Optics · Cross-listed from quant-ph
Programmable cavity-enhanced telecom quantum memory in thin-film lithium niobate
Chengdong Yang, Hanwen Guo, Yu-Yang An et al. (+6 more)
Spectrally multiplexed telecom
quantum networks require
quantum memories combining efficient storage with programmable frequency addressing. An integrated implementation should therefore unite a native telecom transition, efficient storage, and fast on-chip spectral control. Here we demonstrate a cavity-enhanced
memory in an isotopically purified $^{167}\mathrm{Er}^{3+}$-doped thin-film lithium niobate microring. Long-lived hyperfine shelving states enable persistent, high-contrast atomic frequency comb preparation with a single-component lifetime of $277.6(52.6)$~s, while cavity impedance matching yields $23.3(5)\%$ on-chip efficiency for 100-ns storage. The intrinsic electro-optic response enables frequency-selective storage and routing at rates up to 20~MHz. We further store and retrieve time-energy-entangled telecom
photons, violating an
entanglement-witness bound by more than 11 standard deviations. Our results establish erbium-doped thin-film lithium niobate as a programmable light–matter interface for spectrally multiplexed
quantum networks.
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All authors Chengdong Yang, Hanwen Guo, Yu-Yang An, Qian He, Chi Lu, Ziheng Jiang, Yan-Qing Lu, Shining Zhu, Xiao-Song Ma
Optics · Cross-listed from cond-mat.mes-hall
Optimizing strong light-matter coupling of plasmonic lattices and monolayer semiconductors
Lukas Krelle, Lukas Husel, Kenji Watanabe et al. (+4 more)
Exciton-polaritons provide a versatile platform for the study of a wide range of phenomena, including polariton
lasers, topological polaritons, and bosonic condensation. Transition metal dichalcogenide monolayers host
excitons with large oscillator strength and binding energies constituting a robust matter constituent that forms polaritons from cryogenic to room temperature when embedded in optical microcavities. Plasmonic nanoparticles arranged in
lattice geometries offer strong field-confinement and high quality factors. However, the high sensitivity of monolayer
excitons to strain and dielectric disorder necessitates encapsulation in atomically flat hBN to ensure a high optical quality, rendering plasmonics more challenging. Here, we employ our recently developed fabrication method for
embedding gold nanodisk arrays into van der Waals
heterostructures and compare two samples with opposite layer order. We observe that strain and etching-induced surface contamination can reduce the
exciton quality and thus the light-matter interaction strength significantly. Our fabrication approach reduces interfacial irregularities and enables homogeneous large-area polariton
lattices for a wide range of applications, such as polarization-control or topological polaritonics.
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All authors Lukas Krelle, Lukas Husel, Kenji Watanabe, Takashi Taniguchi, Ismail Bilgin, Alexander Högele, Farsane Tabataba-Vakili
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Functional and Density-Driven Errors in Density Functional Theory: Quantum Monte Carlo Benchmarks for Solids
Ayoub Aouina, Nicolas Tancogne-Dejean and Silvana Botti
We introduce a systematic analysis of density functional approximation errors in solids by separating functional-driven from density-driven contributions using
quantum Monte Carlo densities of silicon, sodium chloride, and copper as reference. Typically, functional errors dominate, but we identify important exceptions where density-driven errors exceed functional errors by factors of 2-3, notably for SOGGA11 and {\tau}-HCTH in the
semiconductor and the
insulator. Material dependence is striking: 63% of functionals show error cancellation in silicon versus 18% in copper, and only five functionals surpass LDA accuracy for metallic copper even with exact densities. For silicon and sodium chloride, GILL or BECKE exchange combined with PBE, PW91, or P86 correlation achieves near-exact xc energies on QMC densities, while copper requires specialized functionals like PBEsol or PBELYP. High-quality densities consistently reduce density-driven errors across all systems. Historical analysis reveals that 1990s GGA functionals outperform many modern meta-GGAs, contradicting expectations of systematic improvement along Jacob's ladder. These results provide practical guidance for functional selection and highlight implications for machine learning potential development, where material-dependent error cancellation may compromise transferability.
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Fluid Dynamics · Cross-listed from math-ph
Weakly nonlinear dynamics of follower-force-induced oscillations in Cosserat rods
Mohamed Warda
We investigate the weakly nonlinear dynamics of the flutter instability of a planar Cosserat rod in a viscous fluid driven by a terminal follower force. Building on our previous linear stability analysis, we derive Stuart-Landau amplitude equations governing the emergence and saturation of oscillations near the
Hopf bifurcation. The Landau coefficients are expressed in terms of the critical eigenmode, its adjoint, and quadratic correction fields arising from the asymptotic expansion. The reduced theory predicts the criticality of the
Hopf bifurcations, the saturated oscillation amplitude, and the nonlinear frequency correction, in quantitative agreement with direct numerical simulations for representative material parameter regimes. Applying the theory to both stability boundaries of the finite oscillatory window, we find that the lower
Hopf bifurcations are supercritical, whereas the upper restabilization threshold is subcritical. These results provide a normal-form description of follower-force-driven oscillations in geometrically exact Cosserat rods and a reduced framework for studying nonconservative elastohydrodynamic instabilities in soft robotic structures and active filaments.
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Optics
Integrated photonic computing: towards high-dimensional information processing
Ji Qin, Zhi-Kai Pong, Xuke Qiu et al. (+14 more)
The rapid growth of artificial intelligence, coupled with the slowing of Moore's law, is straining computing infrastructure, as CMOS electronics face inherent limits in bandwidth, energy efficiency, and parallelism. Integrated photonic computing encodes and processes information using the phase, amplitude, spatial modes, wavelength channels, and polarisation of guided optical fields, offering a scalable and energy-efficient route beyond charge-based signalling. Here, we review on-chip photonic computing, emphasising the progression from low-dimensional to high-dimensional architectures. At the foundational level, low-dimensional approaches manipulate the phase and amplitude of guided light through Mach-Zehnder interferometers, diffractive structures, microring resonators, and absorptive elements, forming a programmable basis for optical
matrix-vector multiplication. Crucially, high-dimensional architectures exploit spatial modes and wavelength channels to carry multiple independent data streams through a single waveguide, achieving higher throughput with moderate hardware overhead. Practical deployment, however, demands more than device innovation. We examine how system-level techniques, from time-wavelength interleaving to hardware-aware training, address energy efficiency, precision, and
algorithm-hardware co-design. Five challenges nevertheless remain: electro-optic conversion efficiency, computing parallelism, spatial integration, reconfigurability, and robustness. We highlight emerging topological structures, such as optical skyrmions, as a promising route to fault-tolerant, topologically protected encoding that exploits the largely untapped polarisation degree of freedom. We argue that, by embracing the higher dimensionality of light, photonic computing can offer not merely an incremental improvement but a new paradigm for high-performance, energy-efficient information processing.
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All authors Ji Qin, Zhi-Kai Pong, Xuke Qiu, Liangyu Deng, Runchen Zhang, Yunqi Zhang, Jinge Guo, Yifei Ma, Zimo Zhao, Yuanxing Shen, Patrick Salter, Martin Booth, Stephen Morris, Honghui He, Min Gu, Bowei Dong, Chao He
Chemical Physics
Generalized Suzuki-Chin Factorization in Bosonic Path Integral Molecular Dynamics
Jacob Higer and Barak Hirshberg
Modern implementations of path integral molecular dynamics (PIMD) simulations of distinguishable particles frequently make use of high order factorization schemes for the Boltzmann operator to expedite convergence of
equilibrium averages. Among these methods is the generalized Suzuki-Chin factorization (GSF), which is accurate up to fourth order in the imaginary-time step. In this work, we show that the GSF decomposition of the Boltzmann operator is applicable to bosonic PIMD, and results in an improved convergence of
estimators. In particular, we show that the recently developed quadratic scaling bosonic PIMD need not change when using the GSF. The GSF scheme is implemented as a re-weighting factor for observables, without affecting the sampling generated by the standard, second-order, primitive factorization. We study the effect of this factorization for
bosons in a harmonic trap and a sinusoidal potential. We also assess the effectiveness of GSF in calculating fermionic expectation values for harmonically-trapped atoms. In all these cases, we find that the GSF speeds up convergence with the Trotter number by a factor of $\sim 2-4$ across a wide temperature range, at only a modest computational cost.
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Optics
Boosting Sensing Performance through Near-Field Engineering in Low-Q Metasurfaces
José Antonio Álvarez-Sanchis, Luis Manuel Máñez-Espina, Teresa Mengual Chuliá et al. (+2 more)
Dielectric metasurfaces have introduced a new paradigm for substance detection by exploiting their resonant properties to enhance light-matter interaction. This enhancement can be used for sensing either through refractive index changes or through absorption-based mechanisms. Most works focus on high-quality factor resonators, aiming to increase field confinement in the vicinity of the resonant structure to improve sensitivity. In this work, we explore an alternative approach based on low-quality factor, fully dielectric metasurfaces, with engineered modes to enhance near-field concentration. We investigate different
topologies that, despite their low-quality factors, achieve sensitivity and detection performance beyond what is typically reported for low-Q structures in the literature. This improvement is enabled by near-field engineering of the evanescent modes, allowing us to control the spatial distribution of the electromagnetic field and maximize its overlap with the analyte. Our results show that careful mode engineering provides a powerful strategy to boost sensing performance without relying on ultra-high-Q resonances.
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All authors José Antonio Álvarez-Sanchis, Luis Manuel Máñez-Espina, Teresa Mengual Chuliá, Amadeu Griol, Ana Díaz-Rubio
Geophysics
Laboratory rivers extremize friction and are cosmological analogues
Valerio Faraoni and Nikki Veilleux
In the shallow water approximation, the cross-sectional profiles of laboratory rivers satisfy a differential equation here shown to be formally the Friedmann equation of cosmology ruling the
evolution of Anti-de Sitter universe. The ensuing
cosmic analogy provides a counterintuitive Lagrangian for the transverse river profile. Extremizing the corresponding action corresponds to extremizing the friction force on the river bottom and the energy dissipation rate. Analysis of the second variation establishes that this extremum is a maximum.
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Optics
Programmable Non-Hermitian Synchronization of Light on a Silicon Photonic Processor
Ze-Sheng Xu, Nan Cheng, Mohammed S. Elmusrati et al. (+6 more)
Synchronization is a pervasive collective phenomenon underlying the firing of
neurons, the beating of the heart, and the coherent emission of
lasers. Across these systems, dissipation plays an organizing role, suppressing microscopic differences and steering coupled units toward a common macroscopic order. Here we harness engineered non-Hermitian dissipation to synchronize light directly in the optical domain. Implementing non Hermitian transition
matrices on a silicon photonic processor, we drive arbitrary multimode optical fields toward a unique collective state with equal modal intensities and a globally locked phase, a process we call dissipation-induced phase synchronization. The synchronization rate and total optical power throughput are independently programmable, enabling control over the dissipative dynamics without compromising reconfigurability. These results recast dissipation as a functional resource and open a route to reconfigurable on-chip synchronization for classical and
quantum photonic technologies.
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All authors Ze-Sheng Xu, Nan Cheng, Mohammed S. Elmusrati, Rohan Yadgirkar, Andrea Cataldo, Rui Wen, Govind Krishna, Jun Gao, Ali W. Elshaari
Computational Physics · Cross-listed from cond-mat.mtrl-sci
N-Graphdiyne as a Tunable Platform for Stabilizing Light Metals toward High-Capacity Reversible Hydrogen Storage
Wael Othman, Ibrahim Alghoul, K-F. Aguey-Zinsou5 et al. (+2 more)
Hydrogen (H2) is a promising carbon-neutral energy carrier. However, its deployment is limited by the lack of lightweight, reversible storage media that operate under practical conditions. Here, we establish nitrogen-doped graphdiyne (N-GDY) as a programmable two-dimensional platform for stabilizing dispersed light-metal dopants and enabling high-capacity physisorption of molecular H2. The computational package involves density functional theory (DFT) combined with ab initio molecular dynamics (AIMD) and Langmuir-based statistical thermodynamic modeling. The results revealed that N-sites of N-GDY bind up to five Li, Na, K, and Ca atoms per primitive
cell with binding energies of -2.27, -1.57, -1.80, and -2.13 eV, respectively, exceeding their respective bulk cohesive energies. AIMD simulations at 400 K further confirm the structural robustness of the decorated frameworks and the absence of metal aggregation. The polarised metal centres activate reversible H2 adsorption through electrostatic and dispersion interactions, with average adsorption energies falling within the optimal window (-0.15 to -0.35 eV per H2). Sequential adsorption analysis reveals uptake of up to 25 H2 molecules per primitive
cell, achieving intrinsic gravimetric capacities of 13.08, 10.82, 9.23, and 9.15 wt% for Li-, Na-, K-, and Ca-functionalized systems, respectively. Thermodynamic analysis indicates favorable adsorption-desorption behavior under near-ambient conditions, with Li- and Ca-functionalized systems exceeding the 6.5 wt% U.S. Department of Energy's ultimate system-level target when considering intrinsic material capacity. These results identify N-GDY as a chemically tunable scaffold for dispersing lightweight metals and provide a mechanistic design strategy for achieving high-capacity, reversible hydrogen storage in porous two-dimensional materials.
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All authors Wael Othman, Ibrahim Alghoul, K-F. Aguey-Zinsou5, Nacir Tit, Tanveer Hussain
Atomic Physics
Development of an electrodynamic balance to study single levitated particles exposed to alkali-metal vapor
Akira Kamada, Borjid Jiyatai and Atsushi Hatakeyama
Electrodynamic balances (EDBs) have been widely used to investigate reactions between levitated particles and background gases. In this paper, we report the development of an EDB that exposes trapped particles to alkali-metal vapor. The apparatus was developed principally to investigate the interactions between such vapor and the paraffin used as a
spin anti-relaxation coating for alkali-metal vapor
cells by atomic physicists. The trap electrodes of the EDB were installed in a
vacuum glass
cell. Particles were loaded via
laser launching, without venting or contaminating the
cell. Alkali-metal vapor was released from a dedicated dispenser. We found changes in the charge-to-mass ratios of trapped particles irradiated with ultraviolet light after exposure to alkali-metal vapor. These results demonstrate the utility of the apparatus.
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Chemical Physics
Full-Dimensional Reactive Potential Energy Surfaces for OCS$^+$ $\rightarrow$ CO+S$^+$ Dissociation: Ground and Excited States
Cangtao Yin, Stefan Willitsch and Markus Meuwly
Full-dimensional reactive potential energy surfaces (PESs) for the OCS$^+$ cation are constructed to describe S$^+$ loss in the electronic ground state and seven low-lying electronically excited states. High-level ab initio reference energies were computed at the MRCI+Q/aug-cc-pVTZ level and were used to generate PESs employing reproducing kernel
Hilbert space representations (RKHS). The PESs accurately reproduce the measured dissociation limits to CO(X$^1\Sigma^+$)+S$^+$ in different electronic states. The
topology of the PESs reveals multiple linear and T-shaped minima, pronounced angular anisotropy, and state-crossing
manifolds. Exploratory quasi-classical trajectory simulations on selected PESs confirm numerical stability and energy conservation, illustrating the suitability of the surfaces for dynamical applications. The present work represents the most comprehensive characterization to date of the lowest PESs of OCS$^+$ and provides a reliable foundation for future studies of the photodissociation of OCS$^+$ and the chem-ionization dynamics of OCS.
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Optics
Collective-Coordinate Fluctuations of Driven-Dissipative Solitons
Yifan Sun, Thomas Bunel, Sofya Glazyrina et al. (+5 more)
Fluctuations of nonequilibrium localized waves are shaped not only by direct
stochastic forcing but also by deterministic transfer among coupled collective degrees of freedom. We develop a pathway-resolved
stochastic collective-coordinate theory that makes this transfer explicit for stationary driven-dissipative
solitons of the generalized Lugiato–Lefever equation with Raman response. The reduction yields a refined stationary phase-locking relation, providing a fixed point for the subsequent
stochastic theory. Projecting field-level fluctuations onto four
soliton coordinates: amplitude, frequency shift, temporal position, and global phase, yields a reduced Langevin model and, after linearization about a stable stationary state, an analytic power-spectral-density
matrix. This framework separates direct
stochastic injection from deterministic inter-coordinate conversion and thereby resolves how each observable spectrum is assembled from distinct internal fluctuation pathways. It shows that timing jitter is governed primarily by Gordon–Haus-type frequency-to-timing conversion, while phase noise is often dominated by amplitude-to-phase transfer rather than by direct phase
diffusion. Raman response opens additional cascaded pathways, and the low-detuning hump in the intensity and phase spectra is traced to the driven response of an underdamped amplitude–phase subsystem preceding the breathing instability. Comparisons with
stochastic simulations of both the reduced model and the full generalized Lugiato–Lefever equation show good agreement throughout most of the stable stationary single-
soliton regime, with systematic deviations mainly near the
Hopf boundary. The theory provides a general route for connecting internal fluctuation-transfer mechanisms of dissipative
solitons to measurable noise observables.
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All authors Yifan Sun, Thomas Bunel, Sofya Glazyrina, Georges Semaan, Fabien Bretenaker, Stephane Coen, Simon-Pierre Gorza, François Leo
Chemical Physics
A Flexible, Automated, and Basis-Set Insensitive Domain-Based Charge-Transfer Decomposition for Correlated Wavefunctions and its Application to Inter- and Intramolecular Cases
Lena Szczuczko, Julia Szczuczko, Marta Gałyńska et al. (+1 more)
We present a flexible, automated, and basis-set insensitive domain-based charge-transfer (CT) decomposition framework that can be combined with any CI-type excited-state wavefunction. Our approach is not based on excited-state densities and allows the excited-state character to be dissected into local and domain-based CT excitations and measures the individual contributions to each excited state. To guarantee a broad applicability, we introduce two domain-accumulation strategies to translate hole-particle substitutions to domain-domain excitations: a strict domain partitioning and a weighted approach suitable for small molecules and a large number of domains. The performance of both schemes is assessed for inter- and intramolecular CT excitations and various basis sets using EOM-CCSD and its simplified counterpart EOM-pCCD+S. Most importantly, the CT character is, to a large extent, basis-set independent, and both domain-accumulation schemes give consistent results. Overall, our framework provides a robust CT analysis and a domain resolution of the excitation character for a variety of computational setups and excited-state models.
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All authors Lena Szczuczko, Julia Szczuczko, Marta Gałyńska, Katharina Boguslawski
Chemical Physics
On the effective rank of canonical polyadic decomposition of electron repulsion integrals
Aleksandra Oszmian and Michał Lesiuk
In this paper, we study the effective rank of the canonical polyadic decomposition applied to the electron repulsion integrals, ubiquitous in
quantum chemistry. We demonstrate, both mathematically and numerically, that in general the effective rank of this decomposition cannot grow linearly as a function of the system size. Moreover, we derive a lower bound for the effective rank in the form $\propto N_{\mathrm{AO}}^2/\log_2^7 N_{\mathrm{AO}}$, where $N_{\mathrm{AO}}$ is the number of atomic orbitals in the molecule, under mild conditions imposed on the decomposition threshold $\epsilon$. As a result, while a subquadratic growth of the CPD rank is not excluded, a linear relationship between the rank and $N_{\mathrm{AO}}$ cannot hold universally. The implications of these findings for the use of the canonical polyadic format to represent electron repulsion integrals in
quantum chemistry are analyzed.
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Optics
Improving Optical Metrology by Engineering the Target Environment
Thomas A. Grant, Cheng-Hung Chi, Kevin F. MacDonald et al. (+1 more)
Measurements of positional coordinates and dimensions - whether by human
vision or optical instrumentation - are fundamental to safety, industrial productivity, manufacturing quality/accuracy, and scientific discovery. The ultimate precision of such measurements is governed by the Fisher information conveyed from an object to a detector through the optical field, and strategies for enhancing measurement performance often focus on reducing detector noise and/or refining estimation
algorithms. Building on the emerging understanding of Fisher information as a physical quantity that propagates through space in a wave-like fashion, we demonstrate that substantial gains in precision can also be made by engineering the electromagnetic environment of a measurement target to optimise the generation and transmission of Fisher information. Using nanowire position metrology based on light scattering at a wavelength {\lambda} = 640 nm as an architype system, we achieve a multifold enhancement in localisation precision, reaching beyond {\lambda}/10,000. Our results establish target environment engineering as a powerful and broadly applicable strategy for advancing measurement and sensing performance across platforms ranging from optical characterisation of micro- and nano-objects to microwave radars and optical
LiDAR navigation systems.
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All authors Thomas A. Grant, Cheng-Hung Chi, Kevin F. MacDonald, Nikolay I. Zheludev
Optics
Entangled Telecom Photon Generation using Twisted Van der Waals Crystals
Nidhin Prasannan, Konstantinos Mourzidis, Vishwas Jindal et al. (+11 more)
Nanoscale
quantum light sources are essential building blocks for integrated
quantum photonic systems. Here, we report a wavelength-scale entangled-
photon source based on van der Waals-engineered NbOBr$_2$, and
benchmark its performance for telecom-wavelength
quantum light generation. By exploiting the material's second-order nonlinearity, we generate
quantum-correlated
photon pairs via spontaneous parametric down-conversion. We then use a 90$^{\circ}$ twisted stacking to induce
quantum interference in
photon-pair generation, yielding polarization-entangled
photons. This approach enables tunability of the
quantum optical state via control of the excitation
laser polarization. We experimentally obtain
entanglement fidelities exceeding 95% for Bell states, along with a high coincidence-to-accidental ratio of $\sim$335, and a brightness approximately one order of magnitude higher than recently reported telecom sources based on transition metal dichalcogenide (TMD) 2D materials. These results establish twisted van der Waals engineering as a powerful platform for highly tunable, high-brightness
quantum light sources at telecom wavelengths.
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All authors Nidhin Prasannan, Konstantinos Mourzidis, Vishwas Jindal, Hanting Li, Di Lin, Wenchen Yang, Deng Hu, Liu Yang, Andrea Balocchi, Delphine Lagarde, Pierre Renucci, Zhiwei Wang, Gang Wang, Xavier Marie
Optics
Sagnac-Loop-Reflector Fabry-Perot Lattices for Modular 1D Topological Photonics
Siwoo Kim, Yung Kim, Semin Choi et al. (+5 more)
We introduce a modular silicon-photonic Fabry-Perot resonator
lattice based on cascaded tunable Sagnac loop reflectors. Each SLR is controlled by a single directional-coupler cross-coupling coefficient, enabling modular control of the effective
lattice hoppings. As a representative example, alternating two SLR types maps the
lattice onto the Su-Schrieffer-Heeger model in the weak-coupling limit. We derive the Bloch dispersion via a transfer-
matrix formulation and obtain an effective tight-binding
Hamiltonian in the weak-coupling limit. S-parameter simulations of a 20-site
lattice show an isolated midgap resonance with edge-localized power profiles in the topological phase, and disorder tests show robustness against
symmetry-preserving hopping perturbations. Our results establish SLR-based FP
lattices as a complementary platform for on-chip topological photonics.
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All authors Siwoo Kim, Yung Kim, Semin Choi, Taeyeon Kim, Seungmin Lee, Kyoungsik Yu, Sangyoon Han, Bumki Min
Chemical Physics
All-atomistic Transferable Neural Potentials for Protein Solvation
Rishabh Dey, Salvina Sharipova and Konstantin Popov
Implicit solvent models are widely used to decrease the number of solvent degrees of freedom and enable the calculation of solvation energetics without water molecules. However, its accuracy often falls short compared to explicit models. Recent advancements in neural potentials have shown promise in drug discovery, but transferability remains a persistent challenge. Here, we introduce the
Protein Hydration Neural Network (PHNN), an implicit solvent model that extends analytical continuum solvation by learning transferable corrections to model parameters instead of applying post hoc adjustments to final energies. The model is explicitly designed to maximize data efficiency by leveraging physical priors embedded in the data. We demonstrate that PHNN improves accuracy relative to traditional analytical methods and maintains predictive accuracy on out-of-domain
protein systems.
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Fluid Dynamics · Cross-listed from math.NA
Verification of reciprocity in anisotropic poroelastic wave simulation using symmetric Strang splitting
Morten Jakobsen and Jose Carcione
Poroelastic wave simulations are important for many applications relating fluid flow and wave characteristics in porous rock formations. Reciprocity is a key physical property of wave propagation in porous media that is important for such applications, even when viscous dissipation is present. However, numerical poroelastic simulations often fail to reproduce reciprocal responses because the discretization does not preserve the balance between reversible wave dynamics and irreversible fluid-solid drag. To address this, we formulate the Biot equations in terms of a continuous
evolution operator split into a reversible (skew-adjoint) wave part and an irreversible (self-adjoint, non-positive) Darcy part, including the leading-order Johnson-Koplik-Dashen correction. This structure clarifies why reciprocity holds in the continuous equations and how it is easily broken in discrete form. Guided by this interpretation, we construct a symmetric second-order Strang-splitting scheme with half-step source injection. The method conserves energy in the reversible subsystem, treats Darcy dissipation unconditionally stably, and retains Courant limits similar to elastic solvers. Using a staggered pseudo-spectral discretization, we model multimode propagation in 2D VTI media and obtain cross-component reciprocity with a relative L2 misfit approaching machine precision, demonstrating that the discrete scheme inherits the
symmetry properties of the continuous
evolution operator.
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Atomic Physics · Cross-listed from quant-ph
Quantum-enabled complete RF-polarimetry with an optically-wired atomic sensor
Matthew Chilcott, Laurits N. Stokholm, Matthew Cloutman et al. (+3 more)
Rydberg atomic electrometry leverages the extreme sensitivity of highly excited atoms for calibration-free electric field measurements. The technique uses a non-metallic vapor
cell to link properties of an RF field to a spectroscopic readout in the optical domain. Most demonstrations have so far focused on detecting linearly-polarized fields, for which the induced splitting of dressed atomic levels is rotationally invariant. Here we report on Rydberg atomic measurements of RF fields in a general state of polarization (SOP) which we map onto the Poincaré sphere through spectroscopic fingerprints. For a Stokes vector circumnavigating a Poincaré sphere meridian, we witness a continuous transformation of the atomic eigenenergy spectrum. Because the relative positions of eigenenergies are locked in place by quantization of angular momentum, the framework is universal and calibration free. We provide a specific demonstration in rubidium, which generalizes to all systems with a single valence electron.
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All authors Matthew Chilcott, Laurits N. Stokholm, Matthew Cloutman, J. Susanne Otto, Amita B. Deb, Niels Kjærgaard
Computational Physics · Cross-listed from cs.LG
Lang2MLIP: End-to-End Language-to-Machine Learning Interatomic Potential Development with Autonomous Agentic Workflows
Wenwen Li, Yuki Orimo and Nontawat Charoenphakdee
Developing machine learning interatomic potentials (MLIPs) for complex materials systems remains challenging because it requires expertise in atomistic simulations, machine learning, and workflow design, as well as iterative active learning procedures. Existing automated pipelines typically assume a fixed sequence of stages or depend on domain experts, which limits their adaptability to heterogeneous materials systems where the optimal curriculum is not known in advance. To lower the barrier to developing MLIPs for non-experts, we propose Lang2MLIP, a multi-
agent framework that takes natural-
language input and formulates end-to-end MLIP development as a sequential decision-making problem solved by large
language models (LLMs). At each step, a decision-making
agent observes the current
dataset, model, evaluation results, and execution log, and then automatically selects an appropriate action to improve the model. This removes the need for a predefined pipeline and enables the
agent to self-correct by revisiting earlier subsystems when new failures arise. We evaluate this approach on a solid electrolyte interphase (SEI) system with multiple components and interfaces. These results suggest that LLM-based multi-
agent systems are a promising direction for automating MLIP development and making it more accessible to non-experts.
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Biological Physics · Cross-listed from cond-mat.soft
A Brownian dynamics study of liquid-liquid phase separation in multi-scale chromatin networks
Léa Beaulès, Judith Miné-Hattab, Pierre Illien et al. (+1 more)
In living
cells,
proteins involved in specialized biochemical functions are often spatially organized within biomolecular condensates. Increasing evidence suggests that some of these condensates, including DNA repair condensates, emerge through
liquid-
liquid phase separation (LLPS). In the
nucleus, however, condensates form within a highly heterogeneous environment composed of chromatin fibers, RNA, and additional
protein scaffolds such as PAR chains, all of which may interact with phase-separating
proteins. Moreover, condensate formation is frequently associated with specific chromatin conformations; for instance, loop extrusion has been proposed as a mechanism promoting DNA repair condensates. Here, we investigate how the surrounding fibrous environment controls the morphology and spatial organization of phase-separated condensates. Using Brownian dynamics simulations of minimal models combining Lennard-Jones particles with fixed fibrous substrates, we examine the respective roles of local fiber geometry and large-scale network organization, reflecting the multiscale architecture of chromatin. We show that
protein-fiber interactions strongly influence droplet positioning relative to the substrate, in a manner analogous to wetting transitions in soft condensed matter systems. Both local
geometric constraints and global network organization markedly affect droplet size, morphology, and multiplicity. In addition, large-scale asymmetries in fiber organization can induce robust spatial localization of the dense phase. Our results thus highlight how multiscale structural heterogeneity of the
nuclear environment can regulate the emergence and organization of biomolecular condensates.
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All authors Léa Beaulès, Judith Miné-Hattab, Pierre Illien, Vincent Dahirel
Fluid Dynamics
Systematic Evaluation of Stencil Configuration, Forcing Scheme, and Resolution Effects in the Stratified Taylor–Green Vortex: A Lattice Boltzmann Study
Hongxuan Zhang
The rigorous simulation of stratified
turbulence remains challenging due to pronounced flow anisotropy, suppressed vertical transport, and high sensitivity to numerical dissipation. This study systematically evaluates the predictive capability of the
lattice Boltzmann method (LBM) for a three-dimensional stratified Taylor–Green
vortex. Within a double-distribution-function framework under the Boussinesq approximation, we examine the influence of stencil configurations, forcing formulations, and spatial resolutions up to $256^3$, with validation against spectral DNS
benchmarks. The results demonstrate that the D3Q27$\times$19 configuration achieves an optimal balance between numerical accuracy and computational efficiency, accurately reproducing the temporal
evolution of kinetic and potential energies as well as the characteristic double-peak dissipation structure. Grid-sensitivity analysis further reveals that potential energy and fine-scale turbulent structures are significantly more resolution-dependent than kinetic energy, requiring a minimum resolution of $256^3$ for quantitative convergence. Moreover, under strongly stratified conditions, the velocity-shift forcing schemes outperform discrete source-term approaches, reducing the overall error by approximately 45.54%. Overall, this work provides practical guidelines for high-fidelity LBM simulations of stratified
turbulence and highlights that the coordinated selection of stencil isotropy, spatial resolution, and force discretization is essential for accurately capturing energy cascade and mixing dynamics.
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Physics and Society · Cross-listed from nlin.AO
Analytical foundation for adversarial synchronization control in oscillator networks
Kazuhiro Takemoto
This study provides an analytical foundation for
adversarial synchronization control in Kuramoto oscillator networks, where small gradient-based perturbations applied repeatedly to oscillator phases can dramatically enhance or suppress collective synchronization. Using the Ott–Antonsen reduction, we derive an exact closed-form expression for the effect of a single
adversarial perturbation (kick) on the order parameter. A key finding is that each kick produces a finite, coupling-independent increment in the order parameter even when synchronization is arbitrarily weak, which combined with slow relaxation near the critical coupling and mean-field feedback explains the disproportionate amplification previously observed in numerical simulations. Fixed-point analysis further reveals a fundamental asymmetry between enhancement and suppression, with the latter governed by noise-induced escape in finite systems. Extending the framework to networks via the annealed network approximation, we show that the theory captures the synchronization behavior of representative model networks and identify a decoupling between kick sensitivity and mean-field dominance in scale-free networks. These results offer a tractable theoretical basis for understanding and designing kick-based synchronization control in oscillator networks.
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Optics
ML-assisted Subband Learned Digital Backpropagation for Nonlinearity Compensation in Wideband Optical Systems
Evgeny Shevelev, Oleg Sidelnikov, Vitaly Danilko et al. (+2 more)
Digital backpropagation (DBP) is one of the most effective techniques for compensating nonlinear distortions in coherent optical fiber communication systems. However, its practical application to wideband transmission remains limited by high computational complexity caused by large channel
memory and the requirement for fine spatial discretization. In this work, we propose a subband-based learned digital backpropagation (SbL-DBP) framework for wideband optical transmission systems. The received signal is decomposed into multiple subbands, enabling independent frequency-domain compensation of the chromatic dispersion with reduced effective channel
memory and lower computational complexity. Nonlinear intra- and inter-subband interactions are addressed in the time domain using a trainable multi-input multi-output filtering structure. The parameters of the proposed framework are jointly optimized using end-to-end gradient-based learning. In addition, sparsification techniques are employed to remove insignificant coefficients and further reduce computational complexity. Numerical simulations of an 11$\times$40~Gbaud WDM RRC-16QAM 20$\times$100 km transmission system demonstrate that the proposed method provides a superior performance–complexity trade-off compared to conventional DBP and enhanced DBP. In the low- and medium-complexity regimes, SbL-DBP provides higher signal-to-noise ratio gains while requiring fewer propagation steps.
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All authors Evgeny Shevelev, Oleg Sidelnikov, Vitaly Danilko, Mikhail Fedoruk, Alexey Redyuk
Computational Physics · Cross-listed from cond-mat.mtrl-sci
High-Pressure Crystal Structure Database
Zhenyu Wang, Qingchang Wang, Junwen Duan et al. (+7 more)
High-pressure research is a productive route to new structures and emergent properties. However, crucial high-pressure structural information remains highly fragmented across individual publications and heterogeneous computational repositories. This fragmentation creates a major bottleneck for data-driven materials design. To bridge this gap, we introduce the High-Pressure
Crystal Structure Database (HPCSD), a traceable, pressure-resolved repository that integrates experimental and theoretical high-pressure structures. HPCSD is constructed from two complementary data streams: elemental high-pressure phases and a searchable configuration space of stable and metastable phases generated via CALYPSO
crystal structure prediction. To ensure rigorous comparability, all retained structures underwent re-optimization under a unified density functional theory (DFT) framework , with continuous enthalpy curves systematically generated specifically for the elemental phases across their stability fields. The initial release encompasses 77,346 consistently evaluated structural entries spanning 89 elements. An analysis reveals that pressure-induced polymorphism is ubiquitous and exhibits pronounced family-dependent trends. Structural diversity is strongly influenced by an element's electronic adaptability , with the greatest structural complexity emerging at intermediate rather than highest pressures. By providing standardized, reusable, and rigorously evaluated high-pressure structural data, HPCSD establishes a robust infrastructure to accelerate experimental phase identification, facilitate cross-study thermodynamic comparisons, and support the development of machine-learning interatomic potentials and generative models for high-pressure systems.
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All authors Zhenyu Wang, Qingchang Wang, Junwen Duan, Heng Ge, Xiaoshan Luo, Pengyue Gao, Wei Zhang, Jian Lv, Yanchao Wang, Yanming Ma
Optics
Complex wavefront engineering via decoupled space-time modulation
Virat Tara, Anna Wirth-Singh, Johannes E. Fröch et al. (+1 more)
Solid-state Spatial Light Modulators (SLMs) are fundamentally limited in their ability to achieve high spatial complexity and high temporal bandwidth simultaneously. High-speed, low-energy modulation requires sub-wavelength active mode volumes, and sophisticated spatial wavefront engineering necessitates an ultra-fine pixel pitch. While small pixels can simultaneously solve both, in conventional architectures, the dense 2D electrical routing required for such pixels creates an insurmountable physical bottleneck. This results in a compromise between the SLM refresh rate, number of pixels and the field of view. Here, we demonstrate a hybrid architecture that overcomes this limit by spatially decoupling the electrical modulation plane from the optical output plane. By integrating a metasurface doublet with a photonic integrated
circuit (PIC)-based optical phased array (OPA), we achieve independent 2D electrical control over each phase-element while simultaneously realizing a three-fold reduction in effective pixel pitch. This decoupling allows us to maintain the small active volume required for high-speed operation, while circumventing the routing constraints of dense spatial array of emitters. We utilize this platform to demonstrate tunable varifocal
lensing, 2D beam steering, and 2D holography. Our work provides a scalable foundation for next-generation solid-state SLMs that simultaneously offer high speed, low power consumption, and large field of view.
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All authors Virat Tara, Anna Wirth-Singh, Johannes E. Fröch, Arka Majumdar
Optics
Determination of Poynting Vector Characteristics
I. Mokhun, V. Danko and A. Kovalenko
This paper presents a novel method for measuring the Poynting vector characteristics of monochromatic electromagnetic waves. We outline a specific design for such a meter and provide experimental data to validate the approach. For testing purposes, we utilized
vortex beams with both linear and circular polarization.
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Optics
Tunable spatio-spectral Target Skyrmions and topological multiplexing
Pedro Ornelas, Niladri Modak, Oussama Korichi et al. (+3 more)
Optical Skyrmions have recently garnered much interest providing a potential avenue for high capacity, robust topological information transfer. Typically, Skyrmions are derived from the coupling of just two degrees of freedom (DoFs) limiting their versatility. In this work we realize spatio-spectral Skyrmions derived from the non-separability between three DoFs: wavelength, space and polarization. A compact and simple technique is used to generate the spatio-spectral vector beams (SSVB) carrying the desired Skyrmionic structure, offering simple pathways for complex Skyrmionic beam design. The topological structure, witnessed through a map between the spatio-spectral plane and the Poincaré sphere, exhibits an additional tunable $k\pi$ parameter thereby enhancing the number of controllable DoFs. Our three DoF construction allows us to propose a novel topological multiplexing strategy that independently encodes different Skyrmion numbers at different radii of the field. We experimentally demonstrate the practicality of this approach by transmitting and receiving three distinct Skyrmion numbers encoded into a single topological field, for the first form of mode division multiplexing with Skyrmion
topology. This work opens up new avenues for dense information encoding using multiple topological channels encoded in a single light field.
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All authors Pedro Ornelas, Niladri Modak, Oussama Korichi, Isaac Nape, Andrew Forbes, Robert Fickler