Chemical Physics
An effective bath state approach to model infrared spectroscopy and intramolecular dynamics in complex molecules
Loïse Attal, Cyril Falvo and Pascal Parneix
When a molecule contains more than a few atoms, its full-dimensional dynamics becomes untractable, especially when introducing temperature effects. In such a case, it can be interesting to focus only on a few degrees of freedom and to model the rest of the molecule as a finite-dimensional bath. In this prospect, we extend the effective bath state (EBS) method that we had first developed and benchmarked in [J. Chem. Phys. 160, 044107 (2024)] to describe the spectroscopy and intramolecular dynamics of complex isolated molecules. The EBS method is a system-bath approach based on the coarse-graining of the bath into a reduced set of effective energy states. It allows for a significant reduction of the bath dimension and makes finite-temperature calculations more accessible. In order to treat a realistic molecule, the method is extended to include
polynomial couplings in the bath coordinates. The ability of the method to model temperature-resolved infrared spectra and to follow population transfers between the vibrational modes of the molecule is first tested on a 10-mode model system. The extended method is then applied to the realistic case of phenylacetylene.
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Physics Education
The use of a simple digital weather station (not only) in teaching physics
Martin Hruška and Martin Plesch
One of key goals of contemporary physics (and, realistically, STEM) education is to develop students' science literacy and critical thinking skills. In this paper, we present the construction and use of several versions of a simple school-based digital weather station that students can use to measure fundamental physical quantities (temperature, pressure, air humidity, light intensity) as part of school activities. The weather stations were constructed at our workplace using an Arduino microcontroller, BBC micro: bit, and the school measurement system Coach. This paper proposes not only the design and related programming of the weather stations but also how students can collect, analyse, and interpret measured data, thereby learning scientific methods and developing science literacy and critical thinking. This hands-on approach also develops students' experimental skills, emphasizes the cross-curricular relationships between physics, computer science and geography, and teaches them to work with accurate data in the context of real environmental problems.
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Optics
Merging the characteristics of an exceptional point and a quasi-bound state in the continuum in nanophotonic cavities
Xiao-Jing Du, Xi-Hua Guan, Yue You et al. (+3 more)
In conventional
eigenvalue analyses of non Hermitian two mode systems, mode coupling cannot produce the simultaneous occurrence of an exceptional point (EP) and a quasi bound state in the continuum (QBIC) at the same spectral position. This work shows that this limitation originates from the
eigenvalue framework itself. By introducing an excitation phase degree of freedom, the interference between radiation channels can be reshaped without modifying the intrinsic eigenmodes of the system, thereby overcoming this constraint. Based on coupled mode theory, we demonstrate that the excitation phase enables the merging of an EP and a QBIC (and even a BIC) in nanophotonic cavities, and we validate this mechanism through full wave simulations of practical stacked structures. In the EP-QBIC regime, the mode quality (Q) factor is enhanced by more than one order of magnitude. We further systematically analyze the formation conditions of EP-QBIC states and conventional QBICs. Moreover, in a purely plasmonic structure, introducing an excitation phase leads to a more than 15 fold increase in the Q factor due to QBIC formation-surpassing the theoretical limit imposed by intrinsic material loss.
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All authors Xiao-Jing Du, Xi-Hua Guan, Yue You, Lin Ma, Jun He, Zhong-Jian Yang
Optics
Anomalous Wave-Packet Dynamics in One-Dimensional Non-Hermitian Lattices
Yanyan He and Tomoki Ozawa
Non-Hermitian (NH) systems have attracted great
attention due to their exotic phenomena beyond Hermitian domains. Here we study the wave-packet dynamics in general one-dimensional NH
lattices and uncover several unexpected phenomena. The group velocity of a wave packet during the time
evolution in such NH
lattices is not only governed by the real part of the band structure but also by its imaginary part. The momentum also evolves due to the imaginary part of the band structure, which can lead to a self-induced Bloch oscillation in the absence of external fields. Furthermore, we discover the wave-packet dynamics can exhibit disorder-free NH jumps even when the energy spectra are entirely real. Finally, we show that the NH jumps can lead to both positive and negative temporal Goos–Hänchen shifts at the edge.
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Computational Physics
Optimized Machine Learning Methods for Studying the Thermodynamic Behavior of Complex Spin Systems
Dmitrii Kapitan, Pavel Ovchinnikov, Konstantin Soldatov et al. (+2 more)
This paper presents a systematic study of the application of convolutional neural networks (CNNs) as an efficient and versatile tool for the analysis of critical and low-temperature phase states in
spin system models. The problem of calculating the dependence of the average energy on the spatial distribution of exchange integrals for the Edwards-Anderson model on a square
lattice with frustrated interactions is considered. We further construct a single convolutional classifier of phase states of the
ferromagnetic Ising model on square, triangular, honeycomb, and kagome
lattices, trained on configurations generated by the Swendsen-Wang cluster
algorithm. Computed temperature profiles of the averaged posterior probability of the high-temperature phase form clear S-shaped curves that intersect in the vicinity of the theoretical critical temperatures and allow one to determine the critical temperature for the kagome
lattice without additional retraining. It is shown that convolutional models substantially reduce the root-mean-square error (RMSE) compared with fully connected architectures and efficiently capture complex correlations between thermodynamic characteristics and the structure of
magnetic correlated systems.
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All authors Dmitrii Kapitan, Pavel Ovchinnikov, Konstantin Soldatov, Petr Andriushchenko, Vitalii Kapitan
Chemical Physics · Cross-listed from cond-mat.stat-mech
Generalized density functional theory framework for the non-linear density response of quantum many-body systems
Zhandos A. Moldabekov, Cheng Ma, Xuecheng Shao et al. (+5 more)
A density functional theory (DFT) framework is presented that links functional derivatives of free-energy functionals to non-linear static density response functions in
quantum many-body systems. Within this framework, explicit expressions are derived for various higher-order response functions of systems that are homogeneous on average, including the first theoretical result for the cubic response at the first harmonic $\chi_0^{(1,3)}(\vec{q})$. Specifically, our framework includes hitherto neglected mode-coupling effects that are important for the non-linear density response even in the presence of a single harmonic perturbation. We compare these predictions for $\chi_0^{(1,3)}(\vec{q})$ to new Kohn-Sham DFT simulations, leading to excellent agreement between theory and numerical results. Exact analytical expressions are also obtained for the long-wavelength limits of the ideal quadratic and cubic response functions. Particular emphasis is placed on the connections between the third- and fourth-order functional derivatives of the non-interacting free-energy functional $F_s[n]$ and the ideal quadratic and cubic response functions of the uniform electron gas, respectively. These relations provide exact constraints that may prove useful for the future construction of improved approximations to $F_s[n]$, in particular for warm dense matter applications at finite temperatures. Here, we use this framework to assess several commonly employed approximations to $F_s[n]$ through orbital-free DFT simulations of the harmonically perturbed ideal electron gas. The results are compared with Kohn-Sham DFT calculations across temperatures ranging from the ground state to the warm dense regime. Additionally, we analyze in detail the temperature- and wavenumber-dependent non-monotonic behavior of the ideal quadratic and cubic response functions.
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All authors Zhandos A. Moldabekov, Cheng Ma, Xuecheng Shao, Sebastian Schwalbe, Pontus Svensson, Panagiotis Tolias, Jan Vorberger, Tobias Dornheim
Physics and Society
Social welfare optimisation in well-mixed and structured populations
Van An Nguyen, Vuong Khang Huynh, Ho Nam Duong et al. (+10 more)
Research on promoting cooperation among autonomous, self-regarding
agents has often focused on the bi-objective optimisation problem: minimising the total incentive cost while maximising the frequency of cooperation. However, the optimal value of social welfare under such constraints remains largely unexplored. In this work, we hypothesise that achieving maximal social welfare is not guaranteed at the minimal incentive cost required to drive
agents to a desired cooperative state. To address this gap, we adopt to a single-objective approach focused on maximising social welfare, building upon foundational evolutionary game theory models that examined cost efficiency in finite populations, in both well-mixed and structured population settings. Our analytical model and
agent-based simulations show how different interference strategies, including rewarding local versus global behavioural patterns, affect social welfare and dynamics of cooperation. Our results reveal a significant gap in the per-individual incentive cost between optimising for pure cost efficiency or cooperation frequency and optimising for maximal social welfare. Overall, our findings indicate that incentive design, policy, and benchmarking in multi-
agent systems and human societies should prioritise welfare-centric objectives over proxy targets of cost or cooperation frequency.
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All authors Van An Nguyen, Vuong Khang Huynh, Ho Nam Duong, Huu Loi Bui, Hai Anh Ha, Quang Dung Le, Le Quoc Dung Ngo, Tan Dat Nguyen, Ngoc Ngu Nguyen, Hoai Thuong Nguyen, Zhao Song, Le Hong Trang, The Anh Han
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Improving the Stability of Colloidal CsPbBr3 Nanocrystals with an Alkylphosphonium Bromide as Surface Ligand Pair
Meenakshi Pegu, Hossein Roshan, Clara Otero-Martinez et al. (+9 more)
In this study, we synthesised a phosphonium-based ligand, trimethyl(tetradecyl)phosphonium bromide (TTP-Br), and employed it in the post-synthesis surface treatment of Cs-oleate-capped CsPbBr3 NCs. The photoluminescence
quantum yield (PLQY) of the NCs increased from 60% to more than 90%, as a consequence of replacing Cs-oleate with TTP-Br ligand pairs. Density functional theory calculations revealed that TTP+ ions bind to the NC surface by occupying Cs+ surface sites and orienting one of their P-CH3 bonds perpendicular to the surface, akin to quaternary ammonium passivation. Importantly, TTP-Br-capped NCs exhibited higher stability in air compared to didodecyldimethylammonium bromide-capped CsPbBr3 NCs (which is considered a
benchmark system), retaining 90% of their PLQY after six weeks of air exposure. Light-emitting diodes fabricated with TTP-Br-capped NCs achieved a maximum external
quantum efficiency of 17.2 %, demonstrating the potential of phosphonium-based molecules as surface ligands for CsPbBr3 NCs in optoelectronic applications.
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All authors Meenakshi Pegu, Hossein Roshan, Clara Otero-Martinez, Luca Goldoni, Juliette Zito, Nikolaos Livakas, Pascal Rusch, Francesco De Boni, Francesco Di Stasio, Ivan Infante, Luca De Trizio, Liberato Manna
Plasma Physics · Cross-listed from astro-ph.SR
The influence of Parker spiral on the reflection-driven turbulence
Khurram Abbas and Jonathan Squire
The
solar wind is observed to undergo substantial heating as it expands through the heliosphere, with measured temperature profiles exceeding those expected from adiabatic cooling. A plausible source of this heating is reflection-driven
turbulence (RDT), in which gradients in the background Alfvén speed partially reflect outward-propagating Alfvén waves, seeding counter-propagating fluctuations that interact and dissipate via
turbulence. Previous RDT models assume a radial background
magnetic field, but at larger radii the interplanetary field is known to be twisted into the Parker Spiral (PS). Here, we generalize RDT phenomenology to include a PS, using three-dimensional expanding-box magnetohydrodynamic (MHD) simulations to test the ideas and compare the resulting
turbulence to the radial-background-field case. We argue that the underlying RDT dynamics remain broadly similar with a PS, but the controlling scales change: as the azimuthal field grows it "cuts across" perpendicularly stretched, pancake-like eddies, producing outer scales perpendicular to the
magnetic field that are much smaller than in the radial-background case. Consequently, the outer-scale nonlinear turnover time increases more slowly with heliocentric distance in PS geometry, weakening the tendency (seen in radial-background models) for the cascade to 'freeze' into quasi-static, magnetically dominated structures. This allows the system to dissipate a larger fraction of the fluctuation energy as heat, also implying that the
turbulence remains strongly imbalanced (with high normalized cross-helicity) out to larger heliocentric distances. We complement our heating results with a detailed characterization of the
turbulence (e.g., spectra, switchbacks, and compressive fractions) providing a set of concrete predictions for comparison with spacecraft observations.
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Optics
Wedge Design
Adrian Travis
The space in front of a projector or camera can be folded into a light-guide by total-internal reflection if the guide is tapered like a wedge. This article explains how to calculate both flat and curved wedges by scaling a thin version designed using the principle that the product of thickness and the sin of ray angle is constant in a smoothly varying guide.
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Physics and Society · Cross-listed from cond-mat.stat-mech
Prediction and inference in complex networks: a brief review and perspectives
Francisco A. Rodrigues
Inference and prediction are fundamental to the study of complex systems, where network data are often incomplete, inaccurate or obtained indirectly. In this paper, we review recent advances in network sampling and comparison, as well as in link prediction and network reconstruction from time series. We summarise key methodological developments and emerging approaches that integrate statistical and machine learning perspectives. We also outline promising research directions for enhancing the inference and prediction of complex networked systems.
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Optics · Cross-listed from cond-mat.dis-nn
Non-Hermitian off-diagonal disordered optical lattices
E. T. Kokkinakis, I. Komis, K. G. Makris et al. (+1 more)
Within the framework of non-Hermitian photonics, we investigate the spectral and dynamical properties of one- and two-dimensional non-Hermitian off-diagonal disordered optical
lattices, where randomness is applied to the couplings rather than to the on-site potential terms. We analyze
eigenvalue distributions and the localization properties of the eigenmodes, comparing them with those of the corresponding Hermitian
lattices. Furthermore, we study their transport behavior under single-channel excitation and identify unconventional phenomena such as jumps between distant
lattice regions in systems with a purely real spectrum, as well as complex spectrum-induced Anderson jumps, reported here for the first time in two dimensions. Our results establish a reference framework for non-Hermitian off-diagonal disorder and open new directions for future studies of localization phenomena.
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All authors E. T. Kokkinakis, I. Komis, K. G. Makris, E. N. Economou
Atmospheric and Oceanic Physics · Cross-listed from stat.AP
Bridging CORDEX and CMIP6: Machine Learning Downscaling for Wind and Solar Energy Droughts in Central Europe
Nina Effenberger, Maxim Samarin, Maybritt Schillinger et al. (+1 more)
Reliable regional
climate information is essential for assessing the impacts of
climate change and for planning in sectors such as renewable energy; yet, producing high-resolution projections through coordinated initiatives like CORDEX that run multiple physical regional
climate models is both computationally demanding and difficult to organize. Machine learning emulators that learn the mapping between global and regional
climate fields offer a promising way to address these limitations. Here we introduce the application of such an emulator: trained on CMIP5 and CORDEX simulations, it reproduces regional
climate model data with sufficient accuracy. When applied to CMIP6 simulations not seen during training, it also produces realistic results, indicating stable performance. Using CORDEX data, CMIP5 and CMIP6 simulations, as well as regional data generated by two machine learning models, we analyze the co-occurrence of low wind speed and low
solar radiation and find indications that the number of such energy drought days is likely to decrease in the future. Our results highlight that downscaling with machine learning emulators provides an efficient complement to efforts such as CORDEX, supplying the higher-resolution information required for impact assessments.
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All authors Nina Effenberger, Maxim Samarin, Maybritt Schillinger, Reto Knutti
Optics
Efficient mapping and tracking the properties of micromechanical resonators using phase-lock loops with closely-spaced frequencies
Agnes Zinth, Samer Houri and Menno Poot
Studying the dynamical behavior of micro- and nano-mechanical systems (MEMS and NEMS) is essential in various fields from nonlinear dynamics to
quantum technologies. Hence, it is important to be able to precisely monitor the mechanical properties of MEMS and NEMS devices. In this work, we show how to track and spatially map various properties of a mechanical resonator, such as frequency shift, linewidth, and nonlinearity, by aptly choosing three closely-spaced drive frequencies and using phase-locked loops. This technique tracks changes in the system faster and more efficiently, without the need for repeated frequency sweeps of the oscillator response, simply by employing three phase-locked tones.
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Geophysics
Seismic event classification with a lightweight Fourier Neural Operator model
Ayrat Abdullin, Umair bin Waheed, Leo Eisner et al. (+1 more)
Real-time monitoring of induced seismicity is critical to mitigate operational risks, relying on the rapid and accurate classification of triggered data from continuous data streams. Deep learning models are effective for this purpose but require substantial computational resources, making real-time processing difficult. To address this limitation, a lightweight model based on the
Fourier Neural Operator (FNO) is proposed for the classification of microseismic events, leveraging its inherent resolution-invariance and computational efficiency for waveform processing. In the STanford EArthquake
Dataset (STEAD), a global and large-scale database of seismic waveforms, the FNO-based model demonstrates high effectiveness for trigger classification, with an F1 score of 95% even in the scenario of data sparsity in training. The new FNO model greatly decreases the computer power needed relative to current deep learning models without sacrificing the classification success rate measured by the F1 score. A test on a real microseismic
dataset shows a classification success rate with an F1 score of 98%, outperforming many traditional deep-learning techniques. The reduced computational cost makes the proposed FNO model well suited for deployment in resource-constrained, near-real-time seismic monitoring workflows, including traffic-light implementations. The source code for the proposed FNO classifier will be available at: https://github.com/ayratabd/FNOclass.
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All authors Ayrat Abdullin, Umair bin Waheed, Leo Eisner, Abdullatif Al-Shuhail
Optics
Floquet states on disclinations
K. Sabour, S. K. Ivanov, A. Ferrando et al. (+1 more)
We show that periodic longitudinal modulation of waveguide arrays with disclination can result in the appearance of previously unexplored Floquet modes bound to the disclination core. Such modes arise due to oscillations of the waveguides in the array, periodically switching the structure between topological and trivial phases on each modulation period, so that on average it seems trivial. Localization of such modes depends on the amplitude of waveguide oscillations. Depending on the discrete rotational
symmetry of the arrays with disclinations, these modes exhibit distinct spatial profiles unattainable in periodic
lattices. Propagation in a medium with focusing cubic nonlinearity reveals that these Floquet states remain localized below a critical power threshold, indicating the possibility of the formation of disclination-bound Floquet
solitons. Our results unveil a new regime of localization in photonic systems, bridging disclination
topology, Floquet engineering, and nonlinearity.
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All authors K. Sabour, S. K. Ivanov, A. Ferrando, Y. V. Kartashov
Optics
Determinations of angular stiffness in rotational optical tweezers
Mark L. Watson, Alexander B. Stilgoe and Halina Rubinsztein-Dunlop
Rotational optical tweezers are used to probe the mechanical properties of unknown microsystems. Quantifying the angular trap stiffness is essential for interpreting the rotational dynamics of probe particles. While methods to determine trap stiffness are well established for translational degrees of freedom, angular trapping is often treated analogously even though rotational and translational motions are sensitive to distinct experimental parameters and offer separate insights. This work details passive analysis techniques for determining the angular trap stiffness within the linear restoring torque model and examines the influence of several factors unique to rotational optical tweezers. We show that the parameters of an ancillary measurement beam can be tuned to minimise its influence on angular trapping dynamics, providing necessary improvements for nanoparticle-scale analysis. We also explore the combined effects of shape-induced and material birefringence in spheroidal vaterite probes, and present a framework for assessing hydrodynamic and inertial contributions.
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Fluid Dynamics
Memory effects in wave-induced microplastic transport
Mary Eby and Cathal Cummins
Microplastics are transported by ocean surface waves in ways that depart significantly from the Stokes drift of fluid parcels, and accurate modeling of this transport requires accounting for forces beyond linear drag. Existing modeling of microplastic transport often neglect the Basset-Boussinesq history force, effectively limiting their use to the smallest particle sizes. Here, we extend the applicability of these models by implementing the history term with a multistep integration scheme, allowing us to capture the transport of larger microplastics in linear surface waves of arbitrary depth. We quantify when the Basset-Boussinesq history force significantly affects microplastic transport by surface
gravity waves. We show that
memory effects become the leading-order horizontal drag once $S=St/\gamma^2$ exceeds a critical value $S\approx 0.25$, where $St$ is the Stokes number and $\gamma$ is the density ratio of the particle and the fluid. The corresponding critical $St$ number is found to be a factor of about three smaller than that given by classical inertial estimates that neglect history effects. These results help provide regime maps that can be used to indicate when history effects can be safely neglected. Our simulations also reveal that history effects significantly increase horizontal transport distances and enhance orbit shearing of particle ensembles.
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Applied Physics
A Tri-Band Shared-Aperture Base Station Antenna Array Covering 5G Mid-Band and 6G Centimetric Wave Band
Shang-Yi Sun, Hai-Han Sun, Can Ding et al. (+1 more)
This work proposes a tri-band shared-aperture
antenna array with three wide bands, covering the 5G mid-band and the 6G centimetric band, which is a promising candidate for future 6G base station
antennas. The challenge of suppressing interferences, including scattering and coupling, in the tri-band array is holistically addressed across wide bands. Guided by characteristic mode analysis (CMA), a segmented spiral radiator is efficiently developed to mitigate scattering and coupling at high frequencies while preserving radiation performance at low frequencies. Compared to a conventional tube radiator, the proposed spiral exhibits a reduced radar cross-section (RCS) over an ultra-wide range of 4.7-21.5 GHz (128.2%). With the aid of serial resonators, impedance matching of the segmented-spiral-based dipole
antenna is achieved across the low band (LB) of 3.05-4.68 GHz (42.2%), spanning the 5G band 3.3-4.2 GHz. Moreover, suppressors are placed near the LB ports to further reduce the cross-band coupling. Middle band (MB) and high band (HB)
antennas operate in 6.2-10.0 GHz (46.9%) and 10.0-15.6 GHz (43.8%), respectively, collectively covering the anticipated 5G-Advanced and 6G centimetric band of 6.425-15.35 GHz. Both the MB and HB
antennas employ a planar magnetoelectric (ME) dipole structure, which prevents common-mode resonances in the LB and MB, and mitigates the scattering from the MB
antenna in the HB. In this tri-band array, radiation patterns remain undistorted across the LB, MB, and HB, and the isolation between any two ports exceeds 20 dB over all three bands.
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All authors Shang-Yi Sun, Hai-Han Sun, Can Ding, Y. Jay Guo
Computational Physics · Cross-listed from math.NA
Non-Intrusive Data-Free Parametric Reduced Order Model for Geometrically Nonlinear Structures
Alexander Saccani and Paolo Tiso
We present a fully non-intrusive parametric reduced-order modeling (PROM) framework for geometrically nonlinear structures subject to
geometric variations. The method builds upon equation-driven Galerkin ROMs constructed from vibration modes and modal-derivative companion vectors, while nonlinear reduced tensors are identified from standard finite element outputs. A database of such ROMs is generated over a set of training samples, and all reduced operators-including the linear stiffness
matrix, the quadratic and cubic nonlinear tensors, the Rayleigh damping parameters, and the reduction basis-are interpolated using Radial Basis Functions (RBFs). A global reduced basis is obtained through a two-level POD compression, combined with a MAC-guided reordering strategy to ensure parametric smoothness. The resulting PROM preserves the
symmetry and
polynomial structure of the reduced equations, enabling robust and efficient adaptation to new parameter values. Analytical parameter sensitivities follow directly from the interpolation model. The approach is demonstrated on a parametrically curved panel and a wing-box with
geometric variations, showing excellent agreement with high-fidelity simulations and enabling substantial reductions in computational cost for parametric analyses.
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Instrumentation and Detectors · Cross-listed from quant-ph
Dispersive readout with two orthogonal modes of a dielectric cavity
A.M. Kozodaev, I.S. Cojocaru, S.M. Drofa et al. (+8 more)
Nitrogen-vacancy color centers in diamond have proven themselves as a good, sensitive element for the measurement of
magnetic fields. While the mainstream of magnetometers based on NV centers uses so-called optically detected
magnetic resonance, there has recently been a suggestion to use dispersive readout of a dielectric cavity to enhance the sensitivity of magnetometers. Here, we demonstrate that the dispersive readout approach can be significantly improved if a two-channel scheme is considered.
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All authors A.M. Kozodaev, I.S. Cojocaru, S.M. Drofa, P.G. Vilyuzhanina, A. Chernyavskiy, V.G. Vins, A.N. Smolyaninov, S.Ya. Kilin, S.V. Bolshedvorskii, V.V. Soshenko, A.V. Akimov
Atomic Physics
Lu$^+$ optical frequency references with accuracy verified at the 19th digit
K. J. Arnold, M. D. K. Lee, Zhao Qi et al. (+4 more)
We report a comprehensive evaluation of all known sources of systematic uncertainty for two independent $^{176}$Lu$^+$ single-ion optical references, finding total systematic uncertainty of $1.2\times10^{-19}$ and $1.3\times10^{-19}$ for the two individual systems and $1.0\times10^{-19}$ for the difference. Through direct comparison via correlation spectroscopy, we demonstrate a relative frequency agreement of $-0.1\pm(5.7)_\mathrm{stat}\pm(1.0)_\mathrm{sys}\times10^{-19}$, where `stat' and `sys' indicate the statistical and systematic uncertainty, respectively. The comparison uncertainty is statistically limited after approximately 200 hours of averaging with a measurement instability of $4.8\times10^{-16}(\tau/\mathrm{s})^{-1/2}$.
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All authors K. J. Arnold, M. D. K. Lee, Zhao Qi, Qichen Qin, Zhang Zhao, N. Jayjong, M. D. Barrett
Optics
Three-Octave Supercontinuum Generation in Thick Crystalline Aluminum Nitride Waveguides
Samantha Sbarra, Samuele Brunetta, Pierre Arnaud Demongodin et al. (+4 more)
We report an efficient extension of supercontinuum generation through dispersion engineering of crystalline aluminum nitride (AlN)-on-sapphire waveguides. Using a tailored epitaxial regrowth of AlN epilayers and an optimized fabrication protocol, the dispersion sensitivity to the waveguide cross-section was enhanced allowing for a significant reach extension of both short and long dispersive wave with optimized pumping conditions, reaching down to 550 nm in the visible and up to 4.5 {\mu}m in the mid-infrared.
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All authors Samantha Sbarra, Samuele Brunetta, Pierre Arnaud Demongodin, Jean-François Carlin, Nicolas Grandjean, Raphaël Butté, Camille-Sophie Brès
Chemical Physics
Two-dimensional RMSD projections for reaction path visualization and validation
Rohit Goswami
Transition state or minimum energy path finding methods constitute a routine component of the computational chemistry toolkit. Standard analysis involves trajectories conventionally plotted in terms of the relative energy to the initial state against a cumulative displacement variable, or the image number. These dimensional reductions obscure structural rearrangements in high dimensions and are often history dependent. This precludes the ability to compare optimization histories of different methods beyond the number of calculations, time taken, and final saddle geometry. We present a method mapping trajectories onto a two-dimensional projection defined by a permutation corrected root mean square deviation from the reactant and product configurations. Energy is represented as an interpolated color-mapped surface constructed from all optimization steps using a gradient-enhanced Gaussian Process with the inverse multiquadric kernel, whose posterior variance contours delineate data-supported regions from extrapolated ones. A rotated coordinate frame decomposes the RMSD plane into reaction progress and orthogonal distance. We show the utility of the framework on a cycloaddition reaction, where a machine-learned potential saddle and density functional theory reference lie on comparable energy contours despite
geometric displacements, along with the ratification of the visualization for more complex reactions, a Grignard rearrangement, and a conrotatory bicyclobutane ring opening.
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Applied Physics
Realizing on-demand all-to-all selective interactions between distant spin ensembles
C.-X. Run, K.-T. Lin, K.-M. Hsieh et al. (+5 more)
Achieving all-to-all coherent networks is critical for the advancement of large-scale coherent computing and communication protocols. By exploiting the resonant dipole-dipole interaction between distant
spin ensembles coupled to a one-dimensional coplanar waveguide (CPW) terminated by a mirror, we successfully demonstrate an on-demand all-to-all selective coherent network between four
spin ensembles. Furthermore, by repositioning the
spin ensembles along the CPW, we achieve collective coupling, and demonstrate coherent energy exchange between multiple
spin ensembles in the time domain. These results strongly indicate the potential of this device as a medium-scale all-to-all network structure, which is poised to advance the exploration of many-body physics and enhance coherent information processing capabilities.
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All authors C.-X. Run, K.-T. Lin, K.-M. Hsieh, B.-Y. Wu, W.-M. Zhou, G.-D. Lin, A. F. Kockum, I.-C. Hoi
Optics
Coherent Field Emission Upon Ultrafast Laser Irradiation of the Tip Plasmon
Joonhee Lee, Shawn M. Perdue, Alejandro Rodriguez Perez et al. (+1 more)
Irradiation of sharp silver tips with femtosecond
laser pulses leads to photoassisted coherent field emission without a static field. We reconstruct the time profile of the emission, and show that the process is entirely governed by the collective response of the tip plasmon and its field emission. Weak-field optical excitation leads to multiphoton absorption and field emission from the tip apex due to the enhanced local field. The attendant sharp field gradient ensures ponderomotive acceleration of emitted electrons and non-local light-matter interaction. The crossover regime in which simultaneous multiphoton absorption and optical field emission take place is evidenced by the time profile of electron emission correlation,
laser power dependence, and polarization angle dependence of each harmonic current.
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All authors Joonhee Lee, Shawn M. Perdue, Alejandro Rodriguez Perez, V. Ara Apkarian
Atomic Physics
Bound and Resonant States of Muonic Few-Body Coulomb Systems: Extended Stochastic Variational Approach
Liang-Zhen Wen and Shi-Lin Zhu
We compute the bound and resonant states of hydrogen-like muonic ions ($\mu\mu p$, $\mu\mu d$, $\mu\mu t$) and three-body muonic molecular ions ($pp\mu$, $pd\mu$, $pt\mu$, $dd\mu$, $dt\mu$, $tt\mu$), and the four-body double-muonic hydrogen molecule ($\mu\mu pp$) using an extended
stochastic variational method combined with complex scaling. The approach provides a unified treatment of bound and quasibound states and achieves an energy accuracy better than $0.1~\mathrm{eV}$ across all systems studied. Complete spectra below the corresponding $n=2$ atomic thresholds are obtained, including several previously unresolved shallow resonances in both three- and four-body sectors.
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Biological Physics · Cross-listed from quant-ph
Zhiyuan Zhao, Qian Shi, Shaoyi Xu et al. (+8 more)
Identification of individual
cells within heterogeneous populations is essential for biomedical research and clinical diagnostics. Conventional labeling-based sorting methods, such as fluorescence-activated
cell sorting and
magnetic-activated
cell sorting, enable precise sorting when reliable markers are available. However, their applicability is limited in
cells lacking defined markers or sensitive to labeling, as labeling can compromise cellular viability and function. We present a single-
cell identification approach using
quantum-enhanced NMR with diamond nitrogen-vacancy centers for label-free detection of intracellular
proton ($^1$H) signals. Using this method, we distinguish two human tumor
cell lines by their
proton spin-
lattice ($T_1$) relaxation times, which serve as a
cell-intrinsic physicochemical signature. It lays the groundwork for label-free sorting applications in rare
cell analysis, personalized medicine, and single-
cell diagnostics.
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All authors Zhiyuan Zhao, Qian Shi, Shaoyi Xu, Xiangyu Ye, Mengze Shen, Jia Su, Ya Wang, Tianyu Xie, Qingsong Hu, Fazhan Shi, Jiangfeng Du
Plasma Physics
Modified vacuum polarization in the presence of a plasma
Sebastian Lundström, Philip Semrén, Haidar Al-Naseri et al. (+1 more)
We study
vacuum polarization due to strong fields, in the presence of an electron-positron
plasma. For this purpose, we expand
quantum kinetic equations using weak fields and slow temporal scales as expansion parameters. It is demonstrated that the
evolution of the Dirac field can be described by classical-like distribution functions for electrons and positrons, which are weakly coupled through
quantum interactions. Furthermore, we deduce that these coupling terms give rise to well-known expressions for
vacuum polarization, in addition to
quantum modifications proportional to the content of real particles. Depending on the initial
plasma density, the dominant
quantum corrections to classical
evolution may arise from real particle couplings or from the
vacuum polarization associated with virtual particles. The implications of our results are discussed.
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All authors Sebastian Lundström, Philip Semrén, Haidar Al-Naseri, Gert Brodin
Fluid Dynamics
Preliminary Study of the Effects of Leading-Edge Serration on a Two-Section Planar Wing in ground-effect at Low Reynolds Number
Arnold Lafond-Saunierr, Simone Basile, Paloma Pizarro et al. (+4 more)
A preliminary study has been conducted on the effects of serration on the leading-edge of a two-element trapezoidal wing placed both out-of- and in-ground effect. Aerodynamic performance and flow behaviour were evaluated numerically and validated experimentally. Results indicate an increase in maximum lift coefficient and stall angle obtained implementing a serrated leading-edge geometry due to the flow being re-energized by the formation of a series of counter-rotating pairs of
vortices. Results from the analysis of the wing in ground effect appear less well defined. Both leading-edge geometries – straight and serrated – show an increase in efficiency due to the proximity to the ground. The wing with the straight leading-edge geometry shows constant improvement up to stall, whilst numerical results show a significant decrease in lift performance at high angles of attack. This may be caused by the lower-fidelity numerical model implemented at higher angles of attack, thus yielding less accurate results.
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All authors Arnold Lafond-Saunierr, Simone Basile, Paloma Pizarro, Kiana Yamamoto, Hassan M. Nagib, Ricardo Vinuesa, Raffaello Mariani