Chemical Physics
A State-Space-View of Atom-Diatom Reactions Relevant to Rarefied Gas Flow
Abhirami Vijayakumar, Raidel Martin-Barrios and Markus Meuwly
A microscopically resolved picture of energy flow in atom-diatom collisions is essential for understanding the non-
equilibrium chemistry in rarefied and hypersonic gas flow. Here, a comprehensive ensemble of quasi-classical trajectories on global, reactive, and “vetted” potential energy surfaces are employed to construct state-resolved probability maps and to determine the dependence of the outcomes on the initial ro-vibrational states $(v,j)$. The full range of processes, including elastic, inelastic, atom exchange, reactive, and atomization are quantified, revealing distinct structure reactivity relationships. For the [OOO] system consistent trends are obtained from two high-quality potential energy surfaces, despite their different electronic structure and representation techniques. The resulting state-space description provides a comprehensive picture of energy redistribution in high-energy atom-diatom collisions, forming a basis for improved modeling of non-
equilibrium chemistry in hypersonic and rarefied environments.
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Classical Physics · Cross-listed from cond-mat.soft
High-throughput characterization of snap-through stability boundaries of bistable beams in a programmable rotating platform
Eduardo Gutierrez-Prieto, Gilad Yakir and Pedro M. Reis
We introduce a high-throughput platform that enables simultaneous, parallel testing of six bistable beams via programmable motion of a rotating disk. By prescribing harmonic angular dynamics, the platform explores the phase space of angular velocity and acceleration $(\Omega,\,\dot{\Omega})$, producing continuously varying centrifugal and Euler force fields that act as tunable body forces in our specimens. Image processing extracts beam kinematics with sub-pixel accuracy, enabling precise identification of snap-through events. By testing six beams in parallel, the platform allows systematic variation of beam thickness, pre-compression, tilt angle, and clamp orientations across 65 distinct configurations, generating 23,400 individual experiments. We construct stability boundaries and quantitatively parameterize them as
parabolic functions, characterized by a vertical offset and a
curvature parameter. Tilt angle provides the most robust mechanism for tuning the
curvature parameter, while beam thickness and pre-compression modulate vertical offset. Modal decomposition analysis reveals that antisymmetric clamp configurations can trigger mode switching, in which competing
geometric and inertial effects drive transitions through different deformation pathways. Our work establishes a scalable experimental framework for high-throughput characterization of dynamic nonlinear instabilities in mechanics. The complete experimental
dataset is made publicly available to support data-driven design and machine learning models for nonlinear mechanics with applications to bistability-based metamaterials, mechanical
memory, and electronics-free sensing systems.
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Optics
Cathodoluminescence Study of a Quantum Dot in a Nanowire for Single-Photon Emission
Francis Granger, Fabrice Donatini, Edith Bellet-Amalric et al. (+4 more)
Cathodoluminescence in a scanning electron microscope was applied to a
semiconductor quantum dot in a nanowire able to emit single
photons. We show that cathodoluminescence can be used not only for imaging and spectroscopy, but also to measure the correlation function and characterize the purity of the single-
photon emitter. The electron beam can be manipulated to minimize the collection of parasitic luminescence. At cryogenic temperatures, we observed that the thermal budget, as measured via the
phonon sidebands, is close to that of non-resonant micro-photoluminescence. This makes cathodoluminescence an efficient tool in the quest of novel single-
photon sources.
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All authors Francis Granger, Fabrice Donatini, Edith Bellet-Amalric, Kuntheak Kheng, Gilles Nogues, David Ferrand, Joel Cibert
Fluid Dynamics · Cross-listed from astro-ph.SR
Ultimate large-$Rm$ regime of the solar dynamo
François Rincon
For more than 40 years the quest to understand how large-scale
magnetic fields emerge from turbulent flows in rotating astrophysical systems, such as the Sun, has been a major focus of computational astrophysics research. Using a parameter scan and phenomenological analysis of maximally simplified three-dimensional cartesian magnetohydrodynamic simulations of large-scale non-linear helical turbulent dynamos, I present results in this Letter that strongly point to an asymptotic ultimate regime of the large-scale
solar dynamo at large
magnetic Reynolds numbers, $Rm$, involving helicity fluxes between hemispheres. I obtained corresponding numerical solutions at both $Pm>1$ and $Pm<1$, and show that they can currently only be achieved in clean, simplified numerical set-ups. The analysis further strongly suggests that all global simulations to date lie in non-asymptotic turbulent magnetohydrodynamic regimes highly sensitive to changes in kinetic and
magnetic Reynolds numbers. Ideas are presented to attempt to reach the ultimate regime in such 'realistic' global spherical models at a reasonable numerical cost. Overall, the results clarify the current state, and some hard limitations of the brute-force numerical modelling approach applied to this, and other similar astrophysical
turbulence problems.
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Optics
Four-wave Mixing Mediated Synchronization of Localized Polariton Condensates
Alexey V Yulin
The Letter is devoted to new frequencies generation and its role in the synchronization of two spatially separated polariton condensates affected by the coherent pump with the frequency detuned from the frequencies of the condensates. We focus on the case where the distance between the condensates is so long that their interaction through the evanescent tails is negligible. By numerical simulation we show that the four-wave mixing of the polaritons with the coherent drive produces the free propagating polaritons that can mediate the inter-condensate interaction resulting in the phase-locking of the condensates.
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Computational Physics
Data-driven time-dependent bases for turbulent airfoil wake-extreme gust interactions
Shaghayegh Zamani Ashtiani and Kai Fukami
We analyze interactions between turbulent airfoil wakes and extreme gusts using a data-driven framework with time-dependent bases. The current approach represents each snapshot with time-varying bases consisting of two-dimensional in-plane modes and one-dimensional spanwise modes, together with a reduced covariance
matrix. By deriving closed-form
evolution equations, we advance these components using a small rolling window, eliminating the need for full-history storage. Applied to extreme
vortex gust-airfoil interactions at Re=5000, we reveal that the first in-plane mode dominates before impingement, while the second mode gains energy post-impingement, amplified by gust intensity. During impingement, leading modes exhibit multiscale features such as shear-layer roll-up and fine-scale
turbulence. The temporal
evolution of the mode-energy spectrum and its rank gaps further quantifies these interactions. A large leading-mode gap indicates energy concentrated in a few coherent structures, leading to faster recovery, whereas a smaller gap indicates energy distributed across many modes, consistent with richer multiscale activity and delayed re-stabilization. These trends also follow the transient lift dynamics, with higher amplitude and more oscillations indicated by a rise in the leading singular values. This work may provide a foundation for time-varying data-driven modal analysis of extreme gust encounters.
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Physics and Society
Avalanches of choice: how stranger-to-stranger interactions shape crowd dynamics
Ziqi Wang, Alessandro Gabbana and Federico Toschi
Pedestrian routing choices play a crucial role in shaping collective crowd dynamics, yet the influence of interactions among unfamiliar individuals remains poorly understood. In this study, we analyze real-world pedestrian behavior at a route split within a busy train station using high-resolution trajectory data collected over a three-year time frame. We disclose a striking tendency for individuals to follow the same path as the person directly in front of them, even in the absence of social ties and even when such a choice leads to a longer travel time. This tendency leads to bursty dynamics, where sequences of pedestrians make identical decisions in succession, leading to strong patterns in collective movement. We employ a
stochastic model that includes route costs, randomness, and social imitation to accurately reproduce the observed behavior, highlighting that local imitation behavior is the dominant driver of collective routing choices. These findings highlight how brief, low-level interactions between strangers can scale up to influence large-scale pedestrian movement, with strong implications for crowd management, urban design, and the broader understanding of social behavior in public spaces.
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Computational Physics · Cross-listed from cs.DC
Scalable Construction of Spiking Neural Networks using up to thousands of GPUs
Bruno Golosio, Gianmarco Tiddia, José Villamar et al. (+10 more)
Diverse scientific and engineering research areas deal with discrete, time-stamped changes in large systems of interacting delay differential equations. Simulating such complex systems at scale on high-performance computing clusters demands efficient management of communication and
memory. Inspired by the human cerebral cortex – a sparsely connected network of $\mathcal{O}(10^{10})$
neurons, each forming $\mathcal{O}(10^{3})$–$\mathcal{O}(10^{4})$ synapses and communicating via short electrical pulses called spikes – we study the simulation of large-scale spiking neural networks for computational neuroscience research. This work presents a novel network construction method for multi-GPU clusters and upcoming exascale supercomputers using the Message Passing Interface (MPI), where each process builds its local connectivity and prepares the data structures for efficient spike exchange across the cluster during state propagation. We demonstrate scaling performance of two cortical models using point-to-point and collective communication, respectively.
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All authors Bruno Golosio, Gianmarco Tiddia, José Villamar, Luca Pontisso, Luca Sergi, Francesco Simula, Pooja Babu, Elena Pastorelli, Abigail Morrison, Markus Diesmann, Alessandro Lonardo, Pier Stanislao Paolucci, Johanna Senk
Fluid Dynamics
Emergence of edge state in suspension of self-propelled particles
Yoshiki Hiruta and Kenta Ishimoto
We numerically study a model convection system of a suspension of self-propelled particles, motivated by recent experimental findings of localized and bistable bioconvection pattern, being distinct from classical Rayleigh–Bénard convection. Linear stability analysis of the model system reveals that the trivial noncovection state is stabilized by an increase of self-propelled speed in the vertical direction. Through numerical simulations, we found a nonlinear convection state even when the nonconvection state is stable. Applying ideas and tools developed in wall-bounded flows, we numerically identified an edge state, which is an unstable solution on a basin boundary in the model dynamical systems.
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Instrumentation and Detectors
Commissioning of a mobile neutron spectrometer for LNGS
Francesco Pompa, Klaus Eitel, Alfredo Davide Ferella et al. (+3 more)
Environmental
neutrons are a source of background for rare event searches in underground laboratories. Since the majority of the
neutron background comes from the cavern walls due to the intrinsic radioactivity of concrete and rock, the flux is known to be time and location dependent. Therefore, a precise knowledge of the spectrum and of the total flux is needed to devise shielding and veto mechanisms for rare event searches. Here ALMOND (An LNGS Mobile
Neutron Detector) is presented. It is a mobile
neutron spectrometer, based on capture-gated spectroscopy and comprised of an array of plastic scintillator bars wrapped with gadolinium foils. The detector has been calibrated with Americium-Beryllium source at Karlsruhe Institute of Technology and with an Americium-Boron source and a D-D generator at ENEA Frascati. The results of the
neutron calibration with the time of flight method and the D-D generator are shown here, alongside the first results on capture time profile. Moreover, the first results from the
neutron background run in
Hall A at LNGS are presented.
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All authors Francesco Pompa, Klaus Eitel, Alfredo Davide Ferella, Felix Kratzmeier, Melih Solmaz, Kathrin Valerius
Optics
High-resolution broadband characterization of resonance dispersion in an optical microresonator
Romain Dalidet, Adrien Bensemhoun, Gregory Sauder et al. (+12 more)
Accurate knowledge of the uneven free spectral range of an optical microresonator, which provides direct insight into group velocity dispersion, is essential for understanding and controlling Kerr frequency comb dynamics. In this work, we present a simple and highly precise method formeasuring the free spectral range over a 5 THz bandwidth in silicon nitride microresonators, leveraging a wavemeter with 0.4 MHz resolution. Our fully fibered plug-and-play experimental setup enables the accurate extraction of resonance frequencies. By carefully analyzing the spectral position of each resonance, we measure both second- and third-order free spectral range expansion coefficients. This approach offers a robust and accessible tool for dispersion characterization in integrated photonic
circuits, paving the way for next-generation of Kerr comb sources and
quantum photonic technologies.
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All authors Romain Dalidet, Adrien Bensemhoun, Gregory Sauder, Anthony Martin, David Medina, Carlos Alonso Ramos, Eric Cassan, Laurent Vivien, Jonathan Faugier Tovar, Baptiste Routier, Quentin Wilmart, Ségolène Olivier, Virginia D Auria, Laurent Labonté, Sébastien Tanzilli
Chemical Physics
Deep learning of committor for ion dissociation and interpretable analysis of solvent effects using atom-centered symmetry functions
Kenji Okada, Kazushi Okada, Kei-ichi Okazaki et al. (+3 more)
The association and dissociation of ion pairs in water are fundamental to physical chemistry, yet their reaction coordinates are complex, involving not only interionic distance but also solvent-mediated hydration structures. These processes are often represented by free-energy landscapes constructed from collective variables (CVs), such as interionic distance and water bridging structures; however, it remains uncertain whether such representations reliably capture the transition pathways between the two associated and dissociated states. In this study, we employ deep learning to identify reaction coordinates for NaCl ion pair association and dissociation in water, using the committor as a quantitative measure of progress along the transition pathway through the transition state. The solvent environment surrounding the ions is encoded through descriptors based on atom-centered
symmetry functions (ACSFs), which serve as input variables for the neural network. In addition, an explainable artificial intelligence technique is applied to identify ACSFs that contribute to the reaction coordinate. A comparative analysis of their correlation with CVs representing water bridging structures, such as interionic water density and the number of water molecules coordinating both ions, further provides a molecular-level interpretation of the ion association-dissociation mechanism in water.
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All authors Kenji Okada, Kazushi Okada, Kei-ichi Okazaki, Toshifumi Mori, Kang Kim, Nobuyuki Matubayasi
Geophysics · Cross-listed from math.NA
The Complex-Step Integral Transform
Rafael Abreu, Stephanie Durand, Jochen Kamm et al. (+2 more)
Building on the well-established connection between the
Hilbert transform and derivative operators, and motivated by recent developments in complex-step differentiation, we introduce the Complex-Step Integral Transform (CSIT): a generalized integral transform that combines analytic continuation, derivative approximation, and multi-scale smoothing within a unified framework. A spectral analysis shows that the CSIT preserves phase while suppressing high-wavenumber noise, offering advantages over conventional
Fourier derivatives. We discuss the roles of the real and imaginary step parameters, compare FFT-based and interpolation-based implementations, and demonstrate the method on the advection equation and instantaneous-frequency computation. Results show that the CSIT yields smoother, more robust attributes than
Hilbert-based methods and provides built-in stabilization for PDE solvers. The CSIT thus represents a flexible alternative for numerical differentiation, spectral analysis, and seismic signal processing. The method opens several avenues for future work, including non-periodic implementations, adaptive parameter selection, and integration with local interpolation frameworks such as high-order Finite-Element methods.
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All authors Rafael Abreu, Stephanie Durand, Jochen Kamm, Christine Thomas, Monika Pandey
Optics · Cross-listed from quant-ph
Two-Photon Bandwidth of Hyper-Entangled Photons in Complex Media
Ronen Shekel, Ohad Lib, Sébastien M. Popoff et al. (+1 more)
When light propagates through complex media, its output spatial distribution is highly sensitive to its wavelength. This fundamentally limits the bandwidth of applications ranging from imaging to communication. Here, we demonstrate analytically and numerically that the spatial correlations of hyper-entangled
photon pairs, simultaneously entangled spatially and spectrally, remain stable across a broad bandwidth: The chromatic modal dispersion experienced by one
photon is canceled to first order by its spectrally anti-correlated twin, defining a "two-
photon bandwidth" that can far exceed its classical counterpart. We illustrate this modal dispersion cancellation in multimode fibers, thin diffusers and blazed gratings, and demonstrate its utility for broadband wavefront shaping of
quantum states. These findings advance our fundamental understanding of
quantum light in complex media with applications in
quantum imaging, communication, and sensing.
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All authors Ronen Shekel, Ohad Lib, Sébastien M. Popoff, Yaron Bromberg
Optics
Casimir radiation with Weyl semimetals
Yang Hu, Xiaohu Wu, Haotuo Liu et al. (+2 more)
When Casimir friction torque acts upon a rotated nanoparticle (NP), mechanical energy can be transformed into thermal energy, known as Casimir radiation, which significantly affects the thermal performance of nanoelectromechanical systems. In this work, we investigate Casimir radiation with nonreciprocal Weyl semimetals (WSM) NP levitated on a plate. WSM NP with inherent nonreciprocity has a radiative heat flux 27 times higher than NP with degenerate modes. The underlying physics is elucidated by the coupling and decoupling of the electromagnetic local density of states between nonreciprocal WSN NP and the plate in the near-field. The three-fold localized plasmon modes of WSM NP split into localized circular modes with strong gyrotropic response, which opens up new channels for Casimir radiation. This work provides a new method for nanoscale energy conversion in NP systems.
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All authors Yang Hu, Xiaohu Wu, Haotuo Liu, Mauro Antezza, Xiuquan Huang
Plasma Physics
Dynamics of an impulse dielectric barrier discharge in pure ammonia gas using electrical characteristics and imaging analysis
Ronny Jean-Marie-Desiree, Aymane Najah, Ludovic De Poucques et al. (+1 more)
A glow nanosecond discharge from a plane-to-plane impulse dielectric barrier discharge (iDBD) with ammonia gas has been characterised by employing fast imaging and electrical diagnostics. More precisely, the aim of this study is to investigate the dynamics of the discharge establishment under various conditions of applied voltage, pressure, and gas gap. The comparison between the current measurements and the image analysis exposes a strong correlation between the fast excitation and ionization wave velocity and the rising current velocity. This correlation has been found only for diffuse mode discharge since a front wave could be clearly defined, denoted as the luminous propagation front (LPF). Furthermore, this correlation is supported by a proportionality factor of 1.5 10$^{-3}$ which is systematic over the studied conditions. Further investigations are considered to evaluate the relevance of such a value over more parameters.
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All authors Ronny Jean-Marie-Desiree, Aymane Najah, Ludovic De Poucques, Stephane Cuynet
Physics and Society
Adaptive Punishment in Social Dilemmas
Xingfu Ke, Hao Yu, Xiao-Pu Han et al. (+2 more)
We introduce a coevolutionary framework in which punishment intensity dynamically adapts to the fraction of cooperators in the population. Unlike static models, adaptive punishment reshapes the effective payoff landscape, driving transitions among canonical games, including the Prisoner's Dilemma, Harmony, Stag Hunt, and Chicken games. Analytical results reveal rich dynamical behaviors such as coexistence, bistability, limit cycle and
Hopf bifurcation. These findings highlight adaptive punishment as a robust mechanism for sustaining cooperation by the coevolutionary feedback and offer insights into institutional design, ecological interactions, and social governance.
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All authors Xingfu Ke, Hao Yu, Xiao-Pu Han, Yi-Cheng Zhang, Fanyuan Meng
Optics
Coherent Tunneling by Adiabatic Passage in Silicon Nitride based Integrated Waveguide Structures
Olga Borovkova, Valery Lobanov, Junqiu Liu et al. (+2 more)
Nowadays silicon nitride photonic integrated
circuits serve as a mature platform for numerous applications. Planar waveguides and directional couplers made by CMOS-compatible technology are its basic elements. Here we demonstrate the possibilities of efficient light routing and transfer provided by the integrated planar Si3N4 waveguides structure based on the coherent tunneling by adiabatic passage (CTAP) at the 1.55um telecom band. We addressed both high- and low-confinement silicon nitride CTAP structures and proved high efficiency of light routing in them. The mechanisms that limit the light control efficiency have been revealed. The accessible parameters of such structures have been determined. Besides that, there was proposed the original hybrid Si3N4 Si - Si3N4 waveguides structure providing the enhanced efficiency and flexibility of the CTAP in comparison with the single-material Si3N4 waveguide structures.
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All authors Olga Borovkova, Valery Lobanov, Junqiu Liu, Dmitry Chermoshentsev, Igor Bilenko
Biological Physics · Cross-listed from cond-mat.soft
Exact Screening-Ranged Expansions for Many-Body Electrostatics
Sergii V. Siryk and Walter Rocchia
We present an exact many-body framework for electrostatic interactions among $N$ arbitrarily charged spheres in an electrolyte, modeled by the linearized Poisson–Boltzmann equation. Building on a spectral analysis of nonstandard Neumann–Poincaré-type operators introduced in a companion mathematical work arXiv:2512.08684, we construct convergent screening-ranged series for the potential, interaction energy, and forces, where each term is associated with a well-defined Debye–Hückel screening order and can be obtained evaluating an analytical expression rather than numerically solving an infinitely dimensional linear system. This formulation unifies and extends classical and recent approaches, providing a rigorous basis for electrostatic interactions among heterogeneously charged particles (including Janus colloids) and yielding many-body generalizations of analytical explicit-form results previously available only for two-body systems. The framework captures and clarifies complex effects such as asymmetric dielectric screening, opposite-charge repulsion, and like-charge attraction, which remain largely analytically elusive in existing treatments. Beyond its fundamental significance, the method leads to numerically efficient schemes, offering a versatile tool for modeling colloids and soft/biological matter in electrolytic solution.
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Optics
A power-in-bucket model enabled designs of nanostructure-enhanced waveguides for highly efficient wide-angle light couplings
Wenbo Luo, Yitong Gu, Jianwei Wang et al. (+5 more)
Well-designed nanostructures on fiber facets can boost wide-angle light coupling and thus gain considerable
attention because of the potential for intensive applications. However, previous theories commonly concentrate on the configurations of the bare waveguide, lacking full consideration of structure-assisted couplings. Here, a power-in-bucket (PIB) model is introduced to explore the coupling behavior of structure-modified waveguides. The analytical model investigates two representative coupling scenarios,including Gaussian beam and plane wave excitation. The PIB-computed coefficient {\eta} enhancements agree well with the experimental values, especially for the multiple-mode fibers under large-angle illuminations. Using PIB to optimize the beam-fiber parameters, we show that at the incidence angle of 37 degree, {\eta} could increase from 0.3320 to 0.5102 by the identical ring gratings. Overall, the proposed model provides a useful account of the mechanism of grating-aided light couplings. These findings would be of great help in designing structure-enhanced probes for wide-angle broadband light collection applications.
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All authors Wenbo Luo, Yitong Gu, Jianwei Wang, Fei Yu, Chunlei Yu, Lili Hu, Zhichao Ruan, Ning Wang
Optics
Photophoretic Trapping: Fundamentals, Advances and Future Directions
Anita Pahi, Kirty Ranjan Sahoo, Souvik Sil et al. (+1 more)
Photophoretic forces, several orders of magnitude stronger than radiation pressure, enable particle trapping at remarkably low optical intensities and have opened pathways to applications in aerosol science, free-space 3D volumetric displays, and even deployment of lightweight payloads in space. In this review, we provide a comprehensive explanation of the underlying physics of photophoretic forces and how they facilitate stable three-dimensional manipulation of absorbing particles. We examine the experimental configurations that enable robust trapping, and we detail the physical parameters that govern the magnitude and behavior of photophoretic forces in these geometries. The rich dynamical phenomena exhibited by photophoretically trapped particles are discussed alongside current and emerging applications and possible future research directions. This review thus attempts to systematically unify the theoretical, experimental, and application-oriented aspects of photophoretic trapping, with the aim of advancing and strengthening research in this rapidly developing field.
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All authors Anita Pahi, Kirty Ranjan Sahoo, Souvik Sil, Ayan Banerjee
Accelerator Physics
Stochastic Cooling Enhanced Steady-State Microbunching
Xiujie Deng
In this paper, we propose to combine two promising research topics in accelerator physics, i.e., optical
stochastic cooling (OSC) and steady-state microbunching (SSMB). Our study shows that such an OSC-SSMB storage ring with a circumference of 50 m and beam energy of several hundred MeVs using present technology can deliver kilowatt radiation at 100 nm wavelength. A more ambitious application of OSC in an SSMB ring can push the radiation wavelength to an even shorter wavelength, such as EUV and soft X-ray. Such a powerful compact light source could benefit fundamental science research and industry applications.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Electrical Characterization of High-k (k>115) Crystalline SrTiO3 (STO) thin film integration with GaN with Nanomembrane Transfer Process
Md Tahmidul Alam, Kyoungjun Lee, Guangying Wang et al. (+2 more)
High-k (115), crystalline SrTiO3 (STO) thin film was transferred on GaN for potential applications in power devices (transistor and diodes) by nanomembrane transfer method and the detailed electrical properties such as leakage current, CV profiles, dielectric constant, frequency dispersion was reported from fabricated MOSCAP structures. The leakage current was negligible (under noise-level of tool) up to 6 V and 11 V for 50 nm and 200 nm STO membrane respectively A high-quality dielectric was indicated by the CV profile, which showed almost negligible frequency dispersion in the frequency range of 10 kHz to 500 kHz. The dielectric constant was 50 to 82 with the 50 nm thick STO membrane and 115 to 186 in the 200 nm thick STO membrane. Thermal annealing of the membrane in ambient conditions at 250 degrees for 2 hours led to a slight improvement in the dielectric constant (8 to 20 percent), albeit at the expense of degraded leakage current performance, as indicated by a reduction of 1 V to 3 V in the "no leakage region" of the IV curves after annealing. The possible physical mechanisms responsible for these changes were also analyzed and discussed.
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All authors Md Tahmidul Alam, Kyoungjun Lee, Guangying Wang, Chang-beom Eom, Chirag Gupta
Optics
Twisted light from topological chiral exceptional points in a nanolaser array
Kaiwen Ji, Melissa Hedir, Qi Zhong et al. (+3 more)
We propose and experimentally demonstrate an orbital angular momentum (OAM) nanolaser array arranged in a ring geometry on an InP-based photonic
crystal membrane. The device realizes a non-Hermitian extension of the Rice-Mele model, featuring alternating coupling strengths and imaginary on-site detunings. This configuration supports a
symmetry-protected zero mode stabilized by non-Hermitian particle-hole
symmetry, which enforces a uniform $\pi/2$ phase shift between adjacent nanolasers, establishing a coherent phase winding around the array. By adjusting the gain/loss contrast in a parity-time (PT)-like pumping scheme, the system can be tuned to a
chiral exceptional point, where energy flows unidirectionally between nanocavities despite their reciprocal coupling. This
symmetry-enforced, directional tunneling leads to far-field emission carrying non-zero OAM, providing a direct signature of the phase-structured lasing mode. Our results demonstrate a robust and scalable strategy for engineering compact, phase-locked
laser arrays with controllable angular momentum output, and open new avenues for structured light generation in integrated photonic platforms.
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All authors Kaiwen Ji, Melissa Hedir, Qi Zhong, Ramy El-Ganainy, Alejandro M. Yacomotti, Li Ge
Biological Physics · Cross-listed from q-bio.NC
Meta-learning three-factor plasticity rules for structured credit assignment with sparse feedback
Dimitra Maoutsa
Biological neural networks learn complex behaviors from sparse, delayed feedback using local synaptic plasticity, yet the mechanisms enabling structured credit assignment remain elusive. In contrast, artificial recurrent networks solving similar tasks typically rely on biologically implausible global learning rules or hand-crafted local updates. The space of local plasticity rules capable of supporting learning from delayed reinforcement remains largely unexplored. Here, we present a meta-learning framework that discovers local learning rules for structured credit assignment in recurrent networks trained with sparse feedback. Our approach interleaves local neo-Hebbian-like updates during task execution with an outer loop that optimizes plasticity parameters via tangent-propagation through learning. The resulting three-factor learning rules enable long-timescale credit assignment using only local information and delayed rewards, offering new insights into biologically grounded mechanisms for learning in recurrent
circuits.
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Chemical Physics · Cross-listed from quant-ph
Routes of Transport in the Path Integral Lindblad Dynamics through State-to-State Analysis
Devansh Sharma and Amartya Bose
Analyzing routes of transport for open
quantum systems with non-
equilibrium initial conditions is extremely challenging. The state-to-state approach [A. Bose, and P.L. Walters, J. Chem. Theory Comput. 2023, 19, 15, 4828-4836] has proven to be a useful method for understanding transport mechanisms in
quantum systems interacting with dissipative thermal baths, and has been recently extended to non-Hermitian systems to account for empirical loss. These non-Hermitian descriptions are, however, not capable of describing empirical processes of more general nature, including but not limited to a variety of pumping processes. We extend the state-to-state analysis to account for Lindbladian descriptions of generic dissipative, pumping and decohering processes acting on a system which is exchanging energy with a thermal bath. This Lindblad state-to-state method can elucidate routes of transport in systems coupled to a bath and additionally acted upon by Lindblad jump operators. The method is demonstrated using examples of excitonic aggregates subject to incoherent pumping and draining processes. Using this new state-to-state formalism, we demonstrate the establishment of steady-state excitonic currents across molecular aggregates, yielding a different first-principles approach to quantifying the same.
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Applied Physics
Thin-film magnomechanics in the low gigahertz regime
Yu Jiang, Zixin Yan, Yizhong Huang et al. (+1 more)
The coherent interaction between
magnons and
phonons in the low-GHz regime represents an unexplored frontier in hybrid magnonics, critical for
quantum information processing and microwave-to-acoustic transduction. While previous studies have focused on higher frequencies (>5 GHz), we demonstrate
magnon-
phonon coupling near 2 GHz using spoof surface plasmon polariton (SSPP) waveguides integrated with yttrium iron garnet (YIG) thin films of varying thicknesses. SSPP waveguides provide strong slow-wave enhancement, enabling efficient
magnon readout in this challenging regime. Systematic measurements reveal the dependence of coupling strength on YIG thickness and
phonon wavelength matching, achieving cooperativity C = 1 for a 3 $\mu$m film at 2 GHz. Angle-dependent studies uncover coupling to both transverse and longitudinal
phonon modes. Further investigation shows that thicker films exhibit rich multimode dynamics between high-order
magnons and HBAR
phonons. These results establish a robust low-GHz magnomechanical platform, opening pathways for multimode
quantum transduction and hardware-efficient
quantum technologies.
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All authors Yu Jiang, Zixin Yan, Yizhong Huang, Xufeng Zhang
Optics
133-Tbps 1040-km (13$\times$80 km) Lumped-Amplified Transmission Over 22 THz in S-to-U-Band Using Hybrid Multiband Repeater with PPLN-Based Optical Parametric Amplifiers and EDFAs
Shimpei Shimizu, Takayuki Kobayashi, Masashi Abe et al. (+14 more)
We demonstrated 22.05-THz four-band long-haul transmission with a S-to-U-band lumped repeater consisting of PPLN-based optical parametric amplifiers and EDFAs over an 80-km-span SMF link. The achieved net bitrate was 133.06 Tbps at 1040 km with the 25.5-dBm fibre launch power designed by accounting for ISRS.
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All authors Shimpei Shimizu, Takayuki Kobayashi, Masashi Abe, Takushi Kazama, Akira Kawai, Kosuke Kimura, Masanori Nakamura, Fukutaro Hamaoka, Koji Enbutsu, Takahiro Kashiwazaki, Munehiko Nagatani, Hitoshi Wakita, Yuta Shiratori, Hiroshi Yamazaki, Hiroyuki Takahashi, Takeshi Umeki, Yutaka Miyamoto
Optics · Cross-listed from eess.SP
389.3-Tb/s 1017-km C-band Transmission over Field-Installed 12-Coupled-Core Fiber Cable with >12-Tb/s Spatial MIMO Channels
Akira Kawai, Kohki Shibahara, Megumi Hoshi et al. (+16 more)
We demonstrate 4.65-THz WDM/SDM transmission of 140-Gbaud PS-QAM signals over field-installed 12-coupled-core fiber cable with standard cladding diameter, achieving a record 0.455 Pb/s coupled-core capacity in a field environment. We also demonstrate 0.389 Pb/s over-1000-km transmission of spatial
MIMO channels with >12 Tb/s/wavelength net bitrate.
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All authors Akira Kawai, Kohki Shibahara, Megumi Hoshi, Masanori Nakamura, Takayuki Kobayashi, Ryota Imada, Takayoshi Mori, Taiji Sakamoto, Yusuke Yamada, Kazuhide Nakajima, Munehiko Nagatani, Hitoshi Wakita, Yuta Shiratori, Hiroshi Yamazaki, Hiroyuki Takahashi, Soichi Endo, Takemi Hasegawa, Ryo Nagase, Yutaka Miyamoto
Fluid Dynamics
Sound emission from oscillating bubbles trapped by the collapse of drop-impact craters
Zi Qiang Yang, Yuan Si Tian, Er Qiang Li et al. (+1 more)
When a drop impacts a deep pool, it forms a crater which subsequently rebounds. Under certain conditions, a dimple forms at the crater bottom, which pinches off to entrap a small bubble. The oscillation of this entrapped bubble is the primary source of the
underwater sound produced by rain. We use simultaneous ultra-high-speed
video imaging and synchronized acoustic recording, with an immersed hydrophone, to investigate the details of the sound formation, over a range of impact Weber numbers and different dimple shapes. With frame-rates as high as 5 million fps, we can track the shape
evolution of the pinched off dimple-bubble, which experiences large volumetric compression, by as much as 50%. The subsequent volume oscillations are consistent with the observed $\simeq 125$ Pa acoustic pressure amplitude, for the strongest compression. For our configuration the sound amplitude increases for smaller bubbles pinched off from the dimple. The acoustic forcing mechanism is therefore the inertial focusing of the momentum of the
liquid outside the dimple, as it pinches off. The acoustic frequency agrees well with the Minnaert theory for freely oscillating spherical bubbles, of the same size. The finer details of the acoustic signal reveal an interplay between the larger dimple bubble and the tiny bubble entrapped during the initial contact between the drop and pool. For the singular dimple where no bubble is pinched off, the sound generation has a broader range of frequencies, with the tiny bubble oscillating at $\sim 100$ kHz, after being deformed by the rapid vertical retraction of the dimple below the singular jet.
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All authors Zi Qiang Yang, Yuan Si Tian, Er Qiang Li, Sigur{\dh}ur Tryggvi Thoroddsen