Atomic Physics · Cross-listed from quant-ph
Scheme for Transport-based Global Entanglement Distribution using Quantum Processors
Erik Lundblad, Mira Abu Yahia, Antonius Johannes Renders et al. (+3 more)
We propose a scheme for distributing
entanglement over global distances in a heralded manner by using satellites to physically transport entangled processor nodes with rare-earth-ion
qubits. A full analysis of channel losses, errors and background light is performed to determine the fidelity and number of entangled pairs that can be distributed between two ground stations. We show that the scheme works already with a single satellite and can distribute close to the theoretical maximum number of entangled pairs that can be generated in a satellite overpass. In addition, we argue that in theory transportation-based schemes outperform other satellite-based schemes and can be scaled up to a constellation without additional channel losses. Daytime operation seems feasible as long as the sky is clear, with an EPR pair fidelity ranging from 99.3% at shorter network lengths to 93.9% with global coverage and can be further improved by active error correction or
entanglement purification.
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All authors Erik Lundblad, Mira Abu Yahia, Antonius Johannes Renders, Andreas Walther, Adam Kinos, Lars Rippe
Fluid Dynamics
Filtering effects on entropy transport and entropy-production structure in a supersonic reacting shear layer
Sriram P. Kalathoor and Joseph C. Oefelein
Spatial filtering is examined in time-resolved mid-plane DNS fields of a supersonic reacting shear layer using a sequence of box filters. The analysis tracks a nondimensional
entropy-like scalar $s^\ast$, its in-plane material derivative $D s^\ast / D t^\ast$, a residual $\Pi_s^\ast$, and viscous and conductive
entropy-production diagnostics, $\sigma_\mu^\ast$ and $\sigma_k^\ast$. Filtering changes $s^\ast$ only weakly, attenuates $D s^\ast / D t^\ast$ and the strongest tails of $\sigma_\mu^\ast$ and $\sigma_k^\ast$, but broadens the residual distribution and increases the residual RMS with filter width. The residual remains concentrated in the layer core that carries the largest mechanical and thermal activity. Conditional statistics show that $|\Pi_s^\ast|$ rises with both
entropy-production intensity and
entropy-gradient strength. Spectral and structural diagnostics show that increasing filter width removes high-wavenumber content and simplifies the geometry of the high-$|\Pi_s^\ast|$ sets. Coarser filtering therefore increasingly distorts
entropy transport preferentially through the most dynamically and thermally active structures, rather than uniformly across the plane.
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Optics
Multi-channel high-speed flip-chip packaging platform for thin-film lithium niobate photonic circuits
Zhenzheng Wang, Xiangzhi Xie, Yikun Chen et al. (+11 more)
To address the urgent need for multi-channel high-speed electrical interfacing of thin-film lithium niobate (TFLN) photonic
circuits, we realize a flip-chip packaging platform capable of simultaneously delivering 13 high-speed and 32 low-speed electronic signals to a centimeter-sized TFLN chip. The platform exhibits low flip-chip bonding loss and low inter-channel crosstalk over a broad bandwidth up to 50 GHz. Leveraging this packaging platform, we demonstrate high-speed electrical interfacing with two proof-of-concept TFLN photonic
circuits, namely a 2x8 optical switch and an electro-optic comb-based transmitter. The switch achieves arbitrary 8-channel routing with ~3 dB insertion loss, < -20 dB crosstalk, and an equipment-limited switching time of <= 34 ps. The transmitter
circuit includes a 50 GHz electro-optic comb generator with 2.8-dB flatness, a tunable microring to arbitrarily filter one comb line, and a modulator for data transmission at 20 Gbit/s. The packaging platform could significantly advance large-scale TFLN
circuits in optical communications, microwave photonics, and photonic computing.
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All authors Zhenzheng Wang, Xiangzhi Xie, Yikun Chen, Yifan Wu, Zeyu Luo, Hanke Feng, Yulong Chen, Zengyi Xu, Zixi Wang, Yuansong Zeng, Mandie Huang, Ke Zhang, Yingxia Liu, Cheng Wang
Chemical Physics · Cross-listed from quant-ph
Quantum optimal control of steady orbits
Shebha Anandhi Jegadeesan, Yujie Zhao, Robert Hunter et al. (+6 more)
Periodically driven dissipative systems can settle into steady orbits - fixed loops on their dynamical
manifolds. In
quantum mechanics, steady orbits occur in cooling engines (used to initialise
quantum devices), coherent oscillators (such as
lasers and masers), precision metrology devices (atomic clocks, optical and
spin magnetometers), and
magnetic resonance (steady state free precession, dynamic
nuclear polarisation). Steady orbits and stroboscopic steady states are a promising target for
quantum optimal control, but the numerical complexity is prohibitive: the infinite loop defeats gradient ascent pulse engineering (GRAPE) which relies on explicit numerical propagation in the time domain. Here we propose an efficient
quantum control strategy for stroboscopic steady states and limit cycles that are approached asymptotically when a control sequence is repeated infinitely many times. The formalism is different from Floquet-Lindblad state engineering and effective
Hamiltonian theories: it finds control sequences that drive a dissipative
quantum system towards a steady orbit passing through user-specified waypoints. The software implementation (same numerical complexity scaling as GRAPE) is done for the Spinach library.
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All authors Shebha Anandhi Jegadeesan, Yujie Zhao, Robert Hunter, Hassane El Mkami, Maximilian Keitel, Callum Musselwhite, Graham Smith, Guinevere Mathies, Ilya Kuprov
Optics · Cross-listed from quant-ph
Single-Image Entanglement Verification with Spatially Encoded Measurement Contexts
Nazanin Dehghan, Alessio D'Errico, Yingwen Zhang et al. (+3 more)
Entangled
photon pairs produced by spontaneous parametric down-conversion exhibit rich spatial
entanglement structure that is often difficult to probe with conventional measurements. Here, we show that
spin-orbit optical elements can convert this spatial structure into directly observable
quantum interference patterns. Using a $q$-plate, we demonstrate that the relative wavefront
curvature of biphoton states generated by a pair of nonlinear
crystals can be retrieved from the spatial modulation of coincidence images. Building on this principle, we introduce a
liquid-
crystal metasurface that performs spatially multiplexed Bell measurements across the transverse profile of the
photon field. The device, which we call a Clauser-Horne-Shimony-Holt (CHSH) plate, assigns different polarization projections to different azimuthal sectors of the beam, allowing the sixteen joint measurements required for a CHSH test to be realized simultaneously in a single acquisition. In this architecture, the spatial coordinate acts as a classical register selecting the measurement context, while
photon pairs sample these contexts according to their emission directions. We further demonstrate that the same measurement concept can be implemented using a programmable spatial light modulator, providing a dynamically reconfigurable realization of the scheme. Our results show that spatially structured optical elements can transform Bell tests into parallel measurements distributed across the transverse plane, enabling rapid characterization of spatially varying
entanglement. This approach opens new possibilities for structured-light
quantum measurements, Bell-inequality-based imaging, and the study of spatially engineered entangled
photon sources.
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All authors Nazanin Dehghan, Alessio D'Errico, Yingwen Zhang, Hugo Defienne, Daniele Faccio, Ebrahim Karimi
Geophysics · Cross-listed from cs.LG
Learning Earthquake Wave Arrival Time Picking from Labels with Inaccuracies
Sen Li, Xu Yang, S. Mostafa Mousavi et al. (+5 more)
Inaccurately labeled training data, or "label noise", poses a significant threat to the integrity of supervised machine learning models. This corruption directly degrades performance by teaching the model erroneous mappings between features and labels, which leads to poor generalization and reduced accuracy on properly labeled validation and test data. Current seismological applications mainly rely on large-scale training sets or data augmentation to reduce the label-noise impact, which can be labor-intensive and costly. Here, we introduce a Label Noise-Contrastive Robust Learning (LaNCoR) approach that can effectively handle noisy labels in seismic signal processing tasks, without requiring large-scale training
datasets. In this approach, the input waveform feature and label representation distributions are aligned in the feature space to correct mislabeling and reduce its impact on the training process. We present LaNCoR's performance on the task of P-phase arrival-time picking of real microseismic data using two baseline models and training approaches. Our results indicate that LaNCoR can improve performance by up to 28.8% across performance metrics. This approach holds great promise for model training in seismology and geosciences.
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All authors Sen Li, Xu Yang, S. Mostafa Mousavi, Anye Cao, Keting Fan, Yaoqi Liu, Changbin Wang, Qiang Niu
Optics · Cross-listed from cond-mat.mes-hall
Topological Surface Charge Detection via Terahertz Time-domain Spectroscopy
Tong Shen, Yiyang Xie, Yucheng Dai et al. (+4 more)
The topological magnetoelectric effect (TME) is a condensed-matter realization of the four-dimensional
quantum Hall effect (4D-QHE), manifesting as quantized surface charge accumulation proportional to an applied
magnetic field. To date, however, no optical technique has been developed to directly probe this charge accumulation. Here, we demonstrate a terahertz time-domain spectroscopy method for direct detection of surface charge accumulation—a physical quantity relevant to both the 4D-QHE and 2D-QHE, in sharp contrast to the previous optical measurements, which focused on the
Hall conductivity $\sigma_{xy}$ of the 2D-QHE. Using a chromium-doped (Bi,Sb)$_2$Te$_3$ thin film, we achieve sub-milliradian Faraday rotation precision. Extending this scheme to
axion insulators, we predict that the TME gives rise to an imaginary Faraday rotation linear in frequency, whose slope directly reflects the single-surface charge density. With further improvements in sample thickness and precision, this approach offers a viable pathway toward direct verification of the TME and 4D-QHE.
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All authors Tong Shen, Yiyang Xie, Yucheng Dai, Yifan Zhang, Yuanze Li, Xufeng Kou, Tian Liang
Optics
Super-Gaussian approximations for optimum far-field irradiance in intersatellite optical communications: coherent and incoherent beam shaping
Mario Badás Aldecocea, Yves van Gennip, Pierre Piron et al. (+2 more)
Intersatellite optical communication links are strongly affected by transmitter pointing jitter, which stochastically modulates the received optical power and degrades communication performance. While adjusting the divergence of a conventional Gaussian beams can partially mitigate this effect, the optimum far-field irradiance distribution for maximizing link performance has not been formally derived. In this work, we introduce a variational formalism to determine the optimum far-field irradiance for an intersatellite link affected by pointing jitter. The flat-top beam is found to be the optimum beam shape for minimizing outage probability. In particular, it requires $\sim37,8\%$ of the power needed by a conventional Gaussian beam to achieve the same outage probability. However, the flat-top profile is discontinuous and physically unrealizable. To address this, we analyze a continuous family of super-Gaussian beam shapes that approximate the flat-top as the order increases. In addition, several coherent and incoherent beam shaping techniques are evaluated to assess their ability to reproduce the optimum irradiance distribution. The results show that these techniques can reduce the required transmitted power by up to $\sim50\%$ compared with conventional Gaussian beams.
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All authors Mario Badás Aldecocea, Yves van Gennip, Pierre Piron, Jasper Bouwmeester, Jérôme Loicq
Data Analysis and Statistics · Cross-listed from stat.ME
Matched generating elements in maximum entropy density reconstruction
Serhii Zabolotnii
Moment-constrained maximum
entropy (MaxEnt) reconstructs a density as an exponential family whose sufficient statistics are chosen constraint functions. We study this choice separately from the numerical coordinates used to solve the dual problem. An odd-only family on a symmetric support forces f(x)f(-x) to be constant, so parity matching is necessary. A logarithmic-rational constraint produces the Student/Cauchy family and remains population-defined when required integer moments do not exist; a parity-matched one-parameter path provides a reproducible fractional-exponent alternative containing the monomials. The numerical study uses a common damped-Newton solver and audits the six-distribution
benchmark of Rajan et al. Stable parity-block divided differences, residual replay in the original constraint coordinates, and independent adaptive integration identify a raw-coordinate false convergence on D5. Under the corrected computation, the selected PATP arm is within 1.22 times the oracle on D5 but retains selected-to-oracle error ratios of 30.7, 8.88, and 3.33 on D2, D4, and D6 at n=12. These checks preserve the negative selector conclusion without treating a numerical artifact as statistical evidence. The Pearson row is reproduced, whereas the published GOPoly rows are not under the printed protocol. Matched LogRat results show family capacity; neither tested selector supports automatic choice among constraint families.
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Fluid Dynamics
ShipNet: A Geometric Deep Learning Surrogate for Real-Time Ship Hydrodynamics
Kirsten Odendaal and George Drakoulas
Accurate prediction of hydrodynamic performance is central to ship design, yet high-fidelity computational fluid dynamics remains prohibitively expensive for large-scale parametric exploration. This motivates the development of data-driven surrogate models that provide rapid approximations to hydrodynamic predictions at substantially reduced cost. We present ShipNet, a
geometric deep-learning surrogate that predicts both hull-surface pressure distributions and far-field free-surface wave patterns directly from hull geometry and speed. The network employs a regularized dynamic graph convolutional backbone on hull point clouds, with a multi-head decoder for simultaneous near-body pressure and free-surface elevation outputs. Training data consist of 420 inviscid free-surface simulations generated using a potential-flow panel method for two parent yacht hulls, each parameterized into 70 variants and evaluated at three speeds. ShipNet predicts per-point pressure coefficient and two-dimensional wave elevation map using a composite loss that combines point-wise regression and image-structure terms. On a geometry-held-out test set, ShipNet achieves R^2=0.98 for hull pressure and R^2=0.91 for wave fields. Inference requires approximately 0.15s per case, yielding over a 550x speedup relative to the potential-flow solver on conventional hardware. Limitations include the restricted geometry and speed ranges and the inviscid training data, while future work will extend the model to high-fidelity viscous simulations with physics-informed regularization.
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Optics · Cross-listed from cond-mat.dis-nn
Generative modelling powered by room-temperature polariton condensates
Yuan Wang, Marcin Muszynski, Avinash Dash et al. (+3 more)
Generative modelling requires efficient
stochastic nonlinear transformations and physical platforms that can naturally realise them. We experimentally demonstrate that nonlinear optical systems operating in the strong light-matter coupling regime can serve as physical transformation layers for conditional generative modelling. Specifically, we develop a workflow in which room-temperature
exciton-polariton condensates formed in organic dye microcavities act as a physical
stochastic transform within a generative
adversarial network and enable conditional digit-to-image translation. By using the nonlinear many-body dynamics and intrinsic stochasticity of polariton condensates, the workflow outperforms baseline approaches based on digitally injected perturbations. We find that polariton-enabled sampling via generative
adversarial network (Polariton GAN) yields improved inception score, digit preservation accuracy and structural similarity compared with both digital sampling and
laser-based systems. We further show that spatially correlated output variations can naturally regularise
adversarial training and enhance output diversity. Our results establish polariton condensation as a new computational resource for generative modelling, opening a pathway towards physics-enhanced machine learning systems.
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All authors Yuan Wang, Marcin Muszynski, Avinash Dash, Rishabh Kaurav, Vinod M. Menon, Oleksandr Kyriienko
Instrumentation and Detectors
Beyond Linearity: Full-scale response modelling and experimental validation of LVDTs
Kumar Akhil Kukkadapu
Linear Variable Differential
Transformers (LVDTs) are widely used as high-precision, contactless displacement sensors in industrial, metrological, and scientific applications. Their performance is typically characterised only within the central linear operating region, whereas their behaviour across large displacements, where
geometric and electromagnetic effects introduce significant non-linearity, remains poorly researched. In this work, we present a comprehensive analysis of the full-range response of an LVDT, spanning its entire mechanical stroke. Using a combination of custom-developed finite-element modelling pipeline and dedicated laboratory measurements, we demonstrate that the LVDT response comprises several distinct dynamical regimes. We introduce an analytically unified expression that accurately reproduces the measured response over all displacement scales, including linear and non-linear ranges, capturing the underlying physical features of the device. The model achieves high fidelity across the full range and provides closed-form first and second derivatives, enabling unambiguous displacement reconstruction, even in the non-linear regime where the voltage is multivalued. The derivative structure further clarifies the contribution of
geometric coupling, noise-dominated central behaviour, and envelope decay. This study establishes, for the first time, a systematic framework for modelling, interpreting, and utilising the full-range behaviour of LVDTs. It offers guidance for systems that undergo large quasi-static excursions, overload recovery, or long-range
alignment.
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Optics
Imaginary Poynting momentum driven particle bidirectional rotation along arbitrary trajectory
Lifang Zhao, Xue Yun, Yansheng Liang et al. (+1 more)
Research on optical rotational manipulation leveraging the imaginary Poynting momentum (IPM) force has predominantly centered on cylindrically polarized Gaussian and annular beams. Here, we extend this framework to tightly focused cylindrically polarized structured light fields possessing closed or open arbitrary-intensity trajectories. We systematically elucidate the rotational dynamics induced by IPM in such fields, characterizing the underlying mechanical effects and trapping flexibilities. Notably, despite carrying zero net angular momentum, these fields drive microparticles into bidirectional rotation along predefined trajectories, thereby challenging conventional paradigms reliant on
spin or orbital angular momentum. This IPM-mediated optical spanner offers unprecedented spatial degrees of freedom, paving the way for high-precision optical manipulation along arbitrarily tailored paths.
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All authors Lifang Zhao, Xue Yun, Yansheng Liang, Ming Lei
Atomic and Molecular Clusters · Cross-listed from quant-ph
Light-induced nonadiabatic dissipative quantum dynamics of the Na2 molecule
Patrick Barron, Krisztián Szabó, Gábor J. Halász et al. (+2 more)
Strong light-matter coupling between molecules and optical or plasmonic cavity modes has emerged as a promising platform for advancing photonics, materials science, and chemistry. However, optical cavities and plasmonic resonators in particular are inherently lossy systems characterized by finite
photon lifetimes. Accurate theoretical descriptions of molecular dynamics under strong coupling therefore require a proper treatment of cavity losses. In this work, we compare three theoretical approaches for modeling dissipative molecule-cavity dynamics within a realistic parameter regime: the Lindblad master equation, the
stochastic Schrödinger equation, and the non-Hermitian Schrödinger equation. As an example, we consider the two lowest energy state of Na2 molecule coupled to a cavity mode and analyze the time
evolution of the excited-state population and the mean
photon number. Our results demonstrate that the
stochastic Schrödinger equation provides an accurate and computationally efficient alternative to the Lindblad master equation, while the non-Hermitian Schrödinger approach is found to be applicable only within a limited range of conditions. Furthermore, we show that inclusion of molecular rotation leads to rotational-vibrational-photonic coupling and gives rise to pronounced nonadiabatic dynamics through light-induced conical intersections. These findings highlight the importance of both dissipation and rotational degrees of freedom for a realistic description of molecular dynamics in strongly coupled molecule-cavity systems.
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All authors Patrick Barron, Krisztián Szabó, Gábor J. Halász, Kálmán Varga, Ágnes Vibók
Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Hybrid NARX-LLM for Greenland Iceberg Discharge: Prompt-Driven Residual Correction
Yiquan Gao and Duohui Xu
Greenland iceberg discharge exhibits complex nonlinear dynamics with limited observability, challenging traditional predictive models. We present a Hybrid NARX-LLM framework that combines a nonlinear autoregressive model with exogenous inputs (NARX) and a large
language model (LLM) for residual correction. We further propose a Physics-Informed
Prompt (PIP) method that transforms unstructured physical knowledge into structured
prompts for zero-shot in-context
reasoning. The primary objective is to explore the corrective potential of this framework for modeling Greenland iceberg discharge, rather than merely optimizing predictive accuracy. The NARX component captures intrinsic temporal dependencies, while the LLM, guided by PIP, encodes glacier dynamics and environmental drivers and perceives key trend patterns to correct systematic prediction errors. This integration allows the model to reason about unmodeled factors and produce interpretable residuals, enhancing overall predictive accuracy. Applied to Greenland iceberg discharge time series, our approach addresses extreme events that are difficult to predict due to rare variations and nonstationary trends, a limitation often overlooked by traditional methods. By fusing structured time-series modeling with knowledge-driven foundation AI, the framework offers a scalable and interpretable pathway to bridge data-limited
climate forecasting with physics-informed LLM
reasoning. The code is available.
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History and Philosophy of Physics
Symmetry Breaking through Superselection by Boundary Conditions
Silvester G.A. Borsboom and José P. Dupont
Spontaneous
symmetry breaking (SSB) is central to modern physics but is conventionally defined only for infinite systems, raising challenges for its interpretation in finite, real-world setups. This paper argues that the key to resolving this issue lies in the underappreciated role of boundary conditions in
quantum systems. Inspired by both the relational approach to
symmetries and the physical mechanism behind
symmetry breaking, we formulate a relational interpretation of SSB: a finite system exhibits SSB relative to a reference environment which can induce perturbations across the boundary. This eliminates the need for the thermodynamic limit, offering a more physical picture of SSB that emphasizes the observable consequences of the interactions that real-life systems inevitably have with their environment. We show how, in this relational interpretation, SSB for both
lattice systems and (gauge) field theories should be understood as subtle, rather than spontaneous,
symmetry breaking, still in contrast to explicit
symmetry breaking. We also explain how algebraic definitions of SSB for infinite systems relate to the intuitive picture of SSB in finite systems and illustrate how asymptotic boundary conditions push the environment "to infinity". In this way, our relational interpretation of SSB provides a unified conceptual framework applicable to
symmetry-breaking in systems of any size.
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Biological Physics
Imaging biofilms in three dimensions: modalities, quantitative readouts, and the path to four-dimensional measurement
Seongsoo Lee and YongKeun Park
Biofilms are spatially structured microbial communities whose architecture, chemistry, mechanics, and cellular states evolve over time. Bulk assays and two-dimensional projections remain useful, but cannot alone resolve how these properties vary with depth or change during growth, treatment, dispersal, and regrowth. Imaging provides complementary routes to three-dimensional measurement: fluorescence microscopy supplies molecular, taxonomic, and functional specificity; optical coherence
tomography resolves mesoscale architecture and dynamics; quantitative phase imaging and holotomography report refractive index and biomass-related changes; Raman methods provide chemical and metabolic contrast; and Brillouin microscopy probes mechanical response. We compare these modalities using four independent descriptors-contrast provenance, live volumetric capability, perturbation, and demonstrated biofilm use-and connect their signals to quantitative biological readouts. No single modality simultaneously maximizes spatial coverage, resolution, acquisition speed, molecular specificity, and low perturbation. Implementations from any contrast class can serve as a longitudinal backbone when perturbation is empirically controlled at the relevant spatial and temporal scale, while molecularly specific measurements remain indispensable for identifying species, molecules, and functional states. We therefore frame four-dimensional biofilm measurement as a validated measurement architecture that integrates a low-perturbation volumetric backbone with spatially registered, molecularly specific measurements acquired continuously or at predefined validation points. Achieving this integration will require compatible cultivation formats, controlled imaging dose, shared quantitative parameters, and robust cross-modality registration.
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History and Philosophy of Physics · Cross-listed from gr-qc
General Relativity and Background Independence
Antonio Vassallo
General Relativity (GR) is widely regarded as a paradigmatic example of a background independent theory, a feature often taken to mark a decisive conceptual advance over its Newtonian and special relativistic predecessors. Yet the notion of background independence admits multiple formalizations, and its precise physical and philosophical significance remains contested. This chapter offers a systematic analysis of the strategies that have been proposed to capture background independence in classical spacetime physics. The discussion then turns to a central open question: whether, and in what sense, a successor theory of GR – such as a theory of
quantum gravity – should be expected to inherit GR's background independence. Drawing on contemporary debates and a range of case studies, the chapter argues that background independence is best understood as a diagnostic and comparative tool rather than as a necessary physical requirement. The resulting perspective highlights both the conceptual virtues and the interpretive costs of eliminating background structures, and helps to explain why background independence remains an open problem in contemporary foundational research.
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Computational Physics
Atomic Design Transformer: xTB-Validated 3D Molecule Generation from Scaffolds
Takao Kotani
We present an SE(3)-invariant
transformer for 3D-molecule generation, the Atomic Design
Transformer (ADT). ADT places atoms one at a time, autoregressively. The SE(3) invariance is achieved by tokenization: each new atom's position is encoded in a local coordinate frame of a previously placed atom. The network is a plain causal
transformer. For evaluation, we introduce xTB-Validated Rate (XVR), which checks whether the molecular
topology is preserved after xTB GFN2 geometry relaxation. On QM9, ADT is competitive with state-of-the-art baselines. For GEOM-Drugs, we present a quantitative
benchmark of scaffold-conditional 3D generation, evaluating seven scaffolds (benzene, pyridine, pyrimidine, pyrazine, furan, thiophene, cyclohexane) on the 30-atom-truncated ground-state GEOM-Drugs
dataset. XVR ranges from 11.1% (pyrazine) to 29.7% (benzene), all from a single trained model. The generated molecules are chemically diverse, and generation is fast by virtue of the plain causal-
transformer backbone. Application to the 50-atom-truncated GEOM-Drugs
dataset yields lower XVR while the per-bond and per-angle quality is retained. These results position ADT as a practical proposer for in silico molecular design.
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Atomic Physics
Atom Optics for Multidimensional Raman Interferometry
Yingpeng Zhao, Yiyang Shao, Wenjian Tong et al. (+7 more)
The coherent control of atomic wave packets in multiple momentum dimensions is a central challenge in Raman atom optics and a key requirement for multidimensional atom interferometry. In this paper, a momentum-basis theoretical framework is developed for two-dimensional Raman interactions. We formulate the atom-
laser interaction for two-dimensional Raman beams and obtain the effective two-level ground-state
Hamiltonian after adiabatic elimination of the excited states. The resulted
Hamiltonian is constructed on the reachable momentum-state
lattice and includes AC Stark shifts, intra-dimensional Raman couplings, and cross-dimensional Raman coupling terms, thereby describing multidimensional Raman dynamics beyond a simple superposition of independent single-dimensional models. The framework is used to analyze the principles and operating conditions of two-dimensional atom interferometry. Cross-dimensional Raman coupling and sequential reverse Raman transitions are identified as the main mechanisms that redistribute atoms into non-target momentum states and reduce the contrast of atomic interferometer fringe. Experimentally, Ramsey fringes are observed in a cold-atom fountain interferometer, with a contrast of $14.8\%$ at an interrogation time of $T=10~{\rm ms}$, in good agreement with the theoretical calculation. The conditions required for velocity-sensitive multidimensional atom interferometry are further clarified, including detuning control, velocity-class selection, and suppression of undesired inter-dimensional transitions. This work provides a theoretical and experimental basis for multidimensional Raman atom interferometry.
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All authors Yingpeng Zhao, Yiyang Shao, Wenjian Tong, Shuning Bao, Yuanlong Zhang, Mengnan Yi, Shengzhe Wang, Ke Shen, Bin Wu, Yanying Feng
Plasma Physics
Effects of external magnetic field ripple on FRC equilibrium
Zitong Qu, Ping Zhu, Zhipeng Chen et al. (+1 more)
The two-dimensional
equilibrium of Field-Reversed Configuration (FRC)
plasma in presence of an external ripple
magnetic field is computed to show the emergence of multiple
magnetic axes for hollow
equilibrium current profiles. An increase in ripple amplitude reduces the hollowness threshold required for the development of multiple
magnetic axes. For an intermediate range of the ripple axial period, the formation of multiple
magnetic axes becomes the most likely. The ripple's radial extension and the
curvature of the axial field are the critical factors underlying the non-monotonic effect of ripple's axial period. When the axial period increases from the lower range, the ripple's radial extension gradually grows and enhances the chance of forming multiple
magnetic axes. Once the ripple's radial extension covers the entire radial domain, further increasing the ripple axial period decreases the ripple field
curvature, which becomes the dominant factor for lowering the hollowness threshold for the formation of multiple
magnetic axes.
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All authors Zitong Qu, Ping Zhu, Zhipeng Chen, Haolong Li
Applied Physics
Acoustic propagation of a vortex beam in typical Arctic sound environments
Chengjun Wang, Liwei Chen, Tengjiao He et al. (+2 more)
This study investigates the propagation of acoustic
vortex beams carrying orbital angular momentum (OAM) in the Arctic
underwater environments including the half-channel and the double duct. We produce a
vortex beam with a 126-element hexagonal transducer array and model the acoustic propagation based on the ray method. It is found that under the typical Arctic circumstances,
vortex beams with helical phase structures exhibit two unique capabilities. First, in the near field, the divergent components of
vortex beams traveling at steep grazing angles illuminate shadow zones without mechanical steering of the acoustic source, which cannot be obtained by point or coherent sources at the same configuration. Second, despite strong boundary interactions and sound-speed inhomogeneity, the phase singularities and OAM modal content remain remarkably robust and can be identified at long ranges to some extend. The ice cover induces a larger transmission loss compared to the pressure release boundary condition because of the acoustic absorption in the ice canopy modeled as an elastic layer. These results advance the understanding of structured acoustic wave propagation in complex polar environments and thus provide a theoretical basis for subglacial exploration and under-ice acoustic communication.
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All authors Chengjun Wang, Liwei Chen, Tengjiao He, Lisheng Zhou, Zhixiong Gong
Fluid Dynamics
Effects of permeability on hindered settling of porous particles
Alexander Metelkin and Bernhard Vowinckel
We investigate the settling behavior of suspensions of highly porous and permeable particles in the viscous regime using particle-resolved direct numerical simulations (DNS). The simulations employ a coupled Euler-Lagrange framework that accounts for particle permeability. The results show that the settling behavior of permeable particles follows the classical power-law relationship of Richardson-Zaki in terms of their settling velocity, but particles with higher permeability settle faster as the particle volume fraction increases. At a particle volume fraction of 30 percent, the difference in settling speed is up to 106 percent between the least and most permeable particles investigated in this study. We explain this effect by the alteration of counter flows induced by the fluid displacement of settling particles. Quantitative analysis of the mean vertical fluid velocity confirms that suspensions composed of more permeable particles generate weaker counterflows, posing less resistance to the settling motion. We furthermore show how velocity fluctuations and self-diffusivity depend on the permeability of the porous particles and the particle volume fraction. Both quantities increase with volume fraction and are largest for the least permeable particles, except at the highest volume fraction, where reduced settling velocities reverse this trend. The influence of particle permeability also reveals two effects in the particle microstructure. First, the analysis showed that particle clustering decreases with increasing permeability. Second, the overall probability of finding a neighbor within the lubrication range is lowest for the least permeable particles. We attribute this to the weakening of repulsive pressure forces between tumbling particles with increased permeability.
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Atomic Physics
Simultaneous Determination of Multiple Nuclear Parameters of $^{229}$Th Using Highly Charged Ions
Hong-Yuan Zheng, Yan-Ling Xu, Xi-Chen Yu et al. (+4 more)
Development of a $^{229}$Th
nuclear optical clock requires precise and model-insensitive
nuclear-structure parameters, which presently suffer from limited accuracy and poor consistency. We propose a joint spectroscopy scheme using two highly charged $^{229}$Th ions with $J=1/2$ electronic ground states, where the lowest electronic excitation energy of each ion far exceeds the
nuclear transition energy. This configuration effectively forms a three-level system comprising the electronic ground state and the
nuclear ground ($g$) and isomeric ($m$) states, resulting in strongly enhanced
nuclear hyperfine mixing. Within this framework, a unified analysis of precision measurements on both ions enables the simultaneous determination of five key
nuclear parameters without relying on external
nuclear inputs: the
magnetic dipole moments $\mu_g$ and $\mu_m$, the bare-
nucleus transition energy $\omega_n$, the charge-radius difference $\delta\langle r^{2}\rangle_{gm}$, and the $M1$ transition
matrix element $T_{M1}$. With this approach, the uncertainties in $\omega_n$ and $\delta\langle r^{2}\rangle_{gm}$ are estimated to be reduced by factors of 3 and 2, respectively, relative to their current uncertainties. %compared with current values. This work could provide a useful
benchmark for
nuclear theory and serve as a foundation for future development of a $^{229}$Th-based
nuclear optical clock.
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All authors Hong-Yuan Zheng, Yan-Ling Xu, Xi-Chen Yu, Yong-Hui Zhang, Zong-Chao Yan, Li-Yan Tang, Xiaojun Liu
Medical Physics
MR Simulation with Phase Distribution Graphs: Off-Resonant Pulse Response and Slice-Selection
Felix Dietz, Jonathan Endres, Simon Weinmueller et al. (+2 more)
Purpose: Phase Distribution Graphs were introduced as a powerful tool for on-resonant MRI simulations. Herein, we extend the concept beyond the assumptions of hard and on-resonant RF pulses in Phase Distribution Graph simulations, while retaining differentiability across all parameters. The extension into the frequency domain further generalizes the Phase Distribution Graph simulation framework for sequence simulation and optimization. Theory and Methods: Using an effective axis rotation model, the RF operator is generalized to off-resonant rotations, originating from field inhomogeneities, chemical shift, and field gradients. Discretization of the RF pulse shape enables the modeling of the magnetization response to shaped RF pulses and thus slice selection. Results: Including off-resonant pulse response into a PDG based MRI simulation enables the simulation of key MRI features, such as fat suppression, binomial pulses, or Bloch-Siegert shifts. The discretization of RF shapes enables the simulation of their respective frequency response and thus slice selective excitation, refocusing or saturation pulses, including multi-band excitation. In combination with flow, typical inflow artifacts in slice-selective MRI can be simulated. Discussion and Conclusion: Extension for off-resonance removes a major limitation of phase distribution graphs and makes the simulation framework more realistic. As the method is not restricted to specific RF shapes, optimization of RF pulse shapes in amplitude, phase and frequency is now possible in the context of or jointly with specific MR sequences.
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All authors Felix Dietz, Jonathan Endres, Simon Weinmueller, Johanna Link, Moritz Zaiss
Optics
Single Nanoparticle Dynamics in Opto-Thermal Tweezers: Resolving the Temporal Resolution of Depletion Force Trapping
Jinchao Chen, Robert Talla Kontchou, Saurabh Rai et al. (+4 more)
Optothermal tweezers enable the manipulation of a wide range of nano-objects through optically induced depletion forces. Despite significant advances, the temporal dynamics of optothermal trapping remain elusive, as existing methodologies rely almost exclusively on time and ensemble averaging. Consequently, stable trapping cannot be distinguished from local transient accumulation, where the time-averaged concentration increases but particles exhibit rapid, dynamic motion in and out of the trap. Here we investigate optothermal trapping with single-nanoparticle-level analysis and sub-millisecond temporal resolution. Our data resolve the elusive dynamics of 40 nm polystyrene nanoparticles trapped within depletion force potentials in polyethylene glycol solutions, enabling to differentiate the conditions leading to extended trapping times from those leading to transient localization. Numerical simulations corroborate our experimental findings, elucidating how the interplay between thermophoresis and diffusiophoresis governs nanoparticle dynamics. These insights deepen our mechanistic understanding of optothermal trapping and unlock opportunities for single-molecule studies, nanoscale assembly, and targeted drug delivery.
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All authors Jinchao Chen, Robert Talla Kontchou, Saurabh Rai, Guillaume Baffou, Sylvain Blaize, Quanbo Jiang, Jérôme Wenger
Fluid Dynamics
Vorticity-dynamical analysis of Richtmyer-Meshkov instability based on orbital-spin vorticity decomposition
Xi Chen, Tao Chen and Tianshu Liu
The present study provides a detailed vorticity-dynamical analysis of shock-driven hydrodynamic physics in canonical Richtmyer-Meshkov instability (RMI) flows: shock interaction with a single-mode perturbed interface, and a cylindrical air bubble immersed in Krypton. These findings provide insights into vortical flow physics beyond the conventional vorticity paradigm, and the DVD approach holds promise for the diagnosis of practical instability-induced flows.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Interaction-enabled topological pumping of Rydberg electrons
Chenxi Huang, Tao Chen, Kaden R. A. Hazzard et al. (+2 more)
Topological pumping is a paradigmatic realization of quantized transport in band systems, yet its fate in strongly correlated regimes, especially with long-range interactions, remains largely unexplored. Here we report the experimental observation of interaction-enabled topological pumping of correlated Rydberg electrons in a synthetic
lattice. We show that dipolar exchange interactions induce a controllable shift of the underlying topological singularity in parameter space, such that a fixed pumping trajectory can be driven through successive topological transitions by tuning the interaction strength alone. This leads to the emergence and breakdown of quantized transport. The observations are consistent with an effective Rice-Mele description with interaction-renormalized onsite potentials and are supported by characterizing the adiabaticity and robustness to control trajectory imperfections. Our results establish a platform for exploring interaction-controlled topological transport beyond perturbative regimes and open a route toward engineering correlated topological matter in synthetic
quantum systems.
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All authors Chenxi Huang, Tao Chen, Kaden R. A. Hazzard, Jacob P. Covey, Bryce Gadway
Atomic Physics · Cross-listed from cond-mat.quant-gas
Programmable Gauge-Field Textures with Ultracold Atoms in Momentum Space
Hongru Wang, Hang Li, Yichen Pan et al. (+4 more)
Synthetic gauge fields with ultracold atoms offer a route to
quantum matter in which electromagnetic environments can be designed rather than merely imposed. While the Harper-Hofstadter model has been realized in several cold-atom systems, existing implementations are largely limited to spatially uniform
magnetic fluxes. Here we experimentally realize a highly programmable two-dimensional momentum-state
lattice of ultracold atoms with local control over the Peierls phase pattern, enabling direct implementation of Harper-Hofstadter
Hamiltonians with tunable and spatially structured synthetic gauge fields. We observe a crossover from ballistic to strongly flux-modified bulk dynamics with suppressed transport. By introducing a synthetic electric field through site-dependent energy gradients, we further demonstrate
Hall-type transverse drift arising from the interplay between electric and
magnetic fields. In addition, we engineer a synthetic flux domain wall separating regions with opposite
magnetic fluxes and observe anisotropic propagation guided along the interface. These results move cold-atom gauge-field engineering from uniform
magnetic backgrounds toward designer gauge textures, providing an experimental setting for transport across programmable topological interfaces.
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All authors Hongru Wang, Hang Li, Yichen Pan, Yuyan Luo, Bryce Gadway, Tao Chen, Bo Yan
History and Philosophy of Physics
Information Is Not Physical: Possibility Spaces, Erasure, and the Structure of Unrealized Alternatives
Madhurendra Mishra
The slogan “information is physical,” introduced by Rolf Landauer and developed through
quantum information theory and black-hole thermodynamics, has achieved near-axiomatic status in modern physics. Yet the ontological status of information remains surprisingly underexamined: most discussions either reduce information to a form of energy or treat it as a purely mathematical object. This paper proposes a third position. I argue that information is neither a physical substance nor a free-floating abstraction, but rather the structure of physically realizable alternatives – a counterfactual structure that a physical system instantiates in virtue of the possibility space available to it. Building on Shannon's combinatorial definition, the Landauer principle, the no-cloning
theorem, and the black-hole information paradox, I show that the informational content of any physical event is constituted by the set of outcomes that could have occurred but did not. This counterfactual reading dissolves several persistent confusions: it explains why erasing information dissipates heat without making information “material,” why
quantum superposition is informationally richer than any classical mixture, and why information loss in black holes is physically significant beyond mere bookkeeping. The proposal sits within a structural-realist framework but departs from standard structural realism by locating the relevant structure in modal, not merely actual, relations. I conclude by sketching implications for the foundations of
quantum mechanics,
quantum gravity, and scientific ontology more broadly.
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