HAL Portal IOGS (nstitut d'Optique Graduate School)
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Nanostructures de Pérovskite à base d’halogénure de plomb comme sources de photons uniques
No full textThe generation of pure and indistinguishable photon states is essential for quantum photonic devices, which are expected to enable secure communication and enhanced computational capabilities. Lead halide Perovskite nanocrystals have become an attractive platform for photovoltaics and light emitting devices and more recent research has focused on lead halide perovskite nanostructures as single-photon emitters. The first part of this thesis investigates the photophysical properties of inorganic colloidal perovskite nanorods of cesium lead halide using magneto-photoluminescence and time-resolved spectroscopy. The results reveal a strong dependence of the fine structure on nanorod size and aspect ratio, with emission from a shortlived sublevel concentrating the oscillator strength into a highly polarized, narrow zero-phonon line. Single-photon emission is demonstrated by g(2) correlation function measurements, showing strong antibunching. Fourier spectroscopy analysis of decoherence time and its temperature dependence shows photon coherence up to the limit set by the lifetime of the excited state. Photon indistinguishability in two-photon Hong-Ou-Mandel interference experiments is demonstrated with a visibility up to 60%. The second part explores a new platform of buried organic lead halide perovskite quantum dots of FAPbI3−xBrx embedded in a 3D perovskite thin film of FAPbI3 via flash annealing. This integration mitigates issues due to surface interactions usually found in colloidal nanostructures, achieving performance on par with colloidal emitters. Using magneto-photoluminescence spectroscopy, a bright triplet exciton structure is revealed with a red shifted dark singlet and trion state. The emission spectra show lines of good stability and narrow sub ∼ 130μeV linewidths, and single photon antibunching. This system holds great promise as a low-cost, on-chip single-photon source for quantum devices.La génération d’états de photons purs et indiscernables est cruciale pour le développement des dispositifs photoniques quantiques, qui devraient permettre des communications sécurisées et des capacités de calcul accrues. Les nanocristaux de pérovskite à halogénure de plomb sont devenus une plateforme prometteuse pour les applications photovoltaïques et les dispositifs d’émission lumineuse. Plus récemment, l’attention s’est portée sur les nanostructures de pérovskite à halogénure de plomb en tant qu’émetteurs de photons uniques.La première partie de cette thèse étudie les propriétés photophysiques des nanorods colloïdaux inorganiques de pérovskite à base de césium et de plomb, au moyen de spectroscopie de magnétophotoluminescence et de spectroscopie résolue en temps. Les résultats révèlent une forte dépendance de la structure fine à la taille et au rapport d’aspect des nanorods, avec une émission issue d’un sousniveau à durée de vie courte concentrant la force d’oscillateur dans une raie de zéro phonon étroite et fortement polarisée. L’émission de photons uniques est confirmée par des mesures de la fonction de corrélation g(2), mettant en évidence un antibunching marqué. L’analyse par spectroscopie de Fourier du temps de décohérence et de sa dépendance à la température montre une cohérence photonique approchant la limite imposée par la durée de vie de l’état excité. L’indiscernabilité des photons est démontrée dans des expériences d’interférence Hong-Ou-Mandel à deux photons, avec une visibilité atteignant 60 %. La seconde partie explore une nouvelle plateforme fondée sur des boîtes quantiques de pérovskite organique à halogénure de plomb de type FAPbI3−xBrx, enfouies dans un film mince 3D de pérovskite FAPbI3 grâce à un recuit éclair. Cette intégration permet de surmonter les limitations liées aux interactions de surface typiques des nanostructures colloïdales, tout en atteignant des performances comparables à celles des émetteurs colloïdaux. La spectroscopie de magnétophotoluminescence révèle une structure excitonique triplet brillante, accompagnée d’un état singulet sombre et d’un état de trion décalés vers le rouge. Les spectres d’émission présentent des raies stables et étroites, de largeur inférieure à ∼ 130μeV , ainsi qu’un antibunching photonique clair. Ce système représente une solution prometteuse et peu coûteuse pour des sources de photons uniques intégrables sur puce dans les technologies quantiques
Numerical and Experimental Study of Mode Coupling Due to Localised Few-Mode Fibre Bragg Gratings and a Spatial Mode Multiplexer
No full textInternational audienceMode conversion effects in Fibre Bragg Gratings (FBGs) are widely exploited in applications such as sensing and fibre lasers. However, when FBGs are inscribed into Few-mode optical Fibres (FMFs), the mode interactions become highly complex due to the increased number of guided modes, rendering their practical use difficult. In this study, we investigate whether the addition of a spatial mode multiplexer, used to selectively excite specific fibre modes, can simplify the interpretation and utility of few-mode FBGs (FM-FBGs). We focus on point-by-point (PbP)-inscribed FBGs, localised with respect to the transverse cross-section of the fibre core, and study their interaction with a range of Hermitian Gauss input modes. We present a comprehensive numerical study supported by experimental validation, examining the mechanisms of mode coupling induced by localised FBGs and its implications, with a focus on sensing applications. Our results show that the introduction of a spatial mode multiplexer leads to slight simplification of the FBG transmission spectrum. Nevertheless, significant simplification of the reflection spectrum is achievable after modal filtering occurs as the reflected light re-traverses the spatial mode multiplexer, potentially enabling WDM monitoring of FM-FBGs. Notably, we report a novel approach to multiplexing FBGs based on their transverse location within the fibre core and the modal content initially coupled into the fibre. To the best of our knowledge, this multiplexing technique is yet to be reported
Characterization and Radiation Testing of an Embedded, Distributed Fiber Dosimetry System for Space Applications
No full textInternational audienc
Implémentation Efficiente de Fonctions de Convolution sur FPGA à l'Aide de Blocs Paramétrables et d'Approximations Polynomiales
No full textInternational audienceAbstract -Implementing convolutional neural networks (CNNs) on field-programmable gate arrays (FPGAs) has emerged as a promising alternative to GPUs, offering lower latency, greater power efficiency and greater flexibility. However, this development remains complex due to the hardware knowledge required and the long synthesis, placement and routing stages, which slow down design cycles and prevent rapid exploration of network configurations, making resource optimisation under severe constraints particularly challenging. This paper proposes a library of configurable convolution Blocks designed to optimize FPGA implementation and adapt to available resources. It also presents a methodological framework for developing mathematical models that predict FPGA resources utilization. The approach is validated by analyzing the correlation between the parameters, followed by error metrics. The results show that the designed blocks enable adaptation of convolution layers to hardware constraints, and that the models accurately predict resource consumption, providing a useful tool for FPGA selection and optimized CNN deployment.La mise en oeuvre de réseaux de neurones convolutifs (CNNs) sur des field-programmable gate arrays (FPGAs) représente une solution alternative aux GPU, en raison d'une latence réduite, une meilleure efficacité énergétique et une flexibilité accrue. Cependant, elle reste complexe en raison des compétences matérielles requises et des longues phases de synthèse, placement et routage, qui allongent les cycles de conception et limitent l'exploration rapide des configurations, compliquant l'optimisation sous fortes contraintes. Cet article propose une bibliothèque de Blocs de convolution configurables, visant à optimiser l'implémentation sur FPGA et à s'adapter aux ressources disponibles. Il présente également un cadre méthodologique pour développer des modèles mathématiques capables de prédire l'utilisation des ressources FPGA. L'approche est validée par une analyse de corrélation entre les paramètres suivie de mesures d'erreur. Les résultats montrent que les blocs conçus permettent l'adaptation des convolutions aux contraintes matérielles, et que les modèles prédisent avec précision la consommation des ressources, constituant un outil utile pour le choix d'architectures FPGA et le déploiement optimisé des CNN.</div
Optimizing Key Recovery in Classic McEliece: Advanced Error Correction for Noisy Side-Channel Measurements
No full textInternational audienceClassic McEliece was one of the code-based Key Encapsulation Mechanism finalists in the NIST post-quantum cryptography standardization process. Several key-recovery side-channel attacks on the decapsulation algorithm have already been published. However none of them discusses the feasibility and/or efficiency of the attack in the case of noisy side-channel acquisitions. In this paper, we address this issue by proposing two improvements on the recent key-recovery attack published by Drăgoi et al.. First, we introduce an error correction algorithm for the lists of Hamming weights obtained by side-channel measurements, based on the assumption, validated experimentally, that the error on a recovered Hamming weight is bounded to ± 1 . We then offer a comparison between two decoding efficiency metrics, the theoretical minimal error correction capability and an empirical average correction probability. We show that the minimal error correction capability, widely used for linear codes, is not suitable for the (non-linear) code formed by the lists of Hamming weights. Conversely, experimental results show that out of 1 million random erroneous lists of 2 t = 128 Hamming weights, only 2 could not be corrected by the proposed algorithm. This shows that the probability of successfully decoding a list of erroneous Hamming weights is very high, regardless of the error weight. In addition to this algorithm, we describe how the secret Goppa polynomial g , recovered during the first step of the attack, can be exploited to reduce both the time and space complexity of recovering the secret permuted support
X-Ray Fault Injection Localization with a Shield on Powered and Unpowered Devices
No full textInternational audienceThis study explores the use of X-ray fault injection localization techniques to evaluate the security of integrated circuits, particularly Flash memory in microcontrollers. Utilising a tungsten shield with an injection aperture, the experiments demonstrated precise targeting of the fault injection. The method was applied to both powered and unpowered devices, successfully discharging floating gate transistors in Flash memory, resulting in localised faults. The findings emphasise the effectiveness of the shield in localization X-ray exposure and highlight the vulnerabilities of critical integrated circuits to such attacks. The results obtained demonstrate the feasibility of injecting single bit faults into the Flash memory with X-ray of both powered and unpowered chips. This research contributes to the advancement of our understanding of X-ray fault injection mechanisms and underscores the importance of implementing robust security measures to counteract the emergence of novel threats
Side-Channel Exploitation of DRAM Access Patterns for Fingerprinting FPGA-CPU Environments
No full textInternational audienc
Saturated plasmonic colors for identity security features obtained by magnetron sputtering and laser treatment
No full textInternational audienc
Silicon nitride-based photonic integrated circuit to control a cold atom source
No full textInternational audienceWe have developed a silicon nitride-based photonic integrated circuit (PIC) that is responsible for the cooling, pumping, and imaging of cold rubidium 87 atoms. The photonic integrated circuit consists of two chips placed next to each other and has a total area of 2 × 2 cm2. This greatly minimizes the area needed while still having all the optical control functions to create, control, and measure a magneto-optical trap (MOT). The piezoelectric material lead zirconate titanate (PZT) on the PIC is employed for phase shifting a Mach–Zehnder-type configuration where extinction ratios up to 50 dB and switching speeds of 1 MHz are achieved. This resulted in the realization of two- and three-dimensional rubidium 87 MOT using an active PIC. For the three-dimensional MOT, we measure 7·107 atoms with a temperature of 270 μ K
