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Classically Prepared, Quantumly Evolved: Hybrid Algorithm for Molecular Spectra
No full textWe introduce a hybrid classical-quantum algorithm to compute dynamical correlation functions and excitation spectra in many-body quantum systems, with a focus on molecular systems. The method combines classical preparation of a perturbed ground state with short-time quantum evolution of product states sampled from it. The resulting quantum samples define an effective subspace of the Hilbert space, onto which the Hamiltonian is projected to enable efficient classical simulation of long-time dynamics. This subspace-based approach achieves high-resolution spectral reconstruction using shallow circuits and few samples. Benchmarks on molecular systems show excellent agreement with exact diagonalization and demonstrate access to dynamical timescales beyond the reach of purely classical methods, highlighting its suitability for near-term and early fault-tolerant quantum hardware
Live-cell SICM imaging: An Introductory Guide for New Users
No full textHigh-resolution, minimally invasive imaging of live cells is essential for investigating cellular morphology and its dynamic changes. Among available approaches, Scanning Ion Conductance Microscopy (SICM) offers a unique combination of precise topographic imaging down to nanoscale with experimental conditions that preserve true livecell behavior. Here, we present a practical guide based on our own experience and experiments, intended to be a resource to help first-time SICM users, covering critical aspects from instrumentation, probe characterization, to cell preparation and morphometric data extraction and presentation, to accelerate their implementation, learning and to gain confidence in exploring live-cell structure and dynamics
Demonstrating Aeolus capability to observe wind-cloud interactions
No full textInternational audienceModel based studies have shown interactions between wind vertical profiles and cloudiness, but few observational studies corroborate them. The unique observations of Aeolus spaceborne Doppler wind lidar can contribute to fill this gap. In this paper, we merged global Aeolus observations of cloud profiles at full horizontal resolution (3 km along orbit track) with co-located profiles of horizontal winds.We first observed wind-cloud interactions at regional scale over the Indian Ocean. Aeolus captures the strengthening of the Tropical Easterly Jet in early June 2020, with wind speeds exceeding 40 m s -1 in its core, and a simultaneous increase of high cloud fraction up to above 30 %, until the decay of the jet during fall.Secondly, we observed wind-cloud interactions at cloud scale (between 3-100 km) in different regions. Over the Indian Ocean as well as over cumulus and stratocumulus dominated regions, we found that the wind shear inside clouds is smaller than the wind shear in the clear sky surrounding the clouds (statistically significant). In addition, we found that the wind speed difference between the cloud and its surrounding clear sky increases with the clear sky wind shear, especially in cumulus (R = -0.94) and stratocumulus (R = -0.87) dominated regions. This study demonstrated that despite its coarse resolution, Aeolus can capture wind perturbations induced by convective motion.</div
Competing effects of charge-carrier and impurity scattering limiting phonon heat conduction in heavily-doped silicon
No full textWith respect to undoped semiconductors, thermal transport by phonons is limited by two additional mechanisms when doping increases: charge-carrier and impurity scattering. Previous works provided contradicting conclusions on the dominant doping-induced scattering mechanism in silicon. In this work, we clarify the competing roles of impurity and charge-carrier scatterings of phonons in the reduction of the lattice thermal conductivity in n-and p-doped silicon, by comparing experimental results obtained with the 3ω method and predictive DFT-based calculations for a large set of doping concentrations and a wide temperature range. The analysis allows delimiting the doping and temperature ranges where (i) extrinsic scattering surpasses intrinsic (phonon-phonon and phonon-isotope) one and (ii) one of the two doping-induced mechanisms plays the dominant role. We observe that the experimental setup impacts both the thermal conductivity value and the critical doping concentration at which the thermal conductivity is reduced by half
Bigraded Castelnuovo-Mumford regularity and Groebner bases
No full textInternational audienceWe study the relation between the bigraded Castelnuovo-Mumford regularity of abihomogeneous ideal in the coordinate ring of the product of two projective spaces and the bidegrees of a Groebner basis of with respect to the degree reverse lexicographical monomial order in generic coordinates. For the single-graded case, Bayer and Stillman unraveled all aspects of this relationship forty years ago and these results led to complexity estimates for computations with Groebner bases. We build on this work to introduce a bounding region of the bidegrees of minimal generators of bihomogeneous Groebner bases for . We also use this region to certify the presence of some minimalgenerators close to its boundary. Finally, we show that, up to a certain shift, this region is related to the bigraded Castelnuovo-Mumford regularity of
Uncovering thermodynamic origin of counterflow and coflow instabilities in miscible binary superfluids
No full textInternational audienceIn this paper, we explore instabilities in binary superfluids with a nonvanishing relative superflow, particularly focusing on counterflow and coflow instabilities. We extend recent results on the thermodynamic origin of finite superflow instabilities in single-component superfluids to binary systems and derive a criterion for the onset of instability through a hydrodynamic analysis. To verify this result, we utilize both the Gross-Pitaevskii equation (GPE) for weakly interacting Bose-Einstein condensates (BEC) and a holographic binary superfluid model, which naturally incorporates strong coupling, finite temperature, and dissipation. We find that the counterflow and coflow instabilities in binary superfluids are all essentially thermodynamic. Except the one due to order competing via global thermodynamic instability, the others are caused by an eigenvalue of the free energy Hessian diverging and changing sign. We also observe that the critical velocities of these instabilities follow a general scaling law related to the interaction strength between superfluid components. The nonlinear stages of the instabilities are also studied by full time evolution, where vortex dynamics is found to play a significant role, resulting in the reduction of superfluid velocity back to a stable phase
Towards Laboratory Electron-Positron Plasma via Electromagnetic Showers in Matter
No full textInternational audienceThe kinetic equations describing electromagnetic showers from high-energy electron beams interacting with targets are solved, building on the analytical framework developed in [Phys. Rev. Lett. 134, 135001 (2025)]. Two regimes are defined by the ratio of the target thickness L to the radiation length Lr , which depends on the electron energy and target composition. For thin targets (L Lr ), we obtain the total pair number and photon spectrum. Analytical results agree well with Geant4 simulations, which show that significant pair escape requires L<Lr . The divergence, density and characteristic dimensions of the escaping pair jets are obtained, and a criterion for pair plasma formation is derived. While current laser wakefield beams are not well adapted, multi-petawatt lasers may provide new electron or photon sources suitable for laboratory pair plasma production, opening new avenues for studying extreme plasma astrophysics in the laboratory
A stochastic use of the Kurdyka-Lojasiewicz property: Investigation of optimization algorithms behaviours in a non-convex differentiable framework
No full textInternational audienceAsymptotic analysis of generic stochastic algorithms often relies on descent conditions. In a convex setting, some technical shortcuts can be considered to establish asymptotic convergence guarantees of the associated scheme. However, in a non-convex setting, obtaining similar guarantees is usually more complicated, and relies on the use of the Kurdyka-Łojasiewicz (KŁ) property. While this tool has become popular in the field of deterministic optimization, it is much less widespread in the stochastic context and the few works making use of it are essentially based on trajectory-by-trajectory approaches. In this paper, we propose a new framework for using the KŁ property in a non-convex stochastic setting based on conditioning theory. We show that this framework allows for deeper asymptotic investigations on stochastic schemes verifying some generic descent conditions. We further show that our methodology can be used to prove convergence of generic stochastic gradient descent (SGD) schemes, and unifies conditions investigated in multiple articles of the literature
Probabilistic Computing with Neuromorphic Elements
No full textThe paper introduces a new low power and low transistor count approach to realizing a Bayesian engine that is simulated in TSMC 130 nm technology. Analog spiking neuron circuits produce deterministic streams that represent probabilities for computation. Synapse-like circuits encode the conditional probability distribution of features directly into their parameters and enable the determination of likelihood probabilities. The paper explores Gaussian and arbitrary distribution circuits, showing how a variety of different features can be considered. The calculation of the posterior is done using either an analog AND or a Muller C-element. While both are found to produce similar accuracies, the Muller C-element implementation enables faster computations. The final inference is accomplished with a time-tofirst-spike neuron that determines the most likely class. The architecture eliminates the need for random number generators, memory elements, and analog-to-digital conversion. It is validated on a breast cancer detection task, achieving classification accuracies of 73-90%, comparable to equivalent implementations in software. The system exhibits a compact footprint and operates in the μW range. This work provides a proof-of-concept for scalable, interpretable, compact and low-power probabilistic inference framework for edge computing
Inhibition of TRAP1 in the C-terminal domain influences mitochondria properties and breast cancer cell metabolism
No full textInternational audienceBreast cancers are characterized by complex energy metabolisms involving the Warburg effect but also mitochondria, although this area is not yet well understood. Tumor cells are particularly flexible by choosing oxidative phosphorylation (OXPHOS) or glycolysis depending on the needs and aggressiveness. Within the mitochondria, a HSP90-chaperone protein, TRAP1, exerts regulatory effects on several vital functions such as OXPHOS, production of reactive oxygen species and apoptosis by interacting with members of the respiratory chain or the mPTP. However, not all of its roles have yet been elucidated. Here, we propose to modulate TRAP1 functions using a mitochondriotropic molecule (containing triphenylphosphonium) targeting its C-terminal domain, 6BrCaQ-C 10 -TPP, in breast tumor cells. Its blocks proliferation with no massive apoptosis, after 24 h of treatment, and induces dissipation of the mitochondrial membrane potential. 6BrCaQ-C 10 -TPP also appears to modulate regulators of epithelial-mesenchymal transition (Snail and ZEB1) without a common response in all cell lines. Furthermore, the chaperone machinery is affected with a decrease of HSF1 and HSP70, but without degradation of HSP90 or TRAP1, while decreasing the levels of SDH-A and/or SDH-B, partner of TRAP1. Finally, short-term treatments (1 and 3 h) with 6BrCaQ-C 10 -TPP modify energy metabolism by promoting glycolysis. In conclusion, modulation of TRAP1 on the C-terminal domain by 6BrCaQ-C 10 -TPP exerts a cell-line dependent antitumor effect by modulating major mitochondrial functions in vitro. The differences between cell types need to be clarified. This study confirms that TRAP1 is a target of interest in breast cancer cells, but some of its functions still need to be elucidated