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Physics

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Wednesday 26 August

Optics

Nonconcentric Multi-shell Nanowires: Geometry-Induced Plasmon Hybridization and Near-Field Localization

Gino Wegner, Jer-Shing Huang and Kurt Busch

Localized surface plasmons (LSPs) in multi-shell nanostructures provide a versatile route for controlling optical fields at the nanoscale, yet the influence of deviations from concentric geometries remains insufficiently understood. Here, we investigate the impact of shell nonconcentricity on the quasistatic optical response of core-single-shell and core-multi-shell nanowires. Exploiting the conformal properties of bipolar coordinates, we derive analytical solutions for nonconcentric cylindrical interfaces and systematically analyze the evolution of LSP resonances, absorption spectra, and near-field distributions. Starting from single-shell structures, we show that nonconcentricity enables finite coupling of incident radiation to higher-order plasmon modes that are optically inactive in the quasistatic concentric limit. Extending the analysis to multi-shell bull's eye wires, we identify how shell thickness, number of fixed-thickness shell units, each defining a set of a dielectric and metal shell, as well as interface nonconcentricness shape the hybridized plasmon spectrum. Increasing the number of metal-dielectric interfaces broadens the spectral response, while nonconcentric geometries additionally increase the density of accessible resonances and localize electromagnetic fields preferentially within and around the thinner shell sections. Eventually, comparison of concentric with bipolar and Doppler-grating-inspired nonconcentric bull's eye wires based on Mie theory and full-wave Discontinuous Galerkin Time-Domain simulations, respectively, allows to assess the impact of nonconcentricness for typical nanowire dimensions. These results provide insight into geometry-induced plasmon hybridization and suggest routes toward nanoscale control of optical energy localization for applications in active nanophotonics and plasmon-assisted photochemistry.
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High Energy Physics (Experiment)

A Weighting Method for Incorporating Mass Resolution Effects in Amplitude Analysis

Benhou Xiang, Wenqian Zheng, Hongxun Yang et al. (+2 more)

We present a phase-space weighting method for incorporating detector mass-resolution effects into amplitude analysis in an efficient and flexible way. The method uses fully simulated Monte Carlo samples containing both truth-level and reconstructed kinematics to estimate the local detector response around each observed event. Based on these truth-reconstruction correspondences, event-by-event weights are constructed to map theoretical amplitudes from the true phase space to the smeared observational space. In this way, detector smearing can be included in the likelihood fit without performing an explicit multidimensional convolution or on-the-fly detector simulation. The procedure naturally handles nonuniform resolution across the Dalitz plane and can be extended beyond invariant masses to momentum and angular variables. Applied to the decays $J/\psi \rightarrow \Xi^{-} \bar{\Xi}^{+}\pi^0$ and $J/\psi\rightarrow K^-\Lambda\bar{\Xi}^+$, the method significantly reduces biases in fitted resonance parameters and interference patterns, suppresses artificial structures, and improves the reliability of partial-wave analysis and resonance spectroscopy in high-precision hadron experiments.
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All authors Benhou Xiang, Wenqian Zheng, Hongxun Yang, Xiaolin Kang, Shuangshi Fang

Earth and Planetary Astrophysics

An Approximately 70-Year Core-Related Modulation of Earth Rotation and Its Implications for the Leap Second

Zewen Zhang, Yuanwei Wu, Xishun Li et al. (+4 more)

Recent observations of Universal Time (UT1) indicate an acceleration in Earth's rotation. If sustained under the current leap-second framework, this behavior could eventually prompt consideration of a negative leap second. We examine whether the recent acceleration is consistent with an approximately 70-year, core-related modulation of length of day (LOD). After removal of modeled tidal, surface-fluid, and secular contributions, residual LOD contains a near-70-year component, and a similar component is present in core angular momentum (CAM)-derived equivalent LOD inferred from geomagnetic observations. All harmonic, spectral, and LOD-CAM analyses reported here use the common 1883–2022 interval. Harmonic regression over trial periods of 50–100 yr gives periods of 69.7 yr for residual LOD and 71.8 yr for CAM-derived equivalent LOD, with amplitudes of 2.87 and 1.94 ms, respectively. Lomb–Scargle spectra show peaks near 67.8 and 70.5 yr. The annual series have a zero-lag correlation of 0.918. Their lagged correlation has a broad maximum for a CAM lead of approximately 1-3 yr, with a numerical maximum of 0.932 at 2 yr. Because both records are strongly autocorrelated, these coefficients are used to characterize their correspondence rather than to assess predictive significance. The results are consistent with a core-related contribution to low-frequency rotational variability, but they do not uniquely separate the contributions of electromagnetic, topographic, gravitational, and viscous core–mantle coupling mechanisms. Within the fitted model, the multidecadal component alone does not indicate sustained near-term shortening of the day that would, by itself, require a negative leap second. This is a model-dependent geophysical assessment, not an operational prediction of future UTC adjustments.
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All authors Zewen Zhang, Yuanwei Wu, Xishun Li, Dang Yao, Xuan Cheng, Xuhai Yang, Shougang Zhang

High Energy Physics (Experiment)

A High Performance Partial Wave Analysis Framework for Hadron Spectroscopy

Benhou Xiang, Shuangshi Fang and Beijiang Liu

Partial wave analysis (PWA) is a key method in hadron physics for extracting the properties of hadronic resonances. As experimental statistics grow, conventional implementations face severe difficulties in both memory usage and speed. We present CTPWA, a high performance PWA framework based on covariant tensor formalism. This framework adopts extensive precomputation and caching mechanisms, as well as fully GPU-based likelihood computation and minimization. With these optimization, the fitting speed is accelerated by two orders of magnitude relative to autograd-based GPU PWA programs, rendering high-statistics partial-wave analysis feasible at high-precision experiments like BESIII.
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Instrumentation and Methods for Astrophysics

Simulating an imaging atmospheric radio telescope to observe cosmic gamma rays and cosmic neutrinos

Sebastian Achim Mueller, Anne Timmermans, Juan Ammerman-Yebra et al. (+1 more)

Observations of cosmic gamma~rays with energies above the 10$^{12}$ electronvolts (TeV) regime are often a direct probe of events where our theoretical predictions are challenged by extreme conditions. Because high energetic cosmic gamma-rays are rare, one needs collection areas with the size of soccer fields (10$^{5}$ m$^2$) or more to gather significant counting statistics in short time. The imaging atmospheric Cherenkov telescope detects cosmic gamma-rays in such large areas and currently offers the best reconstruction power for the cosmic particle's type, energy, and direction in particular. However, with only about 1,000 hours of dark and clear nights every year, the imaging atmospheric Cherenkov~telescope only has a duty cycle of about $12\%$. To overcome this limitation, we propose a novel imaging atmospheric radio telescope. By observing radio emission in the $10$ GHz regime from air showers, the imaging atmospheric radio telescope could observe 24/7, independent of the day night cycle, and almost independent of the weather. The novelty here is the high resolution imaging of the air shower's radio emission which might result in high resolution images as one finds them in imaging atmospheric Cherenkov~telescopes. We present a technique to simulate the image formation in the radio telescope using wave mechanics instead of conventional ray tracing. The imaging atmospheric radio telescope could increase our access more than eight-fold to an accurately reconstructed high energy gamma-ray-sky. Further, the imaging atmospheric radio telescope might also eight fold the observation power for cosmic neutrinos in the so called Earth-skimming technique.
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All authors Sebastian Achim Mueller, Anne Timmermans, Juan Ammerman-Yebra, Harm Schoorlemmer

Quantum Physics

Superadditivity of classical communication over quantum channels via random and deterministic permutations

Benjamin Lovitz and Peixue Wu

Since Hastings' proof of superadditivity of classical communication over quantum channels, considerable effort has been devoted to finding a structural explanation of this phenomenon that was originally established by concentration of measure for Haar random unitaries. The main observation of this work is that Haar randomness can be replaced by random permutations without changing the limiting geometry responsible for nonadditivity. This replacement turns a continuous problem over unitary matrices into a discrete combinatorial problem over zero–one permutation matrices, and thereby opens a path toward derandomization. The theorem of Bordenave and Collins shows that random permutations have the required limiting behavior and the algorithm of O'Donnell and Wu then provides a deterministic asymptotic construction, running in polynomial time in the size when the channel parameters and accuracy are fixed. Thus the random construction can be derandomized in an asymptotic algorithmic sense. Finally, a quantitative random permutation estimate by Chen, Garza-Vargas, Tropp and van Handel gives a fully numerical estimate: there exists a tuple of 57,836,025 permutations acting on a set of size \[ N \le 5.422\times 10^{116216}\] such that the associated finite dimensional channel exhibits nonadditivity. This enormous value remains an obstacle to a practical construction.
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Quantum Physics

Dissipatively Stabilized 0-n Fock Qubits for Noise-Biased Quantum Computing

Su Direkci, Simon Lieu, Kyungjoo Noh et al. (+1 more)

Noise-biased qubits have bit-flip errors that are exponentially suppressed relative to phase-flip errors, and offer a promising route toward fault-tolerant quantum computing. However, this bias can be compromised during gate operations with non-biased control qubits. To address this limitation, we propose a "0-n" Fock qubit architecture that maintains the noise bias by encoding information in the ground state and n-th excited state of a nonlinear multi-level system, such as a transmon. This encoding is achieved via a dissipative stabilization that acts as decay and gain for lower and upper intermediate levels, respectively. We first analytically demonstrate that bit-flip errors are exponentially suppressed with the number of levels. Then, we present a practical implementation using a multi-mode lossy filter to achieve the frequency-selective dissipation. Finally, we numerically demonstrate that bit-flip probabilities approaching $10^{-8}$ are achievable for controlled-X gates on cat qubits using the 0-n qubit as an ancilla with $n \geq 9$ (i.e. ten or more levels), for realistic experimental parameters. Building on this, we simulate syndrome extraction in a repetition code, achieving logical error rates in the megaquop regime with only a distance of $d=9$.
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All authors Su Direkci, Simon Lieu, Kyungjoo Noh, Connor T. Hann

Solar and Stellar Astrophysics

Exploring Late Stellar Evolution in the Era of Large Surveys: Machine Learning Prospects for Hot Subdwarfs and White Dwarfs

Princy Ranaivomanana and Murat Uzundag

The rapid growth of large-scale astronomical surveys and advances in data-driven analysis techniques have transformed the study of late-stage stellar evolution. Modern facilities are producing large volumes of photometric, spectroscopic, and astrometric data, enabling systematic investigations of compact stellar populations across the Milky Way. Among the most important tracers of these advanced evolutionary phases are hot subdwarfs and white dwarfs: hot subdwarfs are core-helium-burning tracers of late, binary-driven stellar evolution, while white dwarfs represent the final evolutionary endpoint of low- and intermediate-mass stars. These compact objects provide important laboratories for studying stellar interiors, binary evolution, and the long-term fate of planetary systems. This paper explores how recent advances in machine learning are being applied to the detection, characterization, and, when combined with follow-up spectroscopy and modeling, the physical interpretation of hot subdwarfs and white dwarfs. By combining photometric, spectroscopic, and time-domain observations with these computational tools, it is now possible to efficiently discover rare objects, detect stellar variability, and probe the internal structure and evolutionary pathways of compact stars. Ultimately, these developments highlight the growing role of advanced algorithms in supporting the study of the final stages of stellar evolution, provided their outputs are validated against physical observables.
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History and Philosophy of Physics

Dark Matters of Principle: Principles in the Dark Matter Paradigm

Patrick Duerr and James Read

This paper re-examines the Dark Matter (DM) problem through the lens of physical principles. We first develop a functionalist account and taxonomy of principles. We propose to define principles in terms of their intended functions or purposes. Their argumentative force boils down to context-sensitive and often tentative reasons for believing them adequate for those purposes. In research contexts in which novel theories or models are sought which push the boundaries of knowledge into new domains, reliance on well-motivated principles as principal building blocks is a historically widespread, natural, and methodologically prudent research strategy—what we'll dub "principled inquiry". In a second step, we apply this methodological machinery to the DM problem. Through detailed analyses of four mainstream DM approaches—supersymmetric WIMPs, axions, sterile neutrinos, and primordial black holes—we substantiate four claims. (C1) The DM paradigm is formed by the framework of possibilities, circumscribed by a shared cluster of regulative and constitutive principles of gravitational and non-gravitational physics. (C2) Besides those common principles, the four DM models also depart from other principles of orthodox physics in distinct ways. (C3) They do so to different degrees—displaying different forms and extents of "minimal mutilation" with respect to some of the principles of established non-gravitational physics. (C4) The guidelines of principled inquiry clarify the sense in which the DM problem constitutes an ever-more disconcerting crisis: worries are growing that the principles on which DM researchers have routinely and rationally relied may have run out of heuristic steam. Pressure is mounting to "leave no stone unturned" (Bertone and Tait 2018): scientists ought to increasingly explore ideas that stray more radically from the cautious explorations of principled inquiry.
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Quantum Physics

Position- and Momentum-Space Quantum Information Measures of the Double-Morse Oscillator

Firoz Chogle, Ernesto Damiani and Berihu Teklu

We investigate the quantum-information properties of a particle confined by the double Morse potential in position and momentum spaces. The quasi-exact solvability of the model gives analytical expressions for the first two bound states, allowing the corresponding probability densities to be analyzed directly. Shannon entropy, Onicescu energy, Fisher information, statistical complexity, and Fisher-Shannon products are evaluated as functions of the parameter $A$, which controls the transition from a well-separated double well to a merged single-well profile. The position distribution is more delocalized and structurally complex when the double-well character is pronounced, whereas the momentum distribution exhibits the complementary trend. As the wells merge, the ground-state Fisher–Shannon product approaches its Gaussian reference value, whereas the excited state retains stronger non-Gaussian structure.
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Other Condensed Matter

Landau Theory for Commensurate Charge-Density Waves Coupled to Uniform Lattice Deformation

Keiji Nakatsugawa, Toshiyuki Fujii and Satoshi Tanda

We formulate a minimal Landau theory for a charge-density wave (CDW) whose commensurability is defined with respect to a deformed lattice. The motivation is provided by recent observations on an isolated single NbS$_3$ chain, which exhibits a commensurate CDW state accompanied by a $6\%$ shrinkage of the lattice constant. A uniform stretch $a_0\to a_0(1+\varepsilon)$ changes the reciprocal lattice wave number to $G(\varepsilon)=G_0/(1+\varepsilon)$, so that an $N$-fold commensurate CDW has the wave number $Q_\mathrm{C}(\varepsilon)=G(\varepsilon)/N$, whereas the wave number $Q_\mathrm{IC}$ favored by the incommensurate instability remains fixed. We propose an amplitude-strain free energy for both $N=3$ and $N=4$, in which the CDW induces a finite uniform strain by relieving the mismatch between $Q_\mathrm{C}(\varepsilon)$ and $Q_\mathrm{IC}$. The mismatch is shared between the CDW and the lattice in a proportion set by their stiffness ratio; since the CDW stiffness grows with the CDW amplitude, the lattice takes up an increasing share of the mismatch as the CDW develops. Our results suggest a reexamination of lock-in theories and of strain-tuning experiments on density-wave systems.
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Quantum Physics

Entirely nonlocal quantum magic without entanglement

Fuchuan Wei, Ruixia Wang, Yujia Zhang et al. (+4 more)

Nonstabilizerness, or magic, is an archetypal quantum resource that is necessary for quantum computational advantage. Here we uncover a phenomenon seemingly at odds with the quantum nature of magic: entirely nonlocal magic (ENM)—magic present only in correlations and absent from each party's marginal—can live without entanglement. We systematically study this separation and show it is universal and operationally reversible: every magical state or channel can be encoded into and recovered from a separable ENM realization using only local stabilizer processing and classical communication. We leverage this mechanism to devise an activation key protocol in which a classical key controls access to non-Clifford operations. We further formulate magic secret sharing, in which computational power inaccessible to any party alone becomes accessible through cooperation. On a superconducting quantum processor, we experimentally demonstrate activation key and network computing primitives, together with separable ENM state preparation and extraction protocols. Together, our results establish that magic can be classically activated, localized, and secret-shared without entanglement, providing new resource-control primitives for distributed quantum computation.
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All authors Fuchuan Wei, Ruixia Wang, Yujia Zhang, Huihui Li, Junfeng Li, Fei Yan, Zi-Wen Liu

High Energy Astrophysical Phenomena

Evidence for a spectral steepening of the gamma-ray emission from the Galactic Center ridge

A. Acharyya, F. Aharonian, H. Ashkar et al. (+131 more)

Very-high-energy (VHE) $\gamma$-ray emission detected from the central molecular zone (CMZ) hints at diffusive propagation of cosmic rays (CRs) injected continuously near the Galactic center (GC). Using H.E.S.S. VHE $\gamma$-ray observations, we aim to construct a multi-component description of the region in order to derive the spatial and spectral distributions of CRs and discuss their potential origin. We rely on a spectro-morphological analysis, in which spectral and spatial parameters of different components are fit simultaneously, and on a three-dimensional description of the CMZ and CR distributions. The GC ridge emission is well reproduced with the assumed gas distribution model weighted by a $1/r^{\alpha}$ CR density profile with $\alpha = 1.10 \pm 0.05_{\rm{stat}} \pm 0.10_{\rm{syst}}$. We detect no significant spectral variations across the CMZ, which supports a continuous injection from the GC. We report a significant (> 3 $\sigma$) curvature in the GC ridge $\gamma$-ray spectrum, implying a parent proton break (or cutoff energy) of $E_b \sim 15-50$ TeV ($E_{\rm{cut}} \sim 60-160$ TeV). We also derive the best-fit spectral parameters of the other sources in the region and report a significant cutoff at $E \sim 5$ TeV in the spectrum of the pulsar wind nebula G0.9+0.1. Finally we constrain the position of the injection site to be close to the GC (ruling out the Arches and Quintuplet clusters as major contributors to the emission). We discuss possible origins for the GC ridge emission, potential mechanisms for causing the observed curvature, a possible contribution of the gas content to the emission of HESS J1745-290 and derive qualitative constraints on the line-of-sight positions of the clouds shaping the CMZ.
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All authors A. Acharyya, F. Aharonian, H. Ashkar, M. Backes, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, M. Böttcher, C. Boisson, J. Bolmont, F. Brun, C. Burger-Scheidlin, T. Bylund, S. Casanova, D. Cecchin Momesso, M. Cerruti, M. Chakraborty, A. Chen, M. Chernyakova, J. O. Chibueze, O. Chibueze, T. Collins, B. Cornejo, G. Cotter, G. Cozzolongo, J. de Assis Scarpin, M. de Naurois, E. de Ona Wilhelmi, J. Devin, A. Djannati-Ataï, A. Dmytriiev, K. Egberts, K. Egg, C. Escanuela Nieves, P. Fauverge, S. Fegan, K. Feijen, M. D. Filipovic, G. Fontaine, S. Funk, S. Gabici, Y.A. Gallant, M. Genaro, J.F. Glicenstein, J. Glombitza, P. Goswami, M.-H. Grondin, L. Heckmann, B. Heß, W. Hofmann, T. L. Holch, M. Holler, M. Jamrozy, F. Jankowsky, A. Jardin-Blicq, I. Jaroschewski, D. Jimeno, I. Jung-Richardt, K. Katarzynski, D. Kerszberg, B. Khélifi, N. Komin, K. Kosack, D. Kostunin, R.G. Lang, S. Lazarevic, A. Lemière, M. Lemoine-Goumard, J.-P. Lenain, P. Liniewicz, A. Luashvili, J. Mackey, D. Maheso, D. Malyshev, D. Malyshev, V. Marandon, M. G. F. Mayer, A. Mehta, A.M.W. Mitchell, R. Moderski, L. Mohrmann, H. Ndiyavala, J. Niemiec, P. O'Brien, L. Olivera-Nieto, M.O. Moghadam, S. Panny, M. Panter, R.D. Parsons, P. Pichard, T. Preis, G. Pühlhofer, M. Punch, A. Quirrenbach, A. Reimer, O. Reimer, Q. Remy, H. X. Ren, B. Reville, F. Rieger, G. Roellinghoff, G. Rowell, B. Rudak, K. Sabri, V. Sahakian, A. Santangelo, M. Sasaki, F. Schüssler, J.N.S. Shapopi, I. Shebalkova, W. Si Said, H. Sol, L. Stawarz, R. Steenkamp, S. Steinmassl, T. Tanaka, A.M. Taylor, G. L. Taylor, R. Terrier, Y. Tian, M. Tsirou, N. Tsuji, T. Unbehaun, C. van Eldik, C. Venter, J. Vink, V. Voitsekhovskyi, T. Wach, S.J. Wagner, A. Wierzcholska, M. Zacharias, A. Zech, W. Zhong

Plasma Physics

Machine learning methods for modelling local, linear gyrokinetic simulations of MAST-U pedestal turbulence

Anna Niemelä, Daniel Jordan, Aaro Järvinen et al. (+8 more)

Gyrokinetic (GK) stability strongly influences the performance of high-confinement-mode pedestals in spherical tokamak plasmas. High-fidelity gyrokinetic codes such as GENE can model microinstability-driven transport, but the computational cost limits their routine use in integrated pedestal modeling workflows. Instead, present workflows often rely on reduced transport assumptions, such as the ballooning-critical pedestal model used in EPED. This work investigates machine-learning surrogate models for local linear gyrokinetic simulations in a MAST-U-relevant pedestal parameter space, with the aim of providing faster gyrokinetic-based inputs to reduced pedestal models. A sampling workflow is developed in which pedestal profile parameters are varied within experimentally motivated bounds and used to generate physically self-consistent Grad-Shafranov equilibria. This reduces the dimensionality of the data-generation problem compared with sampling local gyrokinetic inputs directly, while maintaining physically plausible combinations of plasma profiles, geometry, and local stability parameters. The surrogate models are trained to predict linear growth rates, real frequencies, and diffusivity-ratio transport fingerprints from local linear GENE simulations. A multi-head multilayer perceptron accurately reproduces the growth rate, while the diffusivity ratios and real frequency exhibit more clustered, regime-dependent behavior. A multi-head classification-regression model using frequency-based regime classes reduces the mean absolute error for these clustered targets and better captures sharp transitions associated with changes in the underlying instability regime, although errors near mode-transition regions remain a limitation.
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All authors Anna Niemelä, Daniel Jordan, Aaro Järvinen, Amanda Bruncrona, Adam Kit, Lorenzo Frassinetti, David Hatch, Leonhard Leppin, Samuli Saarelma, the MAST Upgrade team, EUROfusion Tokamak Exploitation team

Superconductivity

Fluxtube Bouquets and Type-1.5 Clustering in Superfluid Neutron Star Cores

Adarsh Karekkat, Gabriele Montefusco and Marco Antonelli

We study mesoscopic configurations of a neutron superfluid coupled to a proton superconductor in the outer core of a neutron star. The condensates are described by a two-component Ginzburg-Landau free energy with local couplings, neglecting genuine phase-gradient entrainment. In two spatial dimensions, we minimize the free energy using quasi-periodic boundary conditions and constrained phase-imprinting calculations to study vortex-fluxtube and fluxtube-fluxtube interactions. We find that, for locally attractive couplings in the free energy, vortex-fluxtube overlap is energetically favoured and several pre-existing proton fluxtubes can bind around a neutron vortex, forming finite vortex-centred aggregates that we call fluxtube bouquets. These bouquet configurations may become so dense that a vortex can effectively accommodate several quanta of magnetic flux. We also confirm the possible presence of a type-1.5-like regime and find that it survives in the zero-entrainment regime considered here. In this type-1.5 regime, the fluxtube-fluxtube interaction is repulsive at short distances and attractive at intermediate distances, leading to self-assembled clusters while the individual fluxtubes remain topologically distinct. Possible implications for dissipative coupling and transport in neutron stars are discussed.
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High Energy Physics (Theory) · Cross-listed from math.AG

Quasimaps to Nakajima varieties as critical loci

Spencer Tamagni

$X$ is a Nakajima quiver variety. In this note we report the observation that the space parameterizing quasimaps from $\mathbb{P}^1$ to $X$, sending infinity to a given point, may be presented globally as the critical locus of an explicit function.

Geophysics

Continually learning neural-operator surrogate for three-dimensional airborne electromagnetic Bayesian inversion

Jaehong Chung, Andrew Lockwood and Jef Caers

Three-dimensional probabilistic inversion of time-domain airborne electromagnetic (AEM) data is limited by the cost of the forward solve. Even though one simulation takes only tens of seconds, a Bayesian inversion of a survey of millions of soundings requires of order $10^{10}$ forward evaluations. To address this, we develop a continually learning neural-operator surrogate of the three-dimensional AEM forward operator that replaces the solver inside the Bayesian inversion. We start from the point of view that regardless of what geological prior is specified, Maxwell's laws remain invariant. Secondly, we avoid the limitation of learning on a single prior by continual learning on consecutive priors, which means our surrogate becomes richer as it is applied in future case studies, either by the authors, or by the scientific community. We use a validity check built on ensemble disagreement to divert cases with measurements outside the training range to the solver. Driven by the surrogate, the identical Markov chain Monte Carlo sampler reproduces the full-solver posterior, and its credible intervals cover the truth within 2.6 percentage points. Applied to the 2013 Capricorn TEMPEST survey in Western Australia, the surrogate inverts over two million soundings in seconds, a computation infeasible for the solver. Testing the geological prior against the entire survey costs minutes. The framework delivers uncertainty-quantified conductivity imaging at survey scale, which we believe is essential to perform near real-time mineral-systems targeting with geophysics.
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Mesoscale and Nanoscale Physics

Size and Impurity Effects on Scattering of Valley Hall Modes in Gate-Defined Bilayer Graphene Superlattices

Marcus N. Kanestrøm, Antonio L. R. Manesco and D. O. Oriekhov

In the present paper we perform a tight-binding simulation of gate-defined islands in Bernal bilayer graphene (BLG). The inversion of the gap sign on the boundaries of the islands creates topologically-protected valley Hall modes. We focus on the specific questions of whether the valley Hall modes around such islands could serve as a host for quantum walks or simulate weakly coupled systems, and how their tunneling is affected by in-gap impurities. In addition, we discuss the effect of misalignment of top and bottom gate patterns on the tunneling properties between islands. Our main results show that resonant tunneling via an impurity enhances overlap between superlattice islands, while misalignment does not break topological protection over a wide parameter regime. In addition, we study the two-island geometry and show that it is possible to leverage suppressed scattering to place islands more densely on a single sample.
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Quantum Physics

Magic of Kitaev spin liquids

Eleonora Lamma, Tim Bauer, Marcello Dalmonte et al. (+1 more)

Quantum spin liquids (QSLs) are long-range entangled phases of matter and a natural setting for exploring how quantum correlations generate quantum complexity. Motivated by the emergence of magic, or nonstabilizerness, as a diagnostic of many-body complexity beyond entanglement, we study magic of QSLs by computing the stabilizer Rényi entropy (SRE) of the Kitaev honeycomb model. We derive a correspondence between Pauli strings and products of itinerant Majorana operators in the model's free-fermion description; this enables the sampling of SRE using an optimized algorithm for Gaussian states in systems with thousands of spins. Our results show that magic is largest in the gapless phase, where subleading volume-law corrections indicate nonlocal contributions, while in the gapped phases, SRE decreases in quantitative agreement with a perturbative expansion that we develop in the anisotropic limit. At the topological phase transition, SRE exhibits universal scaling dictated by critical exponents.
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All authors Eleonora Lamma, Tim Bauer, Marcello Dalmonte, Mario Collura

Astrophysics of Galaxies

HII-CHI-mistry for active galactic nuclei: optical sulphur abundances without empirical ionisation correction factors

E. Pérez-Montero, O.L. Dors Jr., I.A. Zinchenko et al. (+2 more)

> The determination of sulphur abundances in active galactic nuclei (AGN) is uncertain because ionisation correction factors (ICFs) are commonly calibrated for HII regions. We extend the HII-CHI-mistry methodology to derive total S/H in AGN from optical emission lines through comparison with photoionisation models. Tests against Seyfert galaxies with direct-method ionic abundances favour models with alpha_ox=-1.2 and a 98% free-electron stopping criterion. While O/H agrees with previous determinations, HCm yields systematically larger S/H than direct-method analyses using classical ICFs, suggesting that these prescriptions underestimate higher sulphur ionisation stages in AGN. Applied to MaNGA Seyfert and LINER-like regions, the method reveals a common positive S/O-metallicity relation. Seyferts show slightly larger median S/O than star-forming regions at high O/H, while LINERs occupy an intermediate position. These differences become weaker when S/H rather than O/H is used as the metallicity tracer, although Seyferts still tend to populate the upper envelope. Sulphur may therefore provide a robust tracer of gas-phase metallicity, while the differences between Seyferts and LINERs may reflect differences in their ionisation conditions and ionising SEDs.
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All authors E. Pérez-Montero, O.L. Dors Jr., I.A. Zinchenko, B. Pérez-Díaz, J.M. Vílchez

Statistical Mechanics

Current fluctuations in a gas of active Ornstein-Uhlenbeck particles

Sandeep Jangid, Aman Kumbhakar, Juliane U. Klamser et al. (+1 more)

We investigate the statistics of the time-integrated current in an infinite one-dimensional gas of independent active Ornstein–Uhlenbeck particles, as a model system for studying an active generalisation of the corresponding passive (diffusive) phenomenology. Unlike the latter, where current fluctuations exhibit universal sub-diffusive scaling, active systems display diffusive, super-diffusive, and sub-diffusive regimes over different time scales. We fully characterise the distribution of current in terms of large-deviation asymptotics, showing that all of these scaling regimes are described by a single scaled cumulant generating function. Moreover, the statistics retain a dependence on the initial condition even at large times, revealing a persistent memory of the initial state. We further obtain the joint large-deviation statistics of currents measured at two distinct times, characterising temporal correlations. Our analytical predictions are verified using rare-event importance sampling, which resolves probabilities as small as $10^{-1000}$.
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All authors Sandeep Jangid, Aman Kumbhakar, Juliane U. Klamser, Tridib Sadhu

Quantum Physics

Computing key rates for one-sided device-independent quantum key distribution

Andreas Bluhm, Gereon Koßmann, Martin Sandfuchs et al. (+3 more)

The defining feature of one-sided device-independent quantum key distribution is its asymmetric trust model in which only one party is characterized. This scenario sets an interesting middle ground between high key rates achievable by characterizing devices and the security of full device-independence. Here, we provide new tools, methods, and benchmarks for calculating key rates in this setting. To achieve this, we develop and compare two extensions of the NPA hierarchy and derive finite-size security bounds against general attacks with arbitrary device memory. The latter is based on the Generalized Entropy Accumulation Theorem. We then investigate the performance of various protocols: the BB84 protocol both with and without losses, a qutrit mutually unbiased bases protocol, and protocols based on Bell inequalties such as CHSH and $I_{3322}$. We find that the choice of which party is characterized can strongly affects the key rate, surprisingly without a universal ordering. Our work thus offers a general toolbox for calculating key rates for one-sided device-independent QKD protocols.
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All authors Andreas Bluhm, Gereon Koßmann, Martin Sandfuchs, René Schwonnek, Giuseppe Viola, Ramona Wolf

Mesoscale and Nanoscale Physics

Switchable heavy-hole/light-hole spin qubit

Zoltán György, Dmitry Miserev, Jelena Klinovaja et al. (+1 more)

Compressively strained Ge quantum wells in planar SiGe/Ge heterostructures are the state-of-the-art platform for hole spin qubits. While they exhibit robust coherence times, they possess weak intrinsic spin-orbit interaction (SOI) due to the heavy-hole (HH) character of the wavefunction. Recently, light-hole (LH) qubits were proposed in GeSn/Ge heterostructures, offering strong, intrinsic, linear-in-momentum SOI. In this work, we propose a switchable HH-LH spin qubit in a bilayer Ge heterostructure with SiGeSn barriers, combining the advantages of HH and LH devices. The character of the qubit can be changed by shuttling from an LH well to an HH well, which also enables fast, hopping-based single-qubit rotations. Additionally, we observe an HH-LH resonance introduced by the in-plane confinement, resulting in $g$-factor peaks and first-order charge noise sweet spots. Our calculations reveal a sweet spot with Rabi frequencies on the order of 100 MHz, comparable to the LH regime, but with a more than tenfold increase in coherence time, on the order of 100 $\mu$s.
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All authors Zoltán György, Dmitry Miserev, Jelena Klinovaja, Daniel Loss

Atmospheric and Oceanic Physics

A place for stabilization alongside tipping cascades: the AMOC-cryosphere system

Sacha Sinet

The Atlantic Meridional Overturning Circulation (AMOC) and cryosphere are central to tipping-point research, where their interactions are typically framed as pathways for cascading transitions. Here, I review evidence that these interactions can also oppose change, affecting its magnitude and timing or, in some cases, whether a transition occurs at all. I argue that a more complete assessment of tipping risk requires progress on three fronts: systematic attention to stabilizing alongside destabilizing dynamics, conceptual frameworks that accommodate competing and context-dependent effects, and methods to detect, anticipate, and attribute stabilization.
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Cosmology and Nongalactic Astrophysics

An Inverse Lyth Bound for Non-Attractor Inflation

William H. Kinney

I present a novel physics result generated entirely autonomously by ChatGPT 5.6 Sol. The Lyth bound relates an observable primordial tensor amplitude to a lower limit on the field excursion during single-field slow-roll inflation. We show that non-attractor evolution obeys a complementary upper bound. For a canonically normalized scalar field, the nonconstant superhorizon curvature mode is anti-damped whenever the second Hubble-flow parameter satisfies $\epsilon_2\equiv d\ln\epsilon/dN<-3$. The same condition requires the inflaton kinetic energy to decrease sufficiently rapidly that the field-space distance traversed during a non-attractor interval obeys $\Delta\phi_{\rm NA} / M_{\text{P}} < \left(2\sqrt{2\epsilon_{\rm in}}/3\right) \left(1-e^{-3\Delta N/2}\right) < \left(2\sqrt{2\epsilon_{\rm in}}/3\right)$.The result is independent of the potential and does not require the slow-roll approximation. If $\epsilon_2=-p<-3$ is constant, the stronger bound $\Delta\phi/M_{\text{P}}<2\sqrt{2\epsilon_{\rm in}}/p$ is saturated asymptotically. In ultra-slow-roll inflation, $p=6$, giving $\Delta\phi<\sqrt{2\epsilon_{\rm in}}M_{\text{P}}/3$. We derive an exact relation between field excursion and amplification of the velocity of the nonconstant curvature mode, and give the corresponding scalar-power relation in the quasi-de Sitter limit. In contrast with the usual Lyth relation, arbitrarily large non-attractor amplification approaches a finite field distance. This provides a model-independent field-range constraint on canonical single-field mechanisms for amplifying primordial fluctuations.
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Quantum Physics

Structured Non-Locality and Emergent Locality in Cavity-QED Many-Body Dynamics

Mark A. Oehlgrien, Błażej Jaworowski, Darrick E. Chang et al. (+1 more)

Cavity quantum electrodynamics (QED) modifies many-body systems by combining cavity-mediated collective interactions with microscopic short-range interactions. The resulting dynamics lies between the local and fully collective limits, such that neither locality nor collectivity alone provides a complete organizing principle. In the clean conceptual limit of dominant collective coupling, we show that the effective dynamics within each energetically isolated subspace is generically controlled by whether that subspace admits a local product-state basis, and identify exceptions imposed by angular-momentum selection rules. Product-state subspaces generically retain the spatial structure of the microscopic interaction. Entangled subspaces instead generically dress local processes with global operators, generating non-local but highly structured dynamics. We illustrate this by deriving the corresponding effective Hamiltonians in two representative cavity-QED spin models. The cavity-isolated subspace thus becomes a resource for generating competing short-range interactions or globally conditioned local processes, opening a class of many-body dynamics without local or fully collective counterparts.
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All authors Mark A. Oehlgrien, Błażej Jaworowski, Darrick E. Chang, Charlie-Ray Mann

Optics

From rings to resonance: an inverse method links biophotonic structural color to inverse photonic glasses

Florin Hemmann, Matthias Saba, Ullrich Steiner et al. (+2 more)

Structural color arises from the interaction of light with nanoscale structures and is widespread in nature. As structural complexity increases, the mechanisms governing coloration become progressively less understood. The optical response of periodic photonic crystals with a spatially periodic refractive index is well described by Bloch theory, whereas that of photonic glasses composed of randomly assembled uniform spheres is more subtle yet well studied. In contrast, disordered photonic networks found in many beetles are among the most complex natural photonic architectures, and the fundamental relationships between their structure and color remain unclear. Here, we use an inverse method to identify the structural features encoded in the reflectance spectrum. By comparing the spectrum of an unknown system with a database of simulated spectra from computer-generated photonic networks, we infer its structural properties. Applying this approach to both simulated networks and the biophotonic network responsible for the blue coloration of the weevil Pachyrhynchus congestus mirabilis, we identify rings and pores as the key local scattering motifs. Their characteristic sizes govern the spectral position of the reflectance peak, whereas short-range disorder controls its width. The inverse method reveals clear spectral signatures of short-range order, whereas the influence of hyperuniformity and primitive similarity appears comparatively weak. This suggests that blue structural coloration is governed by local scattering mechanisms rather than photonic band-gap effects. We propose an analogy to an inverse photonic glass, in which pores and rings act as correlated local resonators. This perspective provides new design principles for bio-inspired structural-color materials.
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All authors Florin Hemmann, Matthias Saba, Ullrich Steiner, Mauro S. Ferreira, Felipe A. Pinheiro

Quantum Physics

Distributed Trotterization with optimal time-scaling entanglement cost

Tianfeng Feng, Jinzhao Sun, Yunlong Xiao et al. (+1 more)

Distributed architectures extend quantum simulation of many-body dynamics beyond the reach of any single processor, with shared entanglement mediating interactions between spatially separated devices. Conventional implementations rely on quantum teleportation, which provides a universal realization of nonlocal operations but incurs a fixed entanglement cost per gate, irrespective of its strength. This becomes increasingly inefficient in product formula simulation, where higher accuracy requires ever more numerous, yet progressively weaker, nonlocal rotations, causing the entanglement cost to diverge in the high-accuracy limit. Here we introduce a simple repeat-until-success protocol that makes entanglement consumption adaptive to interaction strength. Incorporating this primitive into distributed product formulas yields a total entanglement cost that scales linearly with evolution time and remains independent of Trotter error. A matching lower bound from quantum communication complexity proves this time scaling to be optimal, establishing a resource-efficient foundation for high-accuracy quantum simulation across networked processors.
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All authors Tianfeng Feng, Jinzhao Sun, Yunlong Xiao, Qi Zhao

Optics

Room-temperature graphene sub-terahertz detector integrated on a silicon dielectric waveguide

A. Titchenko, K. Shein, M. Titova et al. (+6 more)

Terahertz (THz) photonics offers a promising platform for next-generation 6G wireless communications, on-chip spectrometers, and non-invasive biomedical sensors. In the near- and mid-infrared, monolithically integrated photodetectors are a cornerstone of photonic integrated circuits (PICs). In the THz range, however, such integration on low-loss dielectric waveguides remains an open challenge: to date, room-temperature on-waveguide detection has been realized only through hybrid flip-chip assembly of discrete elements, which leads to poor mode coupling, larger footprint, and reduced mechanical stability. Here we address this gap by demonstrating a room-temperature graphene sub-THz detector monolithically integrated on a high-resistivity silicon dielectric waveguide for D-band (110-170 GHz) operation. We couple an hBN-encapsulated graphene channel to the guided mode using a tapered slot-line antenna patterned directly onto the silicon surface. The detector achieves a voltage responsivity of 11.5 V/W and a 3 dB bandwidth of 1.94 GHz, with the latter currently limited by parasitic inductance of the readout interconnects rather than by the intrinsic graphene response. This platform provides a practical pathway to fully integrated room-temperature THz photonic circuits, where electrostatic gating and impedance matching can improve both responsivity and bandwidth by roughly an order of magnitude.
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All authors A. Titchenko, K. Shein, M. Titova, M. Kashchenko, O. Popova, R. Izmaylov, E.I. Titova, I. Gayduchenko, G. Goltsman

Nuclear Theory

Evidence for Quartet Binding of Valence Neutrons in $^8$He

Young-Ho Song, Yuan-Zhuo Ma and Dean Lee

Multimodal neutron superfluidity predicts quartets formed as bound states of two spin-singlet $s$-wave neutron pairs. We present evidence that the four valence neutrons of $^8$He realize the finite-system analogue. Quartet binding depends not only on the strength of neutron-neutron attraction but also on the number and symmetry of sufficiently strong attractive pair modes. Pauli blocking limits reuse of the same pair structure, while additional modes can provide extra binding. A partial-wave analysis of the neutron-neutron interaction in Daejeon16 no-core shell-model calculations identifies cooperative $^1S_0$ pairing and additional $^3P_2$ attraction as the dominant neutron-neutron contributions to this nonadditive binding, while density cumulants reveal connected four-neutron correlations.
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