Optics · Cross-listed from cond-mat.mes-hall
Plasmonic enhancement of the infrared radiation absorption in an ultrathin InSb layer
Yurii M. Lyaschuk, Vadym V. Korotyeyev, Viacheslav A. Kochelap et al. (+1 more)
Indium antimonide (InSb) is a fundamental material for infrared radiation detectors based on interband transitions. Its narrow bandgap enables detection of infrared radiation within the $3-5 \mu m$ atmospheric window, while its high
quantum efficiency ensures excellent sensitivity in InSb-based detectors. We propose a plasmonic structure that significantly enhances infrared absorption in an ultrathin InSb film. The resonant characteristics of this plasmonic enhancement effect could serve as a foundation for developing highly sensitive multi-color detectors.
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All authors Yurii M. Lyaschuk, Vadym V. Korotyeyev, Viacheslav A. Kochelap, Oleksandr O. Raichev
Chemical Physics
Nested State and Degradation Estimation of a Satellite Battery with In-flight Data
Linda Bolay, Omar Mendoza-Hernandez, Eiji Hosono et al. (+6 more)
Li-ion batteries are essential for the energy supply of satellites. The accurate estimation of their states is important for the reliable and safe operation in space. This paper introduces a new
algorithm for the estimation of SOC and SOH. The multi-timescale
algorithm combines Kalman filters and physics-based models for batteries. We use a P2D model combined with a degradation model that describes capacity fading due to SEI growth. The state estimation
algorithm combines two extended Kalman filters for the two states evolving on different timescales, with one filter nested within the other one. We test the
algorithm with synthetic data as well as with in-flight data from Japanese satellite REIMEI. The
algorithm adequately estimates the SOC and SOH in both cases. Furthermore it gives insight into the reliability of the chosen model.
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All authors Linda Bolay, Omar Mendoza-Hernandez, Eiji Hosono, Daisuke Asakura, Sayoko Shironita, Minoru Umeda, Yoshitsugu Sone, Arnulf Latz, Birger Horstmann
Fluid Dynamics
Helicity controls the direction of fluxes in rotating turbulence
Sébastien Gomé and Anna Frishman
Turbulence sustains out-of-
equilibrium energy fluxes shaped by conservation laws. Three-dimensional flows conserve energy and sign-indefinite helicity, both being transferred to small scales. Yet in 3D rotating
turbulence, energy is observed to flow simultaneously toward large-scale two-dimensional structures and toward small-scale three-dimensional waves. We uncover the origin of this dual behavior. When sufficiently fast inertial waves interact with a large-scale 2D flow, they conserve their helicity separately by sign, enforcing an inverse transfer of energy from 3D waves to 2D motions and promoting spectral condensation. Slower modes, by contrast, exchange helicity across sectors of opposite helicity signs and drive a forward transfer, like in non-rotating
turbulence. Using a mean-wave kinetic theory, we derive analytical expressions for these competing bi-directional transfers and quantitatively predict the rotation- and Reynolds-number dependence of the large-scale 2D flow in fully nonlinear simulations, unifying the picture from small to infinite rotation.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Benchmarking Universal Machine Learning Interatomic Potentials for Supported Nanoparticles: Decoupling Energy Accuracy from Structural Exploration
Jiayan Xu, Abhirup Patra, Amar Deep Pathak et al. (+3 more)
Supported nanoparticle catalysts are widely used in the chemical industry. Computational modeling of supported nanoparticles based on density functional theory (DFT) often involves structural searches of stable local minimum energy configurations and molecular dynamics simulations at finite temperature. These are computationally demanding tasks that are intractable within DFT for large systems. In the last two decades, machine learning interatomic potentials (MLIPs) have been successfully used to substantially increase the size and time scales accessible to simulations approximating DFT accuracy. However, training reliable MLIPs is non-trivial as it requires many costly DFT calculations. Recently, several universal MLIPs (uMLIPs) have been developed, which are trained on large
datasets that cover a wide range of molecules and materials. Here, we
benchmark the accuracy and the efficiency of these uMLIPs in describing Cu nanoparticles supported on Al$_2$O$_3$ surfaces against our domain-specific DP-UniAlCu model. We find that the MACE-OMAT can reproduce reasonably well the low-energy structures found in global optimization at an energy accuracy comparable to DP-UniAlCu. Interestingly, the MatterSim-v1.0.0-1M model, which exhibits larger deviations in the binding energies, can find even more stable configurations than the other two models in some supported nanoparticle sizes, showing its capability in structure exploration. For MD simulations, MACE-OMAT and MatterSim-v1.0.0-1M can qualitatively reproduce the mean-squared displacements of Cu atoms (MSD$_\mathrm{Cu}$) predicted by DP-UniAlCu, albeit at roughly two orders of magnitude higher cost. We demonstrate that the uMLIPs can be very useful in simulating supported nanoparticles even without any fine-tuning, though their reduced efficiency remains a limiting factor for large-scale simulations.
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All authors Jiayan Xu, Abhirup Patra, Amar Deep Pathak, Sharan Shetty, Detlef Hohl, Roberto Car
Plasma Physics · Cross-listed from astro-ph.HE
Lagrangian versus Eulerian Methods for Toroidally-Magnetized Isothermal Disks
Yashvardhan Tomar and Philip F. Hopkins
A number of simulations have seen the emergence of strongly-toroidally-magnetized
accretion disks from interstellar medium inflows. Recently, Guo et al. 2025 (G25) studied an idealized test problem of toroidally-magnetized disks in isothermal ideal MHD with an Eulerian static-mesh method, and argued the midplane behavior changes qualitatively (with a significant loss of toroidal
magnetic flux) when the the thermal scale-length is resolved ($\Delta x < H_{\rm thermal}$). We rerun the G25 test problem with two Lagrangian methods: meshless finite-mass, and meshless finite-volume. We show that Lagrangian methods reproduce the high-resolution ($\Delta x \ll H_{\rm thermal}$) Eulerian G25 results. At low resolution ($\Delta x \gg H_{\rm thermal}$), behaviors differ: Lagrangian methods still lose flux and evolve 'as close as possible' to the converged solution, while Eulerian methods show no
evolution. We argue this difference in convergence behavior is related to the ability of Lagrangian codes to follow flows to an arbitrarily thin midplane layer, analogous to the well-studied difference in Jeans fragmentation problems. This and results from other higher-resolution simulations and different codes suggest that the sustained midplane toroidal fields seen in recent Lagrangian multi-scale, multi-physics simulations cannot be a numerical resolution effect, and some physical difference between those simulations and the G25 test problem explains their different behaviors.
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Instrumentation and Detectors
Development of a Modular Optically Detected Magnetic Resonance Setup for Optical Experiments in a Variable Temperature Insert
Anh Tong, Andreas Bauer, Markus Kleinhans et al. (+6 more)
We developed an optically detected
magnetic resonance (ODMR) setup designed for compatibility with a widely used, commercially available helium bath cryostat equipped with a variable temperature insert. The optical path extends nearly two meters, spanning the full length of the cryostat insert, enabling excitation of the nitrogen-vacancy (NV) centers and detection of the resulting fluorescence from outside the cryostat. The setup preserves optical
alignment and beam quality along this extended path allowing integration into existing cryogenic systems without significant modifications. We demonstrate the setup's performance by measuring the temperature dependence of the resonance signal and its behavior under small applied
magnetic fields, as well as the
magnetic transition of a SrRuO$_3$ sample, thereby showcasing the feasibility of NV magnetometry on a sample in constrained cryogenic environments.
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All authors Anh Tong, Andreas Bauer, Markus Kleinhans, James S. Schilling, Christian H. Back, Karl D. Briegel, Fabian A. Freire-Moschovitis, Dominik B. Bucher, Christian Pfleiderer
Applied Physics · Cross-listed from cond-mat.supr-con
Fluorine-substitution-dependent phase diagram and superconducting properties of Sm-based oxypnictides synthesized by a high-pressure growth technique
Mohammad Azam, Tatiana Zajarniuk, Ryszard Diduszko et al. (+5 more)
A series of SmFeAsO1-xFx (Sm1111) bulk samples (x = 0.05 to 0.40) are synthesized by an in-situ cubic-anvil high-pressure technique at 4 GPa and systematically characterized through structural, microstructural, Raman, transport, and
magnetic measurements. Structural analysis confirms that the tetragonal Sm1111 phase remains dominant across the entire substitution range, with
lattice parameters decreasing smoothly as fluorine content increases, demonstrating effective incorporation of F even in the overdoped regime (x = 0.4). Raman spectroscopy provides complementary, local-phase-sensitive evidence that supports the structural analysis and confirms fluorine substitution in the main Sm1111 phase. In the underdoped region, the superconducting transition temperature (Tc) is enhanced by 10-17 K and the critical current density (Jc) is increased by up to an order of magnitude compared with conventionally synthesized samples at the ambient pressure. The upper critical field, estimated using the WHH model, reaches values approaching 200 T, reflecting strong paramagnetic limitation and multiband effects. TAFF analysis reveals a power-law field dependence of the activation energy, consistent with collective
vortex pinning in polycrystalline iron-based
superconductors. The superconducting phase diagram constructed from Tc and Jc versus fluorine content reveals a dome-like trend, with a maximum Tc of 57 K and Jc of 10^4 A cm^-2 at the optimal doped region. Comparison with conventionally synthesized Sm1111 samples demonstrates that high-pressure growth significantly extends the effective fluorine substitution range and enhances the superconducting performance, particularly in the underdoped regime. These results establish high-pressure fluorine substitution as an effective materials-engineering approach for tuning the phase diagram and optimizing the superconducting properties of Sm1111.
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All authors Mohammad Azam, Tatiana Zajarniuk, Ryszard Diduszko, Taras Palasyuk, Cezariusz Jastrzebski, Andrzej Szewczyk, Hiraku Ogino, Shiv J. Singh
Optics
Quantum open system description of a hybrid plasmonic cavity
Marco Vallone
We present a unified
quantum open system framework for lossy plasmonic cavities in which coherent dynamics, relaxation, dephasing, and irreversible absorption are treated on equal footing. The Dyson equation for the cavity
photon propagator in the random-phase approximation yields a complex self-energy S that accounts for both the renormalization and the damping of hybrid plasmon-
photon modes (polaritons, in a quasi-particle description). Tracing out the electronic and photonic environments leads to a Liouvillian for the upper (UP) and lower (LP) polaritonic branches, incorporating leakage through the imaginary part of the self-energy, internal UP-LP scattering rates, and dephasing. Time
evolution equations for polariton populations, interbranch coherence, and driven amplitudes in closed form also provide analytic expressions for their steady-state values, the quench rate of UP-LP oscillations and polaritonic lineshapes, valid in the limit of low polaritonic density, but covering light-matter ultrastrong coupling. The theory establishes a self-consistent description of dissipative polariton dynamics in plasmonic and nanophotonic cavities, directly applicable to response spectra, time-domain measurements, and dissipation engineering.
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Atomic Physics · Cross-listed from cond-mat.mtrl-sci
Modeling Compressive Instability in Two-Dimensional Ti2COx MXenes
Hossein Darban
In practical applications, MXenes are often subjected to a variety of loads, including compression. While their mechanical response under different loading conditions, such as tensile loading, has been extensively studied, their compressive instability remains largely unexplored. The compressive and post-buckling behavior of Ti2C and Ti2CO2 MXene nanosheets is studied using molecular dynamics (MD) simulations and a nonlocal formulation. The employed interatomic potential is first validated against experimental and density functional theory (DFT) data for structural and mechanical properties. The results indicate that classical continuum mechanics underestimates the buckling strains, whereas the nonlocal formulation adequately captures the observed response. A systematic examination of various defect types up to a defect fraction of 3% reveals that while isolated point defects primarily reduce the critical buckling stress, vacancy clusters significantly alter the buckling mode shapes. Lateral confinement pressure and oxygen surface termination substantially increase the buckling stress. Atomistic analysis reveals opposite stress states in the top and bottom Ti layers due to
curvature-induced strain gradients. Under biaxial compression, the nanosheet buckles in a dome-like shape, whereas shear loads produce elliptical deflection modes. The presented findings may stimulate future studies on MXene morphological transformations, such as the development of nanotube, nanoscroll, and folded architectures.
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Classical Physics
Identifying bound states in the continuum by their boundary sensitivity
Vincent Laude and David Röhlig
We introduce a method for effectively identifying bound states in the continuum (BICs) - notably without computing the imaginary part of the
eigenvalues - thereby simplifying the modeling and potentially reducing computation time. In real, open, physical systems, wave decay must be taken into account. This phenomenon is captured by complex-valued solutions of the harmonic wave equation, the so-called quasi-normal modes (QNMs). BICs, however, constitute a limiting class of solutions that do not radiate energy to infinity and are therefore, by their very nature, insensitive to the region surrounding the physical structure. Building on this observation, we identify BICs by varying the external boundary conditions that close the computational domain; the resulting behavior is displayed in the form of spectral histograms. We demonstrate the effectiveness of this procedure by comparing it with conventional QNM analysis employing perfectly matched layers. Two representative examples are considered: a periodic system of permeable inclusions supporting guided Rayleigh-Bloch waves, and a whispering-gallery resonator constructed from this configuration. Finally, we provide a mathematical explanation for the method's validity by deriving integral reciprocity statements.
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History and Philosophy of Physics · Cross-listed from quant-ph
From Kinematics to Interference: Operational Requirements for the Quantum Principle of Relativity
Mikołaj Sienicki and Krzysztof Sienicki
The
quantum principle of relativity (QPR) puts forward an ambitious idea: extend special relativity with a formally superluminal branch of Lorentz-type maps, and treat the resulting consistency constraints as hints about why
quantum theory has the structure it does [1]. The discussion that followed has emphasized a basic point: writing down coordinate maps is not the same thing as providing a physical theory. In particular,
quantum superposition is not operationally defined by drawing multiple paths on paper: it is defined by what happens when alternatives recombine in an interference loop [2, 3]. In parallel, careful 1+1 analyses have clarified how sign conventions and time-orientation choices enter the superluminal formulas [4]. Finally, tachyonic QFT proposals suggest a possible mathematical bridge via an enlarged (twin)
Hilbert space [5], although this proposal remains contested (e.g., on commutator covariance and microcausality grounds) [6]. The aim of this short note is organizational. We keep three layers separate: (K) kinematics (which maps exist and what they preserve), (O) operational content (what an experiment must actually reproduce, especially closed-loop interference), and (D/B) dynamics and bridges (how amplitudes and probabilities are generated, and how subluminal and superluminal sectors might be linked). The goal is not relativity derives
quantum theory, but a clear checklist of what must be added for that ambition to become a well-posed programme.
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Optics
Breaking the bandwidth-efficiency trade-off in soliton microcombs via mode coupling
Yang Liu, Andreas Jacobsen, Thibault Wildi et al. (+9 more)
Dissipative Kerr
solitons in optical microresonators have emerged as a powerful tool for compact and coherent frequency comb generation. Advances in nanofabrication have allowed precise dispersion engineering, unlocking octave-spanning
soliton combs that are essential for applications such as optical atomic clocks, frequency synthesis, precision spectroscopy, and astronomical spectrometer calibration. However, a key challenge hindering their practical deployment is the intrinsic bandwidth-efficiency trade-off: achieving broadband
soliton generation requires large pump detuning, which suppresses power coupling and limits pump-to-comb conversion efficiencies to only a few percent. Recent efforts using pulsed pumping or coupled-resonator architectures have improved efficiency to several tens of percent, yet their bandwidths remain below one-tenth of an octave, inadequate for applications demanding wide spectral coverage. Here, we overcome this limitation by harnessing mode interactions between spatial modes within a single microresonator. The mode hybridization creates an additional power-transfer channel that supports large pump detuning while maintaining strong pump-to-resonator coupling, enabling broadband
soliton formation at substantially reduced pump power. Using this approach, we demonstrate an octave-spanning
soliton microcomb with a record pump-to-comb conversion efficiency exceeding 50%. These results resolve the fundamental bandwidth-efficiency dilemma in
soliton microcombs and paves the way toward fully-integrated, high-efficiency, ultrabroad comb sources for next-generation photonic systems.
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All authors Yang Liu, Andreas Jacobsen, Thibault Wildi, Yanjing Zhao, Chaochao Ye, Yi Zheng, Camiel Op de Beeck, José Carreira, Michael Geiselmann, Kresten Yvind, Tobias Herr, Minhao Pu
Optics
Anisotropic Response in Metamaterials with Elliptically Perforated Plates: Applications to Near-Field Radiative Heat Transfer
J. E. P'erez-Rodr'iguez, R. Esquivel-Sirvent and A. Camacho de la Rosa
Metamaterials with tunable optical properties provide a versatile platform for controlling electromagnetic interactions at the nanoscale. This study explores the anisotropic thermal behavior of metamaterials composed of planar plates perforated with periodic arrays of cylinders possessing elliptical cross sections. In contrast to conventional circular perforations, elliptical geometries inherently break rotational
symmetry, introducing anisotropy in the effective electromagnetic and thermal response of the structure. Using a fluctuation electrodynamics framework combined with full-wave numerical simulations, we quantify the near-field radiative heat transfer between such elliptically perforated plates as a function of ellipse orientation, aspect ratio, and separation distance. The results reveal that elliptical perforations enable enhanced spectral and directional control of evanescent mode coupling and surface polariton excitation, leading to significant modulation of the near-field heat flux. These findings highlight the potential of geometrically engineered anisotropy for advanced thermal management and energy conversion applications, and offer new design strategies for the development of thermally functional metamaterials operating in the near-field regime.
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Applied Physics
Debt, Growth, and the Carbon Lock-In
Silvia Montagnani, Barnabe Ledoux and David Lacoste
Despite decades of
climate policy and rapid improvements in energy efficiency, global CO2 emissions continue to rise, suggesting the presence of structural drivers that offset efficiency gains. Here we identify financial leverage as a key mechanism underpinning this persistent overshoot. We develop a
stochastic macro-financial model linking credit dynamics, economic growth, bankruptcy risk, and cumulative carbon emissions. The model shows that debt-financed growth systematically amplifies cumulative emissions, locking economies into high-carbon trajectories even as emissions intensity declines. This arises from a double constraint: debt repayment requires sustained growth, while growth remains energy-dependent and thus generates emissions. When growth becomes increasingly dependent on leverage, financial instability and cumulative emissions rise, while gains in real wealth diminish, revealing a leverage frontier beyond which additional credit primarily generates risk. Calibrating the model to multi-decade data for the US, China, France and Denmark, we find a robust coupling between debt accumulation, cumulative GDP and cumulative emissions across distinct economic structures. These results indicate that achieving net-zero targets requires aligning credit allocation with decarbonisation objectives
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Optics
Structured Light at the Extreme: Harnessing Spatiotemporal Control for High-Field Laser-Matter Interactions
Sergio Carbajo, Seung-Whan Bahk, Justin Baker et al. (+19 more)
This review charts the emerging paradigm of intelligent structured light for high-field
laser-matter interactions, where the precise spatiotemporal and vectorial control of light is a critical degree of freedom. We outline a transformative framework built upon three synergistic pillars. First, we survey the advanced electromagnetic toolkit, moving beyond conventional spatial light modulators to include robust static optics and the promising frontier of
plasma light modulators. Second, we detail the optimization engine for this high-dimensional design space, focusing on physics-informed digital twins and AI-driven inverse design to automate the discovery of optimal light structures. Finally, we explore the groundbreaking applications enabled by this integrated approach, including programmable electron beams, orbital-angular-momentum-carrying {\gamma}-rays, compact THz accelerators, and robust communications. The path forward necessitates overcoming grand challenges in material science, real-time adaptive control at MHz rates, and the extension of these principles to the
quantum realm. This review serves as a call to action for a coordinated, interdisciplinary effort to command, rather than merely observe, light-matter interactions at the extreme.
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All authors Sergio Carbajo, Seung-Whan Bahk, Justin Baker, Andrea Bertozzi, Abhimanyu Borthakur, Antonino Di Piazza, Andrew Forbes, Spencer Gessner, Jack Hirschman, Maciej Lewenstein, Yuhang Li, Inhyuk Nam, Eileen Otte, James Rozensweig, Yijie Shen, Liwei Song, Ye Tian, Yu Wang, Yuntian Wang, Logan Wright, Xiaojun Wu, Hao Zhang
Computational Physics · Cross-listed from hep-ph
CNN on `Top': In Search of Scalable & Lightweight Image-based Jet Taggers
Rajneil Baruah, Subhadeep Mondal, Sunando Kumar Patra et al. (+1 more)
While
Transformer-based and standard Graph Neural Networks (GNNs) have proven to be the best performers in classifying different types of jets, they require substantial computational power. We explore the scope of using a lightweight and scalable version of EfficientNet architecture, along with global features of the jet. The end product is computationally inexpensive but is capable of competitive performance. We showcase the efficacy of our network in tagging top-
quark jets in a sea of other light
quark and
gluon jets. The work also sheds light on the importance of global features for both the accuracy and the apparent redundancy of the network's complexity.
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All authors Rajneil Baruah, Subhadeep Mondal, Sunando Kumar Patra, Satyajit Roy
Computational Physics
Engineered Inclined Energy Landscapes Enabling Free Flow of Magnetic Microstructures for Artificial Neuron Applications
Anmol Sharma, Ranjeet Kumar Brajpuriya, Vivek K. Malik et al. (+2 more)
Spintronic-based
brain-inspired neuromorphic computing has recently attracted significant
attention due to the exceptional properties of
magnetic microstructures, including nanoscale dimensions, high stability, and low energy consumption. Despite these advantages, the practical integration of such microstructures into functional devices remains challenging. Fabrication processes are often complex and prone to
stochastic effects, such as unwanted pinning and thermal-induced instabilities, which limit device reliability and scalability. Addressing these challenges is crucial for advancing spintronic neuromorphic architectures toward real-world applications. Thus, to reduce these effects we have proposed a design which is experimentally feasible and require less energy as compared to existing one. By engineering the system anisotropy into a sawtooth-type energy landscape, we have achieved free flow of these microstructures and successfully emulated integrate and fire (IF) function of biological
neuron. Thus, proposed design presents an experimentally reliable and energy efficient external stimuli approach for tailoring
magnetic microstructures dynamic behaviours, resulting in low energy consumption of 23.66 fJ per spike paving the way for the development of skyrmion-based futuristic neuromorphic computing device applications.
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All authors Anmol Sharma, Ranjeet Kumar Brajpuriya, Vivek K. Malik, Vishakha Kaushik, Sachin Pathak
Optics
Millimetre-Wave Comb Generated by an Optical Microcomb
Luke Peters, Antonio Cutrona, Andrew R. Cooper et al. (+13 more)
Metrological-grade millimetre wave baseband comb sources covering the subterahertz window are a key building block for next-generation wireless communications, precision sensing, and positioning systems. While optical microcombs have set new
benchmarks in ultra-low phase noise single-frequency microwave generation, to date, no microcomb source has directly produced a millimetre-wave baseband comb. Here, we present a 50 GHz repetition rate carrier-envelope offset estabilised millimetre-wave baseband comb source covering the sub-terahertz region, generated from an optical microcomb source. Our microresonator-filtered microcomb enables direct, coherent downconversion via photoconductive
antennas, even without external amplification. The metrological-grade optical
soliton source produces single-cycle, naturally zero carrier-envelope offset millimetrewave baseband combs. It supports time-domain spectroscopy without any need to temporally align the source and detection pulses, as the ultra-high phase coherence allows significant differences between the optical paths of the source and detection pulses, which we tested over 8m, finding no degradation even in freerunning operation. Finally, the multisoliton operation regime provides a simple way of spectrally tailoring the microwave output by selecting different optical
soliton states.
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All authors Luke Peters, Antonio Cutrona, Andrew R. Cooper, Luana Olivieri, Fedor Getman, Vittorio Cecconi, Nitish Paul, Debayan Das, Maxwell Rowley, Sai T. Chu, Brent E. Little, Roberto Morandotti, David J. Moss, Juan S. Totero Gongora, Alessia Pasquazi, Marco Peccianti
Optics
Frequency and intensity noise of a grating-tuned external-cavity quantum cascade laser
Irene La Penna, Tecla Gabbrielli, Cristina Rimoldi et al. (+6 more)
Quantum cascade
lasers (QCLs) are
semiconductor-
heterostructure devices known for their emission in the mid-infrared and THz spectral regions. Due to their operating regime, their intrinsic linewidth is significantly narrower compared to bipolar
semiconductor lasers. Here, we demonstrate that by implementing an external-cavity (EC) configuration based on a commercial diffraction grating, we have successfully induced a Fabry-Perot QCL to emit on a single mode with a broadly-tunable wavelength in the range 4.29-4.44 {\mu}m. This very simple setup enhances the
laser's performance in terms of threshold current and emitted power. We further prove that the EC configuration positively impacts the
laser's noise properties. In particular, the intrinsic linewidth is substantially reduced, the full linewidth is also decreased (depending on the integration timescale), and the relative intensity noise is slightly reduced. These characteristics, which hold within the whole tuning range, make the EC-QCL a good candidate for spectroscopy applications where broad tunability and narrow linewidth are highly demanded.
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All authors Irene La Penna, Tecla Gabbrielli, Cristina Rimoldi, Davide Mazzotti, Jérôme Faist, Luigi Consolino, Simone Borri, Paolo De Natale, Francesco Cappelli
Computational Physics
LEDDS: Portable LBM-DEM simulations on GPUs
Raphael Maggio-Aprile, Maxime Rambosson, Christophe Coreixas et al. (+1 more)
Algorithmic formulations of GPU programs provide a high-level alternative to device-specific code by expressing computations as compositions of well-defined parallel primitives (e.g., map, sort, reduce), rather than through handcrafted GPU kernels. In this work, we demonstrate that this paradigm can be extended to complex and challenging problems in computational physics: the simulation of granular flows and fluid-particle interactions. LEDDS, our open-source framework, performs fully coupled
Lattice Boltzmann – Discrete Element Method (LBM-DEM) simulations using only algorithmic primitives, and runs efficiently on single-GPU platforms. The entire workflow, including neighbor search, collision detection, and fluid-particle coupling, is expressed as a sequence of portable primitives. While the current implementation illustrates these principles primarily through
algorithms from the C++ Standard Library, with selective use of Thrust primitives for performance, the underlying concept is compatible with any HPC environment offering a rich set of parallel
algorithms and is therefore applicable across a wide range of modern GPU systems and future accelerators. LEDDS is validated through
benchmarks spanning both DEM and LBM-DEM configurations, including sphere and ellipsoid collisions, wall friction tests, single-particle settling, Jeffery's orbits, and particle-laden shear flows. Despite its high level of abstraction, LEDDS achieves performances comparable to those of hand-tuned CUDA solvers, while maintaining portability and code clarity. These results show that high-performance LBM-DEM coupling can be achieved without sacrificing generality or readability, establishing LEDDS as a blueprint for portable multiphysics frameworks based on algorithmic primitives.
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All authors Raphael Maggio-Aprile, Maxime Rambosson, Christophe Coreixas, Jonas Latt
Plasma Physics
Operator Formalism for Laser-Plasma Wakefield Acceleration
Mostafa Behtouei, Carlos Salgado Lopez and Giancarlo Gatti
In this paper, we develop an operator-based framework for
laser–
plasma wakefield acceleration (LPWA) in capillary discharges, providing a compact and systematic description of the coupled dynamics of
laser fields and
plasma response. The formalism employs key operators: the transverse modal operator $\hat{K}$, the nonlinear
plasma operator $\hat{N}[\Psi]$, the
plasma oscillation operator $\hat{\Omega}_p^{\,2}$, and the ponderomotive source operator $\hat{\alpha}$, which together describe mode coupling,
plasma oscillations, and nonlinear feedback induced by the ponderomotive force. In the linear regime, the system is characterized by invariant subspaces associated with stable modal structures, while nonlinear interactions break these invariances, leading to mode mixing and complex dynamics. The approach establishes a direct connection between LPWA and
Hilbert-space operator theory, including the invariant subspace, providing a formal mathematical interpretation of energy transfer and wakefield formation. Furthermore, the operator formalism integrates with neural operator methods, allowing efficient approximation of $\hat{N}$ and $\hat{\alpha}$ for reduced-order modeling and predictive control. This hybrid physics–AI framework offers a robust foundation for modeling, analysis, and optimization of high-intensity
laser–
plasma interactions in next-generation accelerator experiments.
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Instrumentation and Detectors
Characterization of thin optical filters for high purity Cherenkov light readout from scintillating crystals
Andrea Benaglia, Flavia Cetorelli, Marco Toliman Lucchini et al. (+3 more)
A hybrid dual-readout calorimeter concept, comprising both electromagnetic and hadronic sections, has recently been proposed to meet the performance requirements of experiments at future e$^{+}$e$^{-}$
colliders. The front compartment consists of a homogeneous electromagnetic calorimeter made of high-density
crystals, each coupled to a pair of Silicon Photomultipliers (SiPMs) providing the simultaneous readout of scintillation and Cherenkov light. To efficiently detect Cherenkov
photons in the presence of dominant scintillation signals, an optical filter is placed in front of one of the two SiPMs to suppress
photons in the wavelength region corresponding to that of scintillation emission. In this study, PWO, BGO, and BSO
crystals with different dimensions were tested to measure their scintillation light yield and decay time, as well as their transmission and emission spectra. A set of $\sim 100~\rm \mu m$-thick optical filters was also characterized by measuring their transmittance curves. The experimental results were used to model and estimate the expected filter performance in attenuating scintillation light for the various
crystals. The performance of each filter was experimentally validated by measuring the
crystal light output with and without the filter using a $^{22}$Na radioactive source and a LYSO:Ce
crystal, confirming the accuracy of the calculations. The results show that interference filters are unsuitable for this application because their transmittance strongly depends on the
photon incidence angle. Conversely, two absorptive long-pass filters with cutoff wavelengths around 590 nm were found to block more than 99% of the scintillation light from PWO
crystals, satisfying the calorimeter specifications.
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All authors Andrea Benaglia, Flavia Cetorelli, Marco Toliman Lucchini, Etiennette Auffray, Louis Roux, Julie Delenne
Chemical Physics · Cross-listed from quant-ph
Convergence of sample-based quantum diagonalization on a variable-length cuprate chain
L. Andrew Wray, Cheng-Ju Lin, Vincent Su et al. (+1 more)
Sample-based
quantum diagonalization (SQD) is an
algorithm for hybrid
quantum-classical molecular simulation that has been of broad interest for application with noisy intermediate scale
quantum (NISQ) devices. However, SQD does not always converge on a practical timescale. Here, we explore scaling of the
algorithm for a variable-length molecule made up of 2 to 6 copper
oxide plaquettes with a minimal molecular orbital basis. The results demonstrate that enabling all-to-all connectivity, instituting a higher expansion order for the SQD
algorithm, and adopting a non-Hartree-Fock molecular orbital basis can all play significant roles in overcoming sampling bottlenecks, though with tradeoffs that need to be weighed against the capabilities of
quantum and classical hardware. Additionally, we find that noise on a real
quantum computer, the Quantinuum H2 trapped ion device, can improve energy convergence beyond expectations based on noise-free statevector simulations.
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All authors L. Andrew Wray, Cheng-Ju Lin, Vincent Su, Hrant Gharibyan
Computational Physics · Cross-listed from cs.LG
Amortized Inference of Multi-Modal Posteriors using Likelihood-Weighted Normalizing Flows
Rajneil Baruah
We present a novel technique for amortized posterior estimation using Normalizing Flows trained with likelihood-weighted importance sampling. This approach allows for the efficient inference of theoretical parameters in high-dimensional inverse problems without the need for posterior training samples. We implement the method on multi-modal
benchmark tasks in 2D and 3D to check for the efficacy. A critical observation of our study is the impact of the
topology of the base distributions on the modelled posteriors. We find that standard unimodal base distributions fail to capture disconnected support, resulting in spurious probability bridges between modes. We demonstrate that initializing the flow with a Gaussian Mixture Model that matches the cardinality of the target modes significantly improves reconstruction fidelity, as measured by some distance and divergence metrics. Finally, we apply this method to a curated problem in heavy flavour physics — the extraction of the Wolfenstein parameters from the CP asymmetry in $B^0\to J/\psi\,K^0$; it is
multimodal, non-Gaussian, and asymmetric in its mode weights — and compare the results against a well-converged Markov Chain Monte Carlo reference using different metrics.
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Atomic Physics
Exploring vibronic dynamics near a sloped conical intersection with trapped Rydberg ions
Abdessamad Belfakir and Weibin Li
We study
spin-
phonon coupled dynamics in the vicinity of a sloped conical intersection created by
laser coupling the electronic (
spin) and vibrational degrees of freedom of a pair of trapped Rydberg ions. We show that the shape of the potential energy surfaces can be engineered and controlled by exploiting the sideband transitions of the
crystal vibration and dipole-dipole interactions between Rydberg ions in the Lamb-Dicke regime. Using the sideband transition, we realize a sloped conical intersection whose cone axis is only tilted along one spatial axis. When the
phonon wavepacket is located in the potential minimum of the lower potential surface, the
spin and
phonon dynamics are largely frozen owing to the
geometric phase effect. When starting from the upper potential surface, the electronic and
phonon states tunnel to the lower potential surface, leading to a partial revival of the initial state. In contrast, the dynamics drastically change when the initial wavepackets are away from the conical intersection. The initial state is revived, and is almost entirely irrelevant to whether it is from the lower or upper potential surface. Complete Rabi oscillations of the adiabatic states are found when the wavepacket is initialized on the upper potential surface. The dynamics occur on the microsecond and nanometer scales, implying that Rydberg ions provide a platform for simulating nonadiabatic processes in the vicinity of a sloped conical intersection.
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Atomic Physics
First observation and measurement of the ${}^{198}\text{Hg}$ bosonic transition in an optical lattice clock
Clara Zyskind, Thomas Lauprêtre, Haosen Shang et al. (+4 more)
We report the first observation of the
magnetic-field-induced (5d10 6s2)1S0-(5d10 6s6p)3P0 transition in a bosonic isotope of mercury, 198Hg, realized in an optical
lattice clock. We characterize this new isotope, determining key features such as the quadratic Zeeman shift, the probe light shift, and the magic frequency. We also report a first comparison between the 198Hg optical
lattice clock and 87Sr. In this comparison, the 198Hg clock has a relative frequency stability of 6x10-16/sqrt(tau/s) and a total relative systematic uncertainty of 6.9x10-16. This comparison yields the first direct determination of the 198Hg/87Sr optical frequency ratio: 198Hg/87Sr = 2.629 315 734 684 118 1, with the same relative uncertainty.
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All authors Clara Zyskind, Thomas Lauprêtre, Haosen Shang, Benjamin Pointard, Rodolphe Le Targat, Jérôme Lodewyck, Sébastien Bize
Atomic Physics
Doppler Shift Mitigation in a Chip-Scale Atomic Beam Clock
Alexander Staron, Gabriela Martinez, Nicholas Nardelli et al. (+3 more)
Chip-scale microwave atomic systems based on thermal atomic beams offer a promising approach to realize low-power and low-drift clocks for timing holdover applications. Miniature beam clocks are expected to suppress many of the shifts that commonly limit existing chip-scale atomic clocks based on coherent population trapping, including collisional shifts and some light shifts. However, the beam geometry can amplify some challenges such as Doppler shifts, which generate a strong sensitivity to
laser frequency variation. Using a cm-scale 87Rb atom beam clock, we identify a surprisingly strong competition between Doppler shifts and resonant light shifts arising from asymmetric decay in the clock spectroscopy {\Lambda}-system. Leveraging this competition between Doppler and resonant light shifts, we demonstrate clock operation at specific, convenient experimental parameters consistent with zero sensitivity to
laser frequency variation and white-noise-limited clock frequency averaging for 1000 s of integration.
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All authors Alexander Staron, Gabriela Martinez, Nicholas Nardelli, Travis Autry, John Kitching, William McGehee
Optics
Adaptive Optics-Enhanced Michelson Interferometer for Spectroscopy of Narrow-Band Light Sources
Jesneil Lauren Lewis and Ayan Banerjee
Adaptive optics enables the deployment of interferometer-based spectroscopy without the need for moving parts necessary for scanning the interferometer arms. Here, we employ a Michelson Interferometer in conjunction with a Spatial Light Modulator (SLM) for determining the spectral profile of a narrow-band light source. Interestingly, we observe that the fringes across the interferometer output beam are inherently shifted in wavelength even when a constant phase profile is provided to the SLM. We calibrate the spectral shifts as a function of fringe spatial location by measuring the incident light spectrum at various points across the fringe pattern, and observe that the spectral peak traces out a `teardrop' shape, whose width is dependent on the spectral bandwidth of the source, the relative tilt and path difference between the two arms of the interferometer, and the divergence of the beam. Next, we demonstrate that this inherent spectral variation of the fringes can be used to perform fast single-snapshot spectroscopy of narrow-band light sources, while a time-varied phase profile provided to the SLM leads to multi-step spectroscopy with lower noise, higher resolution, and better contrast. Our findings establish that the Michelson Interferometer can be used to perform spectroscopy of any source within a certain spectral range from simple images of the fringe pattern, so as to facilitate exciting applications towards hyperspectral imaging.
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Data Analysis and Statistics · Cross-listed from quant-ph
Bayesian stepwise estimation of qubit rotations
Mylenne Manrique, Marco Barbieri, Assunta Di Vizio et al. (+4 more)
This work investigates
Bayesian stepwise estimation (Se) for measuring the two parameters of a
unitary qubit rotation. While asymptotic analysis predicts a precision advantage for SE over joint estimation (JE) in regimes where the
quantum Fisher information
matrix is near-singular ("sloppy" models), we demonstrate that this advantage is mitigated within a practical
Bayesian framework with limited resources. We experimentally implement a SE protocol using polarisation
qubits, achieving uncertainties close to the classical Van Trees bounds. However, comparing the total error to the ultimate
quantum Van Trees bound for JE reveals that averaging over prior distributions erases the asymptotic SE advantage. Nevertheless, the stepwise strategy retains a significant practical benefit as it operates effectively with simple, fixed measurements, whereas saturating the JE bound typically requires complex, parameter-dependent operations.
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All authors Mylenne Manrique, Marco Barbieri, Assunta Di Vizio, Miranda Parisi, Gabriele Bizzarri, Ilaria Gianani, Matteo G.A. Paris
Medical Physics
FENCE: Flexible Electric Noise reduCtion Endo-shield for the Suppression of Electromagnetic Interference in Low-Field MRI
Julia Pfitzer, Martin Uecker and Hermann Scharfetter
Electromagnetic interference (EMI) is a significant challenge for low-field MRI systems operating without conventional Faraday-shielded rooms. Traditional EMI mitigation approaches include external shields, subject grounding via electrodes, or active noise cancellation requiring synchronized receive channels. These methods either limit portability, introduce patient discomfort, or demand advanced hardware. In this work, we start from the hypothesis that EMI primarily couples capacitively from the body to the RF coil. We investigated two methods of blocking capacitive coupling while preserving inductive MRI signal detection: First, we employed capacitive
segmentation of the RF coil and studied its effect on EMI coupling. Second, we present FENCE (Flexible Electromagnetic Noise reduCtion Endo-shield), a novel approach blocking capacitive coupling using flexible PCB shields placed inside the RF coil. FENCE can be retrofitted to existing RF coils. Finite element (FE) simulations were used to estimate the expected shielding performance and the impact on RF coil losses prior to practical implementation. Testing in various realistic scenarios then demonstrated that the combination of FENCE with segmented solenoid coils is effective against both environmental noise sources and controlled EMI. In phantom experiments, FENCE significantly improved imaging performance and reduced EMI levels to near-baseline levels with 9% reduction in coil quality factor (Q factor), showing good agreement with the predictions from the FE simulations. In-vivo head imaging confirmed these results across diverse electromagnetic environments significantly improving imaging performance while showing an ~18% decrease in Q factor. FENCE provides a simple method for EMI mitigation in low-field MRI, enhancing image quality while maintaining system portability and accessibility.
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