les principes existants car la couleur n’est pas le seul attribut visuel exploité par les peintres : le brillant, le relief, la texture jouent aussi un rôle essentiel, en témoigne l’analyse en mars 2023 d’une toile de Pierre Soulages
Communications cachées dans des SoC hétérogènes
No full textInternational audienceLes systèmes-sur-puce (SoC, pour leur nom en anglais "System-on-a-Chip") sont des architectures numériques complexes qui incluent plusieurs composants pour le traitement d'informations dans la même puce en silicium. Ils peuvent inclure plusieurs clusters de processeurs, coprocesseurs, accélérateurs matériels, et même un noyau reconfigurable. Cette diversité des composants a pour objectif de permettre au programmeur de distribuer plus efficacement des tâches informatiques en fonction du type de problème. Cependant, cela complique également la tâche de prévention des vulnérabilités architecturales. L’une de ces attaques est la transmission cachée de données via des canaux intrinsèques. Les canaux intrinsèques sont essentiellement le support qui permet à deux composants du SoC d'échanger des informations, par exemple, une mémoire partagée ou une horloge commune. Le problème est que ces canaux peuvent être utilisés par un attaquant pour transférer des informations entre des composants qui ne seraient normalement pas autorisés à communiquer entre eux. Dans cette présentation, nous examinons en détail certains types de canaux intrinsèques et comment ils peuvent être utilisés pour compromettre la sécurité d'un SoC
Design, Processing, and Challenges of Multicomponent Polymer Composites for Improved Electromagnetic Interference Shielding Properties: A Review
No full textInternational audienceAbstract The colossal development of modern electronic devices has inevitably led to an increase in electromagnetic interference (EMI), which has gradually become the fourth most prevalent type of pollution in the world. It is therefore necessary to seek more effective EMI‐shielding materials to overcome the shortcomings of conventional metal‐based materials, which include high density, a lack of mechanical flexibility, low corrosion resistance and costly processing. Conductive polymer composites (CPCs) have attracted more and more attention due to their superiority in many aspects. However, their performances should be further enhanced for future applications. One polymer with only one type of filler often cannot meet this kind of requirement. In this paper, filled polymer materials for EMI shielding are reviewed in terms of their processing, rheological properties, conductivity, and shielding effectiveness. Moreover, the combination of different ingredients and fillers when fabricating multicomponent composites for EMI shielding is also highlighted. The coordination of various components in composites with different structures, including solid, segregated, layered/sandwiched, and foamed/porous structures, is then discussed