Optics
Optical forces, helicity, angular momentum and how they are all intertwined
Iker Gómez-Viloria, Enrique Ayllón García, Jorge Olmos-Trigo et al. (+4 more)
The theoretical description of optical forces and torques on micron_sized particles is a crucial area of research and has formed the foundation for advancements in optical trapping and manipulation technologies. In this study, we derive analytical expressions for optical forces and torques on micron_sized spherical particles illuminated by focused Laguerre_Gaussian (LG) beams, employing the well_defined helicity multipolar decomposition of electromagnetic fields and Mie theory. We developed a multifunctional program, Multipolar Optical Forces Toolbox, based on this theoretical framework. The program, available on GitHub, was used to generate optical trapping stability maps. These maps predict trap stability across a wide range of system parameters and serve as a practical tool for designing advanced optical trapping experiments. Our analysis reveals the important role of helicity p and orbital angular momentum l on the dynamics of particles trapped off_axis in LG beams and demonstrates the unique nature of the tangential torque. Our findings also highlight notable differences in longitudinal optical forces resulting from pure helicity modifications in Gaussian beams. Furthermore, we showcase the ability of LG beams to isolate Mie resonances, offering a novel approach to locate the spectral positions of the resonances of high multipolar modes. These insights deepen the understanding of helicity in LG optical traps and pave the way for the development of more advanced optical manipulation techniques.
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All authors Iker Gómez-Viloria, Enrique Ayllón García, Jorge Olmos-Trigo, Quimey Pears Stefano, Jon Lasa-Alonso, Martín Molezuelas-Ferreras, Gabriel Molina-Terriza
Physics and Society · Cross-listed from astro-ph.HE
Human versus Artificial Inteligence; a significant example in astrophysics, alas
A. De Rújula
There are two well documented models of gamma ray bursts (GRBs), the "Standard' model and the "Cannonball" model. They have often been reviewed [1] and sometimes compared [2]. Here, to avoid understandable biases, I show below the results of an experiment: letting an AI compare the data and the two models. All of what follows (but two references, two footnotes and the next sentence) is the result of asking Perplexity.ai to perform this confrontational task. It should be easy for an impartial reader to reach very clear conclusions.
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Optics
Detection of Hybrid Optical Anapoles in Dielectric Microspheres
Uttam Manna, Iker Gómez-Viloria, Robert Sevik et al. (+4 more)
Nonradiating optical anapoles are special configurations of charge_current distributions that do not radiate. It was theoretically predicted that, for microspheres, electric and
magnetic dipolar coefficients can simultaneously vanish by engineering the incident light, leading to the excitation of nonradiating hybrid optical anapoles. In this work, the experimental detection of hybrid optical anapoles in dielectric microspheres (TiO2) is reported using dual detection optical spectroscopy, developed to enable sequential measurement of forward and backward scattering under tightly_focused Gaussian beam (TFGB) illumination. The results show that the excitation of TiO2 microspheres (diameter, d approx. 1 um) under TFGB illumination leads to the appearance of scattering minima in both the forward and backward directions within specific wavelength ranges. These scattering minima are found to be due to vanishing electric and
magnetic dipolar coefficients associated with hybrid optical anapoles. The ability to confine electromagnetic fields associated with hybrid optical anapoles can give rise to several novel optical phenomena and applications.
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All authors Uttam Manna, Iker Gómez-Viloria, Robert Sevik, Isaac Tribaldo, Mahua Biswas, Gabriel Molina-Terriza, Jorge Olmos-Trigo
Optics
Characterizing the Backscattered Spectrum of Mie Spheres
Martín Molezuelas-Ferreras, Álvaro Nodar, María Barra-Burillo et al. (+10 more)
This study describes both experimentally and theoretically an important hitherto undiscovered feature of the scattering of micron_sized spherical objects when illuminated with highly focused circularly polarized light. This is a regime of high experimental relevance which has not been described in full detail. The experiments are complemented with the analytical formulas explaining the field scattered directed toward the backward hemispace. In particular, it is proven that this field shows a very regular oscillatory dependency with the optical size. This phenomenon is typically hidden in the total scattered field, as the field is scattered much less toward the backward hemisphere than toward the forward one. These regular oscillations are measured experimentally. It is proven that, by analyzing them, it is possible to determine the index of refraction of isolated micron_sized particles, opening new paths for applications in sensing and metrology.
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All authors Martín Molezuelas-Ferreras, Álvaro Nodar, María Barra-Burillo, Jorge Olmos-Trigo, Jon Lasa-Alonso, Iker Gómez-Viloria, Elena Posada, J. J. Miguel Varga, Rubén Esteban, Javier Aizpurua, Luis E. Hueso, Cefe Lopez, Gabriel Molina-Terriza
Optics
High-Efficiency Hexagonal Nanowire MAPbI3 Perovskite Solar Cell with Broadband Light Trapping
Kawshik Nath, Bibekananda Nath and Ahmed Zubair
Perovskite
solar cells (PSCs) have emerged as strong contenders for the next generation of photovoltaic (PV) technologies due to their exceptional light absorption properties, tunability, and affordability in manufacturing. Here, we presented an ingenious hexagonal nanowire (HNW)-based PSC that achieves broadband absorption, minimizes reflectance, and offers robust polarization insensitivity by improving light-matter interaction and increasing charge-collection efficiency. The rotational
symmetry of the HNW configuration yielded polarization-independent absorbance under both TE and TM illumination across the visible and near-infrared spectra. The optimization of the geometrical parameters of CH3NH3PbI3-based HNW structure, including diameter, period, and fill ratio, offered a wide rangeof variations that influenced both optical properties and device performance. To further intensify
photon confinement, a dielectric SiO2 sphere is partially embedded in the ITO layer, improving long-wavelength absorbance and increasing electron-hole pair generation near the active region. We analyzed the finite-difference time-domain (FDTD) method to examine the optical properties of our proposed structure. This study demonstrates that our proposed structure has achieved a higher generation rate, enhanced absorbance, and a higher optical short-
circuit current density (Jsc) of 29.53 mA/cm2. Electrical performance is assessed by solving the coupled drift-
diffusion and Poisson equations for the dynamics of carrier transport. The optimized HNW structure achieved a notable power conversion efficiency of 24.2%, highlighting a strong connection between optical confinement and effective carrier transport. These attributes render the proposed HNW PSC a viable option for high-performance PV systems and scalable thin-film
solar technologies.
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Atmospheric and Oceanic Physics
Hybrid physics-data-driven modeling for sea ice thermodynamics and transfer learning
Giovanni De Cillis, Alberto Carrassi, Julien Brajard et al. (+5 more)
This study explores a physics-data driven hybrid approach for sea-ice column physics models, in which a machine learning (ML) component acts as a state-dependent parameterization of forecast errors. We examine how perturbations in snow thermodynamics and sea-ice radiative properties affect forecast errors, and train dedicated neural networks (NNs) for each model configuration. The performance of the hybrid models is evaluated for long lead-time forecasts and compared against a
benchmark system based on climatological forecast-error estimates. The NN-based hybrids prove to be stable, robust to initial condition and atmospheric forcing errors, and consistently outperform their climatology-based counterpart. To derive guiding principles for efficiently handling possible physical model updates, we perform transfer learning experiments to test whether pretrained NNs optimized for one model configuration can be successfully adapted to another. Results indicate that direct evaluation of pretrained networks on the target task provides useful insights into their adaptability, recommending transfer learning whenever performance exceeds a trivial baseline. Finally, a feature-importance analysis shows that atmospheric forcing inputs have negligible influence on NN predictive skill, while ice-layer enthalpies play a key role in achieving satisfactory performance.
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All authors Giovanni De Cillis, Alberto Carrassi, Julien Brajard, Laurent Bertino, Matteo Broccoli, Dorotea Iovino, Tobias Sebastian Finn, Marc Bocquet
Geophysics
Forward and Inverse Mantle Convection with Neural Operators
Chenxi Kong, Michael Gurnis and Zachary E. Ross
Thermal state reconstruction–reversing convection to recover the thermal structure of the mantle at an earlier geologic time–is an important tool to understand the
evolution of mantle convection and its relation to seismic tomographic images and observations at the surface. Thermal state reconstructions are computationally expensive. Here we transformed the basic computational element, numerical solvers, into neural operators, a class of machine learning models for learning mappings between function spaces. Focusing on a specific architecture,
Fourier Neural Operators, we demonstrate that they can represent not only a surrogate model like the Stokes system of equations using a purely physics informed approach, but also discover operators without explicit mathematical formulations or even ill-posedness from data, including the direct mapping between two convecting thermal states separated by a long time interval much larger than the Courant-Friedrichs-Lewy condition and its reversal. These neural operators significantly accelerate forward and inverse convection modelling by transforming forward physical processes into surrogate models with lower complexity while utilizing auto-differentiation to calculate gradients. With this framework, we demonstrate the strengths and weaknesses of four methods for thermal state reconstructions: reverse buoyancy, reverse convection operator, an inversion with only the terminal thermal state, and a joint inversion with the terminal thermal state and surface velocity
evolution. The reverse convection operator is shown to perform poorly in the presence of observational noise, but the joint inversion overcomes this limitation. The joint technique could probably become a solution to large-scale thermal state inversion problems using seismic
tomography and plate tectonic reconstructions.
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Plasma Physics
A predictive formula for the H-mode electron separatrix density: Bridging regression and physics-based models across C-Mod, AUG and JET tokamaks
D. Silvagni, O. Grover, A. Stagni et al. (+27 more)
The electron density at the separatrix ($n_{e,\mathrm{sep}}$) plays a central role in balancing energy confinement, detachment achievement, and ELM suppression in tokamaks, thereby influencing core-edge integration. To study what determines this key parameter, a database of H-mode separatrix density measurements from Alcator C-Mod, ASDEX Upgrade, and JET tokamaks has been assembled using a consistent analysis method across all devices. This
dataset is used to derive a regression scaling expression based solely on engineering parameters, and the results are compared to predictions from the two-point model. The agreement found is remarkable: both the regression and model provide similar parameter dependencies and tokamak-specific multiplicative constants. Building on this agreement, a fully predictive formula that combines the regression dependencies and the two-point model multiplicative constant is proposed. This formula is able to estimate $n_{e,\mathrm{sep}}$ across the three machines within a factor of 1.5, and provides projections to next-step devices (ITER, SPARC, DTT, JT-60SA and COMPASS-U) that are in agreement with available SOLPS simulations.
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All authors D. Silvagni, O. Grover, A. Stagni, J. W. Hughes, M. A. Miller, B. Lomanowski, L. Balbinot, G. Ciraolo, W. Dekeyser, M. Dunne, L. Frassinetti, C. Giroud, T. Happel, I. Jepu, A. Kallenbach, A. Kirjasuo, A. Kuang, T. Luda, D. Moulton, O. Pan, C. Perez von Thun, T. Puetterich, G. Rubino, S. A. Silburn, H. J. Sun, D. Umezaki, H. Zohm, the ASDEX Upgrade team, JET contributors, the EUROfusion tokamak exploitation team
Optics
Spontaneous four-wave mixing in a thin layer with second-order nonlinearity
Changjin Son and Maria Chekhova
Pairs of entangled
photons are crucial for photonic
quantum technologies. The demand for integrability and multi-functionality suggests 'flat' platforms - ultrathin layers and metasurfaces - as sources of
photon pairs. With the success in demonstrating spontaneous parametric down-conversion (SPDC) from such sources, an alternative process to generate
photon pairs, spontaneous four-wave mixing (SFWM), also starts to attract interest. In materials with nonzero second-order nonlinear susceptibility $\chi^{(2)}$, SFWM can generate
photon pairs both directly, through the third-order nonlinear susceptibility $\chi^{(3)}$, and in a cascaded way, through second harmonic generation (SHG) followed by SPDC. Usually, the cascaded process is more efficient. Here, we show that in a thin layer, direct SFWM dominates, because the wavevector mismatch for SFWM is much smaller than for SHG or SPDC. To demonstrate it, we implement the
photon pair generation via SFWM in a second-order nonlinear material - a thin layer of lithium niobate (LN). The existence of both second- and third-order nonlinear processes offers broader opportunities for
quantum state engineering.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Loop-gap resonators achieving strong magnon-photon coupling in magnetic insulator thin films
Francesca Zanichelli, Davit Petrosyan, Hanchen Wang et al. (+4 more)
Magnon-
photon hybrid systems consisting of a three-dimensional electromagnetic resonator and a bulk
magnetic insulator constitute the standard experimental platform in cavity magnonics. Here, we demonstrate a modular loop-gap resonator design optimized to couple with thin films of
magnetic insulators. We achieve the strong-coupling regime using this loop-gap resonator coupled to a 75~nm-thick epitaxial film of yttrium iron garnet at room temperature. We further show how to perform field-differential spectroscopy of the hybrid
magnon-
photon system, which eliminates the unwanted signal from other loop-gap modes uncoupled to the
magnetic film. In addition to the uniform
ferromagnetic resonance mode, the loop-gap resonator enables an hybridization with the standing
spin-wave modes forming across the thickness of the film. Our approach unlocks the use of epitaxial films and multilayers of
magnetic insulators to tune the
magnon band structure in cavity magnonics experiments.
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All authors Francesca Zanichelli, Davit Petrosyan, Hanchen Wang, Patrick Helbingk, Richard Schlitz, Pietro Gambardella, William Legrand
Applied Physics
A centimeter-sized gas pressure sensor for high-vacuum measurements at cryogenic temperatures
Christoph Reinhardt, Lea Lara Stankewitz, Daniel Hartwig et al. (+5 more)
Gas pressure sensors based on nanomechanical membranes have recently demonstrated an ultra-wide ten-decade measurement range, a gas-type-independent response, and a self-calibrating operation with uncertainties of approximately $1\,\%$. The readout relied on tabletop free-space
laser interferometers. Here we present a centimeter-sized, portable implementation in which a square Si$_3$N$_4$ membrane is read out via a fiber-based
laser interferometer. We perform pressure measurements between $5\times10^{-5}$ and $10^{-1}$~mbar in a confined $0.7$~L volume cooled to $78$~K. Because no suitable commercial pressure sensor exists for direct cryogenic comparison, we
benchmark our device against room-temperature commercial gauges connected to the cold volume through a pipe of limited conductance. The measured relationship between the two sensors is compared with models accounting for temperature- and pumping-induced pressure gradients within the measurement chamber. These models agree with the measurements to within $<10\,\%$ for helium and $<13\,\%$ for nitrogen. The achieved readout sensitivity of $S_x = 8\times10^{-14}\,\mathrm{m}/\sqrt{\mathrm{Hz}}$ theoretically enables resolving the thermal displacement noise spectrum of a trampoline membrane at atmospheric pressure, with a peak response of $48\,S_x$ $\left(25\,S_x\right)$ at $295\,\mathrm{K}$ $\left(78\,\mathrm{K}\right)$. Our results suggest that the previously achieved pressure measurement range of ten decades with trampoline membranes is compatible with fiber-based optical readout. This paves the way for widely applicable pressure sensors in the centimeter size range in cryogenic environments.
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All authors Christoph Reinhardt, Lea Lara Stankewitz, Daniel Hartwig, Sandy Croatto, Hossein Masalehdan, Nils Sültmann, Axel Lindner, Roman Schnabel
Instrumentation and Detectors
High-bandwidth frequency domain multiplexed readout of transition-edge sensors for neutrinoless double beta decay searches
M. Adamič, M. Beretta, J. Camilleri et al. (+13 more)
The next-generation of cryogenic neutrinoless double-beta decay experiments require increasingly fast readout in order to improve background discrimination. These experiments, operated as cryogenic calorimeters at $\sim$10 mK, are usually read out by high-impedance
neutron transmutation doped (NTD) thermistors, which provide good energy resolution, but are limited by $\sim$1 ms response times. Superconducting detectors, such as transition-edge sensors (TESs) with a time resolution of $\sim$100 $\mu$s, offer superior timing performance over NTD
semiconductor bolometers. To make this technology viable for an application to a thousand or more channels, multiplexed readout is necessary in order to minimize the thermal load and radioactive contamination induced by the readout. Frequency-domain multiplexing readout (fMUX) for TESs, previously developed at Berkeley Lab and McGill University, is currently in use for mm-wave
telescopes with detector sampling rates in the order of 100 Hz. We demonstrate a new readout system, based on the McGill/Berkeley digital fMux readout, to satisfy the higher bandwidth and noise requirements of the next generation of TES-instrumented cryogenic calorimeters. Each multiplexing readout module comprises 10 superconducting resonators in the 1–5 MHz range and a DC superconducting
quantum interference device (DC-SQUID), interfaced to high-speed field programmable gate array (FPGA)-based electronics for digital signal processing and low-latency SQUID feedback. The new readout samples detectors at 156 kHz, three orders of magnitude faster than its cosmology-oriented predecessor, and demonstrates a stable feedback bandwidth of 3 kHz in a real TES-based system.
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All authors M. Adamič, M. Beretta, J. Camilleri, C. Capelli, M. A. Dobbs, T. Elleflot, B. K. Fujikawa, Yu. G. Kolomensky, D. Mayer, J. Montgomery, V. Novosad, A. M. Sindhwad, V. Singh, G. Smecher, A. Suzuki, B. Welliver
Fluid Dynamics
Stability prediction of vortex induced vibrations of multiple freely oscillating bodies
Théo Mouyen, Javier Sierra, David Fabre et al. (+1 more)
The
vortex-induced vibration of multiple spring-mounted bodies free to move in the orthogonal direction of the flow is investigated. In a first step, we derive a Linear Arbitrary Lagrangian Eulerian (L-ALE) method to solve the fluid-structure linear problem as well as a forced problem where a harmonic motion of the bodies is imposed. We then propose a low computational-cost impedance-based criterion to predict the instability thresholds. A global stability analysis of the fluid-structure system is then performed for a tandem of cylinders and the instability thresholds obtained are found to be in perfect agreement with the predictions of the impedance-based criterion. An extensive parametric study is then performed for a tandem of cylinders and the effects of mass, damping and spacing between the bodies are investigated. Finally we also apply the impedance-based method to a three-body system to show its validity to a higher number of bodies.
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All authors Théo Mouyen, Javier Sierra, David Fabre, Flavio Giannetti
Instrumentation and Detectors · Cross-listed from hep-ph
Exploring Long-Range Interactions in the Atmospheric Neutrino Oscillations at IceCube DeepCore
Gopal Garg
The IceCube
neutrino observatory consists of an array of Digital Optical Modules (DOMs) instrumenting one cubic-kilometer of deep glacial ice at the South Pole. DeepCore, a densely-spaced sub-array of DOMs at the bottom central region of IceCube, enables the detection of atmospheric
neutrinos with an energy threshold in the GeV range. The high statistics data of DeepCore provides a unique opportunity to perform
neutrino oscillation studies as well as explore various sub-leading Beyond the Standard Model (BSM) physics signatures. We consider a well-motivated minimal extension of the Standard Model by an additional anomaly-free, gauged
lepton-number
symmetry, such as $L_e - L_\mu$ or $L_e - L_\tau$. These
symmetries give rise to
flavor-dependent long-range interaction mediated through a very light neutral gauge
boson. In this contribution, we present the sensitivity of the IceCube DeepCore detector to search for this
flavor-dependent long-range interaction potential with a runtime of 9.3 years.
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Instrumentation and Detectors · Cross-listed from hep-ph
Study of the internal structure of the Earth using neutrino oscillations at IceCube DeepCore
Sharmistha Chattopadhyay
Earth's mass and internal structure have been primarily studied through gravitational and seismic methods.
Neutrinos, however, offer an independent way to explore Earth's interior via matter effects in
neutrino oscillations that depend on the electron distribution inside Earth, and hence its matter density. Our study uses atmospheric
neutrinos at DeepCore, a densely instrumented sub-detector of the IceCube
Neutrino Observatory, to estimate Earth's mass and layer densities. We also assess how the upcoming IceCube Upgrade, with denser instrumentation, could improve these measurements.
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Physics and Society
A Universal Convolution-Based Pre-processor to Correct the Prevalence-Incidence Gap in SIR, SEIR, and SIRS Modeling
Jose de Jesus Bernal-Alvarado and David Delepine
Traditional compartmental models, including SIR, SEIR, and SIRS frameworks, remain the analytical standard for epidemic
forecasting. However, real-world data validation consistently reveals significant predictive failures, such as peak underestimations of up to 50%. This research identifies a persistent fundamental methodological error: the calibration of prevalence-based (stock) models using raw daily incidence (flow) data without proper transformation. We propose an integrated protocol utilizing an exponentially weighted convolution to reconstruct active cases from reported incidence: $I(t) \approx \frac{1}{p} \int_{0}^{t} NDC(\tau) e^{-\gamma(t-\tau)} d\tau$. This transformation accounts for the recovery rate $\gamma$ and the ascertainment rate $p$. We demonstrate that increasing structural complexity, such as adding latency (SEIR) or waning immunity (SIRS), fails to resolve the incidence-prevalence gap. Simulation results show that without the proposed universal pre-processor, these advanced models inherit the systematic biases of misaligned data types, leading to significant errors in estimating latent periods and the "heavy tail" of endemicity. The proposed convolution transformation must serve as a universal prerequisite for any compartmental framework, bridging the gap between clinical reporting and mechanistic modeling.
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Chemical Physics
ThermoLIB – A Python Library for Constructing and Post-Processing Free Energy Surfaces to Extract Thermodynamic and Kinetic Properties
Massimo Bocus and Louis Vanduyfhuys
ThermoLIB is Python/Cython library designed to be used as a post-processing tool for constructing free energy surfaces from the output of molecular simulations, transforming them between different collective variables (CVs) and extracting thermodynamic and kinetic information. ThermoLIB is available for download on GitHUB and comes with extended documentation as well as many tutorials. The implementation is based on the theory of maximum likelihood
estimators and includes error bars on and full covariance
matrix between all points on the free energy surface using the Fisher information
matrix. The free energy surfaces can be transformed a posteriori to other collective variables, projected towards lower dimensional CV-spaces and even deprojected towards higher dimensional CV-spaces if additional information from the simulation is provided in the form of a conditional probability. Finally, one can extract usefull thermodynamic and kinetic properties such as the reaction free energy and kinetic rate constant. Error bars on the free energy surfaces are propagated throughout al these operations. We briefly illustrate the capabilities of ThermoLIB by means of some tutorials and case studies.
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Optics
Magnetic Skyrmion Encoding by Structured Light
Zhang Qifan, Yu Wangke, Nie Zhongquan et al. (+2 more)
Structured light fields, featuring unique topological properties and high tunability, have opened new frontiers in light-matter interactions with
magnetic systems. However, the ultrafast and reconfigurable optical encoding of various types of topological
magnetic textures remains a significant challenge. Here, we systematically investigate the encoding mechanism of structured light in magnets via the higher-order Poincaré sphere. By uncovering the precise relationship between the winding number of structured light and the topological charge of
magnetic textures, we establish a fundamental topological connection between light and magnetism. This framework enables ultrafast, all-optical encoding of diverse topological
spin textures in
magnetic media, including skyrmions, antiskyrmions and skyrmion bags. Our work advances the fundamental understanding and all-optical control of topological magnetism, offering a promising route for designing skyrmion-based devices.
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All authors Zhang Qifan, Yu Wangke, Nie Zhongquan, Shen Yijie, Lin Shirong
Physics and Society
Missing links prediction: comparing machine learning with physics-rooted approaches
Francesca Santucci, Giulio Cimini and Tiziano Squartini
An active research line within the broader field of network science is the one concerning link prediction. Close in scope to network reconstruction, link prediction targets specific connections with the aim of uncovering the missing ones, as well as predicting those most likely to emerge in the future, from the available information. In this paper, we consider two families of methods, i.e. those rooted in statistical physics and those based upon machine learning: the members of the first family identify missing links as the most probable non-observed ones, the probability coefficients being determined by solving maximum-
entropy benchmarks over the accessible network structure; the members of the second family, instead, associate the presence of single edges to explanatory node-specific variables. Running likelihood-based models such as the Configuration Model, or one of its many fitness-based variants, in parallel with the Gradient Boosting Decision Tree
algorithm reveals that the accuracy of the former is comparable to the accuracy of the latter. Such a result confirms that white-box
algorithms are viable competitors to the currently available black-box ones, being more interpretable and computationally faster.
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Instrumentation and Detectors · Cross-listed from hep-ph
Exploring Layered Structure Inside Earth Using Atmospheric Neutrino Oscillation at IceCube DeepCore
J Krishnamoorthi
The IceCube detector, using its densely instrumented center, called DeepCore, can detect multi-GeV atmospheric
neutrinos. The oscillation pattern of
neutrinos is altered due to interactions with ambient electrons as they pass through Earth. The changes in these patterns are influenced by the amount of matter and its specific arrangement. As
neutrinos propagate, they retain information about the densities they encounter. Our study demonstrates that IceCube DeepCore can utilize the Earth's matter effects to distinguish between a homogeneous matter density profile and a layered structure density profile of Earth. In this contribution, we present that IceCube DeepCore data equivalent to 9.3 years of observation can reject the homogeneous matter density profile with a confidence level of 1.4$\sigma$.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Rotating Magnetocaloric Effect in Sintered La(Fe,Mn,Si)$_{13}$H$_z$ Plates
Rafael Almeida, Tomás Ventura, Ricardo Moura Costa Pinto et al. (+6 more)
La-Fe-Si-based
alloys are among the most application-ready magnetocaloric materials for room-temperature
magnetic refrigeration. Powder metallurgy methods have been previously demonstrated to successfully produce structures with sub-mm features for
magnetic refrigerators in a scalable method. In this work, we explore the rotating magnetocaloric effect (RMCE) present in a 0.27 mm thin plate of sintered and hydrogenated La(Fe,Mn,Si)$_{13}$. The high aspect ratio ($\sim$50) of the thin plate leads to an anisotropic magnetocaloric effect (MCE), dependent on the relative orientation of the external
magnetic field, and an RMCE when the external field is rotated. We find a maximum rotating adiabatic temperature change ($\Delta T_{ad}^{rot}$) of 1.17 K with the rotation of a 1 T
magnetic field and 1.12 K when rotating a 0.6 T
magnetic field, a reduction of only 4% for a 40% reduction in applied field strength. Magnetostatic computations revealed a considerable rotating isothermal
entropy change ($\Delta S_{iso}^{rot}$), comparable to the conventional MCE of Gd for similar fields, reaching 3.97 J K$^{-1}$ kg$^{-1}$ for 1 T and 3.68 J K$^{-1}$ kg$^{-1}$ for 0.6 T (7% reduction), highlighting La-Fe-Mn-Si
alloys as high potential candidates for a
magnetic refrigerator based on the RMCE utilizing relatively low external
magnetic field amplitudes, such as 0.6 T.
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All authors Rafael Almeida, Tomás Ventura, Ricardo Moura Costa Pinto, João Oliveira Silva, Konrad Loewe, Rodrigo Kiefe, João Sequeira Amaral, João Pedro Araújo, João Horta Belo
Instrumentation and Detectors · Cross-listed from hep-ph
Establishing Earth's Matter Effect in Atmospheric Neutrino Oscillations at IceCube DeepCore
Anuj Kumar Upadhyay
The discovery of the non-zero value of $\theta_{13}$ has opened an exciting opportunity to probe the Earth's matter effects in three-
flavor oscillations of atmospheric
neutrinos. These matter effects depend on both
neutrino energy and the electron density distributions encountered during their propagation through Earth. In this contribution, we present preliminary sensitivities from the DeepCore detector, a densely instrumented sub-array of the IceCube
neutrino observatory at the South Pole, demonstrating its ability to observe these matter effects in atmospheric
neutrino oscillations. Using simulated data equivalent to 9.3 years of observations at IceCube DeepCore, we show the sensitivity of the DeepCore to reject the
vacuum oscillation hypothesis and align with the Preliminary Reference Earth Model. Additionally, we present the expected improvement in sensitivity for rejecting the
vacuum oscillations using the upcoming IceCube Upgrade, a low-energy extension of the IceCube detector.
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Optics · Cross-listed from quant-ph
Scalable Memory Sharing in Photonic Quantum Memristors for Reservoir Computing
Chaehyeon Lim, Hyungchul Park, Beomjoon Chae et al. (+4 more)
Although
photons are robust, room-temperature carriers well suited to
quantum machine learning, the absence of
photon-
photon interactions hinder the realization of
memory functionalities that are critical for capturing long-range context. Recently, measurement-based implementations of photonic
quantum memristors (PQMRs) have enabled tunable non-Markovian responses. However, their
memory remains confined to local elements, in contrast to biological or artificial networks where
memory is shared across the system. Here, we propose a scalable PQMR network that enables measurement-based
memory sharing. Each memristive node updates its internal state using the history of its own and neighbouring
quantum states, thereby realizing distributed
memory. By modelling each node as a photonic
quantum memtransistor, we demonstrate pronounced enhancements in both classical and
quantum hysteresis at the device level, as well as enhanced network-level
quantum hysteresis. Implemented as a
quantum reservoir, the architecture achieves improved Fashion-MNIST classification accuracy and confidence via increased data separability. Our approach paves the way toward high-capacity
quantum machine learning using memristive devices compatible with linear-optical
quantum computing.
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All authors Chaehyeon Lim, Hyungchul Park, Beomjoon Chae, Jeonghun Kwak, Soo-Yeon Lee, Namkyoo Park, Sunkyu Yu
Optics · Cross-listed from quant-ph
High-resolution tunable frequency beamsplitter enabled by an integrated silicon pulse shaper
Chen-You Su, Kaiyi Wu, Lucas M. Cohen et al. (+6 more)
We demonstrate high-fidelity, tunable, and ultrafine-resolution on-chip frequency beamsplitters using a
quantum frequency processor based on an integrated pulse shaper with six spectral channels. Near-ideal Hadamard gate performance is achieved, with fidelity F > 0.9995 and modified success probability P > 0.9621 maintained across frequency spacings from 2-5 GHz and down to as few as four spectral pulse shaper channels. The system's support of frequency spacings as narrow as 2 GHz significantly surpasses prior bulk demonstrations and enables arbitrary splitting ratios via spectral phase or modulation index control. These results establish a scalable and resource-efficient platform for integrated frequency-bin
quantum photonics, opening new directions in
quantum information processing, including densely parallel single-
qubit operations and multidimensional gate implementations.
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All authors Chen-You Su, Kaiyi Wu, Lucas M. Cohen, Saleha Fatema, Navin B. Lingaraju, Hsuan-Hao Lu, Andrew M. Weiner, Joseph M. Lukens, Jason D. McKinney
Fluid Dynamics
Dancing rivulets in an air-filled Hele-Shaw cell
Grégoire Le Lay and Adrian Daerr
We study the behaviour of a thin fluid filament (a rivulet) flowing in an air-filled Hele-Shaw
cell. Transverse and longitudinal deformations can propagate on this rivulet, although both are linearly attenuated in the parameter range we use. On this seemingly simple system, we impose an external acoustic forcing, homogeneous in space and harmonic in time. When the forcing amplitude exceeds a given threshold, the rivulet responds nonlinearly, adopting a peculiar pattern. We investigate the dance of the rivulet both experimentally using spatiotemporal measurements, and theoretically using a model based on depth-averaged Navier-Stokes equations. The instability is due to a three-wave resonant interaction between waves along the rivulet, the resonance condition fixing the pattern wavelength. Although the forcing is additive, the amplification of transverse and longitudinal waves is effectively parametric, being mediated by the linear response of the system to the homogeneous forcing. Our model successfully explains the mode selection and phase-locking between the waves, it notably allows us to predict the frequency dependence of the instability threshold. The dominant spatiotemporal features of the generated pattern are understood through a multiple-scale analysis.
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Optics
Perturbative Born theory for light scattering by time-modulated scatterers
Dionysios Galanis, Evangelos Almpanis, Nikolaos Papanikolaou et al. (+1 more)
We present a theoretical framework for electromagnetic scattering by particles with a permittivity that is periodically varying in time, based on a perturbative approach. Within this framework, we derive explicit expressions for the scattering
matrix of the dynamic system in a first-order Born approximation, relating it directly to the corresponding static problem. We show that inelastic scattering amplitudes are governed by overlap integrals between static modes at the input and output frequencies. Using this insight, we analyze scattering from a time-modulated, isotropic, dielectric sphere and a high-permittivity dielectric cylinder, and demonstrate how modal orthogonality can suppress inelastic channels, while appropriate tuning of
geometric parameters can significantly enhance them. In particular, we show that cylindrical resonators support strong inelastic scattering when resonance-to-resonance optical transitions, induced by the temporal variation, involve a high-Q supercavity mode. Comparison with full time-Floquet calculations confirms that the first-order Born approximation remains quantitatively accurate for modest modulation amplitudes and provides clear physical intuition for frequency conversion and resonance-mediated scattering processes in time-modulated photonic resonators.
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All authors Dionysios Galanis, Evangelos Almpanis, Nikolaos Papanikolaou, Nikolaos Stefanou
Plasma Physics · Cross-listed from cond-mat.mtrl-sci
Unlocking the Power of Orbital-Free Density Functional Theory to Explore the Electronic Structure Under Extreme Conditions
Cheng Ma, Qiang Xu, Zhenhao Zhang et al. (+8 more)
Recent advances in X-ray free-electron
laser diagnostics have enabled direct probing of the electronic structure under extreme pressures and temperatures, such as those encountered in
stellar interiors and inertial confinement fusion experiments, challenging theoretical models for interpreting experimental data. Kohn-Sham density functional theory (KSDFT) has been successfully applied to analyze experimental X-ray scattering measurements, but its high computational cost renders routine application impractical. Orbital-free DFT (OFDFT) is a substantially more efficient alternative, with computational cost scaling linearly with system size and a weak temperature dependence, yet it often lacks the accuracy required for electronic structure description. Overcoming this limitation, we present a non-empirical Kohn-Sham-assisted orbital-free density functional framework for calculations at extreme conditions, which enables efficient OFDFT simulations with KSDFT-level accuracy for electron densities, electron-ion structure factors, and equations of state across a broad range of conditions.
Benchmark comparisons with
quantum Monte Carlo data for dense hydrogen and validation against Rayleigh weight measurements of hot dense beryllium demonstrate the reliability of the framework and speedups of up to several hundred times compared with KSDFT. We further show that even at temperatures on the order of 100 eV,
quantum non-locality remains essential for correctly describing the electronic structure of dense hydrogen.
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All authors Cheng Ma, Qiang Xu, Zhenhao Zhang, Ke Wang, Ying Sun, Wenhui Mi, Zhandos A. Moldabekov, Tobias Dornheim, Jan Vorberger, Sebastian Schwalbe, Xuecheng Shao
Atomic Physics
Unambiguous Vector Magnetometry with Structured Light in Atomic Vapor
S. Ramakrishna and S. Fritzsche
Absorption profiles of vector light upon interaction with atomic vapor carries distinct signatures of external
magnetic field vector. However, this signature becomes ambiguous for anti parallel
magnetic field vectors of equal magnitude, which makes their absorption profiles visually indistinguishable. To resolve this ambiguity, we present theoretical analysis of the interaction of vector light with optically polarized atoms immersed in reference and test
magnetic fields. Furthermore, we demonstrate the complete characterization of the arbitrarily oriented test
magnetic field via
Fourier analysis of the absorption profile. This analysis reveals a one to one correspondence between the
magnetic field properties and the profiles contrast and rotational angle. Our findings open an avenue to design an optical vector atomic magnetometer based on structured light fields.
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Atomic Physics
Direct observation of the optical Magnus effect with a trapped ion
Philip Leindecker, Louis P.H. Gallagher, Edgar Brucke et al. (+7 more)
We directly observe and spatially map an optical analog of the Magnus effect, where intrinsic
spin-orbit-like coupling of light generates a
spin-dependent transverse displacement of the atom-light interaction profile for a $^{40}$Ca$^+$ ion. Probed on a quadrupole transition using a tightly focused beam, we observe displacements of the maximum in the profile of the effective interaction by several 100 nm originating from intrinsic longitudinal electric field components beyond the paraxial approximation. The tight focus of the beam induces additional transverse polarization gradients, which we characterize through a phase-sensitive measurement and spatial maps for different beam configurations. The results establish the physical basis of polarization-gradient interactions relevant to optical tweezer-based
quantum control.
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All authors Philip Leindecker, Louis P.H. Gallagher, Edgar Brucke, Dominique Zehnder, Luka Milanovic, Matteo Marinelli, Rene Gerritsma, Robert J.C. Spreeuw, Jonathan Home, Cornelius Hempel
Atomic Physics
Wichmann-Kroll Correction in Muonic Atoms and Hydrogen-Like Electronic Ions: a Comparative Study of Two Methods
Zoia A. Mandrykina, Zewen Sun and Natalia S. Oreshkina
Wichmann-Kroll corrections are calculated in both hydrogen-like electronic ions and muonic systems ($Z = \{36$–$92\}$) using two independent methods. The Gaussian finite basis set approach, enhanced with dual basis construction, analytical large-distance corrections, and $B$-spline representations, provides computational efficiency. The Green function method, based on semi-analytical construction from Dirac solutions with
Fermi nuclear charge distributions, offers higher systematic accuracy and freedom from basis-dependent artifacts. Results are consistent with the literature values, providing reliable reference data for precision spectroscopy of exotic atoms.
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