HAL Portal IOGS (nstitut d'Optique Graduate School)
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Fault Tolerance in Quantized and Pruned Convolutional Neural Networks
No full textInternational audienceConvolutional Neural Networks (CNN), particularly those used in critical applications, such as autonomous driving, medical systems, and aerospace, require high reliability. While these algorithms exhibit inherent resilience, they remain susceptible to Single-Event Effects (SEE) occurring at the hardware and impacting the model execution. These effects, usually induced by interactions with radiation particles, can lead to errors in electronic components, potentially causing incorrect inferences and increasing the risk of mispredictions. Meanwhile, quantization and pruning are widely employed to reduce the hardware footprint of CNN models, facilitating their deployment on embedded systems. Even when the models are reduced, CNN remain too large for an exhaustive fault injection campaign to assess their resilience. To address these challenges, we propose SFI4NN, a Statistical Fault Injection (SFI) framework specifically designed to evaluate the fault sensitivity of fixed-point quantized and pruned CNN architectures. Furthermore, we analyze the model resilience as a function of the pruning rate, showing that CNN sensitivity increases as pruning becomes more aggressive. The obtained results enable the development of hardware hardening strategies with reduced costs that are tailored to the reliability requirements of targeted applications. Experimental results demonstrate a 96\% improvement in resilience, with minimal hardware overhead compared to conventional hardening techniques such as triplication
Noninvasive temperature measurement of magnetic hyperthermia investigated through optical properties
No full textInternational audienceMagnetic nanoparticles present two promising effects: hyperthermia, which has potential in medical treatment approaches, and magneto-optical properties, which are useful in applications such as sensing and theranostics. This study investigates the impact of the heating induced by hyperthermia on the optical and magneto-optical properties of magnetic nanoparticles. A dedicated optical setup allows one to simultaneously induce magnetic hyperthermia with an alternating magnetic field and measure optical properties as well as magneto-induced birefringence and optical absorption. We demonstrate that hyperthermia heating of CoFe2O4 nanoparticles induces a decrease of their magneto-optical birefringence and an increase of their absorption. These results provide noninvasive monitoring methods for in situ temperature measurement in hyperthermia that would be beneficial for several applications and solid-state measurement
Couplage cohérent d'états d'impulsion : sélectivité et contrôle de phase
No full textInternational audienceWe demonstrate the effect of pulse shaping in momentum selective atomic Bragg diffraction. We compare temporal square pulses, which produce sidelobes in momentum space, with other shapes which can produce more nearly square momentum distributions. We produce pulses that simultaneously address two sets of velocity classes and demonstrate that we can control the differential phase imprinted on them in a way that is insensitive to laser phase fluctuations. Our work marks a significant step forward in testing Bell inequalities using massive particles entangled in momentum.Nous démontrons l'effet du façonnage d'impulsions dans la diffraction de Bragg atomique sélective en quantité de mouvement. Nous comparons les impulsions carrées temporelles, qui produisent des lobes latéraux dans l'espace de la quantité de mouvement, avec d'autres formes qui peuvent produire des distributions de quantité de mouvement plus proches d'un rectangle. Nous produisons des impulsions qui couplent simultanément deux ensembles de classes de vitesse et nous démontrons que nous pouvons contrôler la phase différentielle qui leur est imprimée d'une manière qui est insensible aux fluctuations de phase du laser. Notre travail marque une avancée significative vers un test des inégalités de Bell avec des particules massives intriquées en quantité de mouvement
Publishing and Long-Term Archiving 3D Data in Humanities
No full textInternational audienceAbstract We present here the French solution for long-term archiving combined with online publication of 3D research data in the humanities. The focus is on the paradata that document the technical process involved in obtaining the 3D result. Our schema, initially limited to the fields of archaeology and cultural heritage, is now open to other areas of the human sciences. The choice of data organization, metadata, paradata, standards and infrastructure is in line with the FAIR principles of the semantic web. It is aligned with standard vocabularies and mapped to the Europeana Data Model (EDM). The CINES (Centre Informatique National de l’Enseignement Supérieur.), the Open Archival Information System (OAIS) infrastructure for research data in France, is in charge of archiving. We take care of data documentation and propose to publish part of these documented data at the same time. On the user side, we developed aLTAG3D, a desktop UI software to help research teams to create their OAIS Submission Information Package (SIP). On the publication side, we provide a DOI and a 3D viewer on the online plateform to meet the needs of researchers and public communication. On the archiving side, long-term archiving has given direction to the way our description schema works: it is focused on reproducibility. The content of the SIP is centered on the 3D data, its build process and sources. Paradata describing the process to the 3D file is under development and several options are under study with CIDOC CRM-Dig or W3C prov-O ontologies
Towards Embedding Methods For Electronic Excitations At The Interface In 2D Lateral Heterostructures
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Probing Abrikosov vortices in niobium with single nitrogen-vacancy centers in nanodiamonds
No full textInternational audienceAbrikosov vortices play a fundamental role in the magnetic and electric properties of superconductors. The study of their pinning forces is essential to better understand the stability of vortex lattices, with the aim of increasing critical currents in superconductors. However, the study of vortices is challenging because of their nanometric sizes and the large variation in the pinning forces. In this Letter, we use a single nitrogen-vacancy center in a nanodiamond as a nanoscale magneto sensor to locally probe single vortices and their pinning effects in a thin niobium film. This simple, far-field optical approach also offers the possibility of manipulating a single spin with a single flux quantum
Influence of the Wavelength on Femtosecond Laser Ablation Thresholds and Incubation Coefficients of Silicon and Germanium
No full textInternational audienceWhen using an ultrafast laser to irradiate the surface of a material, one can induce different changes in it depending on a set of laser parameters, such as the laser wavelength, laser fluence, and the total number of pulses. In our materials of interest, we are mainly concerned by two different laser-mater interaction regimes: the laser ablation regime and the sub-ablation modification regime, which are separated by the ablation threshold fluence. This fluence, depends on the laser wavelength, and the number of pulses (incubation effect). In this work, we investigated these dependencies, for mono-crystalline silicon (Si) and germanium (Ge). We measured the ablation thresholds for irradiation with 5, 10 and 50 pulses at 343, 515 and 1030 nm, for a laser pulse duration of 350 femtosecond (fs). The ablation thresholds of Si and Ge for these laser conditions are traced experimentally. The single-shot ablation thresholds for the 3 wavelengths are deduced, as well as the incubation coefficient, both of which are based on the experimental data from our study. We then discuss a number of factors which may contribute to the ablation thresholds and incubation coefficient when operating at different wavelengths.</div
CryoRhodopsins: a comprehensive characterization of a group of microbial rhodopsins from cold environments
No full textInternational audienceMicrobial rhodopsins are omnipresent on Earth, however the vast majority of them remain uncharacterized. Here we describe a new rhodopsin group from cold-adapted organisms and cold environments, such as glaciers, denoted as CryoRhodopsins (CryoRs). Our data suggest that CryoRs have dual functionality switching between inward transmembrane proton translocation and photosensory activity, both of which can be modulated with UV light. CryoR1 exhibits two subpopulations in the ground state, which upon light activation lead to transient photocurrents of opposing polarities. A distinguishing feature of the group is the presence of a buried arginine residue close to the cytoplasmic face of its members. Combining single-particle cryo-electron microscopy and X-ray crystallography with the rhodopsin activation by light, we demonstrate that the arginine stabilizes a UV-absorbing intermediate of an extremely slow CryoRhodopsin photocycle. Together with extensive spectroscopic characterization, our investigations on CryoR1 and CryoR2 proteins reveal mechanisms of photoswitching in the newly identified group and demonstrate principles of the adaptation of these rhodopsins to low temperatures
Leveraging the spectral diversity with accurate modeling of the nuisance component for improved exploitation of high-contrast observations
No full textInternational audienceReconstruction of the circumstellar environment and direct detection of exoplanets in the vicinity of nearby stars is challenging due to the very high contrast between the host star and the sought objects. In addition to the use of an extreme adaptive optics and a coronagraph, dedicated processing methods combining images recorded with the pupil tracking mode of the telescope are required to eliminate efficiently the nuisance component (speckles + noise) corrupting the signals of interest. Concerning the reconstruction of the circumstellar environment, we proposed in previous works the REXPACO algorithm tailored for angular differential imaging (ADI). It estimates jointly the sought objects and the statistics (mean and covariance matrix) of the nuisance following an inverse problem approach. It demonstrates state-of-the-art performance with ADI, but room for improvements remains, especially for reconstructing fine structures near the star and disks being partly rotation-invariant (which prevents their unmixing without additional diversity). We will present our most recent developments in that direction (Flasseur+ in prep). In particular, the new method takes benefit of the spectral diversity of the data to improve (drastically) the reconstruction fidelity. Contrary to the most advanced counterpart algorithms dedicated to point-source extraction, spatial and spectral correlations are modeled jointly and directly from the data. The algorithm yields a deconvolved estimate of the objects in an unsupervised fashion. In terms of results, we will first exemplify from simulated disks that a joint modeling of the spectral diversity (even at a low resolution and with a limited bandwidth) is a “game-changer” to improve the reconstruction of disks, without Reference Differential Imaging. We will then show from real data from SPHERE-IFS that the proposed temporo-spatio-spectral model captures accurately the nuisance to eliminate it efficiently. Finally, we will show several reconstructions of emblematic disks with unprecedent quality. Fully exploiting the high spectral diversity of the future ELT instruments will be a challenge to explore the inner environment of nearby solar-type stars. Concerning exoplanet detection, most of the current processing techniques proceed in two sequential steps: (i) a suppression of the stellar continuum by filtering, (ii) a spectral cross-correlation with a model of the sought planets. Based on HARMONI simulations, we will present detection sensitivity of PACO ASDI modeling statistically the nuisance component and making any assumption on the exoplanet’s spectrum. We will also discuss preliminary results obtained on these simulations with PACOME (Dallant+ A&A 23) that efficiently combines observations of the same star while accounting for the Keplerian motion of the sought exoplanets within an end-to-end statistical detection formalism