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Thursday 23 July

High Energy Physics (Theory)

Aspects of Closed Matricial Worlds

Dionysios Anninos and Samuel Brian

We investigate the Hilbert space structure for simple theories of gravity with $\Lambda>0$ on closed spatial sections. Our motivation ties to the presence of gravitational saddles in four-dimensional $\Lambda>0$ Einstein-Maxwell theory with $S^2\times \Sigma_h$ topology, where $\Sigma_h$ is a genus-$h$ Riemann surface. Here, as a concrete starting point, the problem is explored for two-dimensional $\Lambda>0$ quantum gravity. We revisit and elaborate on exact results in the matrix model literature. We study gravitational wavefunctions from both the perspective of the Wheeler-DeWitt equation and the gravitational path integral. Though simple, the setting displays many features of general interest such as large volume effects that disrupt the perturbative expansion, topological corrections to the path-integral wavefunction that offend the exact Wheeler-DeWitt equation, and a sphere path integral ${Z}^{(0)}_{\text{grav}}$ with non-trivial structure in $\Lambda$. We discuss candidate inner products for the infinite-dimensional canonical gravitational Hilbert space uncovered by Lian and Zuckerman. By establishing explicit results up to genus-six, we argue that the dominant contribution to the genus-$h$ gravitational disk path integral at large spatial size mimics the behavior of two-dimensional topological gravity. In passing, we show that for ${Z}^{(0)}_{\text{grav}}$ to give rise to a positive counting problem for discretised Riemann surfaces, it must have a negative pre-factor. We contrast our analysis to the more realistic case of timelike Liouville theory.
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Superconductivity

Supercurrent effect in a charge density wave intertwined superconductor

Zhen Zhu, Wei Cheng, Dang Liu et al. (+15 more)

The energy-momentum (E-k) dispersion of quasiparticles constitutes a fundamental concept in condensed matter systems. The ability to modify the E-k dispersion, exemplified by supercurrent-induced Doppler shifts of Bogoliubov quasiparticle spectra in superconductors, enables manipulation of various emergent quantum properties. However, investigations into the supercurrent effect on superconductors intertwined with charge orders remain scarce. Here, we report that the Meissner current, generated by the diamagnetic response to an applied in-plane magnetic field, can tailor Bogoliubov quasiparticle excitations at the precursor charge density wave (CDW) vectors. Our scanning tunneling spectroscopic imaging reveals a field-driven symmetry breaking of CDW modulations, specifically a C3v-to-Cs transition, in superconducting NbSe2. Model calculations suggest that the observed anisotropy originates from a selective Doppler-shift-induced E-k dispersion reconstruction. Furthermore, altering the field direction enables on-demand tuning of anisotropic CDW modulations and visualization of their momentum-space distribution. These results highlight a novel mechanism for controlling emergent electronic phases through momentum-space engineering.
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All authors Zhen Zhu, Wei Cheng, Dang Liu, Pengyu Hu, Yi Yang, Qiaoyan Yu, Shasha Xue, Ruijun Xi, Xingsen Chen, Jice Sun, Dandan Guan, Yaoyi Li, Shiyong Wang, Canhua Liu, Zhuan Xu, Xin Liu, Hao Zheng, Jinfeng Jia

Soft Condensed Matter

A statistical-physics framework for translocation elastometry of deformable particles

Pierre Ronceray

A soft particle driven through a pore narrower than itself must deform to pass, and how quickly it does so is set by how hard it is to squeeze. We propose a mathematical framework for turning rate measurements of this driven, stochastic passage into quantitative mechanical measurements. Treating the entry of the particle as one-dimensional Brownian dynamics across an elastic barrier, we solve the transport problem exactly and identify two dynamical regimes: at low drive the passage is thermally activated and limited by the energy needed to deform the particle, and at high drive it is friction-limited. We propose a framework to extract the particle's deformation energy and relevant geometrical information by combining measurements in these two regimes. This method could be used in the context of nanopore sensing, where the drive is an applied voltage: the framework then provides a self-calibrating route—translocation elastometry—from a current-voltage measurement to the elasticity and shape of individual soft nanoparticles.
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Quantum Physics

Flow of local sensitivity in a spin chain coupled to a bosonic bath

Marcin Płodzień

We study how local sensitivity to an encoded parameter, captured by the quantum Fisher information, flows between a spin chain, a coupled bosonic bath, and their quantum correlations, where we treat the bath as a full many-body quantum system beyond the Lindbladian approximation. We analyze how the coupling symmetry determines the destination of the departed sensitivity directly at the level of the Hamiltonian. We consider an excitation-exchanging Jaynes–Cummings coupling, which preserves the total number of excitations, and a spin-excitation-conserving Holstein coupling. We find that the Holstein coupling leaves the bath with no first-order information about the phase and stores the lost sensitivity entirely in spin–bath correlations, whereas the Jaynes–Cummings coupling passes this sensitivity to the bath, in full for a single excitation. The bath spectrum then governs whether the sensitivity ever returns to the spins. It revives fully and periodically when the coupled-system frequencies share a common period, but when those frequencies disperse the departed share dephases across the bath modes and never returns. We note that a transported metrological register loses more sensitivity than its arrival fidelity implies.
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Cosmology and Nongalactic Astrophysics

Hubble tension: a short review of theoretical explanations

Jia-Qi Wang and Zong-Kuan Guo

The $\Lambda$ cold dark matter model successfully describes a wide range of cosmological observations. However, the persistent discrepancy between the value of the Hubble constant inferred from cosmic microwave background (CMB) measurements within this model and that obtained from local distance-ladder determinations points to a significant inconsistency. This short review examines theoretical responses across the cosmological inference chain, from the gravitational field equations to the pre-recombination sound horizon and the late-time distance-redshift relation. It discusses early-time and late-time mechanisms, as well as modified gravity, as ways to alter the acoustic ruler, distances, structure growth, or gravitational response. Current proposals can reduce the nominal tension, but often at the cost of correlated shifts in CMB spectra, standard-ruler distances, lensing, structure growth, or calibrator information. Further progress requires unified likelihoods and multi-probe tests linking all key observables under the same model assumptions.
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High Energy Physics (Experiment)

A converged architecture for processing 32 Tbps of physics data in real-time at the LHCb experiment

Roel Aaij, Christina Agapopoulou, Thomas Boettcher et al. (+27 more)

The LHCb detector at the Large Hadron Collider has been upgraded to acquire an unprecedented 32 Tbps of particle-collision data to provide new insights in the High Energy Physics domain. The data produced by the detector is filtered in real-time to select interesting collisions. As part of the upgrade, a pre-filtering stage has been removed leading to a factor 40 increase in data rate. To deal with the high throughput demands of LHCb real-time data processing, we present an off-the-shelf network architecture using zero-copy techniques in conjunction with an efficient, fully-GPU-based filter. Our converged architecture is able to process the full 32 Tbps of particle-collision data in real-time, the highest in any physics experiment to date. Our result extends the reach of the LHCb physics programme and sets a new standard for real-time data processing at particle physics experiments.
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All authors Roel Aaij, Christina Agapopoulou, Thomas Boettcher, Dorothea vom Bruch, Daniel Hugo Cámpora Pérez, Adrian Casais Vidal, Tommaso Colombo, Daniel C. Craik, Tim Evans, Placido Fernandez Declara, Marianna Fontana, Vladimir V. Gligorov, Arthur Hennequin, Louis Henry, Brij Kishor Jashal, Saverio Mariani, Rosen Matev, Niklas Nolte, Niko Neufeld, Arantza Oyanguren, Alberto Perro, Flavio Pisani, Renato Quagliani, Florian Reiss, Kate A. Richardson, Alessandro Scarabotto, Rainer Schwemmer, Patrick Spradlin, Marian Stahl, Jiahui Zhuo

Strongly Correlated Electrons

Strong correlations and local self-energies from on-site ensembles

Alberto Carta, Hugo U. R. Strand, Michael Schüler et al. (+1 more)

Addressing the many-body electronic-structure problem is a central goal of modern condensed-matter physics. Paramagnetic Mott insulators, in particular, have long represented a challenge for standard approaches, such as density-functional theory. Historically, these systems have been tackled either by considering many-body dynamics, as in the case of dynamical mean-field theory (DMFT), or, more recently, by invoking a polymorphous description consisting of large supercells populated with static symmetry-broken motifs whose spatial average restores the paramagnetic state. Inspired by these viewpoints, we introduce the on-site dephased ensemble (DE) approximation, in which the local electronic-structure problem is described by a thermal ensemble of all accessible local static solutions; this gives rise to a strong frequency dependence of the local electronic self-energy, as seen in DMFT or in the coherent-potential approximation of disordered alloys. We show that the DE successfully recovers defining hallmarks of strongly correlated Mott systems, both in terms of the self-energy as well as the persistence of local moments in time, in quantitative agreement with DMFT. By bypassing expensive quantum Monte Carlo solvers or large supercell calculations, this approach offers efficient routes to treating paramagnetic Mott systems in a first-principles setting, and highlights a deeper connection between the physics of strong correlations and that of disorder.
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All authors Alberto Carta, Hugo U. R. Strand, Michael Schüler, Nicola Marzari

Mesoscale and Nanoscale Physics

An on-chip programmable mechano-quantum transducer

Xinrui Zhang, Wei Liu, Duanyu Ma et al. (+13 more)

Solid-state spin defects encode local perturbations as measurable shifts in spin-transition frequencies, but mechanical actuation and quantum readout remain physically separated, resulting in a discrete measurement setup. Integrating these functions requires an on-site mechano-quantum interface that programs the lattice state of a defect host and quantitatively maps it onto the spin Hamiltonian. Here we first report an on-chip programmable mechano-quantum transducer (OCPMQT) that integrates voltage-defined micromechanical actuation with in situ spin-frequency readout in a two-dimensional van der Waals quantum-defect host. Mechanically programmed lattice states are encoded as shifts in the axial zero-field splitting parameter and resolved by optically detected magnetic resonance (ODMR) spectroscopy. Within a chip volume of 2.05*10^-2 cm^3, the transducer accesses ODMR-inferred strains as low as 0.0080% and delivers a volumetric force density of approximately 2.6*10^4 N*m^-3. A micromechanical-to-spin-Hamiltonian framework links on-chip electromechanics, interfacial strain transfer, and strain-spin coupling, enabling the electrical control micromechanical input to be measured directly as spin-frequency response.
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All authors Xinrui Zhang, Wei Liu, Duanyu Ma, Lin-Ke Xie, Nai-Jie Guo, Zhongtao Gou, Yifan Wang, Jianxin Xu, Xiaoguang Luo, Zhao Mu, Honglong Chang, Weizheng Yuan, Jian-Shun Tang, Chuan-Feng Li, Guangcan Guo, Tao Ye

General Relativity and Quantum Cosmology

A story about a tipsy kangaroo: Reversible jump MCMC for model selection in the analysis of gravitational-wave signals from the coalescence of compact objects

Anna Puecher, Tim Dietrich, Hauke Koehn et al. (+4 more)

Bayesian inference is commonly employed in the analysis of gravitational-wave signals not only to estimate the source parameters, but also for model selection. The latter provides insight into the physics of the source and has the potential to inform the direction for future model development. Although model comparison is usually performed by analyzing the data separately with different models and comparing the obtained Bayesian evidences, an alternative approach consists in sampling directly over the model itself. Here, we present t-roo, a reversible jump Markov chain Monte Carlo sampler capable of performing transdimensional inference on gravitational-wave signals from compact binary coalescences. Employing t-roo, a single analysis provides simultaneously the model odds ratio and the parameter posteriors for the favored models, hence yielding a potentially substantial computational advantage, particularly when comparing many models or analyzing highly informative data. t-roo is built on the sampler eryn and is specifically designed to compare models describing different kinds of sources, i.e., binary black hole, binary neutron star, or neutron star-black hole systems, as well as multiple models for the same source class. We validate the sampler on a set of injections, finding agreement with the results obtained with the nested sampler dynesty. We then use t-roo to analyze the real events GW190425 and GW230529, for which the system's parameters alone do not provide conclusive evidence of the presence of a neutron star component. t-roo can be adapted to any model-comparison scenario, thus providing a valuable tool in particular for next-generation detectors, where analyzing data separately with competing models becomes computationally even more demanding.
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All authors Anna Puecher, Tim Dietrich, Hauke Koehn, Jonathan Gair, Gregory Ashton, Luca Negri, Anuradha Samajdar

High Energy Physics (Theory)

3d-3d correspondence for knot complements with finite and large $N$

Hee-Joong Chung

For $G=SU(N)$ at finite and large $N$, with a totally symmetric representation, we realize the homological block $F_K$ for a knot complement $S^3 \backslash K$, given in the form of the inverted Habiro series, as a half-index of a 3d $\mathcal{N}=2$ theory $T[M_3]$ by studying some examples, which we expect to extend to general knots. From the half-index expression, it is also possible to realize the colored HOMFLY-PT polynomial by taking a certain set of poles. Through the half-index realization, we describe a method for obtaining the $G=SU(N)$ homological block and its $a$-deformed version for $S^3 \backslash K$ from a Habiro series expression for the colored HOMFLY-PT polynomial. We also discuss some properties of partition functions for arbitrary $N$.
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Strongly Correlated Electrons

Pseudogap formation in the moderate correlated layered attractive Hubbard model

A. V. Belov, A. N. Rubtsov and B. Krippa

We consider the layered attractive Hubbard model with a moderate interaction strength at quarter filling. The Green's function, self-energy, and density of states are calculated for relatively large clusters using the fluctuating local field method within the approximation of vanishing effective interaction. The emergence of a pseudogap is demonstrated for the cluster system, and it is shown that integration over the fluctuating field is equivalent to the summation of zero-mode ladder diagrams above critical temperature. For the large layered system, a pseudogap in the density of states is obtained within a cluster scheme that treats the coupling between layers as a static $U(1)$ symmetry-breaking field.
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Quantum Physics

An Optimal Analysis of the Product Test

Jacob Beckey, Fernando Granha Jeronimo and Pei Wu

Product testing, i.e., deciding whether a pure multipartite quantum state is fully unentangled across a specified tensor decomposition, serves as a bridge between quantum property testing, unentangled quantum proof systems, and tensor optimization. Despite being a fundamental property testing task and having many applications, the product test's exact (worst-case) acceptance probability curve has yet to be fully determined. In this work, we determine this curve exactly. Let $\omega$ be the maximum squared overlap of the input with a product state, and let $\mathrm{PT}_n(\omega)$ be the largest possible acceptance probability of the product test over all $n$-partite pure states with product overlap $\omega$, allowing arbitrary finite local dimensions. We prove that, for every $n\ge 2 $ and every $\omega\in(0,1] $, $$ \mathrm{PT}_n(\omega)=\frac12\left(1+m\omega^2+(1-m\omega)^2\right), $$ where $m=\lfloor1/\omega\rfloor $. The formula recovers the previously known tight section of the curve for $\omega\ge 1/2 $, resolves all low-overlap regimes $\omega<1/2 $, and implies $\mathrm{PT}_n(\omega)\to 1/2 $ as $\omega\to 0$ answering an open problem in [Soleimanifar and Wright, SODA 2022]. As a complexity-theoretic application, our results improve the one-shot soundness parameter in the Harrow-Montanaro reduction from $\mathsf{QMA}(k)$ to $\mathsf{QMA}(2)$. Our techniques, built upon those of Soleimanifar and Wright, allow us to resolve these open questions while remaining surprisingly elementary.
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Solar and Stellar Astrophysics

CO second overtone line variability in three carbon-rich early post-AGB stage stars

Kārlis Puķītis

Near-infrared CO molecular lines are suggested to be linked with dynamic processes in post-AGB stars; however, they have not been investigated at high spectral resolution. CO second overtone line variability in the H-band is presented for the cool carbon-rich post-AGB stars IRAS 22272+5435, IRAS Z02229+6208, and IRAS 20000+3239. CO features are observed to change intensity, shape, and radial velocity as well as switch between emission and absorption during the pulsation cycle. At all times, the CO line positions are located no more than around 10 km/s away from the systemic velocity. Molecular line variation is qualitatively similar in all three stars, and it appears that the site of formation is the extended atmosphere. Emission in CO lines tends to be strongest during pulsation phases close to light maximum, and weakest emission or absorption tends to be seen when close to light minimum, resembling the behaviour in CN Red and C$_2$ Swan system lines at shorter wavelengths. The connection of molecular line variability with pulsation of the star could be related to a shock that traverses the atmosphere once per pulsation cycle.
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High Energy Physics (Theory)

A universal scaling function for giant graviton OPE coefficients

Miao He and Yunfeng Jiang

We consider the large spin limit $S\to\infty$ of the OPE coefficient for two maximal giant gravitons and a spinning operator with finite twist in planar $\mathcal{N}=4$ super-Yang-Mills theory. Up to an overall normalization factor, this OPE coefficient exhibits a power-law scaling of the form $S^{d(g)}$. We provide strong evidence that the exponent $d(g)$ is free from finite size corrections. Consequently, the all-loop asymptotic expression for the OPE coefficient can be used to determine $d(g)$ exactly. We develop a systematic method to compute the scaling function $d(g)$ for arbitrary values of the 't Hooft coupling $g$. At weak coupling, our result agrees perfectly with the available field-theoretic results up to three-loop order. At strong coupling, we present the first three orders as concrete predictions. We further provide the finite-coupling result and show that it interpolates smoothly between the weak- and strong-coupling regimes.
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Strongly Correlated Electrons

Interlayer interactions reshape charge-density wave through electronic elasticity in 4H$_{\mathrm{b}}$-TaS$_2$

Carolina A. Marques, Martha Rösler, Berk Zengin et al. (+7 more)

Incommensurate charge-density waves (CDWs) in layered quantum materials frequently exhibit widely varying ordering wave vectors, even among nominally identical samples, obscuring their intrinsic electronic properties. Here we identify an inherent origin of this variability through the electronic elasticity of an incommensurate CDW using the model heterostructure 4H$_{\mathrm{b}}$-TaS$_2$, composed of alternating commensurate CDW on 1T and incommensurate CDW on 1H layers. Low-temperature scanning tunneling microscopy, combined with Fourier and quasiparticle-interference analysis, exploits the lattice-pinned 1T CDW as an internal reference to resolve discrete compressive ($-2.3\%$) and tensile ($+3.2\%$) elastic states of the neighboring 1H CDW selected by the interlayer registry of the adjacent layers. Corresponding few-meV shifts of a flat band demonstrate that weak interlayer interactions reshape the low-energy electronic structure through the intrinsic elasticity of the incommensurate CDW. These findings establish electronic elasticity as a mechanism by which subtle interlayer interactions control correlated electronic states in van der Waals heterostructures.
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All authors Carolina A. Marques, Martha Rösler, Berk Zengin, Aleš Cahlík, Edoardo Martino, Konstantin Semeniuk, Helmuth Berger, László Forró, Ana Akrap, Fabian D. Natterer

Chemical Physics

Axel Dieter Becke: Not just the "B" in "B3LYP"

Mark Earl Casida

There is hardly anyone doing electronic structure calculations on molecules who has not used the famous B3LYP functional. Many will even know that the "B" in B3LYP stands for Becke, but how many know the history of the B3LYP functional? Behind this functional, Axel Becke has two of the most highly cited papers in both chemistry and physics—both with several tens of thousands of citations—and many less cited, but arguably equally important accomplishments, that led to B3LYP, as well as continued developments in building ever better density-functional approximatons after the appearance of B3LYP. Axel has received much recognition and many honors for his work. In particular, in 2015, Axel was awarded Canada's highest honor for science and engineering—namely the Gerhard Herzberg Gold Medal. Achievements like this require more than "just" brilliance; they require being the right person in the right place at the right time. I will argue that Axel did indeed fulfill these requirements. At the same time, I will try to give some flavor of the field of electronic structure as seen through my own eyes and those of a few others during the period from the beginning of Axel's career up until very recent times.
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Astrophysics of Galaxies

ALMA CO-CAVITY II. Resolved Scaling Relations in Void Galaxies

S. B. De Daniloff, D. Espada, S. Duarte Puertas et al. (+22 more)

Scaling relations involving star formation rates (SFRs), molecular gas mass, and stellar mass are key to understand galaxy evolution, and have previously been explored at resolved scales. However, they have not been examined with particular emphasis on the large-scale environments (LSEs). In this work, we study the resolved Schmidt-Kennicutt relation (rSK), molecular gas main sequence (rMGMS) and star-forming main sequence (rSFMS) from a sample of 41 void galaxies (VGs) residing in the least dense regions of the Universe. Using high-resolution interferometric CO(1-0) data and optical IFU data from the ALMA CO-CAVITY and CAVITY surveys at scales of 2.5" (0.8-2.1 kpc), we study these relations for the full sample as well as for individual galaxies in voids. We fit the relations, finding a similar parametrisation as that used for galaxies from all LSEs. However, the rMGMS is the tightest of the three relations ($\sigma_{rMGMS}=0.16$ dex, $\sigma_{rSK}=0.21$ dex, and $\sigma_{rSFMS}=0.24$ dex), unlike in other samples. We find that a large source of deviations in the relations comes from galaxy-to-galaxy variations. However, the rMGMS is less affected by these variations. It has been suggested that the rMGMS arises from the concentration of molecular gas within the gravitational potential set by the stellar content and dark matter. We hypothesise that deviations from the rMGMS trace changes in the gravitational potential occurring on longer time-scales, whereas deviations in the rSK and the rSFMS are driven by more rapid variations in the SFR. This distinction is particularly relevant for our sample of VGs because the 41 ALMA CO-CAVITY VGs are more isolated than galaxies in other LSEs, and therefore are less affected by events that can significantly alter the gas distribution or trigger SF on short time-scales. In this sense, the rMGMS is likely the most stable of these relations over time.
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All authors S. B. De Daniloff, D. Espada, S. Duarte Puertas, Y. K. González-Koda, G. Torres-Ríos, S. F. Sánchez, R. García-Benito, S. Verley, I. Pérez, M. Argudo-Fernández, A. Bongiovanni, M. Sánchez-Portal, U. Lisenfeld, M. I. Rodríguez, A. Conrado, A. Jiménez, B. Bidaran, L. Sánchez-Menguiano, T. Ruiz-Lara, A. Zurita, P. Vásquez-Bustos, M. Alcázar-Laynez, P. Villalba-González, E. Florido, R. E. Miura

High Energy Physics (Theory)

Relational path integral, effective actions and quantum frame covariance in gravity

Sergio E. Aguilar-Gutierrez, Renata Ferrero, Philipp A. Hoehn et al. (+1 more)

We propose a relational bundle-geometric formulation of the gravitational path integral by invoking the new tool of quantum reference frames (QRFs), which in gravity are gauge-covariant coordinate systems constructed from the available field content. Formulated in terms of relational (frame-dressed) observables, this yields a manifestly gauge-invariant path integral without ghosts and anomalies, and in which observables and their correlators are local to a frame. While eliminating the need for gauge fixing, it is equivalent to Faddeev-Popov versions in which the QRF is gauge-fixed, recovering certain previous proposals. A key feature is its covariance under QRF changes: it is a perspective-neutral path integral which encodes all internal QRF perspectives and the transformations between them. This leads to several qualitative predictions: local correlators and time evolution of relational observables in one QRF perspective become fuzzy in another, and a new spectrum of relational vacua arises. Comprised of frame-dependent no-boundary and asymptotic ground states, a vacuum from one perspective appears generally excited in another. Finally, we construct gauge-invariant, yet frame-dependent effective actions by coupling sources exclusively to relational observables, setting the stage for a relational definition of renormalization.
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All authors Sergio E. Aguilar-Gutierrez, Renata Ferrero, Philipp A. Hoehn, Luca Marchetti

Atmospheric and Oceanic Physics

Diffusion posterior sampling enables zero shot kilometre scale wind forecasting over complex terrain

Yujiang Cai, Ya Wang, Shuanglei Feng et al. (+6 more)

Reliable prediction of near surface wind over complex terrain is limited by the mismatch between the spatial resolution of operational forecasts and terrain controlled local wind variability. Here, we develop KiloGen, a diffusion posterior sampling framework for kilometre scale wind forecast enhancement. KiloGen learns a high resolution vector wind prior from Weather Research and Forecasting (WRF) model simulations and constrains posterior sampling with 25 km forecasts from the European Centre for Medium Range Weather Forecasts (ECMWF) at inference time. This formulation avoids paired ECMWF and WRF training samples and an explicitly learned mapping from coarse to fine resolution. Applied over Shanxi, China, a region with complex mountainous terrain, KiloGen reconstructs terrain organized wind structures and restores high wavenumber variability while retaining the large scale evolution of the operational forecast. Station verification shows that KiloGen achieves the lowest overall wind speed root mean square error (RMSE) among the evaluated products, with larger benefits at elevated and topographically complex sites. The improvement is strongest under strong wind conditions, reducing RMSE by approximately 10% for observed winds above 20 m s^-1. Across 13 distinct strong wind events, KiloGen improves upon the 0.25 degree ECMWF forecast in all cases and outperforms the 0.1 degree ECMWF forecast in most cases. These results show that diffusion posterior sampling provides an effective approach for terrain aware kilometre scale wind forecast enhancement.
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All authors Yujiang Cai, Ya Wang, Shuanglei Feng, Bo Wang, Yiming Liu, Hui Yuan, Xinyi Sun, Haijie Li, Shenming Fu

Quantum Physics

Rack-integrated quantum dot-based source of single and entangled photons at telecom C-band

Michal Vyvlecka, Raphael Joos, Benjamin Breiholz et al. (+8 more)

For quantum light sources in everyday telecommunication networks, quantum science needs to be fully transformed into quantum technology. The first necessary step to move outside a well-controlled lab environment requires the use of quantum light sources operating in the technologically relevant telecom O- and C-band. This can be provided using epitaxial quantum dots as deterministic sources of quantum light. Particularly intriguing is that emitters operating at telecom wavelengths are rapidly catching up with their short wavelength counterparts in terms of performances. Here, we make a decisive step forward in the development of quantum communication networks: a state-of-the-art source of quantum light, a semiconductor quantum dot (QD), with record coincidence rate for entangled photon emission in the telecom C-band, is operated inside an optimized rack-based setup. This setup includes a tunable pulsed laser for the QD excitation (from quasi- to fully resonant excitation), all optics for the excitation filtering, and QD signal coupling into single-mode fibers. Overall, the setup allows for above $50\%$ transmission for both exciton and biexciton photons. These results show that quantum dots-based telecom light sources can now be transported and integrated into existing fiber infrastructures, an important step to demonstrate the feasibility of the upcoming quantum internet.
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All authors Michal Vyvlecka, Raphael Joos, Benjamin Breiholz, Emma Marmasse, Anna Friederike Köhler, Ponraj Vijayan, Tobias Huber-Loyola, Sven Höfling, Michael Jetter, Simone Luca Portalupi, Peter Michler

Quantum Physics

Directional telecom photons from a chirally coupled quantum dot

Kristina Bodiroga, Jacob Ewaniuk, Andrew N. Wakileh et al. (+7 more)

Chiral quantum light-matter interfaces, where the internal spin state of a quantum emitter determines the direction in which it emits, are essential building blocks of non-reciprocal quantum devices, deterministic quantum logical gates and entanglement generation protocols. Yet, a chiral quantum interface that operates at telecom wavelengths, and is compatible with telecommunication infrastructure and silicon photonics, does not yet exist. Here, we report on an integrated chiral quantum interface in the original telecom band (1260-1360 nm), created by interfacing InAs quantum dots with a waveguide-coupled InP microdisk. We tune the quantum dot transitions through the photonic cavity using a strong magnetic field, observing a peak cavity enhancement of 3.3 and an emission directionality of 0.985, demonstrating the near-ideal chiral quantum coupling required for quantum information processing on integrated photonic devices.
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All authors Kristina Bodiroga, Jacob Ewaniuk, Andrew N. Wakileh, Lucas Rantz, Ivanna M. Boras Vazquez, Dan Dalacu, Philip J. Poole, Robin L. Williams, Xiao-Liu Chu, Nir Rotenberg

Quantum Physics

QuantumChain: Blockchain-Backed Quantum Federated Learning for Financial Fraud Detection

Epameinondas Douros, Konstantinos Dalampekis, Nouhaila Innan et al. (+2 more)

Financial fraud detection is challenged by decentralized data, severe class imbalance, and privacy constraints. This paper presents QuantumChain, a secure Quantum Federated Learning (QFL) framework that combines hybrid quantum-classical neural networks, encrypted federated aggregation, blockchain-based auditability, and quantum-secure communication. Each client trains a local hybrid model in which a variational quantum circuit is embedded between classical neural layers, while model updates are protected through homomorphic encryption, threshold secret sharing, and QKD-based keying. A permissioned blockchain records aggregation events and supports reputation-weighted trust among participants. We evaluate QuantumChain on financial transaction data using a compact, size-matched classical baseline to isolate the effect of the quantum layer. Results show that the HQNN achieves comparable accuracy while improving fraud-class recall in most settings, reaching 94.6% recall compared with 93.2% for the classical model. The Deep QLayer improves performance in full-data settings, suggesting that added circuit depth helps recover representational capacity when the shallow circuit becomes limited. Mixed-state simulations further show that the recall trend persists under non-ideal quantum evolution. In federated deployment with 10 heterogeneous clients, global accuracy increases from 97.7% to 98.8% over five rounds before stabilizing. These results show that QuantumChain can integrate depth-aware hybrid quantum models into a secure federated fraud-detection pipeline while maintaining stable global convergence.
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All authors Epameinondas Douros, Konstantinos Dalampekis, Nouhaila Innan, Ioannis Theodonis, Muhammad Shafique

Quantum Physics

Exponentially enhanced two-mode multiboson entanglement via phase-modulated tunneling

Pritam Chattopadhyay, A. G. Kofman and Gershon Kurizki

The entanglement of quantum systems is commonly restricted by their coupling Hamiltonian and initial state properties. Here, we prove by exact analysis of tunnel-coupled bosonic field modes, that factorized multi-boson two-mode states can become fully entangled via stroboscopic sign flips of the two-mode coupling. Their entanglement can exponentially grow with the number of flips. With the exception of specific prohibitive states that are invariant under such sign-flip control, this effect universally applies to two-mode state preparation. Remarkably, this linear control may provide entanglement resources for diverse quantum technological applications by readily available means.
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Lattice Field Theory

Stochastic Quantization as Optimal Control

Lingxiao Wang

Stochastic quantization defines a Euclidean quantum field theory as the equilibrium of a fictitious-time Langevin dynamics, which reaches the Gibbs measure asymptotically. We show that this quantization can be formulated as a finite-time stochastic optimal control problem. A tractable reference process, naturally supplied by the free theory when available, provides an Ornstein–Uhlenbeck dynamics, while the full interaction enters as a reference-corrected terminal cost. The optimal control is a Doob-transform force that steers the path-reweighted terminal ensemble to the target at a prescribed time and for a given noise amplitude. A neural network learns the residual control, realizing this optimal stochastic quantization (OSQ). Because the path weights are exact, imperfect training increases the variance of estimators but does not introduce model bias. On multimodal potentials we recover all modes at finite time and find that the noise amplitude sets a practical diffusion-horizon window. In two-dimensional lattice scalar $\phi^4$ theory we recover observables from hybrid Monte Carlo simulations near the critical point. Quantization is thereby formulated as control rather than equilibration.
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Instrumentation and Methods for Astrophysics

Atmosphere mitigation in CMB observations using multi-frequency time-domain component separation

Julien Tang, Shamik Ghosh, Jacques Delabrouille et al. (+4 more)

CMB observations from ground-based observatories are limited in sensitivity by the fluctuating emission from the Earth's atmosphere, mostly due to water vapor inhomogeneities. Even in atmospheric windows, this spurious signal remains the dominant source of contamination in the data. Traditional mitigation techniques include low-frequency filtering, or for polarization measurements specifically, pair-differencing or modulation with a rotating half-wave plate. The first method filters out a significant fraction of the target cosmological signal while the second leaves residuals due to imperfections, temperature to polarization leakage, or polarized atmospheric emission. In this work, we present a new data analysis framework, based on estimation of atmosphere emission templates using a multi-frequency focal plane. The core novelty of this setup is to have detectors dedicated to atmosphere monitoring, allowing the removal of atmospheric contamination with time-domain component separation techniques. We introduce a multipole-dependent atmospheric decontamination factor $A^\mathrm{atm}_\ell$ to quantify the relative reduction of the atmospheric contamination angular power spectrum achievable with this approach. Using this criterion, we demonstrate that our component separation pipeline can outperform a classical filter-bin map-making pipeline by a factor of 4000 for $30\le \ell \le 300$.
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All authors Julien Tang, Shamik Ghosh, Jacques Delabrouille, John C. Groh, Oliver Jeong, Reijo Keskitalo, Theodore Kisner

Instrumentation and Methods for Astrophysics

Modeling Dependence Structures in Astronomical Multi-Band Time Series Data via Multi-Output Gaussian Processes

Samata Das, Lishan Shi, Yasaman Hamayouni et al. (+2 more)

Modern astronomical time-domain surveys routinely collect multi-band light curves that provide complementary information about the physical processes governing source variability. Although various multi-output Gaussian process (GP) models have been applied in different astronomical contexts, the statistical and astrophysical implications of their dependence structures have received comparatively limited attention. In this work, we examine three existing approaches to modeling cross-band dependence within a common multi-output GP framework and investigate how their underlying assumptions affect statistical inference and astrophysical interpretation. These include covariance-based, stochastic differential equation (SDE)-based, and latent-process approaches, which differ mainly in how cross-band dependence is introduced. The covariance-based approach directly specifies cross-band covariance functions to characterize dependence, whereas the SDE-based approach specifies joint temporal dynamics, with cross-band dependence arising from coupled dynamics or correlated driving processes. The latent-process approach represents dependence through shared stochastic processes and their transformations, which can reflect physical relationships among multiple light curves. We demonstrate the practical implications of these modeling choices through applications to multi-band active galactic nucleus light curves and emission-line reverberation mapping. Rather than advocating a universally preferred approach, this work provides guidance for selecting dependence structures according to scientific objectives and clarifies how these choices influence the statistical characterization and scientific interpretation of multi-band stochastic variability.
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All authors Samata Das, Lishan Shi, Yasaman Hamayouni, Hyungsuk Tak, Jong-Hak Woo

Strongly Correlated Electrons

Shiba duality and $\eta$-altermagnetism: Pairing and charge orders in bipartite attractive Hubbard models

Yu-Ping Lin

We show that Shiba duality maps the altermagnetic principle of momentum-dependent band splitting from spin to $\eta$-pseudospin, defining $\eta$-altermagnetism ($\eta$-ALM) as a Bogoliubov-de Gennes (BdG) counterpart of ALM in pairing and charge orders. In half-filled pure Hubbard models on bipartite lattices, the duality relates repulsion-driven antiferromagnetism (AFM) to attraction-driven $\eta$-AFM with uniform singlet pairing and staggered charge-density modulation. In the BdG bands, the Shiba-dual parity-time-reversal $\mathcal{\tilde{P}}\mathcal{\tilde{T}}$ symmetry protects a Kramers degeneracy of $\eta$-pseudospin. Anisotropic second-neighbor hopping breaks this degeneracy and generates $\eta$-ALM. Odd-parity $\eta$-ALM shows $\eta$-pseudospin splitting, whereas even-parity $\eta$-ALM has spin-$\eta$-locked splitting. Hartree-Fock-Bogoliubov computations on checkerboard and honeycomb lattices find $\eta$-ALMs with $p$-, $d$-, and $f$-wave splitting structures. Possible generalizations and experimental probes are discussed.
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Chemical Physics

Approximating committor functions: Objective functions and training data sampling

Thomas Pigeon, Gabriel Stoltz and Tony Lelièvre

Many molecular dynamics simulations aim at studying transitions between two states (from reactants to products). In this context, the committor function (which gives for a given molecular configuration the probability to reach the product state before the reactant state) is a pivotal quantity, in particular because it is the optimal importance function for rare event simulation methods such as importance sampling or splitting techniques. These methods are used to sample the reactive path ensemble, and estimate for example the transition rate. However, learning such a function is generally a challenging task due to the high dimensionality of the configuration space. In this work, after reviewing the existing methodologies to construct approximate committor functions, a new loss function based on the application of Itō's formula is proposed to learn the committor function with a minimization procedure on the parameters of a neural network. After comparing this novel approach to existing procedures on the Müller–Brown potential, we introduce a coupling strategy with the Adaptive Multilevel Splitting method to better approximate the committor function using a better sampling of the reactive trajectories. This methodology in which the committor function is iteratively learned only requires initially the knowledge of the reactant and product states.
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General Relativity and Quantum Cosmology · Cross-listed from math.DG

Doubling for chronological diamonds in Lorentzian geometry

Mauricio Che, Sebastian Gieger and Clemens Sämann

We define doubling conditions for measured Lorentzian length spaces in terms of chronological diamonds, and prove that such conditions are implied by suitable timelike curvature bounds. In particular, for the first time, we relate doubling to curvature bounds in Lorentzian geometry. As a consequence, we obtain compactness results for Lorentzian generalized cones with respect to the Lorentzian Gromov–Hausdorff convergence introduced by Mondino–Sämann.
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Earth and Planetary Astrophysics

Experimental Measurements of Benzene Ice Critical Saturation Ratios on Titan Tholins and Impact on the Microphysical Modeling of Titan's South Polar Benzene Cloud

David Dubois, Erika Barth, Laura T. Iraci et al. (+3 more)

The Cassini Composite Infrared Spectrometer (CIRS) revealed the presence of a benzene (C6H6) ice cloud in Titan's autumn south polar stratosphere, following the northern spring equinox in August 2009. This event increased the mixing ratio of benzene and raised the cloud top altitude. We present here new experimental measurements of the critical saturation (Scrit) of pure C6H6 ice at low temperature (from 13.8 at 138 K to 3.3 at 157 K), representative of Titan's atmospheric temperatures, when deposited onto Titan aerosol analogs (tholins) produced in the NASA Ames COsmic SImulation Chamber (COSmIC). Comparisons of Scrit values of benzene vapor deposition obtained on blank substrates versus on Titan tholins reveals the highly favorable role aerosols play as condensation nuclei. We have included these new Scrit measurements to calculate the nucleation contact parameter from m = 2.6e-4 T + 0.9494 in the Community Aerosol and Radiation Model for Atmospheres (CARMA) to investigate the variation in size and number density of C6H6 cloud particles as a function of altitude in Titan's southern polar atmosphere at 87 S. We discuss how these new temperature-dependent measurements impact the microphysical modeling and result in simulated benzene clouds forming about 20 km lower than seen in previous observations. A possible explanation for this discrepancy is that the cloud system was likely influenced by the co-condensation of more than one volatile gas species.
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All authors David Dubois, Erika Barth, Laura T. Iraci, Ella Sciamma-O'Brien, Farid Salama, Sandrine Vinatier