Hal - Université Grenoble Alpes
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Direct demonstration of time-reversal-symmetry-breaking spin injection from a compensated magnet
No full textThe injection, propagation and detection of spin currents are essential physical processes in spintronics. So far, the separation of charge and spin currents was facilitated by the electrical spin injection from a ferromagnet (FM) or the injection by a relativistic spin Hall effect. The devices employed are lateral spin valves comprising spatially separated injection and detection electrodes, connected by a spin-propagation channel. The time-reversal symmetry (TRS) breaking FM spin injection is realized in a geometry with an electrical bias applied between the injection electrode and the channel and is modelled by a conserved spin-polarized drift current. In contrast, the spin injection by the T-symmetric relativistic spin Hall mechanism is driven by an electrical bias applied across the injection electrode alone, and is modelled by a non-conserved spin current transverse to the applied bias. In this work, we use a lateral spin valve with a Mn5Si3 injection electrode to directly demonstrate a TRS-breaking spin injection from a compensated magnet with a vanishing net magnetization. Specifically, the TRS-breaking is demonstrated by the fact that switching between time-reversed states of the compensated magnet changes the detected spin signal. Moreover, the TRS-breaking nature of the spin injection is observed in both experimental geometries with the different electrical biasing, while using the same detection electrode. We show that this unconventional spin-injection is consistent with different magnitudes and propagation angles of electrical currents in the spin-up and spin-down channel in a d-wave altermagnet. Here our symmetry analysis and first-principles calculations are based on the compensated collinear altermagnetic order which has provided a comprehensive microscopic interpretation of earlier structural, magnetic, and anomalous Hall and Nernst measurements in Mn5Si3 thin films
Les thérapies innovantes dans l’hémophilie : impact sur les tests diagnostiques
No full textL’hémophilie A et B sont des maladies hémorragiques héréditaires rares, liées respectivement à un déficit en facteur VIII (FVIII) et en facteur IX (FIX). Longtemps dominée par la substitution en facteurs de coagulation, leur prise en charge a connu, au cours des deux dernières décennies, des évolutions thérapeutiques majeures. L’émergence des facteurs à demi-vie prolongée (EHL), des thérapies non substitutives, notamment les anticorps bispécifiques ou les inhibiteurs du TFPI, ainsi que le développement des thérapies géniques ont profondément modifié le paysage thérapeutique de l’hémophilie. Si ces innovations ont permis une amélioration significative de la qualité de vie des patients, elles ont également complexifié le suivi biologique des patients. Les tests de coagulation conventionnels utilisés en pratique courante (TCA, dosages d’activité des facteurs par méthodes chronométriques ou chromogéniques) ont été initialement développés pour le suivi des traitements substitutifs standards. Or, de nombreuses thérapies innovantes interagissent directement ou indirectement avec ces tests, pouvant conduire à des résultats biaisés, discordants ou difficilement interprétables selon la méthode analytique, les réactifs utilisés ou le traitement administré. L’objectif de cette thèse est d’analyser l’impact des nouvelles thérapies sur la fiabilité et l’interprétation des tests d’hémostase. Après un rappel des bases physiopathologiques de l’hémophilie et des principes des principales méthodes d’exploration de la coagulation, ce travail présente une analyse détaillée des interactions entre les différentes classes thérapeutiques innovantes (EHL, anticorps bispécifiques, agents by-passants, inhibiteurs du TFPI, thérapies géniques) et les tests d’hémostase disponibles. Les recommandations actuelles des sociétés savantes, notamment celles de la World Federation of Hemophilia (WFH) et de l’International Society on Thrombosis and Haemostasis (ISTH), sont discutées à la lumière des données de la littérature et des limites observées en pratique. Une attention particulière est portée aux tests globaux de l’hémostase, tels que le test de génération de thrombine ou la thromboélastographie, qui apparaissent comme des outils complémentaires prometteurs, bien que leur standardisation et leur accessibilité restent limitées. Cette thèse met en évidence la nécessité d’une adaptation des stratégies analytiques, d’une collaboration étroite entre cliniciens, biologistes et industriels du diagnostic in vitro. L’évolution rapide des traitements impose une réévaluation continue des outils biologiques afin de garantir une prise en charge optimale, sécurisée et personnalisée des patients hémophiles
Evaluating solid-state neutron detectors for measuring 14 MeV neutrons at high temperatures
No full textInternational audienceSilicon Carbide 4H Polytype (4H-SiC) and Diamond wide bandgap semiconductors are promising detector materials for fusion environments. Threshold energy nuclear reactions provide information on the energy of impinging fast neutrons and the combination of low intrinsic carrier concentration with high thermal conductivity makes these semiconductors suitable for high-temperature applications, especially for neutron monitoring in tritium production through ITER breeding blankets. While the carrier properties of SiC and Diamond offer interesting charge collection dynamics from room temperature up to 200 °C, the stability of their detection performance at high temperatures above 200 °C remains to be confirmed. To investigate this, we conducted a measurement campaign in a fast neutron field representative of fusion reactors at the GENESIS (Generator of Neutrons for Science and IrradiationS) research platform of LPSC (Laboratoire de Physique Subatomique et de Cosmologie) laboratory in Grenoble, France. Both 4H-SiC and Diamond sensors were irradiated with 14 MeV fast neutrons from a D-T neutron generator while encapsulated in a heating device, recording current signals from room temperature up to 500 °C. Using a direct measurement method of charge carrier collection dynamics as a function of applied bias voltage and temperature by pulse shape analysis provided information on velocity drift and collected charge. The results offer a first representative study of charge carrier mobility behavior with increasing temperature up to 500 °C. The stability of performance in terms of CCE (charge collection efficiency) has been demonstrated for SiC from room temperature up to 500 °C, while Diamond experiences a CCE drop of 60% between 200 °C and 300 °C
Anthologie des Rhétoriqueurs
No full textInternational audienceEntre 1450 et 1530, les Rhétoriqueurs ont formé un vaste réseau de poètes-orateurs en français. Souvent au service des princes, leurs poésies, spectacles, chroniques en prose et vers ont visé à résoudre les crises du présent. 76 extraits d’une trentaine d’auteurs invitent à les redécouvrir
Optimal Fidelity Estimation from Binary Measurements for Discrete and Continuous Variable Systems
No full textInternational audienceEstimating the fidelity between a desired target quantum state and an actual prepared state is essential for assessing the success of experiments. For pure target states, we use functional representations that can be measured directly and determine the number of copies of the prepared state needed for fidelity estimation. In continuous variable (CV) systems, we use the Wigner function, which can be measured via displaced parity measurements. We provide upper and lower bounds on the sample complexity required for fidelity estimation, considering the worst-case scenario across all possible prepared states. For target states of particular interest, such as Fock and Gaussian states, we find that this sample complexity is characterized by the L 1 -norm of the Wigner function, a measure of Wigner negativity widely studied in the literature, in particular in resource theories of quantum computation. For discrete variable systems consisting of n qubits, we explore fidelity estimation protocols using Pauli string measurements. Similarly as for the CV approach, the sample complexity is shown to be characterized by the L 1 -norm of the characteristic function of the target state for both Haar random states and stabilizer states. Furthermore, in a general black box model, we prove that, for any target state, the optimal sample complexity for fidelity estimation is characterized by the smoothed L 1 -norm of the target state. To the best of our knowledge, this is the first time the L 1 -norm of the Wigner function provides a lower bound on the cost of some information processing task
Quantum theory does not need complex numbers
No full textThe longstanding debate over whether quantum theory fundamentally requires complex numbers-or if their use is merely a convenient choice-has persisted for decades. Until recently, this question was considered open. However, in [M.-O. Renou et al, Nature 600, 625-629, 2021], a decisive argument was presented asserting that quantum theory needs complex numbers. In this work, we demonstrate that a formulation of quantum theory based solely on real numbers is indeed possible while retaining key features such as theory-representation locality (i.e. local physical operations are represented by local changes to the states) and the positive semi-definiteness of its states and effects. We observe that the standard system combination rule-the tensor product-was derived after the development of single-system complex quantum theory. By starting from a single-system quantum theory using only real numbers, we derive a combination rule that produces a real quantum theory with properties analogous to those of conventional complex quantum theory. We also prove that the conventional tensor product rule can also lead to a real and representation-local theory, albeit with a modified characterization of the state space. We thus conclude that complex numbers are a mere convenience in quantum theory. CONTENTS 1. Positivity-preserving mapping on a single system 2. Positivity-preserving mapping on two subsystems C. Explicit constructions of the M (•) map D. Proof of Theorem 2
Configurational Energy as a Microstructural Descriptor of Failure Precursors in 2D Frictional Granular Materials
No full textInternational audienceLocalized deformation in dense granular materials, often culminating in the formation of shear bands, is a key failure mechanism in geotechnical and material systems. However, predicting the onset of such localization remains a fundamental challenge due to the system's inherent inelasticity and microstructural complexity. In this study, we propose that the evolution of internal configuration—characterized by changes in contact topology and stored potential energy—governs the collective mechanical response and encodes precursors to material failure. To quantify this evolving internal state, we introduce the notion of configurational energy, defined as the change in contact‐scale elastic potential energy resulting from a controlled loading—unloading probe. This metric is first formulated at the contact level and subsequently analyzed at the specimen scale using Discrete Element Method (DEM) simulations of biaxial compression. Our results demonstrate that configurational energy captures the system's sensitivity to perturbations and reflects local instability: both positive and negative values emerge at the contact level, with large magnitudes concentrated near regions of active rearrangement. Despite this local variability, the specimen‐scale configurational response remains strictly negative, and its magnitude increases systematically as the material approaches failure. Notably, spatial localization of configurational energy precedes the formation of macroscopic shear bands with an evolving internal length scale, offering a mesoscale energetic signature of incipient failure. These findings establish configurational energy as a physically grounded descriptor of microstructural evolution and a promising tool for anticipating failure in frictional granular systems
Multiple comparisons of point clouds acquired by a permanent LiDAR (PLS) to improve the reliability of a rockfall event catalogue
No full textInternational audienceThe ANR C2R-IA project (www.anrc2ria.fr) aims to develop reliable decision-support tools for the dynamic management of rockfall hazard. Its goal is to understand how meteorological forcing influences rockfall occurrence and to anticipate temporary increases in hazard in order to implement risk reduction measures. To this end, a predictive model of rockfall occurrence as a function of meteorological conditions is being developed using artificial intelligence tools (neural network training), which requires a comprehensive and well-labelled dataset. Several monitoring instruments have been deployed at the Saint-Eynard site (Grenoble, France). Among them, a permanent LiDAR scanner (PLS) acquires point clouds continuously, with one acquisition per hour, providing high temporal resolution representative of what could be used for operational monitoring or crisis management. An automated data-processing workflow has been developed in Python. It is based on a pairwise comparison of the clouds (Manceau et al., 2025) and includes the alignment of successive point clouds, filtering of points outside the cliff area, change detection using M3C2 distances computation, clustering with DBSCAN, and volume quantification of rockfalls using alphashapes. This well-structured processing has significantly reduced the detection threshold, identifying relief change of only 10 cm deep (compared to 40 cm previously; Le Roy et al, 2020) and 10 liters in volume, while the scanner is located approximately 1 km from the cliff. Depending on acquisition quality, the effective temporal resolution of detected rockfall events may range from one hour to several days. Combining relief-change detections with simultaneously deployed seismic monitoring should further refine event timing. The completeness of the event catalogue has therefore improved, increasing from fewer than 10 detected rockfalls per month to around 30. However, some false positives remain, mainly related to recurring artifacts despite preprocessing. To mitigate these errors, the previous pairwise comparison of the clouds has been refined to a multiple point-cloud comparison strategy, enabling the tracking of the temporal persistence of changes. This allows distinguishing changes corresponding to real rockfalls, which persist over time, from transient artifacts. This improvement leads to a more reliable and complete rockfall event database. It includes block shape ratios, identified failure mechanisms, and free-fall heights under overhanging sections, providing a suitable basis for future fusion with seismic data.Manceau, L., Chanut, M.-A., Levy, C., Dewez, T., and Amitrano, D.: Enhancing Rockfall Detection Using Permanent LiDAR Scanner (PLS) Data and Automated Workflows at St. Eynard Cliff (Grenoble, France), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6312, https://doi.org/10.5194/egusphere-egu25-6312 Le Roy, G., Helmstetter, A., Amitrano, D., Guyoton, F., & Le Roux-Mallouf, R. (2019). Seismic analysis of the detachment and impact phases of a rockfall and application for estimating rockfall volume and free-fall height. Journal of Geophysical Research: Earth Surface, 124, 2602-2622. https://doi.org/10.1029/2019JF00499
Modification of offshore wind flow and aeolian sand transport by artificial foredunes
No full textInternational audienceAirflow dynamics and aeolian sand transport under offshore wind conditions have primarily been examined over relatively large coastal dunes, where dune morphology significantly alters flow structure and sediment pathways. In contrast, the role of smaller-scale, anthropogenically constructed coastal sand dunes, remains relatively understudied. This study investigates airflow patterns and sand transport over a low (<2.5 m) artificial foredune in Leucate (South of France), exposed to dominant offshore winds. A high resolution network of anemometers and aeolian sand traps was deployed along a cross-shore transect during four field campaigns. Results indicate that the direction of incident offshore winds generated distinct patterns of airflow and sediment transport from the dune's lee slope to the beach. When wind approached within 20 • of crest-normal, flow separation occurred on the lee side, with wind speeds reduced to 10-20 % of crest values. For angles >20 • , flow remained attached but deviated alongshore, with wind speeds reaching 35-50 % of crest values at the dune seaward toe. Wind velocity consistently increased seaward, enhancing sand transport toward the berm, with maximum transport rates exceeding 300 kg/m/h. This seaward-directed transport contributed to a negative sediment budget under persistent offshore wind dynamics. These findings highlight the capacity of small, artificial dunes to modify offshore wind dynamics and sediment pathways, with implications for dune management and coastal sediment budgets.</div