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Physics Physics

physics Watch Physics

Thursday 22 January

Instrumentation and Detectors

Gain-Layer Project

Niels G. Sorgenfrei, Anna Rita Altamura, Cristina Besleaga et al. (+18 more)

Gain-layer degradation from exposure to radiation limits the use of Low-Gain Avalanche Diodes (LGADs) in high energy particle physics detector experiments. Proper understanding of how the gain-layer is destroyed is not available on a defect level. Only measurements for materials with much lower effective doping concentrations are available. The direct study of the gain-layer is not possible with typical defect spectroscopy measurements like Thermally Stimulated Currents (TSC) and Deep-Level Transient Spectroscopy (DLTS). To combat this problem and gain a better understanding of the processes which degrade LGADs, the Gain-Layer Project was started. This project produced 19050 diodes with various Boron, Phosphorus, Oxygen and Carbon concentrations. The material used is low-resistivity p-type Silicon. The effective doping concentrations are in the order of a LGAD gain-layer. These diodes will serve the defect community in the coming years for various studies. This article introduces this project with detailed descriptions of the diodes, their flavours and their processing, and reports on results from I-V, C-V, SIMS and DLTS measurements on unirradiated diodes.
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All authors Niels G. Sorgenfrei, Anna Rita Altamura, Cristina Besleaga, Georgia Andra Boni, Tomas Ceponis, Paul Erberk, Eckhart Fretwurst, Yana Gurimskaya, Kevin Lauer, Ludovico Massaccesi, Luca Menzio, Michael Moll, Marie Muehlnikel, Andrei Nitescu, Ulrich Parzefall, Roxana-Elena Patru, Jevgenij Pavlov, Ioana Pintilie, Stephanie Reiss, Joern Schwandt, Valentina Sola

Chemical Physics

Enhanced Representation-Based Sampling for the Efficient Generation of Datasets for Machine-Learned Interatomic Potentials

Moritz René Schäfer and Johannes Kästner

In this work, we present Enhanced Representation-Based Sampling (ERBS), a novel enhanced sampling method designed to generate structurally diverse training datasets for machine-learned interatomic potentials. ERBS automatically identifies collective variables by dimensionality reduction of atomic descriptors and applies a bias potential inspired by the On-the-Fly Probability Enhanced Sampling framework. We highlight the ability of Gaussian moment descriptors to capture collective molecular motions and explore the impact of biasing parameters using alanine dipeptide as a benchmark system. We show that free energy surfaces can be reconstructed with high fidelity using only short biased trajectories as training data. Further, we apply the method to the iterative construction of a liquid water dataset and compare the quality of simulated self-diffusion coefficients for models trained with molecular dynamics and ERBS data. Further, we active-learn models for liquid water with and without enhanced sampling and compare the quality of simulated self-diffusion coefficients. The self-diffusion coefficients closely match those simulated with a reference model at a significantly reduced dataset size. Finally, we compare the sampling behaviour of enhanced sampling methods by benchmarking the mean squared displacements of \ce{BMIM+BF4-} trajectories simulated with uncertainty-driven dynamics and ERBS and find that the latter significantly increases the exploration of configurational space.
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Optics · Cross-listed from cond-mat.quant-gas

Critical speed of a binary superfluid of light

Pierre-Élie Larré, Claire Michel and Nicolas Cherroret

We theoretically study the critical speed for superfluid flow of a two-dimensional miscible binary superfluid of light past a polarization-sensitive optical obstacle. This speed corresponds to the maximum mean flow velocity below which dissipation is absent. In the weak-obstacle regime, linear-response theory shows that the critical speed is set by Landau's criterion applied to the density and spin Bogoliubov modes, whose relative ordering can be inverted due to saturation of the optical nonlinearity. For obstacles of arbitrary strength and large spatial extent, we determine the critical speed from the conditions for strong ellipticity of the stationary hydrodynamic equations within the hydraulic and incompressible approximations. Numerical simulations in this regime reveal that the breakdown of superfluidity is initiated by the nucleation of vortex-antivortex pairs for an impenetrable obstacle, and of Jones-Roberts solitons for a penetrable obstacle. Beyond superfluids of light, our results provide a general framework for the critical speed of two-dimensional binary nonlinear Schrödinger superflows, including Bose-Bose quantum mixtures.
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Instrumentation and Detectors

Application of zone refining to the development of NaI(Tl) detectors for SABRE North

C. Ananna, F.B. Armani, G. Cataldi et al. (+23 more)

The SABRE North experiment is developing ultra-high radiopurity NaI(Tl) detectors to investigate dark matter. To achieve this, SABRE North utilizes the technique called zone refining for NaI purification. This work details the mathematical model developed to describe the purification process. By comparing this model to the results of the commissioning and production runs conducted prior to crystal growth, the distribution coefficients were determined for various impurities, contained in the powder at the parts-per-billion (ppb) level. Furthermore, the synthesis of data from both zone refining and normal freezing is discussed. These findings can be used to predict the SABRE North detectors background level in the energy region-of-interest for dark matter search and to optimize the production of ultra-high purity crystals through multiple purification strategies.
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All authors C. Ananna, F.B. Armani, G. Cataldi, D. D'Angelo, G. D'Imperio, M.L. De Giorgi, G. Di Carlo, M. Diemoz, A. Ianni, S.G. Khattak, E. Martinenghi, A. Miccoli, M. Misiaszek, D. Montanino, V. Pettinacci, L. Pietrofaccia, S. Rahatlou, K. Szczepaniec, C. Tomei, V. Toso, C. Vignoli, S.Zuhra, L. Cid, A. Mellen-Spencer, S. Nisi, J. Tower

Optics

On-chip Multimode Opto-electronic Neural Network

Jinlong Xiang, Youlve Chen, Chaojun Xu et al. (+5 more)

Opto-electronic computing combines the complementary strengths of photonics and electronics to deliver ultrahigh computational throughput with high energy efficiency. However, its practical deployment for real-world applications has been limited by architectures that rely on delicate wavelength management or phase-sensitive coherent detection. Here, we demonstrate the first multimode opto-electronic neural network (MOENN) on a silicon-on-insulator platform. By utilizing orthogonal waveguide eigenmodes as independent information carriers, our architecture achieves robust single-wavelength computation that is inherently immune to spectral crosstalk and phase noise. The fabricated MOENN chip monolithically integrates all functional components, including input encoders, programmable mode-division fan-in/-out units, and most importantly, the nonlinear multimode activation functions. We report the system's versatility through in-situ training via a genetic algorithm, successfully resolving the nonlinear decision boundaries of a two-class dataset and achieving 92.1% accuracy on the Iris classification benchmark. Furthermore, we reconfigure the MOENN into a one-dimensional convolutional neural network, attaining an accuracy of 90.7% on the electrocardiogram-based emotion recognition task. This work establishes a new opto-electronic computing paradigm of simple control and excellent robustness, providing a compelling path toward scalable, deployable photonic intelligence.
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All authors Jinlong Xiang, Youlve Chen, Chaojun Xu, Yuchen Yin, Yufeng Zhang, Yikai Su, Zhipei Sun, Xuhan Guo

Fluid Dynamics · Cross-listed from math.AP

Real-Time Inviscid Fluid Dynamics and Aero-acoustics on a Sphere

Madhusraba Sinha and Jan Stratmann

Real-time fluid and aeroacoustic simulation on complex surfaces can have interactive applications - from globe-based weather visualizations to immersive computer games with physically accurate wind and sound. However, conventional grid-based solvers struggle with numerical instability near surface singularities, and mesh-based approaches lack a straightforward path to solving partial differential equations (PDEs) with stable, high-order accuracy. Our model presents a unified framework for real-time inviscid fluid simulation and aeroacoustics on spherical surfaces with embedded obstacles, combining the Closest Point Method (CPM), projection-based Navier-Stokes solvers, and the Ffowcs Williams-Hawkings (FWH) analogy. CPM enables surface PDEs to be solved in a Cartesian embedding without parametrization by restricting computation to a narrow band around the sphere. Each band point is mapped to its nearest surface location, where band operators project results onto the local tangent space. Surface obstacles are modelled with signed distance functions (SDFs), enforcing no-slip velocity constraints and Bernoulli-based pressure adjustments for consistent real-world boundary interactions. Aeroacoustic sources are computed directly from surface pressure force derivatives and mapped to real-time audio via frequency and amplitude modulation with artifact-suppressing hysteresis smoothing. Our findings from this model simulate the behaviour of inviscid fluid on spherical surfaces while generating sound using the pressure of the fluid flowing on the surface. This approach gives results that offer stability, geometric consistency, and support applications in scientific visualization, virtual reality, and educational tools.
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Optics

Mid-infrared high-sensitive cavity-free in-situ CO gas sensing based on up-conversion detection

Zhao-Qi-Zhi Han, He Zhang, Fan Yang et al. (+8 more)

Carbon monoxide (CO) is a significant indicator gas with considerable application value in atmospheric monitoring, industrial production and medical diagnosis. Its fundamental vibrational band locates around 4.6 $\upmu$m and has larger absorption line strength than that of overtone band, which is more suitable for the precise identification and concentration detection of CO. In this paper, the up-conversion detection is employed to convert the mid-infrared absorption signal obtained by TDLAS to the visible light band, then a silicon-based detector is utilized for detection. By which, we can achieve the highest sensitivity of 79.6 ppb under the condition of cavity-free in-situ with an absorption range length of only 0.14 m. Furthermore, the single-photon level real-time detection of CO concentration after the diffuse reflection is realized by using SPAD. This work demonstrates the merits of the up-conversion detection in terms of its functionality at room temperature and capacity for sensitivity detection. Furthermore, it presents a design and optimization methodology that has the potential to underpin the advancement of the method towards more practical applications, like industrial process monitoring, medical diagnosis and so on.
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All authors Zhao-Qi-Zhi Han, He Zhang, Fan Yang, Xiao-Hua Wang, Bo-Wen Liu, Jin-Peng Li, Zheng-He Zhou, Yin-Hai Li, Yan Li, Zhi-Yuan Zhou, Bao-Sen Shi

Fluid Dynamics

Assimilating rough features: A data-driven framework to infer rough wall properties from sparse experimental data

Martina Formichetti, Uttam Cadambi Padmanaban, Ping He et al. (+2 more)

Surface roughness influences turbulent boundary layers (TBLs) primarily through the roughness function $\Delta U^+$ and the equivalent sand-grain roughness height \(k_s\). Direct determination of \(k_s\) typically requires detailed velocity and wall-shear stress measurements, which are often impractical. As an alternative, this study presents a data assimilation framework that modifies a smooth-wall Reynolds-Averaged Navier-Stokes (RANS) baseline to match sparse rough-wall particle image velocimetry (PIV) data in the fully rough regime. Through this approach, secondary variables such as the friction velocity, \(u_\tau\), and \(k_s\) can be inferred from the assimilated flow fields. The assimilated TBL reproduces experimental velocity profiles within 1% and predicts friction velocity within 1-6% of the experimental measurements. Furthermore, the \(k_s\) values inferred from the assimilation also match the experimental data up to 1%. These results demonstrate the potential of data assimilation as a cost-effective alternative to high-fidelity methods and support the generalisation of the framework to model streamwise-varying roughness by treating \(k_s\) as a function of fetch length.
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All authors Martina Formichetti, Uttam Cadambi Padmanaban, Ping He, Sean Symon, Bharathram Ganapathisubramani

Applied Physics · Cross-listed from cond-mat.supr-con

Reaching the intrinsic performance limits of superconducting nanowire single-photon detectors up to 0.1 mm wide

Kristen M. Parzuchowski, Eli Mueller, Bakhrom G. Oripov et al. (+13 more)

Superconducting nanowire single-photon detectors (SNSPDs) combine high detection efficiency, low noise, and excellent timing resolution, making them a leading platform for photon-counting applications. However, despite decades of materials and fabrication research, detector performance has never been shown to match theoretical performance expectations. Here, we demonstrate for the first time in situ tuning of a detector from its typical, suboptimal operation, to a regime limited only by material quality, allowing the device to reach its intrinsic performance limit. Our approach is based on current-biased superconducting "rails" placed on either side of the detector that redistribute current across its width to achieve its peak performance. This technique reduces the dark count rate by ten orders of magnitude. Further, we show operation at this intrinsic performance limit for devices up to 0.1 mm wide, and also demonstrate near-unity internal detection efficiency (IDE) at a wavelength of 4um for a 20um-wide detector–a factor of 20 wider than the current state of the art. This work enables future detectors to overcome the Pearl limit for device width, paving the way for arbitrarily large detectors.
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All authors Kristen M. Parzuchowski, Eli Mueller, Bakhrom G. Oripov, Benedikt Hampel, Ravin A. Chowdhury, Sahil R. Patel, Daniel Kuznesof, Emma K. Batson, Ryan Morgenstern, Robert H. Hadfield, Varun B. Verma, Matthew D. Shaw, Jason P. Allmaras, Martin J. Stevens, Alex Gurevich, Adam N. McCaughan

Chemical Physics

Response of fluorescent molecular rotors in ternary macromolecular mixtures

Mingshan Chi, Anh-Thy Bui, Pierre Lidon et al. (+1 more)

For a few decades, Fluorescent Molecular Rotors have been commonly employed as local probes of microviscosity in complex materials. However, without proper calibration, relating microviscosity to a physical parameter is unclear, which strongly limits their quantitative use in biological media for instance. In this study, the response of a molecular rotor in binary and ternary macromolecular aqueous solutions of polyethylene glycol (PEG) of different molecular weights is investigated in order to better rationalize the sensitivity of rotors to their cybotactic environment. More precisely, for the investigated composition range of ternary mixtures, it is shown that a linear mixing rule applies for fluorescence lifetime with the proportion of the two PEG, and with an increasing ratio of heavy PEG leading to larger lifetimes. These results allow to test more precisely the free volume theory, which has been proposed in the context of probing glass transition. Analysis show that while this theory semi-quantitatively captures the observation, its precise use raises some questions.
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All authors Mingshan Chi, Anh-Thy Bui, Pierre Lidon, Yaocihuatl Medina-Gonzalez

Medical Physics

Multimodal Imaging System Combining Hyperspectral and Laser Speckle Imaging for In Vivo Hemodynamic and Metabolic Monitoring

Junda Wang, Luca Giannoni, Ayse Gertrude Yenicelik et al. (+4 more)

We present the development and validation of a novel multimodal optical imaging platform that integrates hyperspectral imaging (HSI) and laser speckle contrast imaging (LSCI) to enable real-time, non-invasive mapping of tissue oxygenation, perfusion and metabolism, via blood flowmetry and targeting of oxy- (HbO2), deoxyhemoglobin (HHb), as well as oxidized cytochrome-c-oxidase (oxCCO). The system architecture features a single high-speed camera and dual optical path, with synchronized alternating illumination: a filtered, supercontinuum laser for HSI and a He-Ne laser for LSCI. The system performances were evaluated through in vivo experiments on rat spinal cord under normoxic and hypoxic conditions, revealing coherent physiological changes in hemodynamics, metabolism and relative blood flow index (rBFI). These results demonstrate the potential of the platform for functional tissue imaging and quantitative dynamic monitoring of both oxygen delivery and consumption.
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All authors Junda Wang, Luca Giannoni, Ayse Gertrude Yenicelik, Eleni Giama, Frederic Lange, Kenneth J. Smith, Ilias Tachtsidis

Physics and Society

Partitioning networks into clusters of synchronized nodes via the message-passing algorithm: an unbiased scalable approach

Massimo Ostilli

Partitioning large networks into stable clusters of synchronized nodes is a challenging task. Recent approaches based on spectral analysis can provide exact results on specific dynamics but remain unfeasible for very large networks. Moreover, within a stochastic framework, it is unclear which dynamics should be chosen to study synchronization. Here we propose an unbiased and scalable method based on the message-passing algorithm. By exploiting the collective behavior emerging across critical points of an effective Ising-like model, we identify dynamically coherent clusters of synchronized nodes and illustrate the approach on some large real-world networks. We find that, unlike continuous-time dynamics, abrupt desyncrhronization occurs even in simple graphs, without the need to invoke higher order interactions. However, when noise is included, the transition to synchronization becomes smoother and proceeds through the formation of plateaus, albeit at the cost of requiring larger coupling strengths.
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Instrumentation and Detectors

Operating a large-diameter dual-phase liquid xenon TPC in the unshielded PANCAKE facility

Julia Müller, Jaron Grigat, Robin Glade-Beucke et al. (+7 more)

Future liquid-xenon (LXe) based observatories for rare processes, such as XLZD, require testing of large components and sub-assemblies in cryogenic liquid or gaseous xenon environments. Here we present results from the stable operation of a shallow dual-phase LXe TPC with an inner diameter of 133.4\,cm and a height of 3.1\,cm in the unshielded PANCAKE platform, without underground suppression of cosmic-ray backgrounds. A total of 340\,kg of xenon was used in the experiment, of which 127\,kg constituted the active TPC mass. Measurements of the LXe purity-dependent electron lifetime and the electron drift velocity in LXe demonstrate that sensitive measurements to characterize the TPC performance are possible in a high-background environment, even with a very basic PMT-based light detection system. Improving this will straightforwardly reduce the TPC threshold, which was observed to be around 15\,keV for electronic recoils in TPC operation.
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All authors Julia Müller, Jaron Grigat, Robin Glade-Beucke, Sebastian Lindemann, Tiffany Luce, Gnanesh Chandra Madduri, Jens Reininghaus, Marc Schumann, Adam Softley-Brown, Andrew Stevens

Instrumentation and Detectors

OPTIMA, a board dedicated to Optimized Precision Timing for Multichannel Acquisition

Federico De Benedetti, Victor Coco, Paula Collins et al. (+5 more)

In the new era of HL-LHC experiments, fast-timing detectors are emerging as critical tools for background rejection. Typical requirements include a temporal hit resolution of about 50 ps, a spatial resolution of around 12 $\mu$m, and radiation hardness up to $10^{17}$n$_\text{eq}$/cm$^2$. To address these challenges, the development of non-standard sensor designs and advanced fast readout electronics is required. The OPTIMA multichannel board addresses the need for testing small sensor demonstrators when they cannot yet be bonded to dedicated readout ASICs. It provides fast readout of up to 16 channels and can be integrated into various test setups, including test beam environments. This contribution presents the design of the OPTIMA board, its integration in test beams, and the first experimental results.
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All authors Federico De Benedetti, Victor Coco, Paula Collins, Raphael Dumps, Edgar Lemos Cid, Alfonso Puicercus Gomez, Efren Rodriguez Rodriguez, Morag Williams

Optics

Quantitative three-dimensional absorption imaging in standard brightfield microscopes

Yoonjae Chung, Sehyun Lee, Herve Hugonnet et al. (+5 more)

Optical absorption is a primary, label-defining contrast across biology, pathology, and materials science, yet three-dimensional quantitative absorption imaging has remained largely inaccessible to the brightfield microscopes used in everyday practice. We introduce quantitative absorption tomography (QAT), which recovers volumetric distributions of the extinction coefficient by treating brightfield image formation as a linear inverse problem in logarithmic intensity space and inverting a three-dimensional absorption optical transfer function. Under weak-scattering conditions, QAT yields spectrally resolved, three-dimensional absorption maps from through-focus image stacks acquired on standard brightfield platforms, without interferometry, coherent illumination, or sample rotation. We use QAT to track melanin dynamics in living melanoma cells without exogenous labels, image pigment organization in intact Petunia hybrida petals in vivo, and reconstruct chromogenic contrast across large H&E-stained human tissue volumes. By establishing absorption as a directly measurable volumetric quantity within standard brightfield workflows, QAT positions chromogenic contrast as a quantitative axis alongside fluorescence- and refractive-index-based imaging.
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All authors Yoonjae Chung, Sehyun Lee, Herve Hugonnet, Chulmin Oh, Weisun Park, Yeon Wook Kim, Seung-Mo Hong, YongKeun Park

Optics

Size-dependent Dielectric Permittivity of Perovskite Nanocrystals

Jehyeok Ryu, Victor Krivenkov, Vitaly Goryashko et al. (+2 more)

Perovskite nanocrystals (PNCs) are promising building blocks for quantum photonic devices. Optical properties of PNCs can be enhanced by integration with optical cavities or nanoantennas. Designing such structures requires accurate size dependent dielectric permittivity of PNCs. However, current reports provide primarily ensemble averaged values with limited access to the intrinsic response of individual PNCs. Here we suggest a methodology to reconstruct the size dependent complex dielectric permittivity of CsPbBr3 PNCs from the measured absorbance spectrum of colloidal solution. The permittivity of PNCs is modeled as a sum of Voigt profile oscillators, with the size dependent transition energies governed by the exciton effective mass. Using a transmission electron microscopy derived size distribution of the PNCs, the solution permittivity is obtained via Maxwell Garnett effective medium approximation. This permittivity is used in a transfer matrix method to simulate and fit the absorbance spectrum, from which the permittivity of PNCs is reconstructed. The extracted spectral linewidth from the imaginary part of the permittivity (78.4 meV) is consistent with single nanocrystal emission linewidths at room temperature. Finite element simulations show enhanced absorption cross section of a single PNC coupled to a nanoantenna, demonstrating applicability of the extracted permittivity. More generally, these findings provide a route to extract intrinsic permittivity of individual nanocrystals from absorbance measurements of their ensembles.
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All authors Jehyeok Ryu, Victor Krivenkov, Vitaly Goryashko, Yury Rakovich, Alexey Y. Nikitin

Instrumentation and Detectors

Large-scale real-time signal processing in physics experiments: The ALICE TPC FPGA pipeline

J. Alme, T. Alt, C. Andrei et al. (+119 more)

For LHC Run 3, the ALICE Time Projection Chamber was upgraded to operate in continuous readout mode. Interaction rates of up to 50 kHz in Pb-Pb collisions require real-time processing of more than 3 TB/s of raw detector data. This requirement is met by a custom FPGA-based processing pipeline that performs the complete front-end data treatment fully in-stream, including common-mode correction, pedestal subtraction, ion-tail filtering, zero suppression, and dense data packing. A central element of the design is a highly parallel common-mode correction algorithm operating directly on the streaming data. It robustly identifies signal-free readout channels on a time-bin basis and applies pad-dependent scaling to compensate for local variations in capacitive coupling in the GEM readout. In combination with pedestal subtraction and ion-tail filtering, this enables accurate baseline restoration under extreme high-occupancy conditions, preventing signal loss while efficiently suppressing noise prior to zero suppression. The pipeline operates continuously at the full detector bandwidth and reduces the raw input rate to about 900 GB/s for Pb-Pb collisions at the target interaction rate. Overall, it represents a large-scale FPGA-based real-time signal-processing implementation for high-energy physics detector readout.
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All authors J. Alme, T. Alt, C. Andrei, V. Anguelov, H. Appelshäuser, M. Arslandok, R. Averbeck, M. Ball, G. G. Barnaföldi, P. Becht, R. Bellwied, A. Berdnikova, B. Blidaru, L. Boldizsár, L. Bratrud, P. Braun-Munzinger, M. Bregant, C. L. Britton, H. Büsching, H. Caines, P. Chatzidaki, P. Christiansen, T. M. Cormier, L. Döpper, R. Ehlers, L. Fabbietti, F. Flor, J. J. Gaardhøje, M. G. Munhoz, C. Garabatos, P. Gasik, Á. Gera, P. Glässel, N. Grünwald, T. Gündem, T. Gunji, H. Hamagaki, J. W. Harris, P. Hauer, E. Hellbär, H. Helstrup, A. Herghelegiu, H. D. Hernandez Herrera, Y. Hou, C. Hughes, M. Ivanov, J. Jäger, Y. Ji, J. Jung, M. Jung, B. Ketzer, S. Kirsch, M. Kleiner, A. G. Knospe, M. Korwieser, M. Kowalski, L. Lautner, M. Lesch, C. Lippmann, G. Mantzaridis, R. D. Majka, A. Marin, C. Markert, S. Masciocchi, A. Matyja, M. Meres, D. L. Mihaylov, D. Miśkowiec, R. H. Munzer, H. Murakami, K. Münning, A. Nassirpour, C. Nattrass, B. S. Nielsen, W. A. V. Noije, A. C. Oliveira Da Silva, A. Oskarsson, K. Oyama, L. Österman, Y. Pachmayer, G. Paić, M. Petris, M. Petrovici, M. Planinic, J. Rasson, K. F. Read, A. Rehman, R. Renfordt, A. Riedel, K. Røed, D. Röhrich, E. Rubio, A. Rusu, S. Sadhu, B. C. S. Sanches, J. Schambach, A. Schmah, C. Schmidt, A. Schmier, K. Schweda, D. Sekihata, D. Silvermyr, B. Sitar, N. Smirnov, H. K. Soltveit, C. Sonnabend, S. P. Sorensen, J. Stachel, L. Šerkšnytė, G. Tambave, K. Ullaland, B. Ulukutlu, D. Varga, O. Vazquez Rueda, B. Voss, J. Wiechula, B. Windelband, J. Wilkinson, J. Witte, A. Yadav, F. Zanone, S. Zhu

Atomic Physics

Dynamics of antiferromagnetic Dimers in Rydberg Atom Chains

Feng-Yuan Kuang, Lin Li and Weibin Li

We investigate the dynamics of antiferromagnetic dimers within a Rydberg atom chain in the regime where laser detuning compensates for nearest-neighbor (NN) interactions. Using an effective PXQ model, we demonstrate that the associated Hilbert space decomposes into disconnected, dimer-conserving subspaces. The classification of these subspaces is provided, and the computational basis states spanning them are identified. Through a combination of analytical mapping and numerical simulations, we compare the dynamics of the PXQ model with those of the full Rydberg atom chain. The deviations are attributed to two factors, laser-induced leakage from the constrained Hilbert subspace and the influence of long-range interactions beyond the NN limit. Our results indicate that subspace leakage can be mitigated by increasing the NN interaction strength. While this simultaneously amplifies the effects of long-range interactions, the conservation of the dimer number remains. Our study opens up possibilities for exploring the dynamics of antiferromagnetic dimers using the Rydberg atom quantum simulator.
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Fluid Dynamics

Turbulent hydrogen premixed flames at high pressure and high temperature

Sofiane Al Kassar, Sara Cantagalli, William Lauder et al. (+2 more)

The combined influence of elevated pressure and temperature, representative of gas-turbine operating conditions, on lean premixed hydrogen flames is investigated using Direct Numerical Simulations (DNS) of a turbulent jet. Three cases are considered: 1 atm/298 K, 5 atm/472 K, and 20 atm/700 K, scaled to maintain the same jet Reynolds number and nominal Karlovitz number in the unburnt mixture, enabling a direct comparison of flame-turbulence interactions. Although the combined effects are moderate overall due to compensating influences, measurable differences arise in flame structure and turbulence-flame coupling. They are driven by reduced turbulence dissipation within the flame at high pressure and temperature, which enhances the interaction between turbulence and thermodiffusive effects. Finally, the tangential strain rate exhibits the same universal Kolmogorov scaling observed in homogeneous-isotropic turbulence and in methane flames, confirming its robustness for modelling turbulence
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All authors Sofiane Al Kassar, Sara Cantagalli, William Lauder, Geveen Arumapperuma, Antonio Attili

History and Philosophy of Physics

Determination of the longitude difference between Baghdad and Khwarezm using a lunar eclipse (the method of Abu Rayhan al-Biruni and Abu al-Wafa al-Buzjani)

Rizoi Bakhromzod

This paper examines how, in the tenth century, medieval Iranian scholars Abu Rayhan al-Biruni and Abu al-Wafa al-Buzjani determined the difference in geographical longitude between the cities of Baghdad and Khwarezm through simultaneous observation of a lunar eclipse. Brief academic biographies of these scholars are presented, with emphasis on their contributions to mathematics and astronomy. The study discusses the importance of determining geographical coordinates - especially longitude - in the science of the 10th-11th centuries, provides an overview of the methods of coordinate determination available at the time, and highlights the problem of synchronizing remote observations prior to the advent of electronic communication. Particular attention is devoted to a detailed analysis of the method based on observing a lunar eclipse to simultaneously measure longitude differences: the necessary conditions and organization of the experiment, the instruments employed, the mathematical calculations, and error estimates are described. The longitude difference obtained by al-Biruni and al-Buzjani is compared with modern values. The conclusion discusses the scientific significance of this method for the history of science and astronomy.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci

Effects of pulsed and continuous light and heavy ion irradiation on the morphology and electrical properties of Ag+C60 and Au+C60 composite thin films

Giovanni Ceccio, Kazumasa Takahashi, Yuto Kondo et al. (+5 more)

Metal - organic nanocomposite thin films represent a versatile class of materials whose properties can be effectively tuned through external stimuli. In this study, Ag+C60 and Au+C60 nanocomposite thin films were briefly investigated to elucidate the effects of ion irradiation on both their morphology and electrical properties. The films were synthesized by co-deposition of noble metals and fullerenes, using ion beam sputtering of metal targets combined with simultaneous thermal evaporation of C60. The as - deposited films were characterized by ion beam analysis to determine their composition and element depth distributions. Subsequently, the samples were irradiated at room temperature with either a continuous Ar ion beam or a pulsed C ion beam, both at an energy of 20 keV and a fluence of 1 x 1015 ions/cm2. Irradiation-induced morphological changes were examined by scanning electron microscopy. While the C-irradiated films retained compact and homogeneous surface morphologies, Ar irradiation induced pronounced surface restructuring, resulting in highly corrugated and porous-like surfaces. In addition to morphology, the electrical resistance of the films was measured. The results indicate that C-irradiated samples exhibit only minor changes in resistivity, whereas Ar irradiation strongly affects the electrical properties, with the most significant impact observed for the Au+C60 system. The observed changes in electrical resistance closely correlate with the irradiation-induced surface morphology. The measurement results are briefly discussed below.
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All authors Giovanni Ceccio, Kazumasa Takahashi, Yuto Kondo, Romana Miksova, Vasily Lavrentiev, Josef Novak, Eva Stepanovska, Jiri Vacik

Accelerator Physics · Cross-listed from hep-ex

Muon beams towards muonium physics: progress and prospects

Siyuan Chen, Mingchen Sun and Jian Tang

Advances in accelerator technology have led to significant improvements in the quality of muon beams over the past decades. Investigations of the muon and muonium enable precise measurements of fundamental constants, as well as searches for new physics beyond the Standard Model. Furthermore, by utilizing muon beams with high intensity and polarization, studies of the dynamics of the muon and muonium within atomic level can offer valuable insights into materials science. This review presents recent progress and prospects at the frontiers of muon beams and high-precision muonium physics. It also provides an overview of novel methods and detection techniques to achieve high sensitivities in different areas, including particle physics, nuclear physics, materials science and beyond.
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Optics

Photorefraction Management in Lithium Niobate Waveguides: High-Temperature vs. Cryogenic Solutions

Nina A. Lange, René Pollmann, Michael Rüsing et al. (+7 more)

Lithium niobate sees widespread use in nonlinear and quantum optical devices, such as for sum- and difference-frequency generation or spontaneous parametric down-conversion. In lithium niobate waveguides, nonlinear optical processes are often limited by the so-called photorefractive effect, which limits the maximum input or output powers and impacts the nonlinear spectral response. Therefore, strategies for the management of photorefractive damage are a key consideration in device design. Usually, the photorefractive damage threshold, i.e. the maximal permissible operating power, can be increased by high temperature operation of devices. This approach, however, is not applicable in cryogenic environments, which may be required for specialized applications. To better understand the impact of photorefraction in nonlinear optical applications, we study the impact of photorefraction on the phase-matching spectra of two nonlinear-optical sum-frequency generation experiments at 1) high temperatures and 2) cryogenic temperatures. Furthermore, we present an approach to reduce the impact of photorefraction which is compatible with cryogenic operation. This comprises an auxiliary light source, propagating in the same waveguide, which is used to restore phase-matching spectra impacted by photorefraction, as well as reduce pyroelectric effects. Our work provides an alternative route to photorefraction management applicable to cryogenic environments, as well as in situations with tight energy budgets like space applications.
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All authors Nina A. Lange, René Pollmann, Michael Rüsing, Michael Stefszky, Maximilian Protte, Raimund Ricken, Laura Padberg, Christof Eigner, Tim J. Bartley, Christine Silberhorn

Atmospheric and Oceanic Physics · Cross-listed from astro-ph.IM

Distance-Independent Atmospheric Refraction Correction for Accurate Retrieval of Fireball Trajectories

Jaakko Visuri, Maria Gritsevich and Janne Sievinen

Accurate determination of fireball direction is essential for retrieving trajectories and velocities. Errors in these measurements have significant implications, affecting the calculated pre-impact orbit, influencing mass estimates, and impacting the accuracy of dark flight simulations, where applicable. Here we implement a new atmospheric refraction correction technique that addresses a significant aspect previously overlooked in the field of meteor science. Traditional refraction correction techniques, originally designed for objects positioned at infinite distances, tend to overcompensate when applied to objects within the Earth's atmosphere. To rectify this issue, our study introduces the concept of the atmospheric refraction delta z correction technique, involving the artificial elevation of the observer site height above sea level. We utilize analytically derived formulas for the delta z correction in conjunction with commonly used refraction models, validating these results against a numerical solution that traces light rays through the atmosphere. This ray-tracing model is applied to finely meshed atmospheric layers, yielding precise correction values. We evaluate multiple sources of error in order to quantify the achievable accuracy of the proposed method. Our approach (1) enables the determination of fireball positions with improved astrometric accuracy, (2) removes the explicit dependence on the fireball distance from the observer or its height above Earth's surface within the limits imposed by realistic atmospheric variability, and (3) simplifies meteor data processing by providing a robust framework for analyzing low-elevation fireball observations, for which atmospheric refraction is significant and is automatically corrected by the method. As a result of this work, we provide open, publicly accessible software for calculating the delta z correction.
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Biological Physics

On the effect of force on DNA in the Peyrard-Bishop-Dauxois model

I.V. Likhachev and V.D. Lakhno

This paper presents a numerical study of the dynamics of DNA double helix breakage under the influence of external forces using the Peyrard-Bishop-Dauxois (PBD) model. The PBD model represents DNA as a chain of nonlinearly coupled oscillators, which makes it possible to analyze the processes of melting and mechanical denaturation. The main focus is on cases where an external force is applied to the terminal or central site of a DNA molecule, simulating stretching at a constant rate. The critical force required to break hydrogen bonds, which depends on the point of application of the force, is calculated. It is found that the denaturation process occurs stepwise, with characteristic peaks in the force-time graphs. The phenomenon of hysteresis under periodic exposure to external forces is also studied, which is important for understanding energy losses and heating of the system.
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Optics

Coherent Mode Decoupling: A Versatile Framework for High-Throughput Partially Coherent Light Transport

Han Xu, Ming Li, Shuo Wang et al. (+5 more)

Accurate and efficient wave-optics simulation of partially coherent light transport systems is critical for the design of advanced optical systems, ranging from computational lithography to diffraction-limited storage rings (DLSR). However, traditional approaches based on Coherent Mode Decomposition suffer from high computational costs due to the propagating massive sets of two-dimensional modes. In this paper, we propose the Coherent Mode Decoupling (CMDC) algorithm, a high-throughput computational framework designed to accelerate these simulations by orders of magnitude without compromising physical fidelity. The method factorizes 2D modes into efficient one-dimensional (1D) components, while crucially incorporating a subspace compression strategy to capture non-separable coupling effects. We demonstrated the generality and robustness of this framework in applications ranging from computational lithography to coherent beamlines of DLSR.
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All authors Han Xu, Ming Li, Shuo Wang, Zhe Ren, Peng Liu, Yi Zhang, Yuhui Dong, Liang Zhou

Optics

Explainable deep-learning detection of microplastic fibers via polarization-resolved holographic microscopy

Jan Appel, Marika Valentino, Lisa Miccio et al. (+6 more)

Reliable identification of microplastic fibers is crucial for environmental monitoring but remains analytically challenging. We report an explainable deep-learning framework for classifying microplastic and natural microfibers using polarization-resolved digital holographic microscopy. From multiplexed holograms, the complex Jones matrix of each fiber was reconstructed to extract polarization eigen-parameters describing optical anisotropy. Statistical descriptors of nine polarization characteristics formed a 72-dimensional feature vector for a total of 296 fibers spanning six material classes, including polyamide 6, polyethylene terephthalate, polyamide 6.6, polypropylene, cotton and wool. The designed fully connected deep neural network achieved an accuracy of 96.7 % on the validation data, surpassing that of common machine-learning classifiers. Explainable artificial intelligence analysis with Shapley additive explanations identified eigenvalue-ratio quantities as dominant predictors, revealing the physical basis for classification. An additional reduced-feature model with the preserved architecture exploiting only these most significant eigenvalue-based characteristics retained high accuracy (93.3 %), thereby confirming their dominant role while still outperforming common machine-learning classifiers. These results establish polarization-based features as distinctive optical fingerprints and demonstrate the first explainable deep-learning approach for automated microplastic fiber identification.
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All authors Jan Appel, Marika Valentino, Lisa Miccio, Vittorio Bianco, Raffaella Mossotti, Giulia Dalla Fontana, Miroslav Ježek, Pietro Ferraro, Jaromír Běhal

Space Physics

Multi-Scale Irregularities Product: a data product utilizing the high-resolution Swarm plasma density data for space weather applications

Yaqi Jin, Luca Spogli, Daria Kotova et al. (+5 more)

We use the high-resolution Swarm faceplate plasma density data at 16 Hz to develop a set of parameters that can characterize multi-scale ionospheric structures and irregularities along the Swarm orbit. We present the methods for calculating density gradients over different window sizes, rate of change of density index, power spectral density and the spectral slope at both low and high latitudes. The faceplate plasma data are not continuously available through the years. However, about 8 years of data from Swarm A are processed from late 2014 to the end of 2025. Some statistical results from Swarm A are presented. The variations of plasma structures and irregularities are dependent on solar activity, season, local time and geomagnetic activities, and the variations show different patterns between low and high latitudes. For example, the high-latitude ionosphere is characterized by persistent ionospheric structures and irregularities poleward of 60 magnetic latitude, while the low-latitude ionospheric irregularities are only dominant during 19-01 local time near the magnetic equator. The occurrence of steep spectral slope at high latitudes shows clear seasonal variations, i.e., it maximizes during local summer and minimizes during local winter in both hemispheres. However, the occurrence of steep spectral slope at low latitudes is only sensible when significant plasma structures and irregularities are present. We further calculate the histogram of spectral slopes at low latitudes when the rate of change of density index is enhanced. The histogram resembles a Gaussian distribution with an expected value of 1.97. The processed data are available to the wider community. Given the high resolution, this new data product will be useful for the scientific communities that are interested in the magnetosphere-ionosphere-thermosphere coupling and near-Earth space environment.
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All authors Yaqi Jin, Luca Spogli, Daria Kotova, Alan Wood, Jaroslav Urbář, Lucilla Alfonsi, Mainul Mohammed Hoque, Wojciech Miloch

Optics

Monolithic tantalum pentoxide microrings with intrinsic Q factors exceeding 4X10(6)

Xinzhi Zheng, Yixuan Yang, Renhong Gao et al. (+3 more)

Tantalum pentoxide (Ta2O5), as a silicon-photonic-compatible material platform, has garnered significant attention for high-performance integrated photonics due to its exceptional properties: a broad transparency window spanning from 0.28 um to 8 um, a moderate refractive index of 2.05 at 1550 nm, and an impressive nonlinear refractive index of 7.2X10^(-19) m^2/W. Despite these advantages, achieving low-loss fabrication of monolithic microrings on the Ta2O5 platform remains challenging due to its inherent hardness and brittleness, which often result in rough sidewalls and significant scattering losses. In this work, we successfully demonstrated monolithic Ta2O5 microring resonators with exceptionally high intrinsic and loaded quality (Q) factors. This was accomplished through the innovative application of photolithography-assisted chemo-mechanical etching (PLACE) technology. By optimizing the coupling region between the microring and the bus waveguide, as well as meticulously controlling surface roughness during fabrication, we achieved near-critical coupling in the resulting microrings. The devices exhibited loaded Q factors of 2.74X10(6) in the telecom band without employing expensive electron-beam lithography, showing an intrinsic Q factor as high as 4.47X10(6) and a low propagation loss of only 0.0732 dB/cm - representing the highest results reported for strongly confined Ta2O5-based microring resonators to date. This work paves the way for the development of advanced photonic devices on the Ta2O5 platform with low manufacturing cost, including low-threshold microlasers, highly sensitive sensors, broad bandwidth supercontinuum sources, and optical frequency combs.
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All authors Xinzhi Zheng, Yixuan Yang, Renhong Gao, Lingling Qiao, Jintian Lin, Ya Cheng

Optics

Blue to Near-IR Integrated PZT Silicon Nitride Modulators for Quantum and Atomic Applications

Nick Montifiore, Andrei Isichenko, Nitesh Chauhan et al. (+8 more)

Modulation and control of lasers and optical signals is necessary for trapped-ion and cold neutral atom quantum systems. Given the diversity of atomic species, experimental modalities, and architectures, integrated optical modulators designed to operate across the visible to near-infrared spectrum are a key step towards portable, robust, and compact quantum computers, clocks, and sensors. Integrated optical modulators that are wavelength-independent, CMOS-compatible, and capable of maintaining low waveguide losses and a high resonator quality factor, DC-coupled broadband frequency response, and low power consumption, are essential for scalable photonic integration. Yet progress towards these goals has remained limited. Here we demonstrate four types of integrated stress-optic lead zirconate titanate (PZT) silicon nitride modulators: a coil Mach-Zehnder modulator, a coil pure phase modulator, and bus-coupled and add-drop ring resonator modulators, with operation from 493 nm to 780 nm. The coil MZM operates at 532 nm with a V${\pi}$ of 2.8V, a 0.4 MHz 3-dB bandwidth, and an extinction ratio of 21.5dB. The coil phase modulator operates at 493 nm with a V${\pi}$ of 2.8V and low residual amplitude modulation of -34 dB at a 1kHz offset. The bus-coupled ring resonator modulator operates at 493 nm and the add-drop ring resonator modulator operates at 780 nm. The ring-based modulators have an intrinsic quality factor of 3.4 million and 1.9 million, a linear tuning strength of 0.9 GHz/V and 1 GHz/V, and a 3-dB bandwidth of 2.6 MHz and 10 MHz, respectively. All four modulator designs maintain the low optical waveguide loss of SiN, are DC coupled with broadband frequency response, operate independent of wavelength, and consume only tens of nW per actuator. Such solutions unlock the potential for further integration with other precision SiN components to realize chip-scale atomic and quantum systems.
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All authors Nick Montifiore, Andrei Isichenko, Nitesh Chauhan, Jiawei Wang, Andrew S. Hunter, Mark W. Harrington, Rahul Chawlani, Ryan Q. Rudy, Iain Kierzewski, Michael Pushkarsky, Daniel J. Blumenthal