Materials Science
Nonadiabatic polaron dynamics from machine-learned hopping trajectories
Daniela Mangano, Luca Leoni, Zhongfei Xu et al. (+2 more)
The formation and motion of small polarons are ubiquitous in energy materials and influence photoinduced processes. Polaron transport is governed by thermally activated
lattice dynamics and rare hopping events, requiring spatial and temporal scales only attainable with machine-learning molecular dynamics, which enables extensive sampling of atomic trajectories and polaron configurations over nanoseconds. Moreover, the Born-Oppenheimer approximation underlying standard ab initio molecular dynamics cannot describe the nonadiabatic coupling between electronic states mediated by nuclear motion, which controls energy exchange and excited-state relaxation. Here, we develop a simulation framework that combines machine-learning-assisted polaron dynamics with nonadiabatic molecular dynamics to bridge these complementary aspects of polaron physics, and determine how different polaron-hopping mechanisms affect excited-state dynamics. The enlarged trajectory space allows us to provide the first direct dynamical confirmation of the adiabatic or nonadiabatic classification of polaron hopping regimes originally proposed on the basis of static Marcus-theory arguments, and to connect individual hopping events directly to nonadiabatic electronic transitions. In bulk TiO$_2$, nonadiabatic hoppings occur preferentially when the energy of the polaron-induced gap state approaches the conduction-band
manifold, promoting both electronic de-excitation and, via a Landau-Zener mechanism, excitation from the ground state. In MgO, the predominantly adiabatic character of hole-polaron hopping suppresses these effects, leading to longer charge-carrier lifetimes and an absence of thermally activated excitations. At the rutile TiO$_2$(110) surface, hopping events are rarer than in bulk because the excess electron is strongly stabilized in the subsurface region, leading to correspondingly longer de-excitation times.
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All authors Daniela Mangano, Luca Leoni, Zhongfei Xu, Li-Min Liu, Cesare Franchini
Materials Science
Error-controlled switching between discrete and continuum dislocations in a unified defect framework
Albert Linda
Simulating defects of every dimension together is expensive, and the savings of adaptive methods are rarely tested at equal accuracy. We present a variational framework in which fields, dislocation lines and defect densities share one free energy, one dissipation law and exact ledgers of mass and Burgers vector, so that a region can change its representation without gaining or losing defects. On this basis, an allocator switches the dislocations themselves between discrete particles, where they are sparse, and a continuous density, where they are dense. The switch is made block by block from local counts, conserves the Burgers vector exactly and is controlled by a single threshold. For $5\times10^5$ dislocations, the allocator reproduces the discrete model to within 1% in the sparse region at 14-37 times lower cost, depending on the machine; the advantage grows to 81 times at $10^6$ dislocations, and a threshold calibrated on one ensemble meets its error target on an independent one. For an idealized array of dislocation walls in copper, the allocator is 37.5 times cheaper than particle dislocation dynamics and, at almost the same cost, six times more accurate than continuum dislocation dynamics between the walls. In a three-dimensional copper model coupling grain-boundary cavitation with damage, ligaments left at nominal coalescence delay creep rupture by 25-48% (post hoc sweep). By contrast, grids refined at interfaces gain less than twofold once the active region exceeds about 30% of the domain, so representation switching, rather than grid refinement, is the effective form of adaptivity for defect-rich microstructures.
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Astrophysics of Galaxies
A heterogeneous set of unusual quasars selected from astrometry and broad-band photometry
C. Cheng, K. Valeckas, L. Christensen et al. (+7 more)
The aim of this study is to explore methods for how to identify new
quasars with different properties with regard to reddening,
redshift, the presence of broad absorption lines from outflows, or other rare properties affecting the broad-band colours. We use Gaia-based astrometric pre-selection to study only sources that have zero parallax and zero proper motion within errors. We subsequently match these sources with information from wide-area photometric surveys and build colour-colour diagrams. Based on these diagrams we select targets for follow-up spectroscopy. In the subsequent analysis we also apply observations from SPHEREx to firmly establish
redshifts. We secure spectroscopic observations for 24 sources. Of these, three are found to be
stars and the remaining 21 are classified as
quasars spanning a
redshift range from z=0.139 to z=3.732. The majority of the sources located away from the normal
quasar locus in colour-colour diagrams are found to be broad-absorption-line
quasars. A single source, the lowest
redshift source at z=0.139, is reminiscent of the so-called Little Red Dots found at high
redshifts with JWST. Using the simple procedure followed here it is possible to locate previously undiscovered
quasars with interesting properties, in particular Broad Absorption Line
quasars and
quasars with unusual extinction.
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All authors C. Cheng, K. Valeckas, L. Christensen, A. Henderson de la Fuente, L. Fuglsang, V. Vuolteennaho, Pyykkinen, R. H. Rasmussen, S. Bijavara Seshashayana, J. P. U. Fynbo
Astrophysics of Galaxies
Strong gravitational lensing with Euclid
Alessandro Sonnenfeld
Euclid data is going to lead to the discovery of approximately 10^5 new strong gravitational lenses, thereby increasing the number of known lenses by a factor of 30. Such an impressive jump has the potential to revolutionise the field of strong
lensing, by covering an ever-increasing range in the parameter space occupied by the lenses and lensed sources, and by uncovering rare and precious strong lens systems. The first quick data release of Euclid has already revealed hundreds of lenses, giving us a taste of what the final Euclid strong lens sample might look like. These lenses include a variety of objects acting as deflectors, from isolated
galaxies to clusters, from early-type
galaxies to edge-on disks. As many as four double-source plane lenses, in which one foreground object lenses two
galaxies at two different
redshifts, have already been discovered. As more data are acquired, it might become possible to detect the strong
lensing signature of dwarf
galaxy satellites, and to find lenses with an unusually large number of images. In this paper, we try to anticipate the kind of discoveries that these data will bring along.
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Mesoscale and Nanoscale Physics
Magnetic field induced modulation of heat transport in CrPS$_4$ probed by TaIrTe$_4$ transverse Seebeck thermometry
Krishnaraajan Sundararajan, Sergio Alvarruiz, Cédric A. Cordero-Silis et al. (+5 more)
Understanding and controlling heat flow in low-dimensional
magnetic materials is central to thermoelectrics and
spin caloritronics. One of the challenges is the absence of sensitive probes of small, field-dependent modulations in thermal transport. Here we demonstrate transverse Seebeck thermometry using exfoliated TaIrTe$_4$ as a probe of thermal conductivity modulated by an external
magnetic field on a van der Waals magnet, CrPS$_4$. With a temperature gradient oriented at $45^\circ$ to its principal crystallographic axes, TaIrTe$_4$ exhibits a transverse thermopower exceeding $200~\mathrm{\mu V\,K^{-1}}$ for 900 nm wide and 30 $\mu$m long electrodes, enabling precise detection of variations in the local temperature gradients. Exploiting this with CrPS$_4$ in a nonlocal geometry, we resolve distinct field dependent thermal conductivity changes associated with both the
spin-flip and
spin-flop
magnetic transitions which we attribute to variations in the
magnon$-$
phonon coupling in CrPS$_4$. At 5 K, the transverse Seebeck response is modulated by more than 8$\%$ by an external
magnetic field, demonstrating strong
magnetic control of heat transport in CrPS$_4$. This all van der Waals platform offers high sensitivity to modulations of thermal conductivity and a broad adaptability to a wide range of exfoliated
magnetic systems.
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All authors Krishnaraajan Sundararajan, Sergio Alvarruiz, Cédric A. Cordero-Silis, Majid Ahmadi, Marcos H.D. Guimarães, Jagoda S\lawińska, Joseph Barker, Bart J. van Wees
Computational Physics
Online reduced-order modeling from primal solver trajectories for PDE-constrained optimization
Zhe Lu, Wenbo Cao and Weiwei Zhang
Repeated high-fidelity state and gradient evaluations make large-scale PDE-constrained optimization computationally expensive. Reduced-order modeling provides a natural way to reduce the cost of these repeated high-dimensional computations. However, existing reduced-order modeling approaches often rely on converged high-fidelity states for model construction or updating, while their reduced spaces may lose accuracy as the design moves beyond the region represented by the available data. To address these limitations, we present Reduced-order Trajectory-based Optimization (RETO), an online framework that constructs local reduced-order models (ROMs) directly from unconverged primal solver trajectories. Each local ROM is built from snapshots collected during a finite number of high-fidelity primal iterations, without requiring full-order convergence, and supports multiple low-cost state evaluations, adjoint-based gradient evaluations, and design updates. New solver trajectories are generated at updated design points to reconstruct the local ROM and continue the optimization. Across three distinct PDE-constrained optimization problems, RETO achieves solution quality comparable to that of full-order optimization, with speedups of approximately 8 to 22 times in cases without discontinuities in the state fields. Even in the transonic inverse-design case involving moving shocks, RETO retains an approximately threefold speedup. The transonic results further show that the online local ROM progressively captures evolving shock-related flow features as new primal solver trajectories are incorporated. These results demonstrate the value of unconverged primal solver trajectories as an online information source for reduced-order optimization, allowing the reduced basis to evolve with the design rather than requiring a basis that covers the entire design space in advance.
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Mesoscale and Nanoscale Physics
Nonadiabatic dynamics under slow parametric modulation in nonlinear graphene resonators
Chris F. D. Wattjes, Haemin Lim, Pierpaolo Belardinelli et al. (+3 more)
Resonantly driven nonlinear systems, from superconducting
circuits to nanomechanical resonators, are often described in a rotating frame, where amplitude and phase evolve slowly within a fixed landscape of stable and unstable states. How such systems behave when this landscape moves on their intrinsic timescale remains to be understood. Here, we exploit the strong tension sensitivity of a
graphene drum's resonance frequency to reshape the rotating-frame phase space of a bistable mechanical mode in real time, combining an MHz-frequency resonant drive with kHz-frequency tension modulation. When the modulation rate becomes comparable to the mechanical relaxation rate, adiabatic tracking of the fixed points breaks down. Instead, parametric instabilities emerge in the slow dynamics at frequencies set by libration around these points rather than by the mechanical resonance; stronger modulation drives period doubling and chaos. A slow-variable theory predicts where the instabilities occur, and Melnikov analysis captures the onset of chaos. These results show that the rotating frame itself can be parametrically driven, offering a general route to controlling nonadiabatic dynamics in systems ranging from Josephson bifurcation amplifiers to cold atoms.
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All authors Chris F. D. Wattjes, Haemin Lim, Pierpaolo Belardinelli, John E. Sader, Peter G. Steeneken, Farbod Alijani
Strongly Correlated Electrons
Interplay of electric field and electronic correlations in pairing competition in bilayer nickelates
Yanmei Cai, Yicheng Xiong, Ying Liang et al. (+1 more)
Layer polarization provides a means of tuning the competition between interlayer and intralayer pairing in bilayer nickelates. Using ground-state constrained-path
quantum Monte Carlo, we study interlayer $s^{\pm}$ and intralayer $d$ pairing in a bilayer two-orbital Hubbard model with a layer potential-energy difference $\varepsilon$ representing an effective perpendicular electric field. Within the parameter range studied, increasing $\varepsilon$ generally enhances the finite-size pairing vertex contribution $V_d$ and reduces $V_{s^{\pm}}$, shifting the relative pairing preference toward the $d$-wave channel. Increasing the onsite repulsion enhances both vertex contributions, more strongly in the $d$-wave channel, whereas increasing the
crystal-field splitting reduces both and makes $s^{\pm}$ pairing relatively more competitive. Hund's coupling increases the relative competitiveness of $s^{\pm}$ pairing at weak bias, while enhancing the relative strength of $d$-wave pairing at large bias. The bias primarily redistributes charge between layers within each orbital sector, accompanied by an increase in the antiferromagnetic
spin structure factor. Hund's coupling also enhances local interorbital parallel-
spin correlations. These observations suggest possible connections between charge redistribution,
magnetic correlations, and pairing competition, offering insight into how layer polarization and multiorbital interactions influence the relative pairing tendencies in the bilayer nickelate model.
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All authors Yanmei Cai, Yicheng Xiong, Ying Liang, Tianxing Ma
Chemical Physics
Density and excess molar enthalpy of 2-butanol + glyme liquid mixtures. Application of the DISQUAC, UNIFAC (Dortmund) and ERAS models to 2-alkanol + linear ether systems
Fatemeh Pazoki, João Victor Alves-Laurentino, Susana Villa et al. (+4 more)
Densities and excess molar volumes ($V_{\text{m}}^{\text{E}}$) at (293.15 to 303.15) K and excess molar enthalpies ($H_{\text{m}}^{\text{E}}$) at 298.15 K are reported for the 2-butanol + 2,5-dioxahexane, or + 2,5,8-trioxanonane, or + 2,5,8,11-tetraoxadodecane, or + 2,5,8,11,14-pentaoxapentadecane systems at 95 kPa. Densities were measured using a densitometer Anton Paar DSA 5000, and excess enthalpies by means of a micro-calorimeter Tian-Calvet. $H_{\text{m}}^{\text{E}}$ and $V_{\text{m}}^{\text{E}}$ data are positive, indicating that interactions between like molecules are dominant and that the main contribution to $V_{\text{m}}^{\text{E}}$ is the interactional one. Our enthalpic data together with data from the literature have been used to evaluate the enthalpy of alcohol-glyme interactions, which are ranged between ($-$31 and $-$22) kJ mol$^{-1}$. From the comparison with $H_{\text{m}}^{\text{E}}$ results for glyme + heptane systems, and from the position of the investigated mixtures in the diagram $G_{\text{m}}^{\text{E}}$ (excess molar Gibbs energy) vs. $H_{\text{m}}^{\text{E}}$, it is shown that interactions are of dispersive type. 2-Alkanol + dipropyl ether (DPE), or + glyme systems have also been studied using the DISQUAC, UNIFAC (Dortmund) and ERAS models. According to ERAS results, physical interactions in glyme systems are dominant, while association effects are predominant in mixtures with DPE. The DISQUAC interaction parameters suggest that interactions related to the OH/O contacts are essentially dispersive. UNIFAC fails when representing thermodynamic properties of the studied solutions.
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All authors Fatemeh Pazoki, João Victor Alves-Laurentino, Susana Villa, Daniel Lozano-Martín, Fernando Hevia, Luis Felipe Sanz, Juan Antonio González
Mesoscale and Nanoscale Physics
Orientation-Dependent Universality of Spin-Transport Fluctuations in Two-Dimensional Altermagnets
Yihan Zhang, Zheng Qin, Donghui Xu et al. (+3 more)
Universal conductance fluctuations are conventionally organized by
symmetry class, but crystalline anisotropy introduces additional structure in
spin transport. Here we demonstrate orientation-dependent universal
spin-transport fluctuations in disordered two-dimensional $d$-wave altermagnets without
spin-orbit coupling. Rotating the altermagnetic orientation changes both longitudinal
spin-conductance and transverse
spin-Hall conductance fluctuations, while each conserved-
spin sector remains in class AI. Altermagnetic orientation controls both the fluctuation amplitudes and the development of disorder-insensitive plateaus. These plateaus become flatter and less sensitive to the altermagnetic strength over the studied parameter ranges as the orientation approaches $45^\circ$, with representative fluctuation amplitudes of approximately $0.60e/(4\pi)$ for the longitudinal
spin conductance and $0.40\,e/(4\pi)$ for the
spin-Hall conductance. The longitudinal fluctuation amplitude correlates strongly with anisotropy of the clean-band Fermi-velocity tensor.
Spin-sector covariances explain how the conserved channels combine into total fluctuations. Our results extend anisotropy-sensitive universal-fluctuation physics to conserved-
spin altermagnetic transport and establish crystalline orientation as a control parameter within a fixed
symmetry class.
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All authors Yihan Zhang, Zheng Qin, Donghui Xu, Junjie Zeng, Zhen Ning, Rui Wang
Quantum Physics
Long Huang
Coherent noise poses a fundamentally greater challenge to
quantum error correction than independent s- tochastic Pauli errors, because
unitary errors preserve interference between error paths, can accumulate over multiple
quantum error correction rounds, and leave the encoded logical channel with a residual coherent com- ponent. If the parameters of such coherent noise can be accurately determined, this knowledge can be exploited to inject correlated priors into the decoding graph, and to perform maximum-likelihood decoding under poly- nomially tractable structures, significantly improving the accuracy of syndrome-based decoding. In this work, we introduce one protocol to determine the model and parameters of coherent noise, and reduce the complexity of the experiment from 16nto O(16), which is of great significance for correcting coherent noise in
quantum error correction.
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Optics
Computational compressive imaging reconstruction with a simulated-annealing-based Ising solver
Ze Zheng, Xiaoyan Wu, Hang Xu et al. (+3 more)
Computational compressive imaging, such as single-pixel imaging and lensless imaging, is a promising imaging technique, enabling the reconstruction of objects from under-sampled measurements through compressed sensing
algorithms or deep learning methods. However, the demand for electronic computational resources grows rapidly when recovering high-resolution and multi-dimensional images and training neural networks with numerous parameters, which has become a bottleneck for the widespread adoption of this technique. Here, we propose a physics-driven reconstruction framework that formulates imaging inverse problems as Ising models and directly recovers target objects through the self-
evolution of non-von Neumann Ising machines toward the ground state of the
Hamiltonian. We employ a simulated-annealing-based Ising solver to demonstrate this proof-of-concept by reconstructing objects in both single-pixel imaging and a lensless diffuser camera at sampling rates ranging from 1% to 25%. By further incorporating a foreground-sparsity constraint and a smoothness constraint, the reconstruction quality of our method is comparable to or even better than that of mainstream
algorithms. This approach has the potential to substantially reduce the electronic computational burden of inverse reconstruction, paving the way for real-time, low-power computational imaging.
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All authors Ze Zheng, Xiaoyan Wu, Hang Xu, Jingzheng Huang, Tailong Xiao, Guihua Zeng
Atmospheric and Oceanic Physics
Unmasking Compensating Errors in Numerical Weather Models: A Process-Additive Neural Network Approach
Yuiko Ichikawa, Edward Groot and Jack Atkinson
This work introduces a Process Additive Neural Network (PANN) framework to disentangle compensating biases in atmospheric models, where errors in different physical processes can offset each other and obscure their origins. Using a single-column model, each PANN branch represents the tendency error associated with a separate physical process, and the summed branch outputs approximate the total error relative to a reference tendency. Once trained successfully, the branch outputs are expected to provide process-level error attributions and, when averaged, estimates of process-level bias. Initial experiments focus on cloud-related processes in OpenIFS SCM case studies, where cloud and convection tendencies are strongly coupled and compensation is difficult to diagnose using standard approaches. The aim is not to replace human interpretation of physical processes, but to extend it to regimes where model complexity, process interaction, and compensating errors make direct diagnosis difficult. By providing a physically structured form of machine-learning interpretability, PANN can help connect complex model behaviour with process-level explanations. This work supports both improved understanding of compensating errors and the development of more physically consistent weather and
climate models.
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Astrophysics of Galaxies
Large dust grains escaping from a supernova remnant
Evgenii O. Vasiliev
Dust grains produced in the
supernova (SN) ejecta at early ages are partially destroyed in hot gas of the SN remnant. Large grains owing to their inertia can overtake the forward shock front of the remnant and move through the ambient interstellar medium. Using one-dimensional gas dynamics including the dust destruction we study the transport of dust grains inside the SN remnant and the ambient medium. Here we estimate the surviving and escaping mass fractions depending on the cut-off (maximum) size in a power-law distribution of grain sizes. We found that these fractions follow closely each other at late age of the SN remnant, i.e. almost all grains, which have survived in the remnant, leave it for the ambient interstellar medium. At the age of 30 kyr – the onset of the radiative phase with density $n\sim 1$ cm$^{-3}$ with solar
metallicity – the escaping/surviving mass fractions for the cut-off size of several microns reach about $0.7-0.8$. The major part of these grains have size larger than $1~\mu$m and initially located at distances $\gtrsim 0.2$ of the ejecta core radius. Later dust grains at velocity of several hundreds km/s escaping the remnant continue to be destroyed due to kinetic sputtering in the interstellar medium. Grains with sizes of several microns are destroyed marginally and therefore will survive in the interstellar gas. After decelerating of grains in the medium the surviving mass fraction of grains produced in the SN remnant, which evolves in an ambient gas with $n$ from 1 to 100 cm$^{-3}$, is from $\sim 0.5$ to $\sim 0.3$, respectively, for the cut-off grain size $a_{cut} = 10~\mu$m. A decrease of the cut-off size in the distribution results in lower surviving mass fraction.
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Strongly Correlated Electrons
Beyond Kitaev exchange: $\Gamma'$-driven magnetism in Ag$_3$LiRh$_2$O$_6$
Efrain Insuasti Pazmino, Shi Feng, Ramesh Dhakal et al. (+4 more)
In Kitaev magnets, frustration arises from bond-dependent
spin anisotropic interactions, which can potentially realize sought-after
quantum spin liquid phases. However, material realizations with dominating Kitaev exchange are scarce and the broad parameter space of extended Kitaev models remains largely unexplored experimentally. Here, we use density-functional theory, cluster many-body,
spin-wave, and density-
matrix renormalization calculations to show that the recently discovered honeycomb rhodate Ag$_3$LiRh$_2$O$_6$ hosts an off-diagonal exchange $\Gamma_1'$ that is second in magnitude only to the ferromagnetic Kitaev exchange $K_1$. This combination of $K_1$ and $\Gamma_1'$ explains key experimental observations, an unusually high
magnetic ordering temperature of 94 K at ambient pressure and its rapid decrease under hydrostatic pressure as Ag$_3$LiRh$_2$O$_6$ evolves from ferromagnetic toward zigzag order within the honeycomb planes. Our
spin-wave calculations further predict an unusual
topology of the
magnon bands arising from the $\Gamma_1'$ term in the
spin Hamiltonian of the honeycomb layer. We show that the large trigonal splitting of $t_{2g}$ states enhances $\Gamma_1'$, the hitherto underappreciated term in Kitaev magnets, and opens the way to new interesting regimes of the extended Kitaev model.
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All authors Efrain Insuasti Pazmino, Shi Feng, Ramesh Dhakal, Ioannis Rousochatzakis, Stephen M. Winter, Johannes Knolle, Alexander A. Tsirlin
Instrumentation and Methods for Astrophysics
Identifying Planetary Nebulae Candidates from IPHAS and VPHAS+ Surveys via YOLO Deep Learning Models
Titouan Sérandour, Anne-Laure Méalier, Bruno Colicchio et al. (+5 more)
We present a deep learning detection method capable of effectively identifying planetary nebulae (PNe) on IPHAS and VPHAS+ surveys. Our detection pipeline is based on the YOLO architecture and is adaptable to other
datasets. Using the HiPS system, we preprocess and augment the $r$, $i$, and $H{\alpha}$ bands to produce two red, green, and blue (RGB) image
datasets: (1) $640 \times 640$ px images at full resolution, and (2) $1 280 \times 1 280$ px images designed to capture extended objects up to $0.2$ deg. Images of $\sim 2600$ PNe are labelled using the HASH database. The loss function and evaluation metrics are adapted to the diffuse and low-contrast nature of PNe; a very low intersection over union (IoU) threshold ($1\%$) is used. A $k$-fold cross validation shows that the YOLOv12m model achieves an average precision of $0.979$ on the first
dataset. At a confidence threshold of $0.15$, it achieves a precision rate of $98.7\%$ and a recall rate of $97.4\%$. We deployed our system (on $1280 \times 1280$ images) on the full surveys' coverage ($\sim 3755$ deg$^2$), and present a preliminary analysis of the detection results. The system is robust against artifacts such as CCD corner defects and HiPS tile joints. Our convolutional-neural-network-based model achieved excellent results on the test set, comparable to-or exceeding-that of a recent Swin
Transformer approach. However, a challenge persists when applying deep learning models to extensive and densely populated Galactic fields: the development of an automated system that can effectively discriminate PNe from mimics that human experts are able to distinguish (e.g., H II regions). We outline possible improvements for future work.
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All authors Titouan Sérandour, Anne-Laure Méalier, Bruno Colicchio, Dominique Daniel, Philippe Gilberton, Philippe Oros, Thomas Boch, Djaffar Ould Abdeslam
Quantum Physics
Quantum-enhanced phase interrogation of a fiber-optic strain sensor
Romain Dalidet, Marialuisa Capezzuto, Hugo Degert et al. (+7 more)
Fiber-optic sensors enable high-sensitivity measurements of various physical parameters. Here, we demonstrate a
quantum-enhanced interrogation of an all-fiber-optic Fabry-Perot resonator, employing entangled two-
photon interference to probe directly strain-induced optical phase shifts. The resonator is interrogated by a narrow-linewidth
laser that is frequency-locked to its resonance mode, thereby exploiting the cavity's inherent sensitivity to variations in the fiber length. To access the phase fluctuations transferred to the interrogation field due to external perturbations on the sensor, we implement an in-fiber Mach-Zehnder interferometer readout. This configuration allows the sensor to operate both with classical coherent light and with entangled
photon pairs generated via spontaneous parametric down-conversion. Harnessing two-
photon entangled states corresponding to an N = 2 NOON state, we experimentally demonstrate a reduction of the measurement noise below the standard
quantum limit. These results provide clear evidence of the
quantum advantage in enhancing fiber-optic sensors under practical constraints on optical power.
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All authors Romain Dalidet, Marialuisa Capezzuto, Hugo Degert, Davide D'Ambrosio, Saverio Avino, Anthony Martin, Sebastien Tanzilli, Laurent Labonte, Paolo De Natale, Gianluca Gagliardi
High Energy Physics (Phenomenology)
Quantum-enhanced Search for Galactic Dark Photons Using Cat-State Cavities
Aoying Wang, Yanjie Zeng, Yanyan Cai et al. (+4 more)
We present a
quantum-enhanced search for the Galactic dark-
photon background (GDPB), a relativistic and anisotropic vector field that can be produced by dark-matter decay or annihilation in the Milky Way
halo. We reinterpret an existing
quantum-enhanced dark-
photon dataset obtained with a superconducting
circuit QED platform originally developed for wave-like dark-
photon dark-matter searches, consisting of a high-$Q$ niobium cavity in the $\mathrm{TM}_{010}$ mode dispersively coupled to a transmon
qubit. By preparing four-component cat states and performing repeated
quantum non-demolition parity measurements, analyzed with a hidden Markov model, we extract
photon-transition probabilities for multiple cat amplitudes and integration times. The coupling to the GDPB is governed by a polarization- and angle-dependent cavity overlap function, which predicts a distinctive diurnal modulation of the excitation rate for both longitudinal and transverse polarizations. From the absence of such modulation, we set 90% confidence-level bounds on the kinetic-mixing parameter $\epsilon$ for two
benchmark production mechanisms (parametric and cascade decay) over the relativistic mass range $m_X \ll \omega_c$.
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All authors Aoying Wang, Yanjie Zeng, Yanyan Cai, Jing Shu, Bin Xu, Yuan Xu, Pan Zheng
Disordered Systems and Neural Networks
Resolving Structural Uncertainty in Stochastic Dynamical Systems via Ensemble-Based Bayesian Inference
Francesco Zambelli, Valeria D'Andrea and Manlio De Domenico
Recovering the interaction structure of complex
stochastic dynamical systems from sparse time-series observations is an inherently ill-posed inverse problem. The posterior over network configurations is high-dimensional, highly degenerate, and shaped by the non-
equilibrium nature of the available data. To address this, we propose a fully
Bayesian, ensemble-based inference framework. Our approach grounds a continuous-time
Stochastic Differential Equation (SDE) likelihood formulation—acting mathematically as an Onsager-Machlup quasi-potential for non-
equilibrium paths—within a non-parametric Minimum Description Length (MDL) structural prior. This framework rigorously penalizes model complexity and avoids kinetic overfitting by forcing continuous parameters into a finite vocabulary of discrete categories. The joint posterior is optimized using a block-coordinate scheme combining sub-quadratic Markov Chain Monte Carlo (MCMC) topological sampling with deterministic Nelder-Mead parameter optimization. Using highly non-linear macroscopic population dynamics as a
benchmark, we demonstrate that inference requires non-stationary transient data to resolve causal information. Furthermore, we prove that propagating structural uncertainty via ensemble-based posterior analysis produces significantly more robust and reliable predictions for downstream perturbation outcomes than traditional single-point (MAP) estimates. The framework is highly generalizable, capturing fundamental topological constraints even under severe generative model mismatches, offering a robust tool for uncertainty-aware inference in complex
stochastic systems.
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Solar and Stellar Astrophysics
High-Frequency Transverse Waves in Chromospheric Fibrils Revealed by DKIST
Qifan Dong, Xiaoli Yan, Zhike Xue et al. (+4 more)
Chromospheric fibrils are ubiquitous dynamical structures that can support magnetohydrodynamic waves and may contribute to energy transport in the solar atmosphere. Using high-resolution observations from the Visible Broadband Imager (VBI) onboard the Daniel K. Inouye Solar
Telescope (DKIST), we investigate transverse oscillations of H$\alpha$ fibrils. Our observations encompass both quiet-Sun and active regions. The results reveal that high-frequency transverse oscillations are highly prevalent in fibrils across different
magnetic environments. The detected oscillations exhibit typical periods of 56 $\pm$ 49 s, displacement amplitudes of 37 $\pm$ 25 km, velocity amplitudes of 6 $\pm$ 4 km\,s$^{-1}$, and phase velocities of 21 $\pm$ 13 km\,s$^{-1}$. Under typical chromospheric conditions, the estimated wave energy flux ranges from 20 to 200 W\,m$^{-2}$. The characteristics of these transverse oscillations are consistent with those of Alfvénic kink-mode waves. Our results reveal the existence of the high-frequency, small-amplitude transverse waves in chromospheric fibrils and providing new constraints on their contribution to the chromospheric and coronal heating.
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All authors Qifan Dong, Xiaoli Yan, Zhike Xue, Liheng Yang, Jincheng Wang, Yadan Duan, Zhe Xu
Quantum Physics
Void-Free Through-Glass Vias for Multilayer Surface-Electrode Ion Traps
Eike Iseke, Jacob Stupp, Friederike Giebel et al. (+6 more)
Through-substrate interconnects are a key technology for scaling surface-electrode ion traps (SEITs) toward large electrode counts and complex architectures. Dielectric substrates such as fused silica offer superior RF performance compared to silicon, but the reliable fabrication of void-free through-glass vias (TGVs) remains challenging. In this work, we demonstrate a SEIT fabricated on a fused silica substrate incorporating TGVs. The via-holes are formed using Selective
Laser-Induced Etching and subsequently metallized with gold by electroplating. A patent-pending geometry-assisted bottom-up plating approach enables void-free filling using constant-current electroplating without electrolyte additives or pulsed deposition schemes. Electrical characterization across multiple wafers confirms a TGV-level yield above 98.8 %, demonstrating the robustness and reproducibility of the developed TGV technology. The TGVs are combined with multilayer SEIT fabrication, enabling vertical signal routing to all electrodes while maintaining an unaffected trapping surface without wire bonds. To interface the trap with external control electronics, a glass interposer providing signal fan-out to a larger pitch is designed and fabricated. The trap chip and the interposer are integrated using thermocompression bonding, forming a compact chip-to-chip assembly. The presented technology demonstrates the first fully integrated multilayer SEIT on fused silica incorporating void-free TGVs.
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All authors Eike Iseke, Jacob Stupp, Friederike Giebel, Nila Krishnakumar, Konstantin Thronberens, Nora D. Stahr, Md. Masum Billah, Marlon Kuhn, Christian Ospelkaus
Strongly Correlated Electrons
Role of Gd 5d-Au 5d hybridization for the magnetic properties of Au-Al-Gd quasicrystal approximants
Goro Nozue, Hidenori Fujiwara, Satoru Hamamoto et al. (+18 more)
We have studied the electronic states of
magnetic Au-Al-Gd quasicrystal approximants, which exhibit different
magnetic ground states at low temperatures, by orbital-selective soft and hard x-ray electron spectroscopies in the paramagnetic phase. Our results reveal that the valence electronic states vary among the Au-Al-Gd approximants with different
magnetic ground states, whereas the Gd 4f electrons are localized in all of them. In particular, we find that the Gd 5d states are hybridized with the Au 5d states around the Fermi level, providing information about a local pathway for the intersite exchange interaction between the localized Gd 4f electrons. This hybridization strength varies among these samples. Our findings bring an orbital-resolved microscopic picture to the magnetism of rare-earth-based quasicrystals and approximants.
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All authors Goro Nozue, Hidenori Fujiwara, Satoru Hamamoto, Yuto Torii, Mai Sakaguchi, Sho Nakajima, Takuya D. Nakamura, Nonoka U. Sakamoto, Takayuki Kiss, Masaki Oura, Akira Yasui, Kotaro Higashi, Naomi Kawamura, Kojiro Mimura, Arata Tanaka, Asuka Ishikawa, Farid Labib, Shintaro Suzuki, Takafumi D. Yamamoto, Ryuji Tamura, Akira Sekiyama
Solar and Stellar Astrophysics
Evidence for Suppressed Non-thermal Broadening in a Flare Ribbon from Stereoscopic Observations
Ziwen Huang, L. P. Chitta and L. Teriaca
Flare ribbons mark the footpoints of newly reconnected
magnetic loops and are commonly associated with strong
plasma flows and enhanced non-thermal broadening of transition-region lines due to impulsive energy deposition. However, the mechanisms governing energy transport into
flare ribbons remain uncertain, particularly under different
magnetic field configurations. We investigate the energy deposition process at a
flare ribbon near a sunspot by determining the physical nature of its small-scale downflows. We study small-scale downflows in a remote ribbon during the M7.7-class event on 30 September 2024, using coordinated observations from SDO, IRIS, and Solar Orbiter. We use stereoscopic imaging from Solar Orbiter and IRIS to detect plane-of-sky motions on small scales (200 km). We conduct spectroscopic analysis of IRIS Si IV profiles, complemented by C II and Mg II diagnostics. Apparent downflow speeds measured from Solar Orbiter imaging (limb view) are 85-130 km/s, while IRIS images (disk view) reveal plane-of-sky speeds of 70-85 km/s. In contrast, IRIS Si IV profiles at the brightest ribbon pixels are well approximated by a single Gaussian, with minimal Doppler shifts and unexpectedly small non-thermal widths (10 km/s). Peak Si IV emission also coincides with a deeper Mg II central reversal, while electron densities are one to two orders of magnitude higher than typical quiet-Sun values. The absence of significant line-of-sight velocities and non-thermal broadening differs from typical
flare-ribbon behavior. Our results are consistent with a scenario in which
plasma motions are guided by highly inclined (nearly horizontal)
magnetic fields in chromospheric canopy and are not accompanied by strong
turbulence or wave motions. This study suggests that
flare ribbons can exhibit a wide diversity of lower-atmospheric responses and emphasizes the critical role of
magnetic field geometry.
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Strongly Correlated Electrons
Room-Temperature Metallic 2D Ferromagnetism Stabilized by Quantum Metric
Teng-Fei Ying, Jianqi Zhong, Songyuan Geng et al. (+3 more)
The recent discovery of long-sought dice-
lattice bands in layered electride YCl opens up unprecedented opportunities for studying correlated electrons in real dice
lattice systems. While the weakly dispersive band at the Fermi level is partially filled and density-wave states are expected due to Fermi surface nesting based on conventional theories, the ARPES measurement nevertheless revealed a uniform flat band splitting of 0.5 eV, suggesting unusual ferromagnetism (FM) borne out of the metallic 2D dice
lattice. In this Letter, we propose that the uniform metallic FM order is stabilized by the prominent
quantum metric near topological band crossing points at K and K', which reconstructs the
magnetic instability in the dice metal and tips the density-wave instability toward a uniform FM order. Importantly, our analysis based on random phase approximation (RPA) and Hartree-Fock theory predicts a remarkably high Curie temperature above room temperature for the 2D FM order. These findings establish the first example of a room-temperature 2D metallic magnet stabilized by
quantum metric, which not only exemplifies the fundamental significance of
quantum geometry in solids but also bears far-reaching applications in energy-efficient high-density
magnetic memories.
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All authors Teng-Fei Ying, Jianqi Zhong, Songyuan Geng, Fangjie Chen, Haoxiang Li, Benjamin T. Zhou
High Energy Physics (Phenomenology)
Decoherence as a Detector-Resolution Flow
Yao Ji and Yuqi Wang
We consider the QED final-state radiation modeled by $\gamma\gamma^\ast\to\pi^+\pi^-+X$, including its finite-temperature generalization, as an open
quantum system, and study the
evolution of the pion-pair momentum density
matrix as the detector resolution scale is varied. We derive an explicit relation between the Lindblad jump operator and the Wilson line associated with soft
photon radiation. We find that real emission and virtual correction serve as two separate contributions to momentum decoherence, and together they give rise to the real–virtual cancellation at the density-
matrix level. The external finite-temperature
photon bath modifies the decoherence rate by a Bose factor consistent with the Feynman–Vernon influence-functional approach. We emphasize that our conclusions also apply to hard
fermion production thanks to the universality of the soft radiation.
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Astrophysics of Galaxies
Microcaustics: Fast GPU-Accelerated Dynamical Microlensing of Time-Dependent Extended Sources
Joshua Fagin, Connor Stone, James Hung-Hsu Chan et al. (+7 more)
Gravitational microlensing probes unresolved
quasar accretion disc structure and compact objects in lens
galaxies and is an important systematic in strong-lens time-delay cosmography. Most analyses use static microlensing map simulations because evolving individual microlenses and caustics is computationally prohibitive. We present Microcaustics, a GPU-accelerated Python package built on PyTorch for dynamical microlensing of time-dependent extended sources in strong gravitational lenses. It combines a local-exact/far-field deflection solver, source-directed lens-plane scouting with temporal reuse, and biquadratic inverse polygon mapping (IPM). GPU batching and fused Triton rasterization accelerate the calculation, while binary caustic labels track source-centred crossings. Across three simulated quadruply lensed
quasar systems, our package generates a 10-year, 147-frame multiband light curve in an amortized median of 0.68 s (0.88 s with labels) on a consumer GPU with a median light-curve RMSE of 0.35 mmag, while recovering every reference source-centred caustic crossing. At comparable map accuracy, the batched throughput is 780 times higher than that of a recent CUDA IPM implementation and extrapolates to a speedup of millions relative to classic GPU-D. We demonstrate that our IPM converges as $N_{\rm ray}^{-0.84}$, approaching the idealized $N_{\rm ray}^{-1}$ convergence rate of piecewise-affine IPM and improving upon the $N_{\rm ray}^{-1/2}$ inverse ray-shooting rate. We also introduce a GPU-resident general relativistic and reverberating
quasar source model and demonstrate our method with an evolving
supernova source. These advances make fully dynamical stellar fields practical for
Bayesian and simulation-based inference.
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All authors Joshua Fagin, Connor Stone, James Hung-Hsu Chan, Sophia Miskiewicz, Henry Best, Paras Sharma, Matthew O'Dowd, Laurence Perreault-Levasseur, Yashar Hezaveh, Simon Birrer
Mathematical Physics
Coherent-State Integrals Beyond the Domain of Operator Products
Ghasem Asadi Cordshooli
Inserting a resolution of the identity between two operators turns a
matrix element of their product into a phase-space integral. For unbounded operators the product need not exist on the vector at hand, while the integral may still converge. We follow this gap through the chain $e^{\mu a^2}e^{\lambda a^{\dagger2}}$ of two-
photon exponentials, where it can be traced completely. Five regions of parameter space appear: where the Bochner conditions of the strong formulation hold, where the product exists as a vector, where it exists as a sesquilinear form, where the coherent-state integral converges, and where the Fock-space series converges. The first three are strictly nested inside the intersection of the last two, and these two overlap without either containing the other. A single Hermite-type function agrees with the
matrix element where it exists and with the integral and the series wherever they converge, so the integral carries the analytic continuation of the
matrix element beyond the domain of the product and beyond the convergence of its Fock series. On the real slice of parameter space, an iterated form of the integral also reaches every point where the series converges. The analysis rests on a weak composition lemma whose hypotheses concern only the bra, the ket and the resolving family. For bounded chains the same identity is unconditional, and worked examples of that kind are given in a companion paper.
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General Relativity and Quantum Cosmology
A catalog of long, eccentric and precessing binary black hole simulations from ICTS-TIFR
Vaishak Prasad, Prayush Kumar, Michael Boyle et al. (+3 more)
We present a catalogue of 31 binary black hole simulations performed with the Spectral Einstein Code (SpEC) on the Sonic cluster at ICTS-TIFR, Bengaluru between August 2023 and December 2024, targeting the sparsely covered corner of parameter space in which orbital eccentricity and
spin-orbit precession are present simultaneously: 17 configurations are both eccentric and precessing, spanning mass ratios $1 \le q \le 11$ and initial eccentricities up to $\hat{e}_0 = 0.40$. The longest, EccPrecDiff002, inspirals for 80 orbits (159 gravitational-wave cycles), to our knowledge the longest simultaneously eccentric and precessing binary black hole
evolution to date. Compile-time optimisation of SpEC and its third-party library stack for the AMD Zen-2 architecture delivered a 90% speedup of the initial-data solver and a 40% speedup of the
evolution, roughly half of the latter traceable to a single defect in how pre-2.34 glibc reported cache
topology on AMD processors. The campaign consumed $1.18 \times 10^{6}$ CPU-hours. We document the post-processing pipeline and validate the frame transformation and waveforms. Eccentricity is measured from the waveforms and compared against the initial data. The first law of binary black hole mechanics, a test of approximate helical
symmetry, is satisfied to better than 0.54% for every configuration with $e_{\omega} < 0.2$, and we show that even precessing systems can be regarded as possessing approximate helical
symmetry in the co-precessing frame. Using the aligned-
spin simulations to calibrate the numerical floor, the co-precessing approximation's mirror-
symmetry violation lies three to four ordersof magnitude above it, growing from 0.7% to 5.3%with opening angle. EccPrecDiff002 spans the band above 5 Hz without hybridisationfor $M \le 62\,M_\odot$, giving a single-interferometer signal-to-noise ratio of 961 in
Cosmic Explorer at 1 Gpc.
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All authors Vaishak Prasad, Prayush Kumar, Michael Boyle, Lawrence E. Kidder, Harald P. Pfeiffer, Mark A. Scheel
General Relativity and Quantum Cosmology
Hierarchical Parameter Estimation for Intrinsic Parameters of Extreme-mass-ratio Inspirals Using Deep Learning
Ping Shen, Wen-Biao Han and Minghui Du
Extreme-mass-ratio inspirals (EMRIs) stand as
prime targets for future space-borne gravitational wave (GW) detectors, yet their precise parameter estimation is severely hindered by waveform complexity and high-dimensional parameter spaces. In this work, we propose a deep learning framework capable of recovering the seven intrinsic EMRI parameters without relying on detailed priors for extrinsic parameters. Our approach first employs a U-Net to extract robust signal features from noisy time-frequency data. These features are then fed into a multi-channel convolutional neural network (CNN) equipped with a dual
attention mechanism, which decouples the time and frequency dimensions to jointly model long-range temporal
evolution and persistent spectral structures, thereby enhancing sensitivity to EMRI time-frequency ridges in noisy data. Remarkably, this method reduces the search ranges for the parameters $\{\log M, a, \mu, e_0, p_0 \}$ and $\{t_p, {x_I}_0 \}$ by factors of $\sim 10^{2}$ and $\sim 10^{1}$, respectively, effectively shrinking the total volume of the seven-dimensional parameter space by $\sim 10^{8}$. Such a dramatic reduction enables a rapid pre-screening of the intrinsic parameter space, substantially saving computational cost for subsequent full parameter estimation. Although our framework is developed with Taiji mission specifications in mind, the methodology is applicable to data from other space-borne GW detectors.
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Nuclear Experiment
Probing the production mechanisms of virtual photons at RHIC
STAR Collaboration
We report the measurement of direct virtual
photon ($\gamma^*_\text{dir} \rightarrow e^+e^-$) in four Au+Au collision energies at $\sqrt{s_\text{NN}}$ = 14.6–54.4 GeV. The $\gamma^*_\text{dir}$ yields scale with charged-particle multiplicity ($(dN_{\mathrm{ch}}/d\eta)^{\alpha}$) as $\alpha=1.43 \pm 0.04 \text{(stat.)} \pm 0.03\text{(sys.)}$, independent of collision energies and centralities, exceeding hadronic expectations and indicating notable contribution from QGP phase. At $\sqrt{s_{\rm NN}}=$ 54.4 GeV, the direct virtual
photon mass distributions are further studied over $0.1 < M_{ee} < 1.1$ GeV/$c^2$, and are found to evolve from exponential to power-law form with increasing $p_\text{T}$, signaling a shift from "blackbody" radiation to emission governed by Kroll-Wada formalism.
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