Optics
Theory of Airy-Beam Wavefront Sensing
Surya Kamal
A new wavefront sensing framework based on the interference of counter-accelerating Airy beams is presented. An engineered cubic phase function transforms a single Gaussian beam into two coherent Airy beams with opposite transverse accelerations, which self-recombine during free-space propagation to form an interference pattern encoding the aberrated incident wavefront. Numerical simulations demonstrate accurate recovery of the aberrated exit-pupil phase across the aberration sets considered, with a root-mean-square phase reconstruction error below $10^{-6} \mathrm{\;rad}$ for the aberration set shown and consistently low errors for the other sets, while maintaining accurate recovery in the presence of measurement noise. The approach eliminates collection optics and enables a compact wavefront-sensing architecture for applications where conventional interferometric systems are difficult to implement, including electron-optical systems, augmented and virtual reality systems.
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Optics
Photonics-GCCE: group collaborative-competitive evolution multi-agent framework for universal and autonomous optical design
Weijie Xu, Ming Wang, Ruicheng Ma et al. (+20 more)
Large
language model (LLM)-empowered photonic
agents connect natural-
language intents to executable solvers, showing significant advantages over conventional optical design approaches. However, current multi-
agent frameworks operate within a collaborative paradigm without extrinsic selective pressure, which could inherit shared blind spots, converge prematurely, and fail to accumulate transferable experience for intricate tasks. Here, we introduce a group photonics collaboration-compete
evolution (GCCE) framework and its LLM instantiation, termed Photonics-GCCE. Two independent
agent groups pursue the same design target and undergo structured competitive evaluation across refractive-index fidelity, fabrication sensitivity, algorithmic adequacy, and physical consistency. Each group comprises a leader and three specialist
agents dedicated to materials, optimization, and code validation.
Agents refine their skills through competitive evaluation across design rounds. Benchmarking across six device categories against single-
agent and multi-
agent baselines shows that Photonics-GCCE elevates composite scores into the high 90s, improves fabrication robustness by 15 to 17 points, and reduces solver iterations to roughly 40 rounds. A representative quasi?BIC demonstration achieves a practically fabricable design with a quality factor of 13120. Our results demonstrate Photonics-GCCE as a general-purpose and closed-loop framework for autonomous optical design, capable of producing high-performance, fabrication-ready devices across diverse nanophotonic tasks.
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All authors Weijie Xu, Ming Wang, Ruicheng Ma, Zeyong Wei, Di Zhang, Jian Chen, Zining Wang, Sijun Hu, Linyuan Dou, Haoyu Li, Haigang Liang, Yijie Luo, Shuqiao Li, Qinghua Song, Huihui Zhu, Hongfei Jiao, Chao Liu, Ali Momeni, Zhanshan Wang, Yuzhi Shi, Romain Fleury, Cheng-Wei Qiu, Xinbin Cheng
Space Physics · Cross-listed from cs.LG
PISCES: Physics-Informed Solar-wind Convolutional autoEncoder for Space-weather Anomaly Detection and Early Warning
Kevin Lee and Alison J. March
Space weather early warning depends on detecting solar wind transients in in-situ measurements at the first Sun-Earth Lagrange point (L1), before they reach Earth. Fixed thresholds can miss combined
magnetic and
plasma structure, and many learning methods provide a single anomaly score. We present the Physics-Informed Solar-wind Convolutional autoEncoder for Space-weather (PISCES), a convolutional autoencoder trained without catalog labels on OMNI solar wind measurements under physics constraints. Its loss includes
magnetic field consistency, an empirical relation between temperature and velocity, the Parker spiral angle, and penalties on changes between consecutive one-minute samples in derived quantities calculated from the reconstruction. At inference, PISCES separates the anomaly score into
magnetic and
plasma reconstruction errors, physics relations, and residual corrections, and reports the magnitude of each contribution. Attenuation of the skip connections, selected on validation data, improves average precision for the trained models, while the untrained scores remain nearly the same. The trained models also give a more consistent ordering of these physical contributions. After smoothing with a trailing median, the alarms can precede independently observed sudden commencements, including positive sudden impulses.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
SoLiD26: A First Principles Solid-Liquid Interface Dataset for Machine-learned Interatomic Potentials
Jonas Busk, Emil J. P. Frost, Yogeshwaran Krishnan et al. (+7 more)
Machine-learned interatomic potentials (MLIPs) for solid-
liquid interfaces in advanced materials applications, e.g., electrochemistry, catalysis and corrosion, require training data that samples both
liquid environments, the solid and the interface itself. We present SoLiD26, a curated solid-
liquid interface
dataset, containing 15.4 million first-principles atomic structures with up to 576 atoms and 15 chemical elements for training and evaluating MLIPs. The structures were compiled from density functional theory (DFT) calculations performed in studies of solid-
liquid interfaces, with most configurations originating from ab initio molecular dynamics (AIMD) simulations. Each record contains atomic species, positions, simulation
cell, periodic boundary conditions, potential energy and atomic forces. SoLiD26 includes aqueous coinage metal interfaces, electrode-electrolyte systems, and selected bulk reference structures, calculated with VASP using the PBE functional and D3 dispersion corrections. We describe the data ingestion and preparation pipeline used to construct the
dataset. The application of SoLiD26 for training and evaluating MLIPs is demonstrated with a suite of MACE models on a simple training, validation and test split. The
dataset enables development and benchmarking of MLIPs for structurally and chemically heterogeneous solid-
liquid interfaces.
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All authors Jonas Busk, Emil J. P. Frost, Yogeshwaran Krishnan, Henrik H. Kristoffersen, August E. G. Mikkelsen, Xueping Qin, Xin Yang, Heine A. Hansen, Arghya Bhowmik, Tejs Vegge
Computational Physics
Optimal Bias Potentials via Ergodic Optimal Control and Generator Learning
Lei Guo, Carsten Hartmann, Thomas Berger et al. (+1 more)
We investigate the computation of optimal bias potentials for accelerating transitions between metastable states and for computation of
equilibrium properties in molecular dynamics simulations. We formulate optimal biasing as an ergodic optimal control problem (OCP), which can be recast as a linear
eigenvalue problem for the infinitesimal generator of the unbiased dynamics. We demonstrate that data-driven learning methods for the generator enable reliable solution of the OCP, computation of biasing potentials, extraction of
equilibrium properties, and acceleration of state transitions. We also explore the relation of the control problem to coarse grained representations and learning of coarse grained dynamics.
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All authors Lei Guo, Carsten Hartmann, Thomas Berger, Feliks Nüske
Optics
Inverse-Designed Chiral Metasurfaces for Enhanced Helical Dichroism
Chia-Chun Pan, Yu-Hsi Chen, Munseong Bae et al. (+5 more)
Helical dichroism (HD), arising from the interaction between structured light carrying orbital angular momentum (OAM) and chiral matter, offers opportunities for enhanced chiroptical characterization at the subwavelength scale. Here, we employ inverse design to develop chiral metasurfaces tailored for enhanced HD under Laguerre-Gaussian (LG) beam illumination. The optimized planar structure exhibits a simulated HD around 115% at 800 nm for opposite OAM states, revealing the strong chiroptical response enabled by the inverse-designed geometry. The optimized metasurfaces were fabricated from Si$_3$N$_4$ and experimentally characterized using a custom-built optical system with controlled OAM excitation. A single chiral metasurface exhibited a maximum experimental HD up to 62% near 800 nm, demonstrating a strong OAM-dependent helical dichroic response from a single 6-micron-large chiral structure. Although the measured HD value is lower than the optimized simulation value, the experimental result validates the feasibility of inverse-designed chiral metasurfaces for structured-light chiroptics. These findings establish inverse design as an effective approach for engineering compact chiral nanophotonic structures with enhanced interactions with structured light, offering potential for miniaturized chiroptical sensing and OAM-resolved imaging.
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All authors Chia-Chun Pan, Yu-Hsi Chen, Munseong Bae, Haejun Chung, Dan Smith, Daniel Fan, Sejeong Kim, Ranjith R Unnithan
Plasma Physics
Anisotropy and energy distribution of leptons and photons in radiative relativistic Alfvénic turbulence
Peng Liu, Xiaochun Wei and Zheng Gong
The anisotropic
evolution of relativistic particles in magnetically dominated Alfvénic
turbulence is a fundamental process governing nonthermal emissions in high-energy astrophysical environments. In this work, we develop a theoretical framework by deriving scaling equations that characterize the pitch-angle dynamics of leptons and
photons across both weak- and strong-radiative cooling regimes. Our model reveals a universal coupling between particle energy and angular distribution, arising from the interplay of field-aligned accelerations, perpendicular drift motions, and radiation reactions. The model can uniquely identify “turning-point energies" that exhibit a nonlinear dependence on the local
magnetic field and the energy-injection scale. The validity of this scaling model is confirmed through radiative particle-in-
cell simulations. We show that the electron pitch-angle distribution fundamentally dictates
photon emission characteristics, further revealing a pronounced statistical correlation between high-energy
photon emission and turbulent
vortices in the reconnection regions. By bridging the gap between small-scale kinetic interactions and broad-band spectral characteristics, this work provides a quantitative basis for interpreting the hardening of radiation spectra and complex polarization signatures in sources such as
pulsar wind nebulae and gamma-ray bursts.
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Physics and Society · Cross-listed from eess.SY
When Gigawatts of Computational Load Disappear: Cycle-Space Certificates for Grid Synchronization and Transient Stability
Michael Chertkov
Rapid growth of data centers and artificial-intelligence services is producing computational loads at scales once associated mainly with largest power plants. Recent grid events show that a routine transmission disturbance can cause several gigawatts of data-center demand to disconnect or transfer to backup nearly at once. This article revisits the classical synchronization and transient-stability theory needed to reason about such events. We organize four lines of work—graph-based synchronization conditions, winding-number descriptions of nonlinear power flow, separable convex network optimization, and direct energy methods—into a single cycle-space certificate framework for the lossless fixed-voltage model. The static layer gives an exact strict-cohesion test within a prescribed winding
cell and reveals the widely used Dörfler–Chertkov–Bullo test as a quadratic surrogate of the same convex problem. The dynamic layer converts the critical-energy calculation into a finite family of convex boundary problems. Standard MATPOWER
benchmarks illustrate both what the stronger static test gains and where it gains nothing: the 118-bus case admits $16.2\%$ more loading than the sufficient screen, while the 39-bus case is bridge-limited and the thresholds coincide. A stylized $2.7$-GW 39-bus event further shows that transient margin can change by about a factor of two depending on where balancing power is supplied, even when every final balanced operating point remains statically feasible. The result is a tutorial synthesis and an extensible deterministic certificate for emerging gigawatt-scale computational-load contingencies.
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Chemical Physics
Uncertainty prediction in composite quantum chemistry approaches
Jakub Lang, Kacper Raczko and Michał Lesiuk
In this work, we consider the problem of uncertainty estimation of the results obtained through theoretical calculations using a composite
quantum chemistry scheme. Each component of the composite scheme carries its own individual uncertainty, originating principally from a finite size of the basis set used in the calculations. Of practical interest is the total uncertainty, i.e. the uncertainty of the sum of all components. We first show that the conventional error propagation rules that treat each component as a statistically uncorrelated variable are not well-justified in practice. To remedy this, we propose a method of estimating the total uncertainty of the composite scheme which does not rely on the assumption that the components are independent. It is formulated as a series of random walks with different starting values that represent the uncertainty of each component of the composite scheme. This method is first applied to two example composite schemes for the water dimer and the nitrogen molecule that illustrate its most salient features and allow for a deeper analysis. Next, the method is tested for a larger set of interaction energies from the S66
dataset for which trustworthy reference data are available and the error can be assessed unambiguously. It is shown that the method provides reliable and reasonably tight uncertainty estimates at an arbitrary predefined confidence level required in a given application. While the focus of the paper is on composite schemes, we believe that the general idea can be useful more broadly in computational chemistry and physics.
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Optics
Order-Dependent Modification of High-Harmonic Generation by Quantum Dissipation and Lamb Shift
Xiangyu Zhang, Tong Wu, Xiang Li et al. (+5 more)
Many-body environments are conventionally incorporated into
quantum dynamics as heat baths, which induce a Lamb shift and
quantum dissipation. In the traditional picture, such environmental coupling is expected to induce suppression and broadening of spectral signals. In this letter, we investigate high-order harmonic generation (HHG) in a two-level system coupled to a heat bath via dipole-dipole interactions using the Lindblad master equation. It is found that the environmental effect does not simply suppress the harmonic efficiency. Instead, when the cutoff frequency of the coupling spectral density exceeds the energy-level spacing, the environment can actually enhance the harmonic yield. Further analysis reveals that this enhancement originates from intense level fluctuations induced by the Lamb shift. Meanwhile, the environmental influence exhibits a distinct dependence on harmonic order, manifesting clearly different behaviors for lower and higher harmonics. Our results challenge the common relaxation-time picture of uniform damping and establish a microscopic, order-dependent mechanism for environmental control of HHG, with direct implications for solid-state attosecond spectroscopy and
quantum material engineering.
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All authors Xiangyu Zhang, Tong Wu, Xiang Li, Jianshi Lu, Zhe Yang, Chao Yu, Shicheng Jiang, Ruifeng Lu
Instrumentation and Detectors
Cryogenic performance and long-term stability of Hamamatsu R8520-506 photomultiplier tubes in liquid argon
Jilong Yin, Gaoshuang Li, Yike Shu et al. (+1 more)
Seven Hamamatsu R8520-506 photomultiplier tubes were characterized at room temperature and in
liquid argon to evaluate their response and operating stability for
liquid-argon light readout. A 405~nm pulsed light source was used to measure gain, peak-to-valley ratio, single-photoelectron charge resolution, and afterpulsing, while dark-count data were acquired with random triggers in the absence of active illumination. Gain and dark-count stability were monitored during a ten-day operating period in
liquid argon. At a motherboard input voltage of 900~V, the extracted gains in
liquid argon were approximately 27.8%–51.3% higher than the corresponding room-temperature values. For all seven tubes, the peak-to-valley ratios were higher and the single-photoelectron charge resolution improved in
liquid argon. The dark count rates ranged from approximately 143 to 252~Hz at room temperature and from 166 to 199~Hz in
liquid argon, with three tubes showing increases and four showing decreases. The mean number of detected afterpulses per selected primary event was approximately 21.0%–63.6% lower in
liquid argon. The relative standard deviations across the ten daily means of gain and dark count rate did not exceed approximately 2.1% and 3.3%, respectively. The measurements provide a quantitative basis for considering R8520-506 tubes as photosensor candidates for
liquid-argon detectors.
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All authors Jilong Yin, Gaoshuang Li, Yike Shu, Yi Wang
Optics
A native signed incoherent photonic matrix core on thin-film lithium niobate supporting in situ backpropagation
Yuan Ren, Yong Zheng, Ruixue Liu et al. (+2 more)
Artificial intelligence workloads increasingly demand computing architectures combining high throughput, energy efficiency, and physical scalability. Here we present a signed incoherent optical
matrix multiplier on thin-film lithium niobate that natively supports signed inputs and weights. We demonstrate closed-loop in situ backpropagation on a 16 X 16 photonic core, including forward computation, nonlinear operations, error propagation, and gradient computation. Measured physical outputs directly participate in optimization, thereby incorporating actual device responses and nonidealities into training. The core achieves 8-bit multiplication and 10-bit accumulation precision across 256 channels, maintains 10-bit accuracy in tiled 256 X 256
matrix computation, and further executes
Transformer linear operations in a BERT-mini workload. This work presents a fundamental, scalable building block that addresses key limitations in practical optical computing, thereby opening avenues for large-scale, high-efficiency photonic neuromorphic systems.
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All authors Yuan Ren, Yong Zheng, Ruixue Liu, Min Wang, Ya Cheng
Computational Physics · Cross-listed from cond-mat.stat-mech
Multiscale Entropies as Order Parameters for Nonequilibrium Phase Transitions
Gerhard Jung and Misaki Ozawa
We develop a multiscale
entropy framework based on the wavelet conditional renormalization group that decomposes the total Shannon
entropy into contributions from different spatial scales. Generative modeling enables accurate estimation of these
entropies from configurations or snapshots, even in nonequilibrium systems whose underlying probability distributions are unknown. Applications to the
equilibrium $\varphi^4$ model and nonequilibrium active Model B+ show that multiscale
entropies reveal criticality and spatial organization obscured in the total
entropy. These
entropies serve as scale-dependent order parameters for characterizing phase transitions and pattern formation.
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Optics
Shift-register synchronization of dual-wavelength pulse trains in resonators with quadratic nonlinearity
Stepan Bogdanov, Anastasiya Bednyakova and Sergei K. Turitsyn
Self-organization of nonlinear waves underpins phenomena ranging from hydrodynamic pattern formation to optical frequency-comb generation. We introduce and numerically demonstrate a shift-register synchronization mechanism for pulse trains in quadratic nonlinear resonators. The synchronized state persists despite substantial group-velocity mismatch through continuous parametric energy exchange, resulting in deterministic discrete pulse shifts after each cavity round trip. Nonlinear parametric interaction modifies the effective walk-off, allowing the pulse trains to satisfy the shift-register synchronization conditions. The proposed mechanism reveals a previously unexplored synchronization regime in quadratic resonators and provides a route toward multicolour frequency combs, optical
memories, and ultrafast photonic information processing.
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Optics
All-Dielectric Ceramic 3-D Printed Unidirectional Leaky-Wave Antenna at mm-Wave Frequencies
Guillaume François, Masoud Sakaki, Henrik Jansen et al. (+3 more)
An all-dielectric leaky-wave
antenna, radiating unidirectionally at broadside without the use of a metallic ground plane, is designed and manufactured. It operates in the 70-90 GHz frequency range with a design broadside frequency of 77 GHz. The design process makes use of the theory of photonic bandgaps to position a -1 harmonic at the broadside frequency on the second Bragg-condition point. The structure is then modified to close the bandgap and to simultaneously guarantee maximum total field coupling to the relevant radiating harmonic, ensuring radiation unidirectionality. The
antenna is manufactured with an Al2O3 ceramic printing process, demonstrating its manufacturing potential for complex low-loss high-frequency structures. Simulations agree well with measurements, with the main deviation being a 1 GHz frequency shift that could be reproduced in simulation. The
antenna prototype shows a scanning range of -18{\deg}-22{\deg} and gain values above 23 dBi. More than 85 % of the radiation power is radiated unidirectionally at broadside, with simulations showing potential to attain 98 %.
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All authors Guillaume François, Masoud Sakaki, Henrik Jansen, Amar Al-Bassam, Niels Benson, Dirk Heberling
Computational Physics · Cross-listed from cs.AI
SHRAV: State-Hypothesis-Reason-Action-Verify Framework for Physical Modeling and Inverse Design
Ziheng Guo and Yang Bu
Physical modeling and inverse design require computation that can continue from reusable state. We introduce SHRAV, an architecture-independent computational framework organized around State, Hypothesis, Reason, Action, and Verify. Its central mechanism is a state-continuation core with declared reuse boundaries and explicit roles for learned
evolution and numerical quantities. Forward configurations evolve predictive state and read out physical responses; inverse-design configurations additionally generate target-directed modifications and consume evaluator feedback. Electromagnetic world-model studies are mapped to forward configurations, with selected readout and reuse diagnostics reported here. Computational lithography demonstrates an inverse-design configuration: four fixed-weight design updates improve thresholded aerial-image intersection-over-union from 0.5313 to 0.8153 under independent scalar-pupil replay, with a maximum absolute IoU difference of approximately 0.000824 between predictor estimates and independent replay.
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Applied Physics
Thermoreflectance-Based Techniques for Micro- and Nanoscale Thermophysical Property Measurements: Principles, Methods, and Recent Advances
Puqing Jiang, Shanshan Chen, Xiaobo Li et al. (+1 more)
As
semiconductor devices shrink toward the nanoscale, heat transport and thermal-energy-storage behavior in materials and interfaces become increasingly dependent on length scale, structure, and interfaces. Accurate characterization of thermophysical properties, including thermal conductivity, interfacial thermal conductance, and volumetric heat capacity, is therefore essential for functional-material design and thermal management of advanced electronic devices. Photothermal thermoreflectance techniques provide noncontact measurements with high spatial and temporal resolution and a broad measurement range, making them important tools for micro- and nanoscale thermophysical characterization. This review examines the physical principles and technical characteristics of transient thermoreflectance (TTR), time-domain thermoreflectance (TDTR), frequency-domain thermoreflectance (FDTR), steady-state thermoreflectance (SSTR), spatial-domain thermoreflectance (SDTR), and the square-pulsed source (SPS) method. A unified heat-
diffusion framework is established to compare these methods in terms of parameter sensitivity, measurement uncertainty, and applicability. Representative applications illustrate their suitability for low-thermal-conductivity materials, anisotropic films, crystalline materials, and multilayer
heterostructures, as well as their complementary capabilities for characterizing thin-film thermal conductivity, interfacial thermal conductance, and in-plane/cross-plane heat transport. Finally, emerging directions are discussed, including ultrahigh spatiotemporal resolution, multiphysics coupling, in-line industrial inspection, intelligent data processing, and natural-
language-driven analysis.
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All authors Puqing Jiang, Shanshan Chen, Xiaobo Li, Ronggui Yang
Optics
Thouless Pumping of Wave Action in Photonic Time Crystals
Minwook Kyung, Younsung Kim, Kyungmin Lee et al. (+3 more)
A topological pump transports a conserved quantity. Yet temporal modulation exchanges energy with the field, so the transported quantity must be identified from Maxwell's equations. Here we connect band
topology to the temporal displacement of conserved Maxwell wave action in a photonic time
crystal. The temporal Wannier function of an isolated positive-action band carries unit action with zero net energy flux, and its temporal center is a Berry polarization. Over one adiabatic cycle, that center shifts by the band Chern number: one
cell for a rigid translation and two for a two-tone cycle within a single band.
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All authors Minwook Kyung, Younsung Kim, Kyungmin Lee, Hee Chul Park, Moon Jip Park, Bumki Min
Accelerator Physics
Integration of Retrieval-Augmented Generation for Knowledge Access in the ELBE Accelerator Control System
Najmeh Mirian
The efficient operation of accelerator facilities increas- ingly relies on rapid access to heterogeneous operational knowledge, including logbooks, interlock reports, machine parameters, and historical archive data. At ELBE, we pro- posed a
Retrieval-Augmented Generation (RAG) frame- work that integrates facility documentation and operational records into a unified AI-assisted support tool for operators. The system is expected to index electronic logbooks, ma- chine archive time-series data, and subsystem manuals using domain-adapted
embeddings stored in a vector database. User queries will be expected to be processed through a large
language model that retrieves the most relevant oper- ational context and generates structured, operator-oriented responses with traceable source references. This contribu- tion presents the system architecture, data integration strat- egy, and challenges toward real-time AI-assisted accelerator operation
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Fluid Dynamics
Mechanisms of transonic buffet over supercritical airfoils revealed by direct numerical simulations
Giulio Soldati, Hang Song, Sergio Pirozzoli et al. (+1 more)
We use direct numerical simulations to study the turbulent transonic flow over a supercritical airfoil, spanning the transition from stable conditions to fully developed buffet at chord-based Reynolds numbers of $3\times10^5$ and $6\times10^5$. The Reynolds number determines the incoming boundary-layer state, thereby affecting the separation behaviour. Spectral proper orthogonal decomposition reveals a single dominant mode that emerges below onset and persists across the transition to buffet. The energy of this mode increases with the angle of attack while its spatial structure and fundamental frequency remain nearly unchanged, consistent with a global instability that saturates into a nonlinear limit cycle. Geometrical acoustics provides a first-order description of the global mode propagation and identifies two paths connecting the acoustic source, located in the near wake, to the shock. A shorter path impinges on the shock from behind, while a longer one circumvents the shock tip before reaching it from the front. Linearised shock–acoustic interaction theory predicts a stronger shock response to low-frequency, front-impinging acoustic disturbances. Space–time correlations link the establishment of a downstream path to complete boundary-layer separation, which is induced intermittently by the upstream motion of the shock. The sum of the upstream acoustic time along the front-impinging path and the downstream convective time is compatible with the measured buffet period at both Reynolds numbers. Together, these results are consistent with a unified picture of buffet, where an aeroacoustic feedback mechanism provides the physical pathways through which perturbations can sustain the global dynamics.
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All authors Giulio Soldati, Hang Song, Sergio Pirozzoli, Sanjiva K. Lele
Classical Physics
Characterizing the Carnot cycle at absolute zero: a reply to "Comment on `Proof of the Nernst theorem' "
José-María Martín-Olalla
This reply addresses a recent comment concerning the proof of the Nernst
theorem. I clarify how a Carnot engine can consistently operate at $T=0$ through a continuous deformation of a cycle operating at $T>0$. By examining the limit where heat exchange with the cold reservoir vanishes, I show that the Nernst
theorem ensures that the concept of temperature remains physically consistent at the absolute zero limit.
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Optics
Programmable and scalable on-chip WDM processing platform enabled by cascaded FSR-free resonators
Boshu Sun, Haojie Zhu, Ying Sun et al. (+17 more)
Wavelength-division multiplexing (WDM) is pivotal for expanding the capacity and functionality of photonic systems, from communications to computing. However, on-chip implementation for broadband operation is fundamentally limited by the narrow free spectral range (FSR) and inefficient drop transmission of conventional optical microcavities. Here, we transcend this limit with a scalable integrated WDM processing platform based on cascaded dual-sided coupled Fabry-Pérot add-drop resonators. This unit achieves a record-large FSR-free bandwidth (> 300 nm) and low insertion loss (< 0.5 dB), while enabling independent manipulation of monochromatic light in both the wavelength and intensity domains. Leveraging these performances, we architect programmable cores with up to 20 channels in a single bus waveguide to demonstrate application versatility by configuring as: a high-capacity on-chip WDM communication fabric (2.4-Tbps single-link WDM transmission and O-to-C-band multi-subband (de)triplexing), a reconfigurable optical processor (broadband and hitless wavelength-selective switching), and a parallel computing accelerator (theoretically capable of 1.28-TOPS convolution operations, 16-channel modulation). This work establishes a unified and versatile WDM processing platform that bridges high-speed optical communication with in-line computing, charting a scalable and backward-compatible path toward petabit-per-second-class links and hundreds of TOPS of on-chip computation, resolving a critical bottleneck for next-generation photonic systems.
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All authors Boshu Sun, Haojie Zhu, Ying Sun, Kunhao Lei, Zijia Wang, Kangjian Bao, Weiqi Lu, Yuhao Fang, Yuting Ye, Danyang Hao, Qingyan Deng, Zequn Chen, Yingchun Wu, Maoliang Wei, Wei Cao, Xu Sun, Qicheng Zhang, Hongtao Lin, William Shieh, Lan Li
Optics
Magnetic Lifting of BIC Symmetry Protection Enables Nonreciprocal Beam Steering and Angular Information Encoding
Chengrui Zhang, Zijing Xianyu, Chufan Zhou et al. (+9 more)
Symmetry-protected bound states in the continuum (SP-BICs) offer exceptional optical confinement but remain nonradiative. Here, we demonstrate that magnetically lifting their protecting
symmetry enables nonreciprocal beam steering with intrinsic angular information encoding. In a magneto-optical photonic
crystal slab, an in-plane
magnetic field converts an SP-BIC into a radiative quasi-BIC and, together with vertical dielectric asymmetry, continuously displaces the associated band extremum away from the Gamma point. The steered beam exhibits two independent locking relations: its wavelength is locked to the elevation angle, while its polarization orientation is locked to the azimuthal angle. These relations embed complementary spectral and polarization information into the scanning beam, providing additional sensing channels for multidimensional
LiDAR. Moreover, the nonreciprocal dispersion gives different resonance frequencies at opposite wave vectors, supporting resonant emission at +k while back-reflected light at the same frequency is off resonance at -k, opening a route to intrinsic self-isolation and reduced optical feedback. These findings establish a unified framework connecting
magnetic beam steering, angular information encoding, and nonreciprocal feedback suppression, with prospects for compact reconfigurable light sources and integrated optical engines.
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All authors Chengrui Zhang, Zijing Xianyu, Chufan Zhou, Qi Jiang, Shengxuan Si, Wanli Xue, Ji Wu, Haoming Zhong, Jiaqi Zhang, Hanqi He, Edoardo Charbon, Zhiyu Wang
Instrumentation and Detectors
kicad-pycbnew: A Python Framework for Automated, High-Precision PCB Design in Particle Detector Instrumentation
Vincent Raspal
kicad-pycbnew is an open-source Python library for the automated, script-based generation of KiCad PCB designs, tailored to the precise
geometric and impedance constraints of particle detector readout electronics. By enabling the programmatic definition of copper traces, zones, vias, and footprints — without a graphical interface — it addresses the challenges of designing large-scale, repetitive, or parameterized layouts (e.g., Resistive Plate Chamber (RPC) strips or controlled-impedance signal paths). Key features include constraint-driven routing, parallel track arrays with rounded corners, via grids with exclusion zones, and full compatibility with KiCad's native file format. Standalone operation (no KiCad runtime required) facilitates integration into CI/CD pipelines and ensures reproducibility. The library, released under the MIT License, includes validated examples such as trapezoidal RPC readout boards and extension boards for the COMET experiment, alongside comprehensive tests and documentation.
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Fluid Dynamics
Concentration of Stationary Measures onto Large Scales in the Fast-Advection Limit of the Stochastically Forced Two-Dimensional Navier-Stokes Equations
Tobias Rohner
We investigate the fast-advection limit ($\varepsilon \to 0$) of the stochastically forced two-dimensional incompressible Navier-Stokes equations on the
torus. Numerical simulations are performed at resolution $N = 128$ for four different forcing shells on both the square
torus and a thin
torus, with the advection parameter $\varepsilon$ varied over approximately one decade. We find that the stationary distributions become increasingly concentrated on the lowest
Fourier modes as $\varepsilon \to 0$, with the energy-to-enstrophy ratio $E/\Omega$ and the fraction $R$ of enstrophy in the lowest modes both increasing monotonically. At finite $\varepsilon$ the degree of concentration depends on the forcing shell through the effective spectral value $B_1/B_0$, in agreement with the condensation bound of Sznitman and Widmayer. Linear extrapolation to $\varepsilon = 0$ suggests that the limiting values may be forcing-independent, with $B_1/B_0$ governing only the rate of convergence. The same qualitative behaviour persists on the thin
torus.
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Plasma Physics
A fully implicit electromagnetic energy- and charge-conserving PIC model for simulations of high-$\beta$ plasma
V.A. Kurshakov and I.V. Timofeev
The paper presents a 3D numerical model of
plasma in which a fully implicit PIC method with exact conservation of global energy and local charge is generalized to the electromagnetic case. This opens the possibility of simulating
plasma equilibria with a high (up to an extreme) ratio of
plasma pressure to
magnetic field pressure, which are formed in open
magnetic traps. The main goal of this work is to find out whether a fully implicit model, which usually performs numerous nonlinear iterations when solving the coupled Vlasov–Maxwell system, can compete in performance with semi-implicit models that achieve the same conservative properties at the cost of only a single particle push per time step. It turns out that in 3D geometry such competition is quite possible due to the growing computational cost of evaluating the mass
matrices in the semi-implicit approach. The software implementation of the proposed numerical model is written in C++ within the parallel xpic code. Testing the code on problems of the development of the Weibel instability and the formation of
plasma with extreme pressure showed good agreement between the semi-implicit and fully implicit approaches and made it possible to establish their relative speed.
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Optics
Spectral Lock-in Detection for High-Sensitivity Spectroscopy
Szu-An Tsao, Joseph J. Hwang and Mona Jarrahi
The ability to recover weak signals without sacrificing their spectral information is central to precision spectroscopy, yet conventional lock-in detection achieves noise rejection at the expense of spectral dimensionality and ultimately imposes a trade-off between detection bandwidth and sensitivity. Here, we introduce spectral lock-in detection, a versatile framework that extends lock-in noise rejection independently to every resolved component of a broadband spectrum. By separating the fast-time coordinate encoding spectral information from the slow-time coordinate carrying temporal modulation, the measured waveform is spectrally resolved before demodulation, enabling each frequency channel to be independently detected and integrated. We show analytically that, for spectrally stable signals, the signal power in each spectral channel remains invariant, while the noise power ideally decreases by 10 dB per decade of integration time, enabling spectral features buried beneath the instantaneous noise floor to emerge without loss of frequency information. We experimentally validate this framework in both phase-incoherent heterodyne terahertz spectroscopy and phase-coherent terahertz time-domain spectroscopy, demonstrating more than six orders of magnitude of sensitivity enhancement across the spectrally resolved channels. Because spectral discrimination is performed computationally on the acquired waveform, the approach requires neither sequential spectral scanning nor additional spectral-selection, multichannel-detection, or interferometric hardware. Spectral lock-in detection therefore provides a broadly applicable route to enhancing sensitivity across diverse spectroscopic platforms and frequency regimes, opening new opportunities for high-sensitivity, information-rich measurements across the electromagnetic spectrum.
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Space Physics · Cross-listed from astro-ph.EP
Kelvin-Helmholtz vortices in the Martian +E hemisphere downstream of crustal magnetic anomalies
Junxi Niu, Tong Dang, Jiuhou Lei et al. (+6 more)
At unmagnetized planetary bodies, the Kelvin-Helmholtz (KH) instability at the solar-wind boundary is a key driver of atmospheric escape, fundamentally shaping long-term
climate evolution. This shear-driven
plasma mixing is theoretically predicted to be asymmetric, strongly favoring the hemisphere where the solar-wind electric field points toward the
planet (-E hemisphere). Here we report the observation of a coherent train of fully developed KH
vortices in the traditionally unfavorable +E hemisphere of Mars, using in-situ MAVEN measurements. Contemporaneous upstream constraints from Tianwen-1 confirm a steady interplanetary
magnetic field, indicating sustained shear-driven growth rather than a transient boundary response. We find that these
vortices developed within an expanded, weak-field boundary layer downstream of strong southern crustal
magnetic anomalies. Our analysis suggests that regional boundary structuring can override the large-scale hemispheric preference to facilitate localized KH growth. These findings demonstrate that shear-driven escape pathways can operate in traditionally unfavorable regions, altering our understanding of atmospheric volatile loss at weakly magnetized
planets.
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All authors Junxi Niu, Tong Dang, Jiuhou Lei, Binzheng Zhang, Wenya Li, Binbin Tang, Junjie Chen, Sudong Xiao, Tielong Zhang
Atomic Physics · Cross-listed from quant-ph
A 75-mL intrinsically stable atom-filtered laser enabling deployable quantum devices
Zijie Liu, Zheng Xiao, Zhiyang Wang et al. (+10 more)
Numerous
quantum devices require
lasers strictly locked to atomic transitions. Atom-filtered
lasers (AFLs) are considered a leading candidate for
quantum device
laser sources due to their ability to self-align to atomic transitions. However, the sub-GHz sharp transmission spectra of conventional atomic filters impose constraints on both
laser miniaturization and output stability. Herein, we demonstrate a micro Faraday anomalous dispersion optical filter ({\mu}FADOF) operating within the extreme hyperfine Paschen-Back regime, generating a 7.5 GHz flat-top transmission window. By integrating this filter, the miniaturization bottleneck of the AFLs is overcome, achieving a 30-fold volume reduction to a compact package volume of 75 mL. Simultaneously, investigations into the optical self-feedback characteristics of the {\mu}FADOF reveal a stable operating regime, where the optical self-feedback of the atomic filter acts as a stabilizing mechanism, enabling the
laser to achieve a power instability of 9 x 10^-6 at 1 s and 3.2 x 10^-5 at 8400 s. The optical frequency standard based on this 75-mL AFL achieves a further improvement in long-term frequency stability to 3 x 10^-13 at 10000 s and maintains turn-key operation under environmental shocks, highlighting the critical role of this
laser in the development of deployable
quantum devices.
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All authors Zijie Liu, Zheng Xiao, Zhiyang Wang, Xiaolei Guan, Xiaomin Qin, Suyang Wei, Hongtian Song, Baoshuai Wang, Jia Zhang, Xiaopeng Xie, Tiantian Shi, Anhong Dang, Jingbiao Chen
Plasma Physics
Calibration of cross-field transport models in SOLPS-ITER on the TCV-X21 case
Stefano Carli, Reinart Coosemans, Claudia Colandrea et al. (+1 more)
Cross-field turbulent transport remains one of the largest uncertainties in edge
plasma simulations and is commonly approximated through empirical transport coefficients. In this work, we calibrate and assess several cross-field transport models implemented in SOLPS-ITER using measurements from the TCV-X21 reference case. The considered models range from conventional constant-diffusivity descriptions to the self-consistent k-model, in which anomalous diffusivities evolve along with
plasma conditions. Model parameters are estimated through gradient-based optimization by minimizing discrepancies between simulated and experimental upstream and divertor profiles in forward field configuration. The calibration results show that increasing the number of free parameters substantially improves agreement with the calibration
dataset. However, these more flexible models exhibit poor predictive capability when applied to the reversed field configuration, indicating overfitting. In contrast, the simplest constant-diffusivity model provides the best overall predictive performance while requiring only a small number of calibrated parameters. The k-model achieves a calibration quality comparable to the constant-diffusivity model and reproduces the experimental profiles with similar accuracy, while simultaneously providing a physics-based description of the spatial variation of anomalous transport. Predictions for a density scan reveal differences that are not apparent near the calibration point. The k-model predicts increasing transport levels around the separatrix with increasing density, leading to broader upstream profiles and an earlier onset of divertor rollover compared to the constant-diffusivity model. The presented framework provides a systematic and efficient route for model calibration in SOLPS-ITER, and a set of calibrated k-model parameters to be employed in future studies.
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All authors Stefano Carli, Reinart Coosemans, Claudia Colandrea, Wouter Dekeyser