Soft Condensed Matter
Laser fragmentation in liquid - constructing a generic reaction map
Anton Plech, Yogesh Pokhrel, Meike Tack et al. (+2 more)
Excitation of absorbing colloids in
liquid by pulsed
laser irradiation creates highly non-
equilibrium states of matter that relax via defined pathways of thermal and non-thermal dissipation channels. The structural fingerprint of these channels can be probed by ultrafast in situ x-ray scattering methods and classified as a function of temporal delay of excitation excitation density, or specifically
laser fluence. We study the example of photo-excitation of a gold colloid by picosecond
laser pulses at the interband absorption band at 400 nm in water. By quantifying
lattice temperature, crystalline fraction, particle sizes and the structural response of the water around the nanoparticles a reaction map is constructed that allows to pinpoint heating, particle melting, water bubble formation and finally particle fragmentation to form nanoclusters of predominant sizes of < 3 nm for applications in theranostics, photonics or catalysis.
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All authors Anton Plech, Yogesh Pokhrel, Meike Tack, Matteo Levantino, Sven Reichenberger
High Energy Physics (Theory)
Quantum Gravity in Asymptotically Flat Spacetimes from Unstable D-Branes
Roji Pius
We present a non-perturbative formulation of
quantum gravity in asymptotically flat spacetimes using Witten's cubic open string field theory (OSFT) on unstable D-branes. Given that the massless
spin-2 sector of the closed string spectrum inherently encodes the degrees of freedom of
quantum gravity, we establish this connection by mapping on-shell closed string excitations directly to gauge-invariant operators in OSFT, realizing a concrete flat-space analogue of the AdS/CFT correspondence. By evaluating the OSFT correlation functions of these operators perturbatively around the tachyon
vacuum, we systematically reproduce the all-orders genus expansion of the closed string S-
matrix for the associated states. This demonstrates that closed string theory-and thus
quantum gravity-emerges dynamically from the open string tachyon
vacuum, establishing Witten's OSFT as a fully calculable, non-perturbative framework for flat-space
quantum gravity.
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Superconductivity
From band reconstruction to Bogoliubov dispersion: How dz2-band enhances iron-based superconductivity
Jingming Yan, Shendong Su, Guihao Jia et al. (+6 more)
Conventional understanding of iron-based superconductivity is usually established based on electronic bands at the Fermi level, leaving deeper bands overlooked as potential factor. Here, we expand this view by demonstrating that a deep-lying dz2 band below the Fermi level can be employed to enhance the superconducting paring strength. By using scanning tunneling microscope to mechanically change the
crystal lattice of an iron-based
superconductor, we observe an upward shift of the deep-lying dz2 band related feature, leading to hybridization with the primary superconducting bands at the Fermi level. We visualize the novel evidence of this band hybridization and resulting enhanced superconducting gap through quasiparticle interference imaging, providing conclusive evidence that engineering such correlations between deep and pairing-active bands is a potent mechanism for amplifying the superconducting gap. This work refines the conventional view of pairing-relevant electronic structures and establishes band hybridization as an effective way to optimize superconducting materials.
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All authors Jingming Yan, Shendong Su, Guihao Jia, Yucong Peng, Xuanyu Long, Zheng Liu, Pei Ouyang, Qi-Kun Xue, Wei Li
Quantum Physics
Quantitative Rules for Parallel Calibration and Drift-Resilient Maintenance of Large-Scale Superconducting Quantum Processors
Zhihao Wu, Kechengqi Zhu, Shichuan Xue et al. (+13 more)
As superconducting
quantum processors scale toward hundreds of
qubits, manual calibration becomes increasingly costly and difficult to sustain. Here we address two system-level factors governing automated calibration, namely, crosstalk induced by parallel operations and temporal drift of control parameters. On a 66-
qubit superconducting processor, cross-
entropy benchmarking shows that single-
qubit calibration tolerates full-chip concurrency with minimal fidelity loss, whereas CZ calibration requires a minimum coupler-graph distance of four to avoid elevated control errors. Continuous monitoring of representative
qubit and coupler parameters further yields quantitative refresh rules that assign refresh priority by error-budget consumption. These results turn two conventionally heuristic choices, the concurrency density of calibration tasks and the refresh priority of each control parameter, into measurable operating rules. Implemented within an automated calibration framework, the rules support a six-
qubit Greenberger-Horne-Zeilinger state with a zero-noise-extrapolated fidelity of 89.64%, distance-dependent logical-error suppression in a single-cycle repetition-code
benchmark, and a reduction of the mean single-
qubit error from 0.023 to 0.011 on a 337-
qubit processor, providing an experimentally grounded reference for the automated calibration and maintenance of current and future large-scale superconducting
quantum systems.
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All authors Zhihao Wu, Kechengqi Zhu, Shichuan Xue, Xinfang Zhang, Zhaohua Yang, Zhida Zhang, Shun Hu, Cong Li, Dingdong Liu, Kangding Zhao, Peng Luo, Lingling Lao, Xiang Fu, Mingtang Deng, Junjie Wu, Kai Lu
Materials Science
Generation, Accumulation, and Utilization of Data in the Automatically Controlled End-Station of a Soft X-ray Beamline
Yasunobu Ando, Masashige Miyamamoto, Keita Hiromori et al. (+4 more)
AI is rapidly transforming materials exploration, yet reliable AI-assisted research depends on experimental data that retains their context, provenance, and machine-readable structure. High-throughput synchrotron measurements therefore require more than automated data acquisition: data generation, accumulation, and utilization must be connected within a continuous workflow. Here, we present a data-centric research framework that integrates the PIONEER system, the OMNES, and ML analysis. The PIONEER system automates sample handling,
vacuum transfer, and scanning XAS at the BL08U soft X-ray beamline of NanoTerasu, systematically generating large volumes of spatially resolved spectral data. Measurement and analysis files are stored in the cloud-based ARIM-mdx data system, while OMNES manages metadata describing samples, preparation procedures, measurement conditions, instrument settings, data locations, and analysis histories. Tabular and JavaScript Object Notation formats are used according to the metadata structure, with numerical values stored separately from units to facilitate machine processing. OMNES organizes these records based on causal relationships among experimental and analytical processes, linking samples, measurements, raw data, processed data, and analysis results through a relational data model and visualizing their relationships as a graph. This causality-based organization preserves experimental and analytical provenance and clarifies how each result was derived from the preceding processes and data. The accumulated spectra can subsequently be processed using ML methods, including dimensionality reduction and materials classification, and the resulting data can be registered back into OMNES. Previously reported ML analysis of BN XAS spectra is presented as an example of the analytical workflow that can be applied to data acquired at the beamline.
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All authors Yasunobu Ando, Masashige Miyamamoto, Keita Hiromori, Takeru Nakashima, Masafumi Horio, Masato Kotsugi, Iwao Matsuda
Fluid Dynamics
Net drag reduction in turbulent pipe flow by airfoil-section grids concentrated near the wall
Takuya Masuda
The frictional drag of turbulent pipe flow is responsible for enormous energy consumption in water and natural gas distribution systems. Flow straighteners can reduce this drag by suppressing
turbulence, but they generally induce a pressure loss that exceeds the reduction; similarly, large-eddy breakup devices installed in pipes have not achieved a net drag reduction. In this study, a grid of NACA0006 airfoils was adopted as a flow straightener to suppress the pressure loss, and its net drag reduction was evaluated by numerical simulations using the $k$-$\omega$ shear stress transport model of the axisymmetric Reynolds-averaged Navier-Stokes equations with periodic boundary conditions. The model was validated against fully developed turbulent pipe flow and a previous experiment on a large-eddy breakup device in a pipe. Under a pressure difference corresponding to a Reynolds number ($\mathit{Re}$) of approximately $10^5$, a grid pattern of concentric rings concentrated near the wall at an axial spacing of 0.5 m increased the flow rate by up to 9.0%, and the flow rate increase remained positive for $5 \times 10^{4} \leq \mathit{Re} \leq 2 \times 10^{5}$. The grid pattern reduced the area-integrated Reynolds shear stress by 29% and brought the velocity profile closer to a laminar one. The effectiveness of the near-wall placement is consistent with the Fukagata-Iwamoto-Kasagi identity, which weights the Reynolds shear stress more heavily closer to the wall.
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Quantum Physics
An iterative Bayesian variational quantum eigensolver with the von Mises-Fisher distribution
Trung Minh Huynh, Gwangil An, Minsu Kim et al. (+2 more)
We develop an iterative
Bayesian variational
quantum eigensolver in which the unknown ground state, parametrised as a real unit vector, is inferred through a von Mises–Fisher distribution sequentially updated from Hadamard-test measurements on a single ancilla
qubit. Building on a companion paper that treated a single success outcome via exact moment matching, we generalise the scheme to condition on $m$ success outcomes for the likelihood function per iteration. Since exact moment matching becomes impractical for $m>1$, we exploit the large-concentration regime, in which a first-order expansion of the log-likelihood yields a closed-form von Mises–Fisher posterior with $m$ entering only through a multiplicative weight. We prove that the two convergence properties of the single-outcome scheme—non-decreasing overlap and non-decreasing concentration—are preserved provided $m$ lies within an explicitly characterised range. Based on the theory, we propose a measurement-based
algorithm and illustrate the convergence on randomly generated three- and four-
qubit Hamiltonian matrices, on $\mathrm{HeH}^+$, and on $\mathrm{H}_2$.
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All authors Trung Minh Huynh, Gwangil An, Minsu Kim, Yu-Seong Jeon, Jinhyoung Lee
High Energy Physics (Experiment)
Observation of single top-quark production in the $s$-channel in proton–proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
ATLAS Collaboration
The first single-experiment observation of single top-
quark production in the $s$-channel is presented. Measurements of this process are essential to fully characterize the electroweak interactions of the top
quark and probe for new physics, however its highly suppressed cross-section has so far caused it to evade direct detection at the Large
Hadron Collider. The analysis uses
proton–
proton collision data collected at a center-of-mass energy of $\sqrt{s}=13$ TeV with the ATLAS detector, corresponding to an integrated luminosity of $140$ fb$^{-1}$. The selected events contain exactly one electron or
muon, missing transverse momentum, and exactly two $b$-
quark-initiated jets. A Graph Neural Network is utilized to separate the signal from the top-
quark pair, $W$+jets, and $t$-channel single top-
quark backgrounds. A likelihood fit to the network output yields an observed (expected) signal significance of $5.1$ ($5.2$) standard deviations. The measured cross-section of $\sigma_{t\bar{b}+\bar{t}b} = 10.8 \pm 1.5 \text{ (stat.)} \pm 1.6 \text{ (syst.)}\,\text{pb}$ is consistent with the Standard Model prediction.
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Instrumentation and Methods for Astrophysics
Pseudo Closed-Loop Bootstrapping for Reinforcement Learning Based AO Control
Eemil Halonen, Jalo Nousiainen, Markus Kasper et al. (+1 more)
High contrast imaging with ground-based
telescopes requires extremely precise wavefront control. The performance of the controller ultimately depends on the quality and efficiency of the wavefront sensing technique, which has led to the development of ever more sensitive wavefront sensors (WFS). However, the increase in sensitivity comes at the cost of greater nonlinearity, which poses challenges for conventional linear reconstructors and controllers. Reinforcement Learning (RL) is a branch of machine learning in which control policies are learned by interacting with the environment. RL has recently attracted interest in the field of XAO, and previous studies have demonstrated that a model-based RL variant, the Policy Optimization for Adaptive Optics (PO4AO), can effectively compensate for temporal delays, misregistration errors, and moderate WFS nonlinearities. PO4AO learns an initial control strategy by collecting closed-loop data from the integrator controller with a linear reconstructor. However, in cases of highly non-linear WFS and challenging conditions, closing the loop with the integrator is difficult, and high-fidelity data cannot be collected. Consequently, learning robust control with PO4AO is challenging. We propose a robust learning strategy in which PO4AO is pre-calibrated using an internal light source and a DM, enabling direct on-sky closed-loop operation without a stable integrator controller for bootstrapping the initial models.
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All authors Eemil Halonen, Jalo Nousiainen, Markus Kasper, Nuutti Hyvönen
Optics
Simulations of Fluorescence and Energy Transfer in Periodic Systems: Pitfalls and Considerations for Bound States in the Continuum
Ilia Lykov, Sergejs Boroviks and Olivier J. F. Martin
Bound states in the continuum (BICs) combine high quality factors with strong electromagnetic-field localization and are therefore widely explored for enhancing light–matter interactions. However, large field amplitudes do not directly translate into useful fluorescence enhancement or energy transfer enhancement between two donor–acceptor fluorophores. Here, we investigate this question for a hybrid plasmonic–photonic resonant waveguide grating supporting a
symmetry-protected BIC. We emphasize some of the pitfalls associated with the numerical simulations, especially the utilization of periodic boundary conditions for fluorescence. Strong BIC-related fields can enhance acceptor absorption while useful fluorescence enhancement remains moderate. Extensive simulations and the comparison of different figures of merit, indicate that, while a BIC can suppress radiative leakage, it can also redirect a large fraction of the energy into Ohmic losses. As a result, the useful fluorescence enhancement of donors remains moderate, whereas absorption by acceptors can be strongly enhanced in Förster resonance energy transfer (FRET) experiments. It is essential to separate near-field FRET from long-range energy transfer and reabsorption mechanisms, both of which are mediated by the delocalized BIC mode. Finally, results obtained for finite gratings are compared with infinite periodic simulations and conceptual inconsistencies explained. This work provides a consistent framework for interpreting fluorescence, absorption, and energy transfer in BIC-based periodic nanophotonic systems.
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Optics
Inverse Design of Integrated Photonic Components for Visible-Light Applications
Christoph Stockinger, Marko Šimić, John O. Adeniran et al. (+3 more)
Photonic integrated
circuits (PICs) operating in the visible spectral range are crucial for
quantum technologies, optical sensing, and nonlinear optics applications. However, their development is hampered by limited integration density and operational bandwidth, linked to low refractive index contrast and restricted parameter space in intuition-based PIC design. We address these bottlenecks with an adjoint-based, fabrication-aware inverse design workflow tailored for visible-spectrum photonics. By expanding the capabilities of FDTDX, an open-source, GPU-accelerated FDTD solver, we provide a versatile
memory and runtime efficient inverse design platform. Demonstrating this approach on a silicon nitride (Si3N4) platform, we design, fabricate, and experimentally validate ultra-compact, broadband components for light routing, multiplexing, and polarization control. This work provides a scalable framework for high-density, high-performance visible-light PICs.
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All authors Christoph Stockinger, Marko Šimić, John O. Adeniran, Natale G. Pruiti, Marc Sorel, Peter Banzer
Quantum Physics
Deterministic generation of large-scale photonic GHZ states utilizing spin echo in a solid-state quantum light source
Zu-En Su, Dan Cogan, Oded Kenneth et al. (+3 more)
Quantum technologies witness rapid contemporary developments transitioning from abstract scientific ideas and fundamental demonstrations, into systems of sufficient quality and scale, enabling real applications. Photonic
quantum technologies are playing a pivotal role in these developments, since
photons are robust, easily controlled, detect and measured, thus qualify as flying carriers of
quantum information and
entanglement distributers. The efforts to develop photonic
quantum technologies benefit from the maturity of the classical optical technologies. It was shown that even a source of heralded three entangled
photons is sufficient for building large scale
quantum computers using otherwise classical optical elements. Here, we demonstrate a novel
semiconductor quantum dot based device, which deterministically generate at GHz rates, indistinguishable single
photons in a robust Greenberger-Horne-Zeilinger (GHZ) state of more than a dozen
photons. The device utilizes novel natural
spin echo concept, provided by the opposite precession directions of the negative and positive carriers'
spins in the excited and ground levels of the periodically excited dot, respectively. The excitation rate is finely tuned to nullify the phase acquired by both
spins' precession. Our record long GHZ state producing device can yet be feasibly improved to provide higher-rate, brighter and more robust deterministic GHZ source, significantly reducing the overhead requirements for photonic
quantum technologies.
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All authors Zu-En Su, Dan Cogan, Oded Kenneth, Shunfa Liu, Jin Liu, David Gershoni
Quantum Physics
Robust quantum key distribution with imperfections in state preparation and characterization
Yi-Fei Lu, Yan-Yang Zhou, Yang Wang et al. (+9 more)
Quantum key distribution (QKD) offers an approach for secure communication over
quantum channels, based on the principles of
quantum mechanics. However, the inevitable imperfections in QKD systems can introduce critical vulnerabilities, posing significant challenges to the deployment of QKD in terms of both practical security and performance. In this work, we present a comprehensive security analysis of QKD in the practical scenarios involving imperfections in modulation spaces. Specifically, our analysis focuses on the imperfections related to encoding, intensity modulation, and their characterization. We provide a unified framework based on the operator dominance method to overcome these issues and achieve a tight estimation of the secret key rate (SKR). The simulation results show that the SKR in practical scenarios, with parameters characterized from commercial QKD systems, closely matches the SKR under ideal conditions. In the finite case, the maximum transmission distance can reach up to 250 km with total pulse number $N=10^{12}$ and the SKR closely approaches the asymptotic limit up to 250 km with $N=10^{14}$. This validates the robustness of our method against imperfections in state preparation and characterization. Furthermore, the feasibility and robustness of method in measurement-device-independent (MDI) QKD have also been demonstrated. Our analysis not only promotes advancements in enhancing practical security and performance but also highlights the feasibility of deploying QKD for actual applications.
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All authors Yi-Fei Lu, Yan-Yang Zhou, Yang Wang, Xin-Hang Li, Yu Zhou, Xiao-Lei Jiang, Jia-Ji Li, Chun Zhou, Hong-Wei Li, Yu-Yao Guo, Lin-Jie Zhou, Wan-Su Bao
High Energy Astrophysical Phenomena
Neutron star cooling with $\Delta$ dUrca processes
Yogeesh N, Monika Sinha and Vishal Parmar
The cooling of
neutron stars (NSs) provides insight into their composition and equation of state. However, a complete understanding of this phenomenon is still an open question. The early stage of NS cooling is dominated by
neutrino emission from the core, which rapidly cools the
star. Urca processes are one such mechanism where
neutrinos escape from the core, carrying away most of the heat. Nucleonic and hyperonic direct Urca processes are known rapid cooling mechanisms. The possible appearance of $\Delta$ baryons in dense matter introduces additional weak-interaction channels, including $\Delta$ direct Urca processes. Although such processes have been discussed in the context of $\Delta$-admixed NS matter, their
neutrino emissivities and impact on NS cooling have not been systematically investigated. In this work, for the first time we incorporate the
neutrino emissivities of the relevant $\Delta$ direct Urca processes into NS cooling simulations. We investigate the thermal
evolution of $\Delta$-admixed NSs and assess the impact of these additional
neutrino emission channels on their cooling behavior. We find that $\Delta$ direct Urca processes can provide an efficient
neutrino-cooling mechanism and significantly accelerate the thermal
evolution of NSs. Our results demonstrate that $\Delta$ baryons and their associated weak-interaction processes can play an important role in explaining NSs with unusually low surface temperatures and provide a new connection between the composition of dense matter and NS cooling observations.
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Instrumentation and Methods for Astrophysics
radio-astro-tools: linking radio astronomical data to the astronomical Python ecosystem
Eric W. Koch, Adam Ginsburg, Thomas P. Robitaille et al. (+15 more)
We present the
radio-astro-tools code suite, which consists of several Python packages that enable analysis of
radio data, especially interferometric spectral cubes, in the context of the Astropy software ecosystem. While these tools were designed with
radio data in mind, they are built to be general and have applications on data sets at other wavelengths. The core package, spectral-cube, handles reading, writing and analysis of cube data, and it enables straightforward parallelization via dask and joblib backends. Support packages include casa-formats-io and
radio-beam, which handle reading of CASA tables & images and reading and manipulation of point spread functions, respectively. The pvextractor package facilitates creation of position-velocity diagrams. The uvcombine package implements the "feather"
algorithm for combining single-dish and interferometric data. The development of
radio-astro-tools included several contributions to other repositories, including matplotlib, astropy, and regions to support interaction between CASA and other parts of the astronomy software ecosystem. We also present a detailed set of tutorials written in Jupyter notebooks that can be run interactively in a browser, providing more accessible access to data analysis for
radio spectral-line data cubes.
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All authors Eric W. Koch, Adam Ginsburg, Thomas P. Robitaille, Erik W. Rosolowsky, Alyssa Bulatek, Savannah Gramze, Jonathan D. Henshaw, Derek Homeier, Preshanth Jagannathan, Amanda A. Kepley, Adam K. Leroy, Sébastien Maret, Stuart Mumford, George Privon, Álvaro Sánchez-Monge, Srikrishna Sekhar, Brigitta Sipőcz, A.J.M. Thomson
Quantum Physics
Experimental Measurement-Device-Independent Quantum Key distribution with Flawed State-Preparation over 300 km
Yi-Fei Lu, Yan-Yang Zhou, Yang Wang et al. (+10 more)
Quantum key distribution (QKD) promises theoretically secure communication. However, it encounters challenges in implementation security and performance due to inevitable device imperfections. Since the proposal of measurement-device-independent (MDI) QKD, the critical step toward practical security is to secure QKD with imperfect sources. The source imperfections manifest as state-preparation uncertainty (SPU) in various aspects, e.g., encoding uncertainty, intensity fluctuation, and imperfect
vacuum states. Here, we perform an MDI-QKD experiment and achieve both high practical security and superior performance. We address the general form of SPU and guarantee a tight estimation of the secret key rate based on the operator dominance method. We achieve secure key distribution over 303.37 km, which not only represents the farthest distance in experiments involving SPU but also considers the most SPU scenarios. Our experimental results represent a significant step toward promoting practical and secure
quantum communication.
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All authors Yi-Fei Lu, Yan-Yang Zhou, Yang Wang, Yu Zhou, Xiao-Lei Jiang, Xin-Hang Li, Hai-Tao Wang, Yan-Mei Zhao, Jia-Ji Li, Chun Zhou, Hong-Wei Li, Lin-Jie Zhou, Wan-Su Bao
Applied Physics
Time-Domain Analysis of Surface Acoustic Wave Magnetoelectric Sensors
Mohsen Samadi, Henrik Wolframm, Felix Weisheit et al. (+4 more)
The transient response of surface acoustic wave sensors is important for understanding their dynamic behavior, propagation delay, and response to time-varying signals. In this work, the time-domain propagation characteristics of a magnetoelectric SAW sensor based on a multilayer Love-wave delay line are investigated using complementary numerical and experimental approaches. Time-domain analysis is employed to determine the delay time and to extract the phase and group velocities, while frequency-domain analysis provides an independent characterization of the wave dispersion. Both numerically and experimentally, the phase and group velocities are found to differ, reflecting the dispersion of the Love wave in the multilayer structure. At the operating frequency of 146 MHz, the simulated group velocity obtained from wave-field tracking agrees within 0.4% with the value determined from the frequency-domain dispersion relation. The simulated delay time and group velocity also show good agreement with experiment, with deviations of 2.7% in delay time and 0.9% in group velocity. These results demonstrate the consistency of the time- and frequency-domain analyses and provide a quantitative characterization of the transient propagation behavior of SAW sensors.
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All authors Mohsen Samadi, Henrik Wolframm, Felix Weisheit, Dirk Meyners, Eckhard Quandt, Michael Höft, Martina Gerken
Optics
Engineering Photon Avalanche Thresholds in Single Nanocrystals with Plasmonic Nanostructures
Marcin Szalkowski, Maciej Fryckowski, Małgorzata Misiak et al. (+3 more)
Optical sub-diffraction imaging has become an essential tool in modern research. Recently, a new imaging strategy has been demonstrated that exploits the strongly nonlinear excitation-emission response of rare-earth-doped nanocrystals operating in the
photon avalanche (PA) regime. This approach benefits from simple optical instrumentation, near-infrared excitation and emission, low cytotoxicity, and high photostability. However, its practical implementation is hindered by relatively high (10-100s of kW/cm2) excitation power densities required to initiate the PA process. We aim to mitigate this limitation through electromagnetic field enhancement provided by metallic nanostructures. The results of microscopic studies of individual
photon-avalanching nanocrystals coupled to a silver island film demonstrate a greater than tenfold reduction in the excitation power density required to trigger the avalanche emission. These experimental results, corroborated by numerical modelling, which elucidates the role of plasmon-mediated electromagnetic field enhancement in modifying the
photon avalanche dynamics, paves the way towards new generation of low excitation power probes for sub-diffraction imaging and sensing.
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All authors Marcin Szalkowski, Maciej Fryckowski, Małgorzata Misiak, Artur Bednarkiewicz, Dawid Piątkowski, Sebastian Maćkowski
Instrumentation and Detectors
Autocorrelation-based beam shape optimization in scanning electron microscopy
Rebecca Guan, Andreas Werbrouck, Matthew M. Maschmann et al. (+1 more)
Many automatically focusing
algorithms for scanning electron microscopes exist. Typically, these optimize a single derived metric (such as image sharpness) without considering the intrinsic beam shape. We describe an
algorithm to automatically focus and stigmate scanning electron microscopes based on the autocorrelation of captured images. In the first part of this work, we develop the theoretical basis of using the autocorrelation to approximate the current beam shape. In the second part, we use this to condition the beam shape on various surfaces, using
Bayesian optimization to tune both working distance and, in particular, stigmation. Through a comparison of the full width at half maximum of the autocorrelation arrays before and after optimization and a visual comparison of images taken of the sample surface before and after optimization, we show that the
algorithm is able to successfully optimize the scanning parameters. Overall, our
algorithm can effectively focus on a variety of topographies at different magnifications.
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All authors Rebecca Guan, Andreas Werbrouck, Matthew M. Maschmann, Matthias J Young
Optics
Impact of Stimulated Brillouin Scattering on Modulation Instability in Fiber Fabry-Perot Resonators
Alice Houard, Thomas Bunel, Matteo Conforti et al. (+2 more)
We report the experimental and numerical demonstration of stimulated Brillouin scattering-induced stabilization of Kerr-driven modulation instability in fiber Fabry–Perot resonators. We show that Brillouin scattering shapes the modulation instability spectrum into a stable multi–free-spectral-range cascade that is otherwise unstable in the absence of Brillouin effects. We further identify that this stabilization originates from the real part of the Brillouin response, leading to an asymmetric Kerr-Brillouin interaction governed by the relative position of the Brillouin frequency shift with respect to the cavity resonances. These results establish stimulated Brillouin scattering as an additional degree of freedom for controlling nonlinear dynamics in Kerr resonators.
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All authors Alice Houard, Thomas Bunel, Matteo Conforti, Saliya Coulibaly, Arnaud Mussot
Statistical Mechanics
Quantum annealing of the random transverse-field Ising model in one, two, and three dimensions
István A. Kovács, Neil Shah and Róbert Juhász
Quantum annealing must be sufficiently slow to prevent defect formation. We study this problem in the random transverse-field Ising model via the adiabatic
theorem to obtain the limiting rate at which defect formation can be avoided. Our approach based on the strong-disorder renormalization group (SDRG) technique views the annealing process as a gradual aggregation of strongly coupled clusters, giving access to the elementary events of error formation. We present a scaling theory of the statistics of these events in general dimensions and confront it to an extensive numerical analysis carried out in one, two, and three dimensions by an efficient implementation of the SDRG method. This approach is also validated by exact diagonalization in one dimension by means of the free-
fermion technique. Our results consistently show a logarithmically slow decrease of the error density with the annealing time, characterized by the dimension-dependent critical exponents of the corresponding infinite-disorder fixed point of the model. Furthermore, we provide a map of individual events of potential defect formation in the excitation energy - control parameter plane, which may help in the design of optimal annealing paths.
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Atmospheric and Oceanic Physics
A Physics-Constrained Implicit Profile Network for Continuous Reconstruction of Tropical Cyclone Near-Surface Wind Profiles
Jian Ma, Yilin Yang, Robert Rogers et al. (+2 more)
Near the ocean surface, tropical cyclone winds change rapidly with height, but direct measurements are limited because aircraft dropsondes provide only sparse and irregular observations. Continuous wind profiles are important for understanding hurricane boundary-layer processes, improving storm-surge prediction, supporting offshore engineering, and assessing coastal hazards. In this study, we developed an artificial intelligence model that combines machine learning with physical principles to reconstruct continuous wind profiles from sparse observations. The model is designed to preserve the observed surface winds while generating realistic changes in wind speed and direction with height. Tests using more than two decades of NOAA hurricane observations show that the method accurately reproduces the vertical structure of tropical cyclone winds over a wide range of storm intensities. The framework can also extend satellite-derived surface wind measurements into three-dimensional near-surface wind fields, providing new opportunities for hurricane research, operational forecasting, and engineering applications.
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All authors Jian Ma, Yilin Yang, Robert Rogers, Jun A. Zhang, Jie Tang
Solar and Stellar Astrophysics
Oxygen isotopic ratio in open cluster RGB stars: A new method for accurate mass and age estimations
O. Straniero, C. Abia, I. Domínguez et al. (+1 more)
Determining precise and homogeneous absolute ages of open clusters (OCs) remains a challenge in stellar astrophysics, mainly due to parameter degeneracies in photometric methods and line-of-sight extinctions. We present a novel method for estimating the ages of intermediate-age and old OCs, based on the strong initial-mass dependence of the surface oxygen isotopic ratio, 16O/17O, measured in RGB
stars following the first dredge-up. Using updated theoretical stellar models computed with the FuNS code, we demonstrate how post-FDU CNO isotopic abundances reflect initial stellar masses. We analysed high-resolution near-infrared spectra for 11 RGB
stars belonging to four Galactic OCs. For the intermediate-age clusters NGC 7789, NGC 7044, and NGC 6819, we derive ages of 1.80, 1.81, and 2.31 Ga, respectively. For the two
stars in NGC 6819 the derived initial stellar mass (1.625 Mo) and age are in excellent agreement with independent estimates from asteroseismology and eclipsing binaries. Conversely, ages estimated by means of machine learning
algorithms, trained to recognise specific features in the cluster CMDs, are systematically lower. Regarding the old and super-metal-rich cluster NGC 6791, the low signal-to-noise ratio and the possible line blending hinder precise mass and age constraints. With these limitations, we can only fix a lower bound of about 4 Ga for its age. The surface oxygen isotopic ratio in RGB
stars provides a powerful, independent stellar clock, making high-resolution near-infrared spectroscopy of oxygen isotopes a key tool for Galactic archaeology.
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All authors O. Straniero, C. Abia, I. Domínguez, P. de Laverny
General Relativity and Quantum Cosmology
A note on decoherence in quantum cosmology by thermal perturbations: an open quantum systems approach
Alexander Kulyabin
We study, within a toy model, how a thermal bath of cosmological perturbations can decohere the minisuperspace degrees of freedom of the universe, treating the perturbations as an environment in the framework of open
quantum systems. Instead of tracing out the perturbations from a semiclassical ansatz for the total wave function, as in earlier approaches, we incorporate their backreaction on the background through an effective second-order coupling and derive a master equation. The model describes a spatially flat semiclassical universe during slow-roll inflation with a dust clock field, while scalar cosmological perturbations in a phenomenologically assumed thermal state constitute the environment. The master equation is non-Markovian, since the bath correlation functions do not decay in time. Within this framework, we find that, for a representative set of parameter estimates, the characteristic decoherence timescale corresponding to the thermal contribution can be shorter than the Hubble timescale. In addition, we address the question of whether the pointer-state structure induced by the decoherence in such a framework could provide a criterion for the choice of semiclassical states in
quantum cosmology.
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Fluid Dynamics
Inertialess instability of elasto-viscoplastic circular Couette flow
James D. Shemilt, Neil J. Balmforth and Duncan R. Hewitt
An exploration is presented of two-dimensional, circular Couette flow of an elasto-viscoplastic fluid described by Saramito's (Bingham) constitutive law. Axisymmetrical base states are constructed. As has been noted previously, such states are not unique, with stresses over any plugs depending on the initial
polymer stress, and the shear rate and stress may jump discontinuously across the yield surfaces. We show that base states with continuous stress profiles are linearly unstable at zero Reynolds number when they contain regions with relatively low shear rate. Unstable modes become stronger and localized to the yield surfaces as the azimuthal wavenumber increases. We report numerical simulations exploring the nonlinear dynamics of the instability. The linear unstable modes saturate at finite amplitude to create spatio-temporally complicated states.
Polymer stress
diffusion is added to ease these numerical simulations, eliminating normal-stress discontinuities and instability at the shortest wavelengths. Instability and transition to complex dynamics occur whenever the base flow contains regions with relatively low shear rate.
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General Relativity and Quantum Cosmology
Probing Kerr spacetime via interferometric signatures of higher-order images
Fabiano Feleppa, Fabio Aratore, Valerio Bozza et al. (+1 more)
Higher-order images produced by
photons that orbit close to the unstable
photon region of a black hole encode information about the spacetime geometry and leave characteristic signatures accessible with long interferometric baselines. We develop an analytical description of these signatures for a compact source in the spacetime of a slowly rotating Kerr black hole. Using the strong deflection limit, we derive the complex visibility function for a source of finite size at linear order in the black-hole
spin. For a static equatorial source, we obtain a direct relation between the dimensionless Kerr
spin parameter and the angular displacement of successive higher-order images belonging to the same parity sequence. We then extend the construction to a compact source on a circular equatorial orbit by evaluating each image contribution at the corresponding retarded source position. Frame dragging and source motion modify the angular positions of the images and leave distinct imprints on the long-baseline visibility pattern. For the configuration considered here, these effects act in opposite angular directions, so that the resulting structure is determined by their competition. Our results provide an analytical framework for identifying the imprints of black-hole
spin and source dynamics in the interferometric signatures of higher-order images.
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All authors Fabiano Feleppa, Fabio Aratore, Valerio Bozza, Lorenzo Albanese
General Relativity and Quantum Cosmology
Probing hairy Kerr black holes through quasi-periodic oscillations II: a study based on the resonance models
Anirban Dasgupta, Supragyan Priyadarshinee, Indrani Banerjee et al. (+1 more)
Hairy black holes (BHs), characterized by nontrivial scalar or matter fields, introduce additional degrees of freedom beyond mass, charge, and
spin, providing a framework for testing deviations from the Kerr paradigm. We investigate a class of rotating hairy black holes constructed within the gravitational decoupling framework, whose spacetime satisfies the Einstein field equations with a conserved energy-momentum tensor consistent with the strong energy conditions. In our previous work (Paper I; Dasgupta et al. 2026), we studied their horizon structure and test-particle dynamics and confronted two kinematic high-frequency quasi-periodic oscillation (HFQPO) models with observations of six black hole sources. Building on that analysis, we here test nine resonance models against the same HFQPO data, enabling a systematic comparison of eleven models (two kinematic and nine resonance) within the hairy Kerr framework. A comprehensive analysis based on the two kinematic models (Paper I) and the nine resonance models reveals that the HFQPO data with the current level of precision cannot rule out the hairy Kerr scenario. By implementing the Akaike Information Criterion and by examining the consistency of the inferred
spins with previous independent
spin estimates, our analysis provides a systematic framework for assessing the relative performance of different HFQPO models for each source. These results highlight the potential of HFQPOs to probe black hole hair and the need for more precise observations and a better understanding of the physical origin of QPOs.
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All authors Anirban Dasgupta, Supragyan Priyadarshinee, Indrani Banerjee, Subhash Mahapatra
Quantum Physics
Minimal Scenarios Witnessing Genuine Multipartite Nonlocality Possibilistically
Soumyadip Patra and Peter Bierhorst
We study a strong form of genuine multipartite nonlocality (GMNL), where an $n$-partite scenario admits a
quantum strategy generating outcomes belonging to a restricted set with certainty, whereas every strategy built from nonclassical resources shared among at most $k<n$ parties fails this criterion with positive probability. This generalizes what is referred to as strong contextuality/nonlocality, or pseudotelepathy, beyond ruling out local models. For the simplest five-party Bell scenario of two binary-outcome measurement settings per party, we use the inflation technique to demonstrate that a game with a perfect
quantum strategy witnesses a robust separation from models built from bipartite resources under local operations and shared randomness (LOSR), establishing the behavior is LOSR-GMNL. We provide broader context for this result by investigating its simulability with resources shared among three or four parties under different resource models and alternative definitions of GMNL. A central open question is whether $n$-party
quantum resources can achieve such a separation from models built from $(n-1)$-party resources, for $n\ge 3$. We make progress here by constructing a family of robustly LOSR-GMNL games with $\epsilon$-optimal
quantum strategies experimentally indistinguishable in the limit from true probability-one-winning strategies for any desired level of precision.
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Quantum Physics
Heisenberg Echo Symmetrization for Gate-Insertion Error Mitigation
Raam Uzdin
Gate insertion (GI)
quantum error mitigation replaces involutory gates such as CZ and CX with 2j+1 repetitions of the same gates to nominally amplify noise by the same factor. Analytical and experimental results show that this amplification scaling fails for non-commuting gate noise, as typically encountered in realistic devices. Here we introduce Heisenberg-echo symmetrization (HES), which combines standard GI with an echo inspired by the Heisenberg representation to cancel the leading GI error. In our simulations, HES reduces the absolute fidelity error by one to two orders of magnitude compared with GI. Unlike the more accurate Layered-KIK method, HES is compatible with any hardware and requires only
circuit-level access. It enables virtual noise scaling across platforms, potentially reducing sampling overhead substantially. Its agnostic noise amplification also provides full resilience to temporal noise drift. For pure initial states, however, high-rank observables can substantially increase the echo variance relative to non-echoed
circuits, whereas rank-one observables incur no additional sampling overhead compared with GI or Layered-KIK. HES is therefore particularly suited to rank-one or nearly rank-one observables.
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Instrumentation and Detectors
From Tunnel Overburden Reconstruction to Tidal Measurements via atmospheric muon
Jiwon Seo, Jongseok Chung, Chang Hyon Ha et al. (+8 more)
Muography with scintillator-based detectors enables the investigation of density distributions within large structures. The Hankuk Atmospheric-
muon Wide Landscaping (HAWL) project is the first real-time portable
muon tomography. It successfully charted the mountainous region of eastern Korea by measuring
cosmic-ray
muons with a detector operated in a moving vehicle. HAWL achieved a tunnel length accuracy of 6.0 % and an overburden measurement range of 8-400 meter-water-equivalent (m.w.e.). The HAWL upgrade (HAWLU) features a more compact design and enables trajectory reconstruction. Using this upgraded system, we measured tidal water-level variations with meter-scale precision over 31.6 days in the Boryeong Undersea Tunnel. The measured
muon rate decreased by $1.72 \pm 0.04$ % per meter of increasing tidal level, while the reconstruction of undersea tunnel scan independently validated the detector performance. These results demonstrate the capabilities of dynamic muography in two approaches, one with a portable detector in motion and the other with a detector measuring a target that changes over time.
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All authors Jiwon Seo, Jongseok Chung, Chang Hyon Ha, TongZhou Huang, Jinyoung Kim, Sooa Kim, Hani Kimku, Byoung-cheol Koh, Minsu Kwak, Sihyun Lee, Yujin Lee