Plasma Physics · Cross-listed from astro-ph.SR
Kinetic-based macro-modeling of the solar wind at large heliocentric distances: Kappa electrons at the exobase
Alexander Vinogradov, Marian Lazar, Ioannis Zouganelis et al. (+2 more)
Recent evidence from Parker
Solar Probe on the suprathermal electrons with Kappa-type velocity distributions in the outer corona has revived interest in the kinetic-based macro-modelling of the
solar (SW), aiming to explain its properties. Invoked in kinetic modelling of nonequilibrium
plasmas, standard Kappa distributions (SKDs) have been adjusted to the regularized Kappa distributions (RKDs) to fix the inconsistencies of SKD and develop consistent fluid modelling of space
plasmas. We propose a new analysis of these properties at large heliocentric distances based on the existence of RKD electrons at the exobase. This new semi-analytic formalism is inspired by the methodology proposed initially by Meyer-Vernet and Issautier (1998), https://doi.org/10.1029/98ja02853. Compared to SKDs, the results for RKDs have extended applicability, since all moments can be defined and calculated consistently for all values of the $\kappa$ parameter, even lower than the critical ones (e.g., $\kappa_c=3/2$ imposed to the second-order moment) of SKDs. However, the excess energy of the more energetic suprathermal electrons associated with low values of $\kappa \lesssim 3/2$, is regulated by the RKD-specific cutoff parameter $\alpha < 1$. The estimates for, e.g., the temperature and bulk velocity of the SW, remain at realistic values even for small $3/2 < \kappa \lesssim 2$, which would otherwise exceed specific observations. One can thus model a higher abundance of suprathermal electrons at the exobase (e.g., $\kappa \leqslant 3/2$), which is plausible for the sources of energetic events (
flares and coronal mass ejections), and also in the astrospheres of
stars with coronas hotter than the Sun's.
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All authors Alexander Vinogradov, Marian Lazar, Ioannis Zouganelis, Viviane Pierrard, Stefaan Poedts
Physics and Society · Cross-listed from cond-mat.stat-mech
Two stroke Pumping Technique for Many-Body Systems
Serge Galam
I introduce a new analytical framework for estimating critical temperatures in interacting many-body systems, focusing on the Ising model. Combining the Bethe cluster setting, the Metropolis update, and the Galam Majority Model developed in sociophysics, I build a two stroke pumping technique (TSP). Applied to the Ising model in dimensions d=2, 3, 4, TSP yields values of T_c which are all at an excess of +0.03 from exact estimates. At d=1 the exact value T_c=0 is obtained. In addition, TSP indicates analytically the practical impossibility to reach full
symmetry breaking at T=0. The results are thus found in good agreement with numerical findings while requiring significantly fewer computational resources than Monte Carlo sampling. Calculations are computationally efficient and transparent. The framework is general and can be extended to a broad class of discrete
spin models. This positions TSP as an intermediate yet scalable tool for studying cooperative behavior in many body interacting systems.
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Optics
Transmission matrix measurement of a single Mie scatterer
Xiaomeng Sui and Allard Mosk
Transmission
matrices are valuable tools to describe and control light transport through scattering media. There are only a few cases where the transmission
matrix can be compared to microscopic theories. Here we measure the polarization-complete transmission
matrix of a single dielectric sphere using off-axis holography with angle scanning and reconstruct complex fields in both transmission and reflection under circular polarization. After aberration correction and angular mapping, the scattering amplitude extracted from the transmission
matrix closely follows Mie theory. This work provides a calibrated
benchmark for angle-resolved transmission
matrix measurement and enables quantitative characterization of spherical and quasi-spherical scatterers.
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Applied Physics
Giant intrinsic dichroism in e̱ta}-Ga2O3 enables filter-free, high-fidelity polarization division multiplexing
Yonghui Zhang, Rui Zhu, Huili Liang et al. (+4 more)
Conventional polarization detection relies on external filters, which incur significant efficiency loss and polarization crosstalk, especially in the deep ultraviolet band where subwavelength nanofabrication is challenging. Here, we report that monoclinic e̱ta}-Ga2O3 exhibits intrinsic
giant polarization dichroism, allowing near-ideal polarization photodetection without external optical elements and coherent polarization-division multiplexing (PDM) capability. The
giant dichroism originates from the crystallographic
symmetry-driven selectivity of optical transitions, which, combined with a large valence band splitting, results in vastly distinct absorption for orthogonal polarizations. A theoretical analysis of the transition selection rules in e̱ta}-Ga2O3 reveals only the E//c-polarized vb1-to-conduction band transition is activated, within the 245-258 nm spectral window. An admirable polarization ratio surpassing 500 and a polarization crosstalk ratio below 0.2% is hence achieved. The polarization-sensitive photodetector exhibits a high responsivity of 73 A/W and fast response (20 ms). Furthermore, we showcase its practical utility in PDM free-space communication, successfully decoding encoded optical signals, and demonstrate its capability for high-fidelity Stokes vector
retrieval. The intrinsic anisotropy of e̱ta}-Ga2O3, dictated by its
crystal symmetry, lays the groundwork for filter-free, high-fidelity polarization polarimetry. This work further paves the way for a general design principle in next-generation optoelectronics that harness polarization transition selection rules.
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All authors Yonghui Zhang, Rui Zhu, Huili Liang, Guochao Zhao, Shuli Wei, Qing Lu, Zengxia Mei
Fluid Dynamics · Cross-listed from hep-th
Hydrodynamics of dilation and spin currents
Zhong-Hua Zhang, Xi-Hu Lv and Xu-Guang Huang
We formulate a relativistic hydrodynamic theory for fluids with
spin and intrinsic dilation charges. Using an
entropy-current analysis, we derive constitutive relations featuring a bulk viscosity and a dilation conductivity governing the relaxation and
diffusion of dilation charge. Linear mode analysis reveals a gapped dilation excitation and the freeze-out of long-wavelength sound modes, similar to the superhorizon modes in cosmology. In the nonrelativistic limit, the theory reduces to that of microstretch fluids. Upon coupling to electromagnetic field, we show that the scale anomaly permits additional contributions in the electric current, dilation current, and energy-momentum tensor. Our theory naturally applies to nearly conformal fluids undergoing rapid expansion or contraction.
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Chemical Physics · Cross-listed from quant-ph
The Convergence Frontier: Integrating Machine Learning and High Performance Quantum Computing for Next-Generation Drug Discovery
Narjes Ansari, César Feniou, Nicolaï Gouraud et al. (+13 more)
Integrating
quantum mechanics into drug discovery marks a decisive shift from empirical trial-and-error toward quantitative precision. However, the prohibitive cost of ab initio molecular dynamics has historically forced a compromise between chemical accuracy and computational scalability. This paper identifies the convergence of High-Performance Computing (HPC), Machine Learning (ML), and
Quantum Computing (QC) as the definitive solution to this bottleneck. While ML foundation models, such as FeNNix-Bio1, enable
quantum-accurate simulations, they remain tethered to the inherent limits of classical data generation. We detail how High-Performance
Quantum Computing (HPQC), utilizing hybrid QPU-GPU architectures, will serve as the ultimate accelerator for
quantum chemistry data. By leveraging
Hilbert space mapping, these systems can achieve true chemical accuracy while bypassing the heuristics of classical approximations. We show how this tripartite convergence optimizes the drug discovery pipeline, spanning from initial system preparation to ML-driven, high-fidelity simulations. Finally, we position
quantum-enhanced sampling as the beyond GPU frontier for modeling reactive cellular systems and pioneering next-generation materials.
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All authors Narjes Ansari, César Feniou, Nicolaï Gouraud, Daniele Loco, Siwar Badreddine, Baptiste Claudon, Félix Aviat, Marharyta Blazhynska, Kevin Gasperich, Guillaume Michel, Diata Traore, Corentin Villot, Thomas Plé, Olivier Adjoua, Louis Lagardère, Jean-Philip Piquemal
Computational Physics · Cross-listed from cond-mat.str-el
Hamiltonian Monte Carlo enhanced by Exact Diagonalization
Finn L. Temmen, Martina Gisti, David J. Luitz et al. (+2 more)
Strongly correlated fermionic systems are of great interest in condensed matter physics and numerical methods are indispensable tools for their study. However, existing approaches such as exact diagonalization (ED) and
stochastic quantum Monte Carlo methods each suffer from fundamental limitations: ED is hindered by exponential scaling in system size, while Monte Carlo methods are plagued by sign problems and long autocorrelation times. These limitations restrict the accessible parameter space and developing
algorithms that efficiently alleviate them remains a central challenge in computational physics. In this work, we propose a hybrid
algorithm that combines ED and
Hamiltonian Monte Carlo (HMC) to simulate 2D arrays of coupled
quantum wires, modeled as interacting fermionic Hubbard chains. We demonstrate how our hybrid implementation of HMC, which we dub H$^2$MC, outperforms either method alone across several key simulation facets. When compared to pure ED, H$^2$MC has a much more favorable computational scaling, which allows us to push simulations to much larger 2D arrays. H$^2$MC also greatly alleviates the sign problem and reduces autocorrelation times when compared to pure HMC formulations utilizing either real or imaginary auxiliary fields. Our formalism demonstrates how complementary strengths of seemingly disparate methods can be leveraged to enable feasible simulations in an extended parameter space.
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All authors Finn L. Temmen, Martina Gisti, David J. Luitz, Thomas Luu, Johann Ostmeyer
Computational Physics · Cross-listed from cond-mat.mes-hall
Magneto-rotation coupling dominates surface acoustic wave driven ferromagnetic resonance in the longitudinal geometry
Gyuyoung Park, OukJae Lee and Jintao Shuai
We present a
phonon-
magnon extension for the mumax+ micromagnetic framework that implements three surface acoustic wave (SAW) coupling mechanisms: magnetoelastic strain coupling, magneto-rotation coupling arising from the antisymmetric displacement gradient, and
spin-rotation (Barnett) coupling from the
lattice angular velocity. Six
benchmark simulations validate the implementation through SAW-driven domain-wall motion, magnetization switching, magneto-rotation and Barnett field validation, nonreciprocal SAW-
magnon absorption from Rayleigh-wave chirality, and spatially resolved coupling in a standing SAW cavity. For the longitudinal geometry (m_0 parallel to k_SAW), we show that the magnetoelastic coupling produces zero transverse torque despite generating a 50 times larger effective field; the magneto-rotation channel provides the sole driving mechanism. The crossover angle below which MR dominates is theta_c approximately 1.1 degrees for YIG parameters. Treating the magneto-rotation coupling constant K_mr as a tunable parameter, we map out the cooperativity phase diagram and show that MR alone can achieve strong coupling (C = 257 for K_mr = 1 MJ/m^3) with an avoided-crossing splitting of 13.6 MHz.
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Optics
Isotopic variations and Zeeman-like splitting in the spectra of nonlinear photonic meta-atoms
S. Zhang, I. Babushkin, U. Morgner et al. (+2 more)
We study photonic meta-atoms, a unique class of composite solitary wave, supported in nonlinear waveguides. We establish an analogy to one-dimensional soft-core atoms, allowing to describe the complex dynamics via concepts from atomic physics. Higher-order dispersive effects cause specific spectral resonances characteristic for the eigenspectrum of a meta-atom. We demonstrate that subtle changes in this level spectrum causes frequency shifts of the resonances. These shifts consist of isotopic and isomeric contributions that can be distinguished in terms of a simple model. We further demonstrate a generic mechanism that causes a Zeeman-like splitting of resonance lines.
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All authors S. Zhang, I. Babushkin, U. Morgner, A. Demircan, O. Melchert
Atomic Physics · Cross-listed from cond-mat.quant-gas
Bosonic quantum mixtures with competing interactions: quantum liquid droplets and supersolids
Sarah Hirthe and Leticia Tarruell
These lecture notes contain an introduction to
quantum simulation of bosonic systems in the continuum, focusing on weakly interacting Bose-Bose mixtures with competing mean-field interactions. When the values of such interactions are fine-tuned to almost completely cancel the mean-field energy,
quantum fluctuations become apparent and dominate the behavior of the system, stabilizing an ultradilute
quantum liquid phase. An analogous situation appears in single-component dipolar
quantum gases. We review the mechanism that gives rise to this exotic
quantum liquid, which can form droplets that are self-bound in the absence of any external confinement, and discuss their properties and dynamics in both the mixture and the dipolar cases. In dipolar gases, arrays of dipolar droplets stabilized by
quantum fluctuations can establish global phase coherence and form supersolids. In bosonic mixtures, supersolidity can emerge already at the mean-field level through
spin-orbit coupling. We discuss the properties of such
spin-orbit-coupled supersolids, comparing them to their dipolar counterparts. Specifically, we focus on their periodic density modulation, phase coherence, and peculiar excitation spectrum, which hosts both superfluid and
crystal excitations. Finally, we conclude by discussing open research directions in the areas of
quantum liquid droplets and
spin-orbit-coupled supersolids, in particular at the interface of the two research topics.
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Popular Physics
Framing the Possibility Space for Technosignature Searches
Jacob Haqq-Misra
This paper develops a two-parameter
matrix that can be used to describe four general strategies in the search for technosignatures. The first parameter is domain accessibility: can the technosignature be accessed within the spatial domain accessible to us today? The second parameter is recognizability: would the technosignature be recognizable to us if discovered today? This yields a
matrix with four options that each comprise different search strategies. "Exploration" is the strategy for technosignatures that are accessible within our domain and recognizable. "Expansion" is the strategy for technosignatures that are recognizable but beyond our spatial domain. "
Evolution" is the strategy for technosignatures that are accessible within our domain but unrecognizable. "Existence" is the strategy for technosignatures that are neither within our domain nor recognizable. The implications of these four options are discussed with relevance to the
Fermi paradox and strategies for searching for technosignatures.
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Fluid Dynamics
Coalescence of viscous blisters under an elastic sheet
W-E. Khatla, L. Duchemin, A. Eddi et al. (+1 more)
We study the coalescence of identical viscous blisters beneath an elastic sheet both experimentally and numerically. Using a time-resolved synthetic schlieren technique, we measure the
evolution of the thickness field of the merging blisters and more specifically the dynamics of the coalescence region. To explain this dynamics, we develop a one-dimensional model based on the lubrication approximation, from which we derive scalings to predict the growth of the coalescence neck. We also numerically solve the full non-linear equation to assess the theory and compare to experiments. Our model illustrates that, at short times, the dynamics of coalescence is mainly controlled by the bending of the elastic sheet, leading to a relationship between the coalescence speed and the radius of
curvature of the interface at the coalescence neck.
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All authors W-E. Khatla, L. Duchemin, A. Eddi, E. Reyssat
Computational Physics
ALPHANSO: Open-Source Modeling of ($\alpha$,n) Neutron Source Terms
Divit Rawal, Anthony J. Nelson, William Zywiec et al. (+1 more)
Applications ranging from
nuclear safeguards to dark matter detection require accurate predictions of
neutron yields and energy spectra produced by ($\alpha$,n) reactions. Legacy tools like SOURCES-4C remain widely used despite significant limitations, including outdated
nuclear data, missing target nuclides, and restricted accessibility. Here, we present ALPHANSO, an open-source Python package for calculating ($\alpha$,n)
neutron source terms. ALPHANSO incorporates modern
nuclear data libraries and formats covering all naturally occurring target nuclides and provides a transparent, modular framework for updating or extending the data as new evaluations are released. Comparison with an updated version of SOURCES-4A, NeuCBOT, and experimental measurements across a range of elements and materials shows that ALPHANSO reproduces
neutron yields and spectra in good agreement with experimental data and state-of-the-art ($\alpha$,n) calculations. These results demonstrate that ALPHANSO is a reliable, accessible, and modern alternative to legacy ($\alpha$,n) source term codes such as SOURCES-4C. Its open-source design and modular data handling make it readily extensible to future evaluated
nuclear data and low-background applications.
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All authors Divit Rawal, Anthony J. Nelson, William Zywiec, Daniel Siefman
Optics · Cross-listed from quant-ph
Reconfigurable circuit for mode tunable topological quantum structured light
Pedro Ornelas, Tatjana Kleine, André G. de Oliveira et al. (+3 more)
Structured light in the
quantum regime has garnered considerable
attention due to the opportunities it offers when mixing light's internal degrees of freedom, for high-dimensional and multi-dimensional
quantum states of light. A popular example is to harness polarisation and spatial entangled
photons with a shared topological invariant that is robust against numerous families of noisy
quantum channels. Yet, producing such states with high purity and adaptability remains challenging. Here we introduce a compact, self-locking Mach-Zehnder interferometer that integrates digital spatial light modulators with static beam displacers to map spatial-mode
entanglement from a parametric down-conversion source onto topological
entanglement with high fidelity. The device also mimics the action of a reprogrammable controlled-
unitary gate, digitally driven by the spatial light modulator. This approach is an enabling platform and provides a practical route to generating reliable, high-purity
quantum-structured light with topological features, both at the single-
photon level and as entangled states, a direction of growing topical interest.
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All authors Pedro Ornelas, Tatjana Kleine, André G. de Oliveira, Carmelo Rosales-Guzmán, Andrew Forbes, Isaac Nape
Chemical Physics
TENSO: Software Package for Numerically Exact Open Quantum Dynamics Based on Efficient Tree Tensor Network Decomposition of the Hierarchical Equations of Motion
Juan C. Rodriguez-Betancourt, Michelle C. Anderson, Luchang Niu et al. (+2 more)
TENSO is a versatile and powerful open-source software package for numerically exact simulations of the dynamics of
quantum systems immersed in structured thermal environments. It is based on a tree tensor network decomposition of the hierarchical equations of motion (HEOM) that efficiently curbs its curse of dimensionality with bath complexity. As such, TENSO enables exact non-Markovian open
quantum dynamics simulations even with complex environments typical of chemistry and
quantum information science. TENSO allows for time-dependent drive in the system, and for non-commuting fluctuations. More generally, TENSO efficiently propagates the dynamics for any method with a generator of the dynamics that can be expressed in a sum-of-products form, including the HEOM and multi-layer multiconfigurational time-dependent Hartree methods. TENSO enables simulations using tensor trees and trains of arbitrary order, and implements three propagation strategies for the coupled master equations; two fixed-rank methods that require a constant
memory footprint during the dynamics and one adaptive rank method with a variable
memory footprint controlled by the target level of computational error. In contrast to the accompanying theory and algorithmic paper [J. Chem. Phys. 163, 104109 (2025)] the focus here is on the practical usage and applications of TENSO with underlying theoretical concepts introduced only as needed.
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All authors Juan C. Rodriguez-Betancourt, Michelle C. Anderson, Luchang Niu, Xinxian Chen, Ignacio Franco
Chemical Physics
In-phase current and temperature oscillations reduce PEM fuel cell resistivity: A modeling study
Andrei Kulikovsky
We have developed a non-isothermal analytical model for the impedance of the cathode catalyst layer (CCL) in a PEM fuel
cell. In-phase harmonic perturbations to the current density and temperature reduce the impedance and the static polarisation resistivity of the CCL due to lowering
proton transport losses. A special selection of the current and temperature perturbation amplitudes allows for complete elimination of these losses.
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Geophysics
Deep Learning-Based 3D Seismic Velocity Inversion Under Dual-Domain Sparse Representation
Guoxin Chen, Wenjie Wang, Haiyang Lu et al. (+1 more)
Three-dimensional seismic full-waveform inversion (FWI) provides high-fidelity subsurface velocity models but is restricted by high computational cost, strong nonlinearity, cycle-skipping, and heavy dependence on initial models. Although data-driven deep learning mitigates these issues, it still produces over-smoothed results with limited physical interpretability and low efficiency. To address these challenges, we propose a dual-domain sparse deep learning framework for 3D seismic velocity inversion using the discrete cosine transform (DCT). DCT compresses seismic data and velocity models into a sparse domain to remove redundancy while preserving key structural features. A geometry-adaptive network named SEDCN (Squeeze-and-Excitation Deformable Convolutional Network) is adopted to better capture irregular salt-dome geometries and sharp velocity boundaries. We train and validate the network on 676 samples from the 3D SEG/EAGE salt model, with two schemes for comparison: the proposed DCT-SEDCN and the baseline SEDCN without DCT. Numerical results show that DCT-SEDCN reduces training time by more than 90% and achieves higher PSNR and SSIM than conventional spatiotemporal-domain methods. It effectively suppresses over-smoothing, recovers salt body boundaries and stratigraphic details clearly, and generates geologically more reliable velocity models. This study confirms that DCT-based sparse representation combined with geometry-adaptive deep learning significantly improves the efficiency, accuracy, and robustness of 3D seismic velocity inversion. The framework offers a scalable solution for large-scale 3D FWI and can be extended to elastic/viscoelastic multi-parameter inversion and field data applications.
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All authors Guoxin Chen, Wenjie Wang, Haiyang Lu, Jinxin Chen
Optics
Two-Step Tapering-Collapse Method Enables Element-Interdiffused Cladding for Enhanced Laser Amplification in Yb:YAG Single Crystal Fibers
Xiangfei Zhu, Xiaofei Ma, Chenxin Gao et al. (+14 more)
The development of high-power single
crystal fiber (SCF)
lasers is critically hindered by the lack of a reliable cladding scheme to confine the optical mode and ensure beam quality. Here, we propose and demonstrate a two-step tapering-collapse method for the first time to fabricate a high-quality cladding on Yb:YAG SCFs based on elemental interdiffusion. This in-situ formed crystalline transition layer with a graded refractive index effectively suppresses
lattice mismatch and abruptly mitigates core-cladding interfacial stress. Consequently, the numerical aperture of the SCF is significantly reduced from 0.280 to 0.199. In a master oscillator power amplifier configuration, the clad SCF delivers a remarkable 46.7% enhancement in slope efficiency compared to its bare counterpart, accompanied by a substantially improved near-field beam profile. This work establishes a facile and effective route to high-performance clad SCFs, unlocking their full potential for next-generation extreme-condition
lasers.
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All authors Xiangfei Zhu, Xiaofei Ma, Chenxin Gao, Tao Wang, Zhen Huang, Jiajia Zeng, Dongran Shi, Xuanfeng Zhou, Baolai Yang, Zilun Chen, Hu Xiao, Feng Xiong, Pengfei Ma, Jian Zhang, Zhitai Jia, Zefeng Wang, Xutang Tao
Plasma Physics
Dielectric response and structural properties of finite-temperature electron liquids
Chengliang Lin, Yong Hou, Jianmin Yuan et al. (+2 more)
The dielectric response and structural properties of finite-temperature electron
liquids are central to accurately describing the physical behavior of electronic systems. This study presents a robust analytical model for the static structure factor of the uniform electron gas, combining physically motivated form for the static structure factor with constraints derived from high-accuracy path integral Monte Carlo simulations. The model accurately reproduces key features of the static structure factor across a broad range of temperatures and densities. Using this static structure factor, the density response function is directly evaluated, enabling a self-consistent definition of the static local field correction. As practical applications, the model is employed to investigate the low-velocity stopping power and the electron-ion friction coefficient. Results derived for the friction coefficient show good agreement with simulation data at moderate coupling and degeneracy. The proposed approach provides a computationally efficient and reliable method for characterizing the static response properties of correlated electron systems, facilitating improved simulations of energy deposition and ionic transport in warm dense matter and other strongly coupled
quantum plasmas.
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All authors Chengliang Lin, Yong Hou, Jianmin Yuan, Yong Wu, Jianguo Wang
Atomic Physics
Design and implementation of a modular laser system for AMO experiments
Klara Theophilo, Scott J Thomas, Georgina Croft et al. (+5 more)
Robust
laser delivery and stabilization are key components in atom-based
quantum technologies, such as
quantum computing. Moving these technologies towards product-like deployment requires scalable, compact, cost-effective, and upgradable modules. Here we describe
laser systems consisting of application-flexible modules and demonstrate their performance by characterizing key metrics and by integration with ion trap systems. The
laser system is confined to a single server rack and a compact locking station. Both are Class 1
laser products with fiber in-out and electronic control of the
laser light. This is achieved through precision manufacture of optical boards that are designed to reduce the degrees of freedom, ease
alignment, and increase the robustness to environmental factors. We present a range of 13 wavelengths from 375 nm to 1092 nm: efficiencies from
laser source to ion trap range from 21 - 28%, with
laser stabilization line widths below 1 MHz.
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All authors Klara Theophilo, Scott J Thomas, Georgina Croft, Yashna N D Lekhai, Alexander Owens, Daisy R H Smith, Silpa Muralidharan, Cameron Deans
Optics
Wake-Tail Effects in Two-Dimensional Wave Refocusing
Theodoros T. Koutserimpas
In even spatial dimensions, solutions of the wave equation violate Huygens' principle, producing a persistent wake tail inside the light cone rather than a sharply localized propagating front. This intrinsic tail complicates refocusing. Here, we examine how the wake-tail structure of the two-dimensional wave equation affects refocusing, using the analytically tractable example of a pulse generated by a source localized in both space and time. Two idealized concentration strategies are considered. A spatial mirror reflects the outgoing pulse and produces refocusing, but the redirected signal is broadened, with the wake tail preserving its causal ordering behind the propagating front. A second strategy employs a time mirror generated by abrupt temporal modulation of the phase velocity, producing temporal reflection and transmission. This mechanism introduces an anti-causal response of the wake-tail, reversing its temporal ordering in a time-reversal-like manner; however, the pulse still undergoes distortion and wake-tail contributions persist through secondary radiation at the refocus point. These results demonstrate the fundamental connection between Huygens' principle and wave concentration, showing that the wake-tail structure intrinsic to two-dimensional propagation imposes a fundamental limit on perfect refocusing, even under idealized conditions.
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Optics
Label-free quantitative imaging of two-dimensional concentration gradients using Fabry-Pérot interferometry
Taieesa Peshkovsky, Stefan Andreas Schmid, David Taylor et al. (+3 more)
Concentration gradients at the microscale play a central role in many physical, chemical, and biological systems, yet their quantitative visualization remains challenging due to the limited optical contrast associated with changes in concentration. Here, we present RIO (the Refractive Index Observer), a label-free interferometric tool for quantitative imaging of refractive index, and thus concentration fields in microfluidic systems. Implemented using a Fabry-Pérot microfluidic chip mounted on a standard optical microscope, RIO achieves a per-pixel refractive index precision on the order of $1\times 10^{-5}$ refractive index units (RIU) using a standard CMOS camera, enabling high sensitivity two-dimensional chemical imaging. We Characterize the refractive index resolution and spatiotemporal performance of the instrument and demonstrate its capabilities by measuring concentration gradients of dissolved NaCl in a co-laminar flow. RIO provides an accessible, label-free platform for quantitative studies of microscale concentration fields in systems where molecular labeling is undesirable or impractical, and enables investigations of a broad range of out-of-
equilibrium phenomena, from polymerization and enzymatic reactions to
cell signaling and electrochemical processes.
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All authors Taieesa Peshkovsky, Stefan Andreas Schmid, David Taylor, Robert W. Style, Lucio Isa, Federico Paratore
Optics
Stability of a high-finesse optical cavity at 493 nm in vacuum for cavity QED with Barium ions
Diptaranjan Das, Ezra Kassa and Hiroki Takahashi
We explore the stability of a high-finesse optical cavity at 493 nm in
vacuum for cavity QED with Barium ions. A high-finesse Fabry-Perot cavity is built using mirrors with high-reflectivity (HR) coatings that are implemented by stacking multiple thin films of low-loss dielectrics on substrates. Applications of such HR mirrors in the near ultraviolet (UV) range have been hampered by degradation of coatings in
vacuum. Here, we explore the degradation of mirrors with HR coatings at 493 nm in
vacuum. We study both
vacuum-induced and
laser-induced effects on
oxide-coated cavity mirrors by probing changes in cavity loss using cavity lifetime measurements. We investigate the role of circulating power in the rate of increase in cavity loss and demonstrate methods of reversal of cavity degradation. While we observe no degradation without long exposure or with short exposures at lower circulating powers, we find evidence of degradation on long exposure to high circulating powers. We discuss potential causes and conclude that
laser-induced deposition is the likely cause while ruling out thermally activated processes due to
laser-induced heating.
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Physics and Society
Allocating Access to Quantum Computing: A Legal-Ethical Framework
Benedict Lane, Anushka Mittal and Ariana Torres-Knoop
Along with the increased availability and capabilities of
quantum computers comes the core question: how can access to
quantum computing be allocated in a responsible way? This report introduces a general legal-ethical framework that providers of access to
quantum computing can apply to develop robust access policies tailored to their specific context. We demonstrate the applicability of this general legal-ethical framework in the specific context of a small, 16-
qubit quantum computer that will be hosted by SURF (the Dutch IT cooperative for research and education), integrated with Snellius (the Dutch national supercomputer), and operated jointly as part of the EuroSSQ-HPC consortium, procured in partnership with the EU-wide EuroHPC Joint Undertaking.
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Physics and Society
Modeling Changing Scientific Concepts with Complex Networks: A Case Study on the Chemical Revolution
Sofía Aguilar-Valdez and Stefania Degaetano-Ortlieb
While context
embeddings produced by LLMs can be used to estimate conceptual change, these representations are often not interpretable nor time-aware. Moreover, bias augmentation in historical data poses a non-trivial risk to researchers in the Digital Humanities. Hence, to model reliable concept trajectories in evolving scholarship, in this work we develop a framework that represents prototypical concepts through complex networks based on topics. Utilizing the Royal Society Corpus, we analyzed two competing theories from the Chemical Revolution (phlogiston vs. oxygen) as a case study to show that onomasiological change is linked to higher
entropy and topological density, indicating increased diversity of ideas and connectivity effort.
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Accelerator Physics · Cross-listed from eess.SY
An Extended T-A Formulation Based on Potential-Chain Recursion for Electromagnetic Modeling of Parallel-Wound No-Insulation HTS Coils
Zhe Pan, Qi Xu, Ruixiang Wang et al. (+2 more)
Parallel-wound no-insulation (PW-NI) high-temperature superconducting (HTS) coils significantly reduce charging delay while maintaining excellent self-protection capability, demonstrating great potential for high-field applications. Existing models that couple the T-A formulation with equivalent
circuits have demonstrated high accuracy in electromagnetic analysis of PW-NI coils. However, eliminating the computational overhead caused by frequent variable mapping and data exchange between electromagnetic and
circuit modules is important for improving computational efficiency, particularly in long-duration transient simulations of large-scale magnets. To address this issue, an extended T-A formulation based on potential-chain recursion, termed PCR-TA, is proposed. By directly
embedding inter-tape current sharing and radial current bypass behaviors into the finite-element framework, this method computes the transient electromagnetic response of PW-NI coils without requiring an explicit equivalent
circuit model. Building upon it, a multi-scale approach is further developed for large-scale PW-NI coils. The validity of the proposed method and its multi-scale extension is verified through comparisons with experimental measurements and field-
circuit coupled modeling results. Comparative analyses demonstrate that the PCR-TA method achieves a speedup of approximately 2.4 over the field-
circuit coupled method, whereas its multi-scale extension further increases this speedup to roughly 5.8. Furthermore, the PCR-TA method is extended to model the continuous transition of PW-NI coils from power-supply charging to closed-loop operation. This work provides an efficient method and tool for the electromagnetic modeling of PW-NI coils under both driven and closed-loop operating conditions.
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All authors Zhe Pan, Qi Xu, Ruixiang Wang, Zhenghao Jin, Jianzhao Geng
Fluid Dynamics · Cross-listed from cond-mat.soft
Non-contact mechanics of soft and liquid interfaces by hydrodynamic confinement using a frequency-modulated AFM
Lucie Corral, Christian Curtil, Medhi Lagaize et al. (+2 more)
Measuring the mechanical response of
liquid interfaces without direct contact remains a major experimental challenge, particularly in
liquid-
liquid systems where no solid reference exists. Here, we develop a frequency-modulation atomic force microscopy (FM-AFM) method that probes
liquid interfaces through the hydrodynamic confinement of a viscous
liquid film between an oscillating probe and the interface. This approach provides simultaneous access to the in-phase and dissipative components of the effective mechanical response under confinement. The method is first validated on a
liquid-solid interface, where the measured confinement thickness and the
evolution of the mechanical impedance are consistent with elastohydrodynamic theory over nearly one decade in elastic modulus. It is then applied to a
liquid-
liquid interface, which exhibits a predominantly viscous response with a finite in-phase contribution and a confinement thickness in the micrometric range. These results show that hydrodynamic confinement provides a sensitive, non-contact approach to compare the mechanical response of soft and
liquid interfaces, and opens new perspectives for investigating complex and highly deformable systems such as
polymer films, biological membranes, and rafts of nanoparticles.
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All authors Lucie Corral, Christian Curtil, Medhi Lagaize, Marc Leonetti, Hubert R. Klein
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Interface-dependent Phase Transitions and Ultrafast Hydrogen Superionic Diffusion of H2O Ice
Pengfei Hou, Yumiao Tian, Zifeng Liu et al. (+5 more)
High-pressure experiments using diamond anvils have revealed novel properties and phase behavior of H2O under extreme conditions. When contained in diamond-anvil
cells, the H2O samples are usually in direct contact with the diamond anvil. However, the extent to which this interface affects measured pressure-induced properties and behavior, including coexistence lines of ice phases, remains unknown. Combining artificial neural network methods and active learning schemes with large-scale molecular dynamics simulations, we elucidate the interfacial effects on various properties of high-pressure ice phases, including superionic states, solid-solid phase transitions, and melting. The results reveal that the presence of this interface can significantly lower the hydrogen superionic transition temperature. Remarkably, the interface can also induce a spontaneous transition from bcc- to fcc-based ice following the inverse Bain mechanism. Further, we redefined a stability field of bcc and fcc ice below the melting line and predicted the existence of fcc ice at much lower pressures than previously thought. More broadly, the results emphasize the importance of interface effects in understanding a wide range of phenomena reported in experimental studies of ice under pressure, including inconsistencies between theoretical and experimental results of this fundamental system.
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All authors Pengfei Hou, Yumiao Tian, Zifeng Liu, Junwen Duan, Hanyu Liu, Xing Meng, Russell J. Hemley, Yanming Ma
Physics and Society
A dynamic mechanism for prevalence of triangles in competitive networks
M. N. Mooij, M. Baudena, A. S. von der Heydt et al. (+2 more)
Triangles are abundant in real-world networks but rare in standard null models for sparse graphs. Existing explanations typically rely on explicit triadic closure mechanisms or geometry-based connection rules. We propose an alternative hypothesis: the frequent appearance of triangles may arise naturally from the requirement of dynamic stability that maintains coexistence of species in Lotka-Volterra systems with equal competitive interactions. To evaluate this idea, we prove that, across all possible interaction graphs, coexistence is guaranteed whenever the coupling strength is below the reciprocal of the graph's maximum degree, and guaranteed not to occur when the coupling strength exceeds 1. This leaves a large gap that is unexplained by the graph degrees alone. We notice that the lower and upper bounds are achieved for
star and complete graphs respectively and to investigate further what structural properties of the interaction graph control the critical coupling within the gap, we optimise networks algorithmically while keeping the degree sequence fixed. We find that networks supporting stronger interaction strengths consistently exhibit higher clustering coefficients in several network models. Moreover, in real-world grassland plant networks, we observe higher clustering and stronger stability than those expected from a configuration model with the same degree sequence. Our result suggests that triangles, and clustering in general, may emerge as a structural signature of stabilising competition.
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All authors M. N. Mooij, M. Baudena, A. S. von der Heydt, L. Miele, I. Kryven
Chemical Physics
Quantum Field Approaches to Chemical Systems
Reza Karimpour, Matteo Gori and Alexandre Tkatchenko
Quantum-matter theory (QMT), based on the Schrödinger or Dirac equations, is firmly established for both intra- and intermolecular interactions. However, there are two key issues with QMT. First, its applicability to large molecular complexes is hindered by the relatively high computational cost of the calculations required to achieve high accuracy. Second, fields are also
quantum objects that produce many intriguing effects beyond standard QMT approaches to molecular systems. This review focuses on recent developments in
quantum-field theory (QFT) approaches to both covalent and non-covalent interactions for molecules in
vacuum and subject to environments such as cavities and solvents. QFT provides a rich playground for novel chemical theories and insights. For example, chemical reactions and van der Waals interactions can be manipulated by cavities, boundaries, and optical excitations; novel interactions emerge when molecules interact with quantized fields; systems with millions of atoms could soon be treated with coarse-grained QFT formalisms; and unexpected scaling laws for atomic and molecular properties can emerge when QFT is applied to sets of chemical systems. This review sets the stage for an exciting QFT-driven path for further development of chemical theory.
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