Plasma Physics
Experimental Determination of Gamma-Ray Polarization in Strong-Field Nonlinear Compton Scattering
Pengpei Xie, Mingyang Zhu, Xichen Hu et al. (+13 more)
The polarization of gamma rays produced in strong-field
quantum electrodynamics (SFQED) is a fundamental and long-standing prediction, the verification of which has remained elusive, limiting both foundational tests and applications. Here, we report the first experimental measurement of gamma-ray polarization generated via all-optical nonlinear Compton scattering. Colliding a
laser-wakefield-accelerated electron beam with an intense counter-propagating
laser pulse reflected from a
plasma mirror, we produce bright gamma rays in the strong-field regime ($a_0 > 1$). For gamma rays with $a_0 \approx 3$, a linear polarization degree of $\sim 50\%$ is measured via the azimuthal asymmetry of photoneutrons from a deuterium target, and independently verified by a Compton polarimeter.The results show excellent agreement with SFQED calculations employing the locally monochromatic approximation, while diverging from predictions based on the locally constant field approximation, highlighting the importance of
quantum interference effects in this regime. Our work provides experimental evidence for polarization dynamics in SFQED, supports a key prediction of nonperturbative QED, and paves the way for compact,
laser-driven sources of polarized gamma rays.}
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All authors Pengpei Xie, Mingyang Zhu, Xichen Hu, Yanfei Li, Yifei Li, Tianbing Wang, Bingjun Li, Huitong Zhai, Bingzhan Shi, Zewei Zhang, Ruiqi Qin, Jie Feng, Jinguang Wang, Xin Lu, Liming Chen, Yutong Li
Biological Physics · Cross-listed from cond-mat.soft
Boundary-Mediated Phases of Self-Propelled Kuramoto Particles
Francesco Arceri, Vittoria Sposini, Enzo Orlandini et al. (+1 more)
Active
agents can transfer energy to their environment through collective motion, generating accumulation patterns near confining obstacles. Here we investigate how the nature of the microscopic drive-self-propulsion or velocity
alignment-selects distinct accumulation patterns, leading to either delocalized or compact clustered states. We first characterize the dynamical regimes emerging from the interplay of these two driving mechanisms under perfectly reflective or smooth boundary conditions. We then introduce boundary friction and observe a drastic change in the accumulation patterns, with new dynamical phases that are absent in the previous case. By connecting emergent macroscopic structures to their underlying microscopic interactions, this work provides a practical route to infer the dominant interaction ruling boundary-mediated collective behavior, with applications ranging from single-
cell migration to bio-inspired robotics.
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All authors Francesco Arceri, Vittoria Sposini, Enzo Orlandini, Fulvio Baldovin
Data Analysis and Statistics
Recent advances and trends in pattern recognition and data analysis for RICH detectors
Luka Santelj
Ring Imaging Cherenkov (RICH) detectors are a key component of particle identification systems in many particle,
nuclear and astroparticle physics experiments. Their ultimate performance depends not only on detector design and hardware implementation, but also crucially on the quality of pattern recognition and data analysis
algorithms used to reconstruct Cherenkov ring images and to perform particle identification. In recent years, significant advances have been made both in traditional reconstruction approaches, such as likelihood-based methods and Hough-transform techniques, and in the application of modern machine learning tools. This contribution reviews the current state of RICH reconstruction
algorithms, highlights representative use cases from operating experiments, and discusses emerging trends including global particle identification strategies and generative machine learning approaches for fast simulation and reconstruction.
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Medical Physics
Mixed Ion Beams Enable Simultaneous Treatment and Real-Time Imaging in Carbon Ion Therapy
Lennart Volz, Ronja Hetzel, Maximilian Dick et al. (+19 more)
Carbon ion therapy is one of the most advanced forms of radiotherapy, promising improved efficacy against resistant cancers. However, the high precision offered by the carbon ion Bragg peak requires precise knowledge of the beam range inside the patient. We report the first experimental realization of range monitoring and portal imaging with a mixed ion beam, where carbon ions are treating the tumor while helium ions simultaneously accelerated to the same velocity fully traverse the patient and provide treatment feedback. Using the GSI synchrotron, a beam of 12C3+ and 4He1+ ions is accelerated, exploiting their nearly identical charge-to-mass ratios. Stable extraction with controlled helium fractions down to 7% is demonstrated. Beam characterization reveals that the helium ion Bragg peak can be cleanly separated from the carbon ion fragment background which enables accurate detection of sub-millimeter Bragg peak displacements. Mixed-beam radiographs of a lung-cancer-like phantom offer target position detection to better than 0.5 mm accuracy. This establishes mixed beams as a powerful modality for real-time image guidance in carbon ion therapy, uniquely providing simultaneous treatment delivery, range probing, and portal imaging. By overcoming range uncertainty inside the patient, mixed beams will enable to fully exploit the precision of carbon ion therapy.
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All authors Lennart Volz, Ronja Hetzel, Maximilian Dick, Maria Chiara Martire, Guangru Li, Christoph Schuy, Sali Ballouz, Mikael Simard, Saad Shaikh, Charles-Antoine Collins-Fekete, Tim Wagner, Michael Galonska, Andrii Patushenko, Ralph Hollinger, Fabio Maimone, Jens Stadlmann, Lars Bozyk, David Ondreka, Simone Savazzi, Marco Pullia, Marco Durante, Christian Graeff
Plasma Physics
On the timescales of controlled termination of tokamak plasmas
Simon Van Mulders and Olivier Sauter
The RAPTOR code is used to model how the time required for controlled termination of Ohmic
plasmas scales from present tokamaks like TCV and JET, to reactor-grade tokamaks like ITER and DEMO. We show that ramping the
plasma current $I_p$ down to 20% of the flat-top value over a time $\Delta t_{ramp-down}=\tau_{LR}=L_i/R$, with internal inductance $L_i$ and resistance $R$ evaluated at flat-top conditions, results in an approximately self-similar peaking of the current density for these four tokamaks, indicating the adequacy of $\tau_{LR}$ as a relevant timescale for cross-machine comparison, yielding $\tau_{LR} =$ 0.033s (TCV), 2.87s (JET), 63.2s (ITER) and 166.9s (DEMO). Note that $\tau_{LR}$ is easy to evaluate, both in systems codes and on a real-time control system. For the simulated ramp-downs with $\Delta t_{ramp-down}=\tau_{LR}$, the end-of-ramp-down normalized internal inductance $\ell_{i3}$ is limited below 2. An $I_p$ ramp-down faster than $\tau_{LR}=L_i/R$ requires a reversal of the boundary loop voltage and leads to the formation of a broad
plasma layer carrying current in the direction opposite to the total
plasma current, concomitant with $\ell_{i3}>2$, a central region with low
magnetic shear and strongly peaked pressure profiles. Significant reduction of
plasma volume and elongation, as foreseen for ITER and DEMO, is shown to counteract the reversal of current density and the $\ell_{i3}$ increase, while easing vertical stability control, potentially enabling faster $I_p$ ramp-down scenarios. Experimental and theoretical studies should be performed to test the feasibility of such fast termination scenarios, notably with respect to vertical position control, shape control and (resistive) beta limits. A simple analytical model is proposed and applied to estimate $\tau_{LR}$ based on 0D engineering parameters for different tokamaks and for different operating points.
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Fluid Dynamics · Cross-listed from cond-mat.soft
Electrohydrodynamic Stresses from Hydrogen-Bond Network Dynamics in Water
Pramodt Srinivasula
The resistance of hydrogen-bond networks to ambient flow in water produces viscoelectric stresses and contributes to electrostrictive pressure. Within Onsager's nonequilibrium thermodynamic framework, a
lattice-gas description of aqueous electrolytes is combined with a coarse-grained hydrodynamic representation of hydrogen-bonded molecular networks, where viscous dissipation is modeled through energetically equivalent Brownian entities. This formulation connects molecular structural information from experiments and molecular dynamics to a unified dipolar Poisson-Nernst-Planck-Stokes (dPNP-S) continuum theory, quantitatively reproducing the measured viscoelectric coefficient of Jin et al. (PNAS 2022) and contributions to electrostrictive pressure. These results identify a microscopic mechanism by which hydrogen-bond dynamics influence electrohydrodynamic flow.
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Optics
Photonic Exponential Approximation via Cascaded TFLN Microring Resonators toward Softmax
Hyoseok Park and Yeonsang Park
The rapid growth of large-scale AI models has intensified energy consumption and data-movement challenges in modern datacenters. Photonic accelerators offer a promising path by executing the linear
matrix multiplications of
transformer inference at high throughput and low energy. However, the softmax
attention layer, which requires element-wise exponentiation followed by normalization, still relies on electronic post-processing, creating an electro-optic conversion bottleneck that negates much of the potential photonic advantage. We present a cascaded micro-ring resonator (MRR) architecture that synthesizes the per-channel exponential function required by softmax, e^{x_n - max(x)}, over a finite interval with tunable worst-case relative error. A control signal detunes each ring via an electro-optic mechanism; a weak probe at fixed frequency experiences Lorentzian transmission, and cascading N identical stages yields a multiplicative transfer function whose logarithm is approximately linear. We derive mapping rules, depth-scaling estimates, and a minimax fitting formulation, and validate the framework with three-dimensional FDTD simulations of X-cut thin-film lithium niobate (TFLN) add-drop micro-ring resonators. Direct multi-ring FDTD validation extends to a five-ring cascade and confirms agreement with theory primarily over the upper operating range; deeper cascades and higher quality factors are assessed analytically. The cascade implements the per-channel exponential block, the key missing nonlinearity for photonic softmax. We further present a WDM-parallel chip architecture with closed-loop PI feedback that completes the full softmax-exponentiation, summation, and normalization-on a single photonic chip without per-channel normalization circuitry.
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Applied Physics
Electronics-free, ultra-low-power, wearable sensor chip for high-frequency electromagnetic field detection
Abdul Mohizin, Leon Abelmann and Baeckkyoung Sung
High-frequency electromagnetic fields (EMFs) are increasingly recognized either as environmental risk factors or as tools for electromagnetic attacks, which are difficult to detect in situ. Existing high-frequency EMF sensors face significant limitations related to structural simplicity, integration with mobile technology, and low energy consumption. To address these challenges, we propose a novel sensor concept based on a magnetically hybridized
liquid crystal (LC) microdevice. The hybrid LC chip is designed to exhibit an optical response to external
radio-frequency fields without the need for electronic components or an external power supply, relying solely on ambient light. Both sides of the chip are covered with
polymer-based crossed polarizer films. The chip is filled with flexible
matrices containing thermotropic LCs, such as the rod-like 4-cyano-4'-pentylbiphenyl, into which a network of thin
ferromagnetic wires is embedded. The resulting field-responsive LC microdisplay operates via a simple magnetothermal mechanism, and its optical response is sufficiently strong to be visible to the naked eye.
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Optics
Dynamic analysis of refractive index evolution and diffraction properties during single-photon polymerization of photopolymers for micro-optical applications
Andreas Heinrich and Manuel Rank
Photopolymerization enables the production of micro-optical elements, such as diffractive optical elements or GRIN optics. This process utilizes targeted spatial modulation of the refractive index, which is achieved through additive manufacturing. In this context, a thorough understanding of the dynamic processes during curing is essential in order to be able to accurately predict the optical function of the element. For this reason, this work investigates the kinetics and resulting optical properties of an acrylate-based photopolymer under UV irradiation using a DLP projection system. The experimental approach combines two measurement methods: On the one hand, the absolute change in the refractive index is determined in a time-resolved manner at the interface of a prism using a method based on total reflection. On the other hand, the formation of a phase grating in the volume of the
polymer is monitored in real time by analyzing the diffraction orders of a coherent sample
laser. The results show a characteristic S-shaped curve of the refractive index change, which reflects the phases of polymerization: oxygen inhibition, autoacceleration, and vitrification. Analysis of the diffraction patterns reveals complex intensity curves and substructures in the diffraction orders. These could be traced back experimentally and through simulations to the discrete pixel structure of the DLP projector and the existing dead zones. Furthermore, the simulation model developed on the basis of
Fourier optics reproduces the experimental diffraction patterns and confirms the hypothesis that scattered light and radical
diffusion lead to time-delayed polymerization in the theoretically unexposed areas. This results in a reduction of the refractive index contrast over time. This work thus provides parameters for the simulation and optimization of exposure strategies in 3D printing of micro-optics.
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Space Physics
Spacecraft wakes in the solar wind
Anders I. Eriksson, Yuri Khotyaintsev and Per-Arne Lindqvist
The
solar wind flow creates a wake behind any spacecraft immersed in it. We study the properties of this wake using the spherical electrostatic probes of the Electric Fields and Waves (EFW) instruments on the Cluster satellites. The satellites
spin in a plane inclined only a few degrees with respect to the ecliptic plane. The
solar wind is often close to this plane, so each probe (44 m away from the
spin axis) passes through the wake once every
spin period (around 4 s), thereby sampling a cut of the wake electrostatic potential structure. The signature of the wake is clearly seen in the data as a pulse with an amplitude typically of a few tenths of a volt. We present statistics of the wake signatures as well as detailed examples, compare to
solar wind parameters, and show a method to remove the wake signature from the electric field measurements.
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Optics
Design of a Dichroic Transmissive Huygens' Metasurface Unit-Cell Presenting Refraction Angle Duality
Georgios Kyriakou, Giampaolo Pisano, Luca Olmi et al. (+1 more)
A purely transmissive Huygens' metasurface model under plane-wave illumination is used to derive
circuit parameters describing a constituent unit
cell, such that diverse refraction angles are attained at two distinct frequency bands. Various levels of accuracy of the
circuit description approaching the analytical are possible by constraining certain numbers of parameters. This theoretical study is then tested by calculating the exact formulas of the two representations for the various strategies proposed. By using simulations of a candidate unit-
cell, we then examine whether such
circuit parameters correspond to rudimentary versions of the geometry of a so-called parallel 'dogbone' structure. A device of this type is intended as dual-band (dichroic), dual-angle beam refractor diverting an incoming beam at different directions in two different bands without reflections.
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All authors Georgios Kyriakou, Giampaolo Pisano, Luca Olmi, Francesco Piacentini
Biological Physics · Cross-listed from cond-mat.soft
Cell-induced wrinkling patterns on soft substrates
Aleksandra Ardaševa, Varun Venkatesh, Daiki Matsunaga et al. (+2 more)
Cells exert traction forces on compliant substrates and can induce surface instabilities that appear as characteristic wrinkling patterns. Here, we develop a mechanical description of
cell-induced wrinkling on soft substrates using a thin film elastic framework based on the Föppl-von Kármán equations coupled to a phase-field model of a single
cell. We model in-plane contractile stresses driven by cellular activity and study how their magnitude, spatial distribution, and
symmetry determine the onset of wrinkling and the resulting pattern selection. The theory predicts transitions between distinct morphologies, such as radial, circumferential, and anisotropic wrinkle arrangements, and provides scaling relations for wrinkle wavelength and amplitude as functions of elastic parameters and imposed cellular forcing. We compare these predictions with available experimental observations of
cell-driven wrinkling on compliant gels and find good agreement for both qualitative pattern classes and quantitative wavelength trends. Our results offer a minimal modelling framework to interpret wrinkling assays and connect observed surface patterns to underlying cellular forces.
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All authors Aleksandra Ardaševa, Varun Venkatesh, Daiki Matsunaga, Shinji Deguchi, Amin Doostmohammadi
Fluid Dynamics
Physics-Constrained Diffusion Model for Synthesis of 3D Turbulent Data
Tianyi Li, Michele Buzzicotti, Fabio Bonaccorso et al. (+1 more)
Synthesizing fully developed three-dimensional turbulent velocity fields remains a long-standing problem in fluid mechanics and an open challenge for generative modeling. The difficulty arises from the coexistence of extreme dimensionality, multiscale rough fluctuations and strong intermittency, together with exact physical constraints such as incompressibility and zero-mean momentum. We propose a physics-constrained
diffusion model (PCDM) in which these a priori constraints are incorporated directly into the generative dynamics. Using rotating
turbulence as a stringent
benchmark, we show that the proposed framework enables stable and statistically faithful synthesis of inertial-range three-dimensional turbulent velocity fields at medium resolution, accurately reproducing anisotropic energy spectra, intermittency statistics, and physical constraints. By contrast, standard denoising
diffusion probabilistic models without such constraints exhibit multiscale statistical deviations, violations of physical consistency, and substantially slower training convergence. These findings point to broader implications for generative modeling of high-dimensional complex systems under physical constraints.
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All authors Tianyi Li, Michele Buzzicotti, Fabio Bonaccorso, Luca Biferale
Applied Physics
Efficient Scattering Synthesis for Beyond-Diagonal Non-Local RISs Coupled with Passive Load Networks
Sravan K. R. Vuyyuru, Francisco S. Cuesta, Viktar S. Asadchy et al. (+2 more)
Realizing advanced functionalities with high efficiencies via reconfigurable intelligent surfaces (RISs) and reflectarrays requires configurations with strong electromagnetic non-local responses. The traditional approach to achieving strong non-locality has relied on modeling and synthesizing RISs with diagonal load impedance
matrices composed of highly dense subwavelength structuring of arrays. In such designs, non-locality is not directly tunable, thereby limiting design flexibility and operational efficiency. This work proposes a rigorous co-simulation-based design and optimization framework for beyond-diagonal RISs with directly controllable non-locality. The co-simulation approach is based on non-local load and coupling networks, integrating electromagnetic
antenna characterization with
circuit-level modeling of cascaded load networks. The method benefits from additional degrees of freedom by generalizing the conventional diagonal load impedance
matrix to a non-diagonal form through a non-local coupling network model. Wide-angle anomalous reflectors based on finite linear and infinite periodic arrays are designed and numerically validated, demonstrating that the proposed non-local loads embedded in realistic cascaded load networks with associated circuitry achieve significantly higher reflection efficiencies than diagonal load
matrices at the given element density. Alternatively, for a fixed efficiency target, the required element density can be significantly reduced for efficient synthesis of beyond-diagonal RIS without compromising the performance of wave manipulations.
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All authors Sravan K. R. Vuyyuru, Francisco S. Cuesta, Viktar S. Asadchy, Sergei A. Tretyakov, Do-Hoon Kwon
Computational Physics · Cross-listed from cond-mat.mtrl-sci
RF magnetron sputtering deposition of multilayers optical filters for ultra-broadband applications with a large number of thin layers
Maxime Duris, Bryan Horcholle, Cédric Frilay et al. (+6 more)
We present recent achievement on manufacturing optical filter and multilayers done with two complementary RF magnetron sputtering approaches: deposition duration control and in situ optical reflectance monitoring. Those approaches were greatly improved thanks to ellipsometry and spectrophotometry cross-studies of optical refractive indexes of Nb2O5, TiO2 and SiO2 materials grown using two sputtering systems. At the same time, we conducted deposition studies of these three materials which have increased the manufacturing reliability and allowed us to consider developing complex optical multilayers with more than 100 layers.
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All authors Maxime Duris, Bryan Horcholle, Cédric Frilay, C. Labbe, Xavier Portier, Philippe Marie, Sylvain Duprey, Franck Lemarié, Julien Cardin
Chemical Physics
Hydrogen-atom roaming reactions in water clusters: Unveiling an unusual dimension of water reactivity through first-principles calculations and machine learning
Rui Liu, Baiqiang Liu, Zhen Gong et al. (+3 more)
Water mediates a broad range of chemical reactions, including
proton transfer, bond rearrangement, and conventional radical processes, defining a continuously expanding repertoire of intrinsic reactivity. However, roaming, a fundamental reaction mechanism that a departing fragment bypasses the minimum energy path to recombine, has not been identified in water itself. Here, we report the discovery of hydrogen-atom roaming reactions in water clusters through high-precision ab initio calculations of first-principles. A neutral hydrogen atom departs as a radical, roams across the flat potential energy surface, and recombines along pathways that connect the same reactants and products as known hydrogen-bond network rearrangements. Interpretable machine learning analysis identifies the reactant dipole moment as the decisive switch governing whether roaming occurs, underpinned by exchange-repulsion and electrostatic interactions. Once roaming is initiated, polarizability and
spin population determine barrier heights, while the charge distribution of the roaming hydrogen atom governs barrier widths, collectively shaped by electrostatic, orbital, and dispersion contributions. These findings establish hydrogen-atom roaming as a previously unrecognized intrinsic reaction class in water, complementing a fundamental dimension to the mechanistic picture of water reactivity.
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All authors Rui Liu, Baiqiang Liu, Zhen Gong, Zhaohua Cui, Yue Feng, Zhigang Wang
Biological Physics
A unifying approach to diffusive transport in annealed heterogeneous media
Yann Lanoiselée, Denis S. Grebenkov and Gianni Pagnini
We introduce the concept of Randomly Modulated Gaussian Processes as a unifying framework for elaborating, analyzing and classifying anomalous
diffusion models in annealed heterogeneous media. This formulation incorporates correlations in the displacements together with correlated fluctuations of their amplitudes. Most known models of anomalous
diffusion (including continuous-time random walk, fractional Brownian motion, and Lévy flights) and random diffusivity can be described and further generalized within this framework. Moreover, the unified view identifies the main statistical properties to be probed experimentally for a reliable classification of diffusive dynamics. The proposed
matrix formulation facilitates the computation of the first four moments and allows for a systematic statistical characterization of the considered processes. The necessary and sufficient conditions are provided for the emergence of anomalous
diffusion. General expressions for the non-Gaussian parameter, the ergodicity breaking parameter and the covariance of squared increments are derived. An expression for the characteristic function and the codifference (i.e., a generalized measure of correlations) are obtained and used to study the special cases of Lévy flights and Laplace motion with correlated displacements. Potential applications of this framework for systematic analysis and biophysical interpretations of experimental single-particle trajectories are discussed.
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Plasma Physics
Weibel Instability in Collisionless Plasmas Across Astrophysical and Laboratory Shocks
Vivek Shrivastav, Mani K Chettri, Hemam D Singh et al. (+2 more)
We present a cold-fluid analysis of the purely transverse Weibel (current-filamentation) instability across four regimes: non-relativistic (NR) single-species, NR multi-species, relativistic single-species, and relativistic multi-species (electron–positron and electron–
proton). Beginning from linearized fluid equations, we derive the dispersion relations in each regime and extract scaling laws for the maximum growth rate $\gamma_{\rm max}$ and characteristic unstable wavenumber $k_{\rm max} = \omega_{pi}/c$. Relativistic corrections suppress $\gamma_{\rm max}$ by up to 40 per cent above $v_0 \approx 0.2c$, peaking near $v_0 \approx 0.9c$. Multi-species effects are significant only for $m_e/m_i \gtrsim 1/500$. For the tabletop
laser experiment of Bai et al., Nat.Commun., 16, 3770 (2025), the cold-fluid prediction gives $d_i = c/\omega_{pi} \approx 31.7\,\mu{\rm m}$, within 2 per cent of the measured filament spacing $\lambda_F \approx 31\,\mu{\rm m}$. The saturation field estimate $B_{\rm sat} \approx 2.3\times10^4$ T is an upper bound, consistent with the measured $\approx 5000$ T under kinetic suppression. Two MMS burst-mode bow shock crossings (October 16, 2015 and November 25, 2017) confirm $k_{\rm max} d_i = 1$ from FGM/FPI data. A multi-environment scatter plot spans 21 orders of magnitude in $n_i$, with all points within a factor of 3 of the 1:1 line.
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All authors Vivek Shrivastav, Mani K Chettri, Hemam D Singh, Britan Singh, Rupak Mukherjee
Fluid Dynamics · Cross-listed from math.AP
Inviscid Limit for Yudovich solution to heat conductive Boussinesq equation on two-dimensional periodic domain
Siran Li
We establish the inviscid limit of the Yudovich solution to the heat conductive Boussinesq equation with initial velocity and temperature/buoyancy in $L^2$ and initial vorticity in $L^\infty$ on the two-dimensional periodic domain ${\bf T}^2$. Given any finite time $T>0$ and $p \in [1,\infty[$, we show that the solution to the diffusive Boussinesq equation converges in $L^\infty(0,T; W^{1,p}({\bf T}^2))$ to the solution to the Euler–Boussinesq equation as the viscosity tends to zero, provided that the initial vorticity, velocity, and temperature/buoyancy converge strongly in $L^2$. Our proof adapts and extends the arguments in [P. Constantin, T. D. Drivas, and T. M. Elgindi, Comm. Pure Appl. Math. 75 (2022), 60–82] to forcing terms in $L^1(0,T; L^\infty({\bf T}^2))$.
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Chemical Physics
Reaction-Level Consistency within the Variational Quantum Eigensolver: Homodesmotic Ring Strain Energies of Cyclic Hydrocarbons
L. Roy, M. Sarkar, M. Tewari et al. (+2 more)
Simulation of chemical reactions on
quantum computing platforms using
quantum classical hybrid
algorithms such as the Variational
Quantum Eigensolver (VQE) is challenged by the need for a reaction consistent treatment of electron correlation in reaction energy evaluations. In this work, we employ a previously reported
symmetry guided active space selection protocol to compute ring strain energies of cyclic hydrocarbons using homodesmotic reaction schemes. The protocol enforces
symmetry consistency across all reactants and products by selecting active spaces that yield identical
symmetry matched fraction (SMF) values, thereby ensuring balanced correlation treatment at the reaction level. When multiple active spaces satisfy this criterion for a given molecule, larger active spaces often provide improved correlation treatment; however, smaller
symmetry consistent active spaces can also yield comparable agreement due to favorable error cancellation within the homodesmotic framework. Using this framework, ring strain energies were evaluated for a series of saturated and unsaturated cyclic hydrocarbons, ranging from cyclopropane to the structurally complex adamantane. The resulting energies achieve chemical accuracy relative to density functional theory (DFT) and remain in close agreement with coupled cluster singles and doubles (CCSD)
benchmarks. The systematic performance across increasing molecular complexity highlights the effectiveness of combining homodesmotic reaction design with
symmetry-consistent VQE calculations. This approach, which enforces physically grounded consistency across reaction species, demonstrates clear potential for extending reaction based
quantum simulations to larger molecular systems and broader classes of chemical reactions.
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All authors L. Roy, M. Sarkar, M. Tewari, A. Kumar, M. Paranjothy
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Slow spin-lattice relaxation dynamics in YbVO4 revealed by extended thermal impedance spectroscopy from AC susceptibility and AC magnetocaloric measurements
Yuntian Li, Jiayi Hu, Dominic Petruzzi et al. (+4 more)
Alternating (AC)
magnetic fields can induce not only an alternating magnetization in materials, but also an alternating temperature via the magnetocaloric effect. The latter effect is typically neglected when performing AC susceptibility measurements, but consideration of both effects on an equal footing is necessary in order to reliably distinguish between internal and external causes of
magnetic response and accurately extract quantitative information about relaxation processes. In order to address this, we have developed a method to measure the AC magnetocaloric effect that is compatible with AC susceptibility measurements, and also a framework to analyze these data in combination. We demonstrate the efficacy of this approach using YbVO4, a material for which strong single-ion anisotropy leads to slow
spin-
lattice relaxation at low temperatures via a
phonon bottleneck effect. We report AC
magnetic susceptibility and AC magnetocaloric effect measurements for this material as a function of field and frequency at a temperature of 3 K. We analyze the data using a discretized thermal model, and extract the field-dependence of the intrinsic
spin-
lattice relaxation rate. This demonstration experiment illustrates a general approach to quantitatively address multiple measured quantities in driven systems using a unified thermal
circuit analysis. The thermal analysis methods presented in this report can be extended to study other
magnetic, dielectric, and elastic materials exhibiting a complex response to an external driving field in the presence of internal and external relaxation, particularly when an energy dissipation process is within an accessible frequency regime.
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All authors Yuntian Li, Jiayi Hu, Dominic Petruzzi, Linda Ye, Mark P. Zic, Arkady Shekhter, Ian R. Fisher
Optics
Two-photon dual-comb LiDAR imaging
Alexander J. M. Nelmes, Simon Fletcher, Andrew Longstaff et al. (+3 more)
Conventional
LiDAR uses time-of-flight data from
laser pulses scanned across a scene to provide accurate multi-meter-scale three-dimensional models at cm precision, limited by the tens-of-picoseconds precision of time-tagging electronics. Here, by using two-
photon dual-comb ranging, we introduce an analog of
LiDAR imaging using the time-of-flight of sub-picosecond
laser pulses to render cm-scale point-cloud
datasets with $\mu$m precision. Using only free-running femtosecond
lasers, the technique combines absolute accuracy with near-interferometric precision, is applicable to discontinuous surfaces with poor optical quality, and provides a stand-off range exceeding that of other optical metrologies. We demonstrate imaging of an aluminum test object and assess its accuracy by comparing our results with those from a touch-probe coordinate measurement machine. At a stand-off distance of 40 cm, we obtain ranging accuracies of 9 $\mu$m - 38 $\mu$m, and precisions averaging to 1.0 $\mu$m after 500 ms.
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All authors Alexander J. M. Nelmes, Simon Fletcher, Andrew Longstaff, Jake M. Charsley, Hollie Wright, Derryck T. Reid
Optics
Cascaded multi-harmonic generation in a e̱ta}-BBO crystal reaching 133 nm from a single 800 nm pump beam
J. Seres, E. Seres and T. Schumm
Nonlinear
crystals are widely used to efficiently generate second or third harmonics, and also for frequency mixing. Generation of multiple cascaded harmonics simultaneously, however, appears much less studied, although supported by the usually large nonlinearity of these
crystals. Here, we demonstrate the generation of multiple harmonics up to 6th order in a e̱ta}-BBO
crystal, extending into the
vacuum ultraviolet spectral range. Phase matched generation of the second or the third harmonic is directly driven by a single 800 nm Ti:sapphire oscillator beam. Our study reveals that the harmonics are generated by ḩi}(2):ḩi}(2) and ḩi}(2):ḩi}(3) cascaded processes and intense harmonic signals are obtained even for the 5th and 6th harmonics, where the e̱ta}-BBO
crystal is mostly absorbing. While higher order harmonics cannot be phase matched simultaneously, limiting the harmonic amplitudes, even the weakest harmonics are more than three orders of magnitude above the measurement noise limit, making them suitable for many spectroscopic applications.
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Computational Physics
Advancing Machine Learning Applications in Quantum Few-Body Systems
Jin Ziqi, Paolo Recchia and Mario Gattobigio
This paper presents a general neural network framework for solving
quantum few-body systems, extending prior methods to handle diverse particle masses, interaction types, and system configurations. Our architecture, which combines an adaptive step size with the Metropolis-Adjusted Langevin
Algorithm for Monte Carlo sampling, accurately approximates the ground-state wave functions of systems featuring harmonic confinement, Gaussian two-body interactions, and including three-body forces. In ten-particle systems, it achieves lower relative energy errors (with respect to the reference values) than previous machine-learning methods. Leveraging GPU-accelerated computation, the method scales favorably with system size while maintaining robust convergence, reduced hyperparameter sensitivity, and stable training. Beyond accurate energy estimation, the model captures spatial distributions and correlation structures, offering physical insights about inter-particle structure. By unifying applicability across identical and nonidentical particles, the proposed approach establishes a versatile computational tool for exploring complex few-body
quantum systems, with significant implications for advancing computational models in few-body
quantum systems.
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Plasma Physics
Mercier–Cotsaftis and Grad–Shafranov equations for anisotropic plasma
Igor Kotelnikov
In this brief review, the historical aspects of the generalization of the Grad–Shafranov equation to the case of anisotropic
plasma are discussed.
Optics
Hybrid Integration of Quantum Dot Single Photon Sources with Lithium Tantalate Photonics for On Chip Routing
Kaili Xiong, Defeng Shan, Xueshi Li et al. (+11 more)
A promising pathway towards scalable
quantum photonic processors involves the simultaneous integration of deterministic single-
photon sources, low-loss photonic circuitry, and fast reconfigurability. Thin-film lithium tantalate on
insulator (LTOI) offers an exceptional electro-optic response and low optical loss at 900 nm wavelength band, yet its lack of efficient
quantum emitters has hindered progress toward fully integrated
quantum technologies. Here, we demonstrate heterogeneous integration of indium arsenide
quantum dots (QDs) with low-loss reconfigurable LTOI waveguides using micro-transfer printing. By directly butt-coupling tapered gallium arsenide waveguides with inversely tapered LTOI waveguides, we achieve robust and
alignment-tolerant inter-waveguide coupling. The hybrid chip operates at cryogenic temperatures, enabling deterministic routing of successively emitted single
photons from the QDs with a halfwave voltage-length product, confirming the cryogenic stability of LTOI's electro-optic coefficient. These results establish the first demonstration of high-speed on-chip routing of single
photons with hybrid QD-LTOI
circuits, providing a scalable pathway toward integrated
quantum photonic processors.
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All authors Kaili Xiong, Defeng Shan, Xueshi Li, Ziliang Ruan, Bin Chen, Zhanling Wang, Jiawei Wang, Ying Yu, Wei Wu, Pingxing Chen, Jin Liu, Liu Liu, Yan Chen, Tian Jiang
Optics
Gas temperature measurement based on contrast reversal in mid-infrared CO2 images
Hideki T. Miyazaki, Takeshi Kasaya, Masahiro Saito et al. (+3 more)
We demonstrate noninvasive measurement of gas temperature based on the optical gas imaging. Gas flows containing carbon dioxide (CO2) appear as either bright or dark images, depending on the relative temperatures of the background and the gas, when using a narrowband mid-infrared camera tuned to the CO2 absorption wavelength at 4.3 micrometers. When the background temperature is varied continuously, the gas image vanishes transiently and then the contrast reverses. The specific background temperature at the point when the gas image disappears provides the gas temperature. This technique is an evolved implementation of the classical line reversal method, made possible by advanced infrared devices. We also apply this technique to two-dimensional temperature mapping and to dynamic emissions from engine exhaust and human breathing.
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All authors Hideki T. Miyazaki, Takeshi Kasaya, Masahiro Saito, Kazuya Kimoto, Yutaro Tsuiki, Tetsuyuki Ochiai
Fluid Dynamics · Cross-listed from cs.LG
Adaptive Diffusion Posterior Sampling for Data and Model Fusion of Complex Nonlinear Dynamical Systems
Dibyajyoti Chakraborty, Hojin Kim and Romit Maulik
High-fidelity numerical simulations of chaotic, high dimensional nonlinear dynamical systems are computationally expensive, necessitating the development of efficient surrogate models. Most surrogate models for such systems are deterministic, for example when neural operators are involved. However, deterministic models often fail to capture the intrinsic distributional uncertainty of chaotic systems. This work presents a surrogate modeling formulation that leverages generative machine learning, where a deep learning
diffusion model is used to probabilistically forecast turbulent flows over long horizons. We introduce a multi-step autoregressive
diffusion objective that significantly enhances long-rollout stability compared to standard single-step training. To handle complex, unstructured geometries, we utilize a multi-scale graph
transformer architecture incorporating
diffusion preconditioning and voxel-grid pooling. More importantly, our modeling framework provides a unified platform that also predicts spatiotemporally important locations for sensor placement, either via uncertainty estimates or through an error-estimation module. Finally, the observations of the ground truth state at these dynamically varying sensor locations are assimilated using
diffusion posterior sampling requiring no retraining of the surrogate model. We present our methodology on two-dimensional homogeneous and isotropic
turbulence and for a flow over a backwards-facing step, demonstrating its utility in
forecasting, adaptive sensor placement, and data assimilation for high dimensional chaotic systems.
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Optics
Tunable supercontinuum in multimode fiber via bending-induced dispersion modification
Li-Yu Yu, Honghao Cao, Kunzan Liu et al. (+4 more)
Nonlinear pulse propagation in multimode fibers (MMFs) offers a compact, low-cost route to broadband, tunable femtosecond light, but most control schemes act by changing the spatial mode composition, typically resulting in irregular or speckled beams in exchange for maximal spectral tunability. Here we introduce a complementary mechanism: bending-induced local dispersion modification of a high-order mode (HOM) to steer the spectrum while keeping the spatial mode fixed. We launch an LP0,7 mode into a step-index MMF and apply programmable macrobends near the input. With a standard Yb pump at 1030 nm, this yields spatially clean, continuous spectral tuning across 700-1350 nm, while the output profile remains Bessel-like and robust to reconfiguration of controlled bends. A perturbative model explains the observed spatial-spectral decorrelation, showing that moderate
curvature produces first- and second-order shifts in group delay and group-velocity dispersion of the HOM with minimal change in its modal composition; these dispersion shifts control
soliton fission, dispersive-wave emission, and the
soliton self-frequency shift. We further validate application utility by driving multicolor, extended-depth-of-focus multiphoton microscopy directly from this all-fiber source. To our knowledge, this is the first demonstration of bending-induced dispersion modification, rather than mode mixing, used to tune MMF supercontinuum spectra without sacrificing beam quality, laying the foundation for an alternative pathway to tunable femtosecond illumination for imaging and spectroscopy.
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All authors Li-Yu Yu, Honghao Cao, Kunzan Liu, Chao Li, Brandon Weissbourd, Subhash Kulkarni, Sixian You
Optics · Cross-listed from quant-ph
Dynamics of Many-Emitter Ensembles: Probing Cooperative Evolution with Scalable Quantum Circuits
Vincent Iglesias-Cardinale, Shreekanth S. Yuvarajan and Herbert F. Fotso
Many-particle
quantum systems often give rise to exotic behaviors in their nonequilibrium dynamics that are rather challenging to reveal with analytical methods or with classical computation. Here, we consider the case of a system of many
quantum emitters coupled through a radiation bath. By adopting an efficient mapping of the bosonic modes onto a set of
quantum bits, we implement
quantum circuits, compatible with NISQ (Noisy Intermediate-Scale
Quantum) era systems, that allow us to investigate the dynamics of the ensemble as a function of various parameters, including the number of emitters, the spectral inhomogeneity in the system, the emission lifetime of independent emitters, and the spatial separation between emitters. The
quantum algorithms afford us the capacity to precisely track the emergence of cooperative dynamics, manifested through superradiant emission, as the system is tuned towards optimal coupling with respect to various parameters. We are particularly able to characterize superradiant emission in an inhomogeneous ensemble as a function of the linewidth of the individual emitters. These
quantum algorithms avoid approximations performed in conventional studies of many-emitter systems and provide a robust and intuitive characterization. Despite being limited to a small number of
qubits, the present calculations are found to provide a reliable characterization validated by comparison with analytical solutions and classical computation results in their respective regimes of validity. These findings indicate that the approach can be employed to effectively simulate a broad variety of many-emitter systems.
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