Data Analysis and Statistics · Cross-listed from cs.CV
A Large-Language-Model Assisted Automated Scale Bar Detection and Extraction Framework for Scanning Electron Microscopic Images
Yuxuan Chen, Ruotong Yang, Zhengyang Zhang et al. (+2 more)
Microscopic characterizations, such as Scanning Electron Microscopy (SEM), are widely used in scientific research for visualizing and analyzing microstructures. Determining the scale bars is an important first step of accurate SEM analysis; however, currently, it mainly relies on manual operations, which is both time-consuming and prone to errors. To address this issue, we propose a multi-modal and automated scale bar detection and extraction framework that provides concurrent object detection, text detection and text recognition with a Large
Language Model (LLM)
agent. The proposed framework operates in four phases; i) Automatic
Dataset Generation (Auto-DG) model to synthesize a diverse
dataset of SEM images ensuring robust training and high generalizability of the model, ii) scale bar object detection, iii) information extraction using a hybrid Optical Character Recognition (OCR) system with DenseNet and Convolutional Recurrent Neural Network (CRNN) based
algorithms, iv) an LLM
agent to analyze and verify accuracy of the results. The proposed model demonstrates a strong performance in object detection and accurate localization with a precision of 100%, recall of 95.8%, and a mean Average Precision (mAP) of 99.2% at IoU=0.5 and 69.1% at IoU=0.5:0.95. The hybrid OCR system achieved 89% precision, 65% recall, and a 75% F1 score on the Auto-DG
dataset, significantly outperforming several mainstream standalone engines, highlighting its reliability for scientific image analysis. The LLM is introduced as a
reasoning engine as well as an intelligent assistant that suggests follow-up steps and verifies the results. This automated method powered by an LLM
agent significantly enhances the efficiency and accuracy of scale bar detection and extraction in SEM images, providing a valuable tool for microscopic analysis and advancing the field of scientific imaging.
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All authors Yuxuan Chen, Ruotong Yang, Zhengyang Zhang, Mehreen Ahmed, Yanming Wang
Fluid Dynamics
Impact of Wind Direction on Flow Over a Realistic Urban Area: A Large-Eddy Simulation Study
Ivette Rodríguez, Josep Maria Duró, Ernest Mestres et al. (+2 more)
We conducted high-resolution large-eddy simulations over a real urban district in Barcelona to examine the impact of wind direction on near-ground flow. The computational mesh resolves over 500 million degrees of freedom, with a spatial resolution on the order of 1 m at pedestrian level. This allows a detailed analysis of mean velocity and
turbulence patterns within the canopy layer. Although instantaneous flow fields differ significantly between cases, double-averaged profiles of velocity and
turbulence intensity remain remarkably consistent across all wind directions. The results reveal a shear-driven mixing layer below the average building height and
turbulence maxima near the tallest buildings, highlighting the influence of urban morphology on the development of flow and
turbulence.
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All authors Ivette Rodríguez, Josep Maria Duró, Ernest Mestres, Ming Teng, Oriol Lehmkuhl
Fluid Dynamics
A paradox of the Navier-Stokes turbulence
Shijie Qin, Kun Xu and Shijun Liao
The Navier-Stokes (NS) equations as a
turbulence model have been widely applied in lots of fields. The NS equations contain such a fundamental assumption that all small physical/artificial disturbances could be neglected. Is this assumption correct? In this paper a two-dimensional Rayleigh-Bénard convection governed by the NS equations is predicted by traditional direct numerical simulation (DNS) using double precision arithmetic and a range of different time-steps. It is found that the final flow type tends either to vortical flow or zonal flow, whose statistics are completely different. Notably, these two flow types frequently alternate as the time-step is reduced to a very small value, suggesting that the time-step corresponding to each turbulent flow type should be densely distributed. Thus,
stochastic numerical noise exerts a huge influence on the final flow type and statistics of numerically simulated NS
turbulence because the time-step has a close relationship with numerical noise. This clearly indicates that small disturbances have significant influences on the NS
turbulence, which therefore should not be neglected. This leads to a logical paradox for the NS
turbulence, which is a great challenge for us, although a paradox often leads to some significant breakthroughs.
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Computational Physics · Cross-listed from cs.LG
Cross-Scale Reservoir Computing for large spatio-temporal forecasting and modeling
Nicola Alboré, Gabriele Di Antonio, Fabrizio Coccetti et al. (+1 more)
We propose a new reservoir computing method for
forecasting high-resolution spatiotemporal
datasets. By combining multi-resolution inputs from coarser to finer layers, our architecture better captures both local and global dynamics. Applied to Sea Surface Temperature data, it outperforms standard parallel reservoir models in long-term
forecasting, demonstrating the effectiveness of cross-layers coupling in improving predictive accuracy. Finally, we show that the optimal network dynamics in each layer become increasingly linear, revealing the slow modes propagated to subsequent layers.
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All authors Nicola Alboré, Gabriele Di Antonio, Fabrizio Coccetti, Andrea Gabrielli
Computational Physics
Computational Crystal Plasticity Homogenization using Empirically Corrected Cluster Cubature (E3C) Hyper-Reduction
Stephan Wulfinghoff
The computational homogenization of elastoplastic polycrystals is a challenging task due to the huge number of grains required, their complicated interactions and due to the complexity of
crystal plasticity models per se. Despite a few successes of reduced order models, mean field and simplified homogenization approaches often remain the preferred choice. In this work, a recently proposed hyper-reduction method (called E3C) for projection-based Reduced Order Models (pROMs) is applied to the problem of computational homogenization of geometrically linearly deforming elastoplastic polycrystals. The main novelty lies in the identification of reduced modes (the 'E3C-modes'), which replace the strain modes of the reduced-order model, leading to a significantly smaller number of integration points. The peculiarity, which distinguishes the method from more conventional hyper-reduction techniques, is that the E3C integration points are not taken from the set of FE integration points. Instead, they can be interpreted as generalized integration points in strain space which are trained such as to satisfy an orthogonality condition, which ensures that the hyper-reduced model matches the
equilibrium states and macroscopic stresses of full-field model data as accurately as possible. In addition, the number of grains is reduced, preserving the main features of the original texture of the finite element model. Two macroscopic engineering parts (untextured and textured) are simulated, illustrating the performance of the method in three-dimensional two-scale applications involving hundreds of thousands macroscopic degrees of freedom and millions of grains with computing times in the order of hours (cumulated online and offline effort) on standard laptop hardware.
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Computational Physics
Tuning Layer Orbital Hall Effect via Spin Rotation in Ferromagnetic Transition Metal Dichalcogenides
Shilei Ji, Jianping Yang, Li Gao et al. (+1 more)
Orbitronics, which leverages the angular momentum of atomic orbitals for information transmission, provides a novel strategy to overcome the limitations of electronic devices. Unlike electron
spin, orbital angular momentum (OAM) is strongly influenced by
crystal field effects and band
topology, making its orientation difficult to manipulate with external fields. In this work, by using first principle calculations, we investigate
quantum anomalous
Hall insulators (QAHIs) as a model system to study the layer orbital
Hall effect (OHE). Due to band inversion, only one valley remains orbital polarization, and thus the OHE originates from a single valley. Based on stacking
symmetry analysis, we investigated both AA and AB stacking configurations, which possess mirror and inversion
symmetries, respectively. The excitation of OAM exhibits valley selectivity, determined jointly by valley polarization and orbital polarization. In AA stacking, the absence of inversion center gives rise to intrinsic orbital polarization, leading to OAM excitations from different valleys in the two layers. In contrast, AB stacking is protected by inversion
symmetry, which enforces valley polarization and causes OAM in both layers to originate from the same valley. Furthermore, the direction of
spin polarization tunes the sign of the Berry
curvature, thereby dictating the transport of OAM. As a result, in
bilayer antiferromagnetic QAHI systems, orbital currents display a distinct layer-contrasting behavior in both flow direction and OAM accumulation.
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All authors Shilei Ji, Jianping Yang, Li Gao, Xing'ao Li
Plasma Physics
Machine Learning-Integrated Hybrid Fluid-Kinetic Framework for Quantum Electrodynamic Laser Plasma Simulations
Sadra Saremi and Amirhossein Ahmadkhan Kordbacheh
High-intensity
laser plasma interactions create complex computational problems because they involve both fluid and kinetic regimes, which need models that maintain physical precision while keeping computational speed. The research introduces a machine learning-based three-dimensional hybrid fluid-particle-in-
cell (PIC) system, which links relativistic
plasma behavior to automatic regime transitions. The technique employs fluid approximations for stable areas but activates the PIC solver when SwitchNet directs it to unstable sections through its training on physics-based synthetic data. The model uses a smooth transition between Ammosov-Delone-Krainov (ADK) tunneling and multiphoton ionization rates to simulate ionization, while Airy-function approximations simulate
quantum electrodynamic (QED) effects for radiation reaction and pair production. The convolutional neural network applies energy conservation through physics-based loss functions, which operate on normalized fields per channel. Monte Carlo dropout provides uncertainty measurement. The hybrid model produces precise predictions with coefficient of determination (R^2) values above 0.95 and mean squared errors below 10^-4 for all field components. This adaptive approach enhances the accuracy and scalability of
laser-
plasma simulations, providing a unified predictive framework for high-energy-density and particle acceleration applications.
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Instrumentation and Detectors
IPbus extension for the ALFRED framework
Krystian Roslon, Maciej Czarnynoga, Sebastian Koryciak et al. (+7 more)
We present a development of the ALFRED framework that includes support for the IPbus protocol, created for the Fast Interaction Trigger (FIT) detector in the ALICE experiment at CERN. This modification resolves the incompatibility between the current GBT-based slow-control protocols and the FIT electronics, which is based on the IPbus. A compatibility layer, named ALF IPbus, was created in C++ and integrated with DIM services, allowing for the transparent conversion of SWT frames into IPbus transactions.
Benchmark tests indicated median execution times of less than 4.2 $\mu$s per frame for sequences above 512 words, comfortably meeting the ALICE Detector Control System requirements. Long-term stability tests conducted in the FV0 detector achieved an uptime close to 100% from the moment of implementation on the FIT-FV0 detector. This solution enables FIT operation without firmware changes, ensures smooth integration with SCADA systems, and provides a scalable pathway for future migration to GBT-based control. The approach is general and can be applied to other ALICE subdetectors and high-energy physics experiments requiring protocol bridging.
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All authors Krystian Roslon, Maciej Czarnynoga, Sebastian Koryciak, Monika Kutyla, Ignacy Mermer, Jacek Tomasz Otwinowski, Wiktor Pierozak, Pawel Grzegorz Russek, Wladyslaw Trzaska, Franciszek Urbanski
Optics
Canalized hyperbolic magnetoexciton polaritons enabled by the Shubnikov-de Haas effect in van der Waals semiconductors
Guangyi Jia, Qizhe Cai, Chunqi Zheng et al. (+2 more)
Polariton canalization exhibits highly collimated and diffraction-free propagation characteristics in natural
hyperbolic materials, holding great promise for molding the energy flow at nanoscale. Previously, the majority of canalizations are realized in
phonon polaritons. Herein, we theoretically explore
hyperbolic magnetoexciton polaritons (HMEPs) in van der Waals
crystals of WTe2, MoS2, and phosphorene. Based on the Shubnikov-de Haas effect, canalized HMEPs with ultralow group velocity (~10-5c) and super-long lifetime (hundreds of microseconds) are predicted at low temperatures. We also show that the inter-Landau-level transitions and non-local dielectric screening effect significantly modify the optical
topologies of canalized HMEPs, manifested by various exotic isofrequency contours (IFCs) including
hyperbolic, witch-of-Agnesi, one-sheet, two-fold, and twisted pincerlike IFCs. Our findings reveal the significant effects of magneto-optical transport on
hyperbolic polaritons, which not only enrich the interplay mechanism between magnetics and polaritonics, but also provide a promising playground for future developments in
hyperbolic materials.
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All authors Guangyi Jia, Qizhe Cai, Chunqi Zheng, Xiaoying Zhou, Cheng-Wei Qiu
Optics
Space-time singularities in spatially-chirped Laguerre-Gaussian beams of any order
Spencer W. Jolly
The electric field distributions and space-time singularity curves are computed for ultrashort pulsed Laguerre-Gaussian
laser beams having spatial chirp. Due to the breaking of cylindrical
symmetry by the spatial chirp, the singularities trace complicated curves in space-time, which also vary for different combinations of radial and vortical orders. Analytical solutions are mostly presented along with a recipe for numerically calculating higher orders. The behavior of the singularities upon propagation is also shown, along with a discussion of the extension towards few-cycle pulses. These results are an example of how a simple physical scenario can result in highly complicated singular behavior in space-time.
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Fluid Dynamics
Analytical and numerical investigation of heat transfer of porous fin in a local thermal non-equilibrium state
Payam Jalili, Salar Ghadiri Alamdari, Bahram Jalili et al. (+2 more)
This research employs a local thermal non-
equilibrium (LTNE) model to analyze the heat transfer phenomenon through a porous fin, considering natural convection and radiation effects. The infiltration velocity within the porous medium is evaluated using the Darcy model, and buoyancy effects are accounted for using the Boussinesq approximation. The Akbari-Ganji method (AGM) is applied to address the governing energy equations. The accuracy of the proposed solution is verified by comparing it with numerical results obtained from the finite difference method (FDM), the finite element method (FEM), and earlier investigations. The results are presented regarding the total average Nusselt number and temperature profiles. These results shed light on the influence of several important parameters, such as the thermal conductivity ratio, dimensionless thickness, convectional heat transfer, and external and internal radiation. The analysis reveals that decreasing Rayleigh and Biot numbers reduces the temperature profiles of the solid phase. Additionally, when the Rayleigh number is low but the assigned Biot number is high, the temperature difference between the solid and fluid phases diminishes. Furthermore, increased thermal conductivity ratio and dimensionless thickness for assigned Biot and Rayleigh numbers lead to higher solid phase temperatures. The Nusselt number exhibits a decreasing trend with a decreasing thermal conductivity ratio but increases with higher Rayleigh and Biot numbers and increased external radiation.
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All authors Payam Jalili, Salar Ghadiri Alamdari, Bahram Jalili, Amirali Shateri, Davood Domiri Ganji
Optics · Cross-listed from quant-ph
Quantum Information Processing with Spatially Structured Light
Suraj Goel, Bohnishikha Ghosh and Mehul Malik
Qudits have proven to be a powerful resource for
quantum information processing, offering enhanced channel capacities, improved robustness to noise, and highly efficient implementations of
quantum algorithms. The encoding of photonic qudits in transverse-spatial degrees of freedom has emerged as a versatile tool for
quantum information processing, allowing access to a vast information capacity within a single
photon. In this review, we examine recent advances in
quantum optical
circuits with spatially structured light, focusing particularly on top-down approaches that employ complex mode-mixing transformations in free-space and fibers. In this context, we highlight
circuits based on platforms such as multi-plane light conversion, complex scattering media, multimode and multi-core fibers. We discuss their applications for the manipulation and measurement of multi-dimensional and multi-mode
quantum states. Furthermore, we discuss how these
circuits have been employed to perform multi-party operations and multi-outcome measurements, thereby opening new avenues for scalable photonic
quantum information processing.
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Fluid Dynamics
Analysis of bio-nanofluid flow over a stretching sheet with slip boundaries
Bahram Jalili, Salar Ghadiri Alamdari, Payam Jalili et al. (+1 more)
A viscous, incompressible, micropolar bio-nanofluid flowing across a stretching sheet in three dimensions while being driven to convect several slip boundaries in the presence of a
magnetic field was studied. With the assistance of the relevant transformations, a mathematical model is presented. The finite difference method numerically solves the converted non-linear ordinary differential equations. A comprehensive assessment was conducted to examine the impact of governing parameters on dimensionless velocity, micro-rotation, temperature, nanoparticle volume fraction, microorganisms, and heat transfer rate. The findings of this investigation showed a strong correlation when compared to previous studies, indicating a high level of agreement and consistency between the results. The study's conclusions indicate that the velocity profile increases with higher values of {\lambda} and {\delta}, while it decreases with higher values of A, {\delta}v, and M. The micro-rotation profile F({\eta}) drops as the
spin gradient viscosity parameter rises, but G({\eta}) increases. The temperature profile decreases with higher Prandtl numbers but increases with higher thermophoresis parameters. The concentration profile decreases with higher Schmidt numbers and Brownian motion parameters. The microorganism profile increases with higher Peclet numbers and microorganism slip parameters but decreases with higher bio-convection Schmidt numbers. Lastly, the local Nusselt number grows with increasing values of the stretching parameter {\lambda}.
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All authors Bahram Jalili, Salar Ghadiri Alamdari, Payam Jalili, Davood Domiri Ganji
Chemical Physics
Enhanced Sampling for Efficient Learning of Coarse-Grained Machine Learning Potentials
Weilong Chen, Franz Görlich, Paul Fuchs et al. (+1 more)
Coarse-graining (CG) enables molecular dynamics (MD) simulations of larger systems and longer timescales that are otherwise infeasible with atomistic models. Machine learning potentials (MLPs), with their capacity to capture many-body interactions, can provide accurate approximations of the potential of mean force (PMF) in CG models. Current CG MLPs are typically trained in a bottom-up manner via force matching, which in practice relies on configurations sampled from the unbiased
equilibrium Boltzmann distribution to ensure thermodynamic consistency. This convention poses two key limitations: first, sufficiently long atomistic trajectories are needed to reach convergence; and second, even once equilibrated, transition regions remain poorly sampled. To address these issues, we employ enhanced sampling to bias along CG degrees of freedom for data generation, and then recompute the forces with respect to the unbiased potential. This strategy simultaneously shortens the simulation time required to produce equilibrated data and enriches sampling in transition regions, while preserving the correct PMF. We demonstrate its effectiveness on the Müller-Brown potential and capped alanine, achieving notable improvements. Our findings support the use of enhanced sampling for force matching as a promising direction to improve the accuracy and reliability of CG MLPs.
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All authors Weilong Chen, Franz Görlich, Paul Fuchs, Julija Zavadlav
Fluid Dynamics · Cross-listed from cond-mat.soft
Thin-film flows of granular suspensions on a solid surface
Alice Pelosse, Elisabeth Guazzelli and Matthieu Roché
This review article examines the complex dynamics of thin-film flows of granular suspensions spreading over rigid solid substrates with free air interfaces. Such systems feature an involved coupling of the free-surface dynamics with the flow and microstructure of the suspension. In particular, we develop two canonical thin-film situations: drop spreading and dip-coating. In drop spreading, confinement of the particulate phase near the advancing contact line alters both the spreading rate and the interface shape. In dip-coating, understanding the entrainment of fluid and particles becomes challenging as the film thickness approaches the particle size.
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Optics · Cross-listed from quant-ph
Efficient and Robust Spatial-to-Fiber Coupling forMultimode Quantum Networks via CascadedAdaptive Feedback Control
Ya Li, WanRu Wang, Weizhe Qiao et al. (+5 more)
Duan-Lukin-Cirac-Zoller (DLCZ)-based multimodequantum networks rely on efficient spatial-to-fiber coupling, yetenvironmental perturbations compromise this performance. Wedevelop a cascaded adaptive feedback control system integratedinto the
quantum entanglement source preparation path.Leveraging a power-feedback hillclimbing
algorithm, itdynamically regulates piezoelectric-actuated mirrors to achieveautonomous multi-dimensional beam
alignment, Experimentsshow it rapidly boosts single-mode fiber (SMF) coupling efficieneyto over 70% within 20 seconds and entering the most efficient andstable transmission state after 75 seconds.Importantly, it enhancesthe stability of the atom-
photon interfacecritical for quantumlight-matter interactionsproviding a practical framework forefficient, robust spatial light transmission in scalable quantumnetworks.
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All authors Ya Li, WanRu Wang, Weizhe Qiao, Qizhou Wu, Changqing Niu, Xiaolong Zou, Youxing Chen, Xin Guo
Medical Physics
Basis for a hands free blood flow measurement with automated vessel focus
Reinhard Fuchs, Nathalie Sumrah, Johannes Schwerdt et al. (+5 more)
Cardiopulmonary resuscitation (CPR) is an essential tool to ensure oxygen supply during cardiac arrest, yet not quantifiable to this day. Low-quality chest compressions or wrong pressure placement go unnoticed. This paper presents a solution for the quantification of blood flow to guide first responders in their efforts. An approach for automated vessel identification with three different steps was developed, featuring a new sensor probe for ultrasonic measurements with non-symmetrically angled piezo ceramics. The probe was used with prototype ultrasound hardware for Pulsed Wave Doppler (PW Doppler) in a phantom. Initial measurements evaluated sensor vessel
alignment at different sensor positions by examining Doppler results with a large sample volume during periodic flow. Afterward, an iterative mode was used for depth-dependent frequency measurements with score calculation of flow periodicity and power. The configuration with the best score was used for a prolonged monitoring mode. Initial mode and iterative mode aligned with ultrasound imaging regarding the best position and vessel depth. Simultaneous flow-sensor data and flow values of monitoring mode calculated via Doppler substitution showed a minimum correlation coefficient of 0.98, a minimum R2 of 0.96, and an average root mean square error of 3.84 ml/s. With the proposed hardware and software solutions, a basis for future developments was made, which could lead to a fully automated vessel identification and blood flow calculation during CPR. When used in emergencies, a miniaturized device could provide vital information about CPR efficiency that has yet to be included in the therapy of people during cardiac arrest.
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All authors Reinhard Fuchs, Nathalie Sumrah, Johannes Schwerdt, Michael Unger, Georg Stachel, Michael Schultz, Karsten Lenk, Thomas Neumuth
Optics
Lattice Boltzmann Method for Electromagnetic Wave Scattering
Mohd. Meraj Khan, Sumesh P. Thampi and Anubhab Roy
In this work, the
lattice Boltzmann method (LBM) is assessed as a time-domain numerical approach for electromagnetic wave scattering. Owing to its explicit formulation and suitability for parallel computation on structured grids, LBM provides an alternative framework for solving Maxwell's equations. The formulation is first validated using canonical
benchmarks, including reflection and refraction at a planar dielectric interface and two-dimensional scattering from infinitely long circular cylinders, where the computed angular scattering intensities are compared with analytical Lorenz-Mie solutions. Additional comparisons are performed for circular cylinders with varying dielectric constants to examine performance across different material contrasts. The framework is then extended to three-dimensional scattering from dielectric spheres, representing the most computationally demanding case considered in this work, and the resulting angular scattering intensities are compared with exact Lorenz-Mie solutions. To further examine performance for non-circular geometries, scattering from an infinitely long hexagonal dielectric cylinder is investigated and benchmarked against results obtained using the Discretized-Mie Formalism. Across all cases, the LBM predictions show close agreement with analytical and semi-analytical reference solutions over a range of size-to-wavelength ratios.
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Instrumentation and Detectors
Improved Pixel-wise Calibration for Charge-Integrating Hybrid Pixel Detectors with Performance Validation
X. Xie, A. Bergamaschi, M. Brückner et al. (+29 more)
The MÖNCH hybrid pixel detector, with a 25 \textmu m pixel pitch and fast charge-integrating readout, has demonstrated subpixel resolution capabilities for X-ray imaging and deep learning-based electron localization in electron microscopy. Fully exploiting this potential requires extensive calibration to ensure both linearity and uniformity of the pixel response, which is challenging for detectors with a large dynamic range. To overcome the limitations of conventional calibration methods, we developed an accurate and efficient correction method to achieve pixel-wise gain and nonlinearity calibration based on the backside pulsing technique. A three-dimensional lookup table was generated for all pixels across the full dynamic range, mapping the pixel response to a calibrated linear energy scale. Compared with conventional linear calibration, the proposed method yields negligible deviations between the calibrated and nominal energies for
photons and electrons. The improvement in energy resolution ranges from 4% to 22% for 15-25 keV
photons and from 16% to 23% for 60-200 keV electrons. Deep learning-based electron localization demonstrates a 4% improvement in spatial resolution when using the proposed calibration method. This approach further enables rapid diagnosis of the cause of bad pixels and estimation of bump-bonding yield.
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All authors X. Xie, A. Bergamaschi, M. Brückner, M. Carulla, R. Dinapoli, S. Ebner, K. Ferjaoui, E. Fröjdh, V. Gautam, D. Greiffenberg, S. Hasanaj, J. Heymes, V. Hinger, M. Hürst, V. Kedych, T. King, S. Li, C. Lopez-Cuenca, A. Mazzoleni, D. Mezza, K. Moustakas, A. Mozzanica, J. Mulvey, M. Müller, K.A. Paton, C. Posada Soto, C. Ruder, B. Schmitt, P. Sieber, S. Silletta, D. Thattil, J. Zhang
Atomic Physics · Cross-listed from gr-qc
Detecting gravitational waves with spin systems
Jiamin Liang, Mingqiu Li, Yu Gao et al. (+3 more)
The observation of gravitational waves has opened a new window into the Universe through gravitational-wave astronomy. However, high-frequency gravitational waves remain undetected. In this work, we propose that
spin systems can be employed to detect gravitational waves in this unexplored frequency regime. We derive the
spin's response to gravitational waves and identify three distinct effects: the well-known Gertsenshtein effect, a metric-induced interaction, and the gravitational
spin Hall effect. We focus on
nuclear spins and utilize
nuclear magnetic resonance to enhance the gravitational response, leveraging the advantages of long coherence time, high polarization, and a small gyromagnetic ratio. The proposed experimental scheme is capable of probing gravitational waves in the kilohertz to gigahertz range, with projected sensitivities reaching $\sqrt{S_h}\approx10^{-20}~\mathrm{Hz}^{-1/2}$.
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All authors Jiamin Liang, Mingqiu Li, Yu Gao, Wei Ji, Sichun Sun, Qi-Shu Yan
Applied Physics
Loss investigations of high frequency lithium niobate Lamb wave resonators at ultralow temperatures
Wenbing Jiang, Xuankai Xu, Jiazhen Pan et al. (+5 more)
Lamb wave resonators (LWRs) operating at ultralow temperatures serve as promising acoustic platforms for implementing microwave-optical transduction and
radio frequency (RF) front-ends in aerospace communications because of the exceptional electromechanical coupling (k^2) and frequency scalability. However, the properties of LWRs at cryogenic temperatures have not been well understood yet. Herein, we experimentally investigate the temperature dependence of the quality factor and resonant frequency in higher order antisymmetric LWRs down to millikelvin temperatures. The high-frequency A1 and A3 mode resonators with spurious-free responses are comprehensively designed, fabricated, and characterized. The quality factors of A1 modes gradually increase upon cryogenic cooling and shows 4 times higher than the room temperature value, while A3 mode resonators exhibit a non-monotonic temperature dependence. Our findings provide new insights into loss mechanisms of cryogenic LWRs, paving the way to strong-coupling
quantum acoustodynamics and next-generation satellite wireless communications.
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All authors Wenbing Jiang, Xuankai Xu, Jiazhen Pan, Hancong Sun, Yu Guo, Huabing Wang, Libing Zhou, Tao Wu
Chemical Physics · Cross-listed from quant-ph
On the Feasibility of Exact Unitary Transformations for Many-body Hamiltonians
Praveen Jayakumar, Tao Zeng and Artur F. Izmaylov
Exact
unitary transformations play a central role in the analysis and simulation of many-body
quantum systems, yet the conditions under which they can be carried out exactly and efficiently remain incompletely understood. We show that exact transformations arise whenever the adjoint action of a
unitary's generator defines a linear map within a finite-dimensional operator space. In this regime, there exists a finite-degree
polynomial that annihilates the adjoint map, rendering the Baker-Campbell-Hausdorff (BCH) expansion finite. We identify the role of Lie
algebras and their modules in producing finite BCH expansions in all known cases. This perspective brings together previously disparate examples of exact transformations under a single unifying principle and clarifies how algebraic relations between generators and transformed operators determine the
polynomial degree of the transformation. We illustrate this framework for previously known cases of efficient
unitary transformations including
unitary coupled-cluster and Pauli product generators. Using this framework, we propose a new class of fermionic generators that can be used for efficient transformations. The result establishes sufficient algebraic conditions for when exact
unitary transformations are possible and provides new strategies for reducing their computational cost in
quantum simulation and constructing feasible
unitary transformations.
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Optics
Packaging of Low-Environmental-Sensitivity WGM Resonators for Practical Applications
Jiajun Wu, Xuanqi Wang, Chengyu Zhang et al. (+3 more)
We present a prism-coupled packaging strategy for whispering-gallery mode resonators (WGMRs). Utilizing an all-solid-state optical adhesive process with active temperature control and hermetic sealing, the package exhibits exceptional long-term stability and environmental robustness. A standalone WGMR module was characterized, demonstrating a temperature sensitivity below 10^-7 /{\deg}C and a low-frequency Z-axis acceleration sensitivity below 10^-10 /g. The module was applied as a stable optical frequency reference, achieving a short-term frequency stability of 2x10^-13 at 2 ms, and as a nonlinear photonic platform, generating Kerr
soliton microcombs with a pump power of 100 mW. This compact, robust packaging solution enhances the applicability of WGMRs in real-world applications such as narrow-linewidth
lasers and portable microcombs, facilitating the transition from laboratory research to practical deployment.
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All authors Jiajun Wu, Xuanqi Wang, Chengyu Zhang, Chenghong Li, Shan Zhong, Songbai Kang
Applied Physics · Cross-listed from eess.AS
Perceptual Compensation of Ambisonics Recordings for Reproduction in Room
Ali Fallah, Shun Nakamura and Steven van de Par
Ambisonics is a method for capturing and rendering a sound field accurately, assuming that the acoustics of the playback room does not significantly influence the sound field. However, in practice, the acoustics of the playback room may lead to a noticeable degradation in sound quality. We propose a recording and rendering method based on Ambisonics that utilizes a perceptually-motivated approach to compensate for the reverberation of the playback room. The recorded direct and reverberant sound field components in the spherical harmonics (SHs) domain are spectrally and spatially compensated to preserve the relevant auditory cues including the direction of arrival of the direct sound, the spectral energy of the direct and reverberant sound components, and the Interaural Coherence (IC) across each auditory band. In contrast to the conventional Ambisonics, a flexible number of Ambisonics channels can be used for audio rendering. Listening test results show that the proposed method provides a perceptually accurate rendering of the originally recorded sound field, outperforming both conventional Ambisonics without compensation and even ideal Ambisonics rendering in a simulated anechoic room. Additionally, subjective evaluations of listeners seated at the center of the loudspeaker array demonstrate that the method remains robust to head rotation and minor displacements.
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Biological Physics · Cross-listed from q-bio.OT
Interplay of Fidelity and Diversity in the Evolution of the Genetic Code
Yudam Seo, Tsvi Tlusty and Junghyo Jo
The origin and organizing principles of the genetic code remain fundamental puzzles in life science. The vanishingly low probability of the natural codon-to-amino acid mapping arising by chance has spurred the hypothesis that its structure is a solution optimized for robustness against mutations and translational errors. For the construction of effective molecular machines, the dictionary of encoded amino acids must also be diverse enough in physicochemical features. Here, we examine whether the standard genetic code can be understood as a near-optimal solution balancing these two objectives: minimizing error load and aligning codon assignments with the naturally occurring amino acid composition. Using simulated annealing, we explore this trade-off across a broad range of parameters. We find that the standard genetic code lies near local optima within the multidimensional parameter space. It is a highly effective solution that balances fidelity against resource availability constraints. These results suggest that the present genetic code reflects coevolution under conflicting pressures of fidelity and diversity, offering new insight into its emergence and
evolution.
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