Materials Science
Substrate-metal interface engineering enhances TaN/Ta thin film superconducting resonator performance
Moritz Singer, Harsh Gupta, Benedikt Schoof et al. (+6 more)
Tantalum has been demonstrated as a promising material for superconducting
qubits. However, comparatively little
attention has been given to its nitrides. Tantalum nitride exhibits a range of stoichiometries, resulting in a variety of material properties, including both superconducting and non-superconducting phases. Owing to this versatility, tantalum nitrides can serve multiple purposes in superconducting
qubits: as seed layers for alpha-Ta growth, as a superconducting base material and as a non-superconducting barrier in the Josephson junction. In this study, we explore the performance of superconducting TaN and Ta thin film combinations on silicon substrates in terms of internal quality factor Qi. We find that standalone TaN films exhibit Qi values of about 1.5x10^5 at 100mK in the single-
photon regime. Surprisingly, a resonator made from Ta grown on a few-nanometers-thick TaN seed layer yields largely the same performance. However, adding an additional, few-nanometers-thick Ta buffer layer between the Si substrate and this TaN seed layer enhances Qi significantly up to 5.9x10^5. Supporting transmission electron microscopy measurements reveal nitrogen accumulation and structural disorder at the TaN-Si interface, while this interfacial modification is suppressed when the Ta buffer layer is introduced. The observed improvement in resonator performance is consistent with a reduction of interface-related two-level system losses and strongly supports the hypothesis that controlling the substrate-metal interface is pivotal for the performance of superconducting
qubit circuitry.
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All authors Moritz Singer, Harsh Gupta, Benedikt Schoof, Elena Willinger, Anton Orekhov, Alexandra Schewski, Samuil Kostadinov, Philip Constantin Schneider, Marc Tornow
Instrumentation and Methods for Astrophysics
CUBES: optical design and analysis of the VLT's high-resolution UV spectrograph past final design review
Lawrence Bissell, Walter Seifert, Ariadna Calcines Rosario et al. (+7 more)
CUBES (Cassegrain U-Band Efficient Spectrograph) will be the most efficient UV spectrograph on an 8-10m class
telescope, exploiting the ESO VLT's higher
telescope efficiency relative to the ESO ELT in ground-based UV wavelengths. The instrument provides wavelength coverage over a range of 300-405nm, with high instrumental efficiency (>37%) and a resolving power of >20,000 (HR) and >6,000 (LR). It will be mounted on the Cassegrain focus of the VLT in Paranal. This paper presents the optical design of the system after the final design review. The optical subsystems detailed include: a pair of UV-optimized atmospheric dispersion correctors designed to function out to a zenith angle of 65{\deg}; high throughput HR and LR image slicers used to reformat the field-of-view; and a dispersion-compensating three-lens spectrographic camera design.
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All authors Lawrence Bissell, Walter Seifert, Ariadna Calcines Rosario, Hans Dekker, Gerardo Avila, Luca Oggioni, Giorgio Pariani, Matteo Genoni, Roberto Cirami, Stefano Covino
High Energy Astrophysical Phenomena
Exploring the optical properties of redback pulsars: The case of J1717+4308A in the globular cluster M92
Jianxing Chen, Greta Ettorre, Cristina Pallanca et al. (+13 more)
Binary millisecond
pulsars (MSPs) in globular clusters (GCs) are key for binary and
stellar evolution studies under extreme conditions. The identification of their optical companion
stars is instrumental in order to characterise these systems and to constrain the possible recycling mechanisms. For this work, we searched for the optical counterpart to PSR J1717+4308A (hereafter M92A) in the GC M92. To this end, we exploited a multi-epoch, multi-wavelength
dataset obtained with the Hubble Space
Telescope. We constructed colour–magnitude diagrams, investigated proper motions to assess cluster membership, and modelled the observed light curves. We identified an object located at only 0.02 arcsec from the nominal
radio position as the likely optical companion to M92A. The
star is significantly bluer than the main sequence at the same luminosity level and exhibits clear photometric variability with a periodicity in agreement with the orbital motion of the binary. The light curve displays two maxima and two minima, indicative of strong
tidal distortion and only mild irradiation. Such mild irradiation is consistent with the ratio of the
pulsar spin-down to the companion flux ($f_\mathrm{sd}$), which for M92A lies close to the boundary between ellipsoidal- and irradiation-dominated regimes ($f_\mathrm{sd} \approx 2.71$). From the light curve modelling we inferred the main physical properties of the companion
star. The best-fit model indicates a high-inclination system with a relatively low-mass companion and a massive
neutron star. With a base temperature of $\sim7200$ K, the companion ranks among the hottest redbacks known to date. This object therefore adds additional pieces to the puzzle of MSP companion properties and contributes to outlining the characteristics of redbacks across the different classes.
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All authors Jianxing Chen, Greta Ettorre, Cristina Pallanca, Mario Cadelano, Bidisha Sen, Devina Misra, Emanuele Dalessandro, Francesco R. Ferraro, Barbara Lanzoni, Alessandro Ridolfi, Marta Burgay, Andrea Possenti, Paulo C. C. Freire, Scott M. Ransom, Manuel Linares, Rene P. Breton
Quantum Gases
Understanding interaction-driven transport in flux lattices with evolution-path symmetry
Jian-Song Pan, Xiaofan Zhou and Wei Yi
The destruction of Aharonov-Bohm (AB) caging by interaction and the emergence of interaction-induced
chiral currents in flux
lattices are two paradigmatic examples of interaction-driven
quantum transport. While various mechanisms, such as bound-state formation and
chiral spectral imbalance, have been proposed, a unifying physical picture remains elusive. Here, we employ the concept of
evolution-path
symmetry (EPS) and its interaction-induced breaking as a framework to understand interaction-induced delocalization in flux
lattices. EPS is defined as the invariance of a path's contribution under combined
geometric and phase transformations. We demonstrate that in a $\pi$-flux rhombic
lattice, interactions break the EPS present in the non-interacting limit by modifying the phase accumulation of many-body paths, thereby lifting the destructive interference responsible for AB caging. Furthermore, we apply this framework to explain interaction-induced
chiral transport in flux ladders, where interactions break the phase relationship between symmetric paths, leading to a non-vanishing
chiral current. Our work establishes EPS as a powerful tool for understanding transport phenomena beyond conventional eigenstate analysis.
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Strongly Correlated Electrons
When Can a Cavity Move a Mott Transition? A Spectral-Density Criterion within Gutzwiller Theory
Nikhil Vamsodharakan Seshadri and Yu Zhang
Can
vacuum electromagnetic fluctuations shift a bulk Mott transition? Within the Gutzwiller variational method, we derive a criterion that separates collective spectroscopic hybridization from thermodynamic phase control. We show that a Mott transition shifts only when the electromagnetic environment supplies finite thermodynamic spectral weight with bond-scale variation. A joint frequency–spatial Pauli–Fierz density gives the leading shift. Surface
phonon polaritons yield a $d^{-3}$-to-$d^{-5}$ crossover, while finite-coordination variational Monte Carlo supports the predicted critical coefficient and $M/N$ scaling.
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High Energy Physics (Phenomenology)
Statistical validation of template-based parameter extraction from toy thrust distributions for future FCC-ee studies
Fatih ilgin
A statistically reliable parameter-extraction procedure should be validated independently of the physical and detector models to which it will eventually be applied. A template-based inference framework is developed and tested using controlled toy thrust distributions as a methodological
benchmark for future FCC-ee event-shape studies. The model contains two-jet-like and three-jet-like event components whose relative contribution is governed by a continuous control parameter. Three extraction strategies are compared: a discrete Pearson-type $\chi^2$ distance, a discrete multinomial negative-log-likelihood
estimator, and a likelihood
estimator based on linearly interpolated templates. Their performance is quantified with 10,000 pseudo-experiments for samples containing 200–2000 events. Off-grid recovery, histogram-binning variations, template-statistics variations, and a model-mismatch test based on modified momentum smearing are also studied. The multinomial likelihood consistently outperforms the simple uncorrelated Pearson-type baseline used here. For an input parameter of 0.30, the correct-template fraction increases from $0.467\pm0.005$ for 200 events to $0.934\pm0.002$ for 2000 events. Interpolation reduces off-grid discretization effects, with a maximum absolute mean bias of approximately 0.003 in the tested configuration. Model mismatch nevertheless produces measurable biases, demonstrating that nominal closure alone is insufficient to establish robustness. This study does not determine the physical strong coupling constant. It provides a controlled framework for comparing
estimators, quantifying statistical resolution, and diagnosing model dependence before application to realistic parton-shower simulations, hadronization models, detector effects, and FCC-ee data.
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High Energy Physics (Experiment)
Decorrelation of neural networks from particle lifetimes in the LHCb topological $b$ trigger
Johannes Albrecht, Alessandro Bertolin, James Connaughton et al. (+13 more)
The LHCb topological beauty trigger is the primary set of
algorithms for selecting collision events containing $b$-
hadrons in the fully software-based LHCb trigger. The
algorithms apply monotonic Lipschitz neural networks (NNs) to select vertices of charged particles consistent with the distinct
topology of a $b$ decay, i.e., those with large lifetimes and transverse momentum. Many analyses of the events recorded require that the selection must be unbiased with respect to the $b$-
hadron lifetime at large lifetimes. Accurate reconstruction is challenging in busier detector environments, in which several visible
proton-
proton collisions occur simultaneously per bunch crossing, such that misassociation of decay products can result in vertices with artificially large measured lifetimes. This paper presents two approaches to mitigate correlations between NN scores and candidate lifetimes at large lifetime, and evaluates the performance of the resulting models.
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All authors Johannes Albrecht, Alessandro Bertolin, James Connaughton, Jonathan Davies, Blaise Delaney, Agnieszka Dziurda, Conor Fitzpatrick, Maciej Giza, Vava V. Gligorov, James A. Gooding, Nicole Schulte, Nicole Skidmore, Mika Vesterinen, Mike Williams, Shunan Zhang, Valeriia Zhovkovska
Fluid Dynamics
Neptuna: A Comprehensive Machine Learning Framework for Benchmarking Complex Multiphase Flows
Harish Ramachandran, Björn Kimpel, Thomas Paula et al. (+3 more)
Compressible multiphase flows involving shocks and material interfaces arise in applications such as bubble collapse and droplet breakup, where strong nonlinear interactions produce complex interface deformation, mixing, and multiscale dynamics. Developing reliable machine learning surrogates for these flows remains challenging due to the simultaneous presence of compressibility, sharp discontinuities, and multiphase effects. In this work, we introduce the first large-scale
benchmark specifically designed for shock-driven compressible multiphase flows, comprising 3 TB of high-fidelity 2D and 3D
datasets featuring shock-induced bubble collapse and droplet breakup. We evaluate diverse surrogate model families on our benchmarking framework: Neptuna, including convolutional, spectral,
transformer-based, and pre-trained PDE foundation models. Beyond standard MSE training, we investigate composite losses that combine MSE with Sobolev, interface-aware, and structure-aware terms, along with adaptive loss balancing using SoftAdapt and GradNorm. Evaluation includes pointwise, spectral, feature-focused, structural, and physics-informed metrics. Results show that no single model performs best across all
datasets and metrics, while composite losses significantly improve interface preservation and spectral fidelity. Among adaptive weighting strategies, SoftAdapt provides the most consistent improvements with almost no overhead compared to MSE-only training. The benchmarking repository and the
dataset are made available at \url{https://tumaer.github.io/Neptuna/}
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All authors Harish Ramachandran, Björn Kimpel, Thomas Paula, Josef Winter, Steffen Schmidt, Nikolaus Adams
Quantum Physics
The Threshold Theorem in Watts: Fault Tolerance as a Question About Objective Probability
Amit Hagar
In 2011 Hagar & Sergioli proposed a new interpretation of objective probability in deterministic physics. On it, the probability of a physical state supervenes on the resources, energy over time, required to realize it from a given state, relative to the resources available (arXiv:1101.3521). The motivation for that paper was an objective alternative to QBism, the view that sees
quantum probabilities as subjective degrees of belief. Here I apply this interpretation to a more practical subject matter: fault-tolerant
quantum computing (FTQC). Under the resource-bounded measure Hagar & Sergioli proposed, the threshold
theorem becomes a claim about classification: it asserts that error-corrected logical states belong to the class of relatively cheaply realizable states, whose probability remains near 1 as the machine grows. The
theorem originally derived this claim from a resource inventory that was partial, and left out four resources consumed by error correction: calibration of a drifting device, decoding within the correction cycle, coherence as a finite time budget, and
entropy flush through fresh ancillas. These entered the original derivation at zero price. Here I translate the feasibility of FTQC into a measurable quantity, watts per decade of suppressed logical error (a decade, in the engineer's usage, being one factor of ten in the error rate). I then show that the published record already contains its first data points for this translation, and I state the two measurements that would settle the question empirically. The three-decade debate on FTQC, conducted so far as an exchange about noise-model assumptions, turns out to be, under this interpretation, a quantitative dispute about a single object: the resource-bounded objective probability of the target logical states.
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Materials Science
Unbiased Diffusion Monte Carlo for non local operators
Carlos Rodriguez Perez, Valerio Olevano, Francesco Sottile et al. (+1 more)
We propose a new mathematically exact method for computing unbiased
Diffusion Monte Carlo (DMC) estimates of non-local operators. We demonstrate that the current state-of- the-art technique, Forward Walking, is only exact for local quantities and fails to yield unbiased results for the non-local components of reduced density
matrices (RDMs). Our method significantly outperforms Forward Walking, as shown in two systems: in the symmetric Hubbard dimer it yields a pure 1RDM; while in the Helium atom it will give an unbiased 1RDM in the limits of zero time step and infinite walkers.
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All authors Carlos Rodriguez Perez, Valerio Olevano, Francesco Sottile, Vitaly Gorelov
Materials Science
SAGE-Net: Semantics-Augmented Geometric Encoder for Material Property Prediction
Guanghui Zhang, Yuxuan Yao, Kieran B. Spooner et al. (+4 more)
Reliable structure-property modeling is crucial for accelerating materials discovery, where
crystal graphs and structure-derived crystallographic descriptions provide complementary
geometric and semantic information. Existing
multimodal materials models primarily incorporate textual information through post-encoding fusion, latent-space
alignment, or
attention-based representation interaction mechanisms. However, in most cases, crystallographic semantics are introduced after structural encoding and therefore cannot directly guide the formation of atom-level
crystal-graph representations. Here, we present Semantics-Augmented
Geometric Encoder Network (SAGE-Net), a flexible
multimodal framework that injects description-derived chemical and crystallographic semantics into
geometric message passing. SAGE-Net introduces Semantic-Guided Message Passing (SGMP), which gates atom-level updates and enables crystallographic semantics to directly modulate local
geometric interactions across multiple graph neural network (GNN) backbones. Across
benchmarks covering bandgap, mechanical, transport-related properties, and synthesizability assessment, the SAGE-Net instantiated with different GNN backbones achieves the lowest MAE on eight out of ten JARVIS-DFT regression targets and delivers strong or highly competitive performance against both structure-based and
multimodal baselines. For synthesizability assessment, the SAGE-Net demonstrate outstanding classification performance and high recall rates. Interpretability analysis unravels that SAGE-Net effectively captures physically interpretable crystallographic features, viz. space group, dimensionality, polyhedral environments, among others. Together, these results demonstrate SGMP-based SAGE-Net as a general and transferable framework for deeply integrated
multimodal materials learning.
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All authors Guanghui Zhang, Yuxuan Yao, Kieran B. Spooner, Jun Yin, Dan Han, David O. Scanlon, Lijun Zhang
Quantum Physics
Low loss superconducting resonators enabled by aluminum microstructural engineering and dielectric trimming
Mahmoud Almansouri, Umar T. F. Alhuwaymel, Ibraheem AlYousef et al. (+5 more)
Material losses in superconducting
circuits fundamentally limit
qubit coherence times and resonator quality factors. Most research efforts focus on mitigating losses at
circuit interfaces, including metal–substrate, substrate–air, and metal–air interfaces. However, the correlation between TLS and non-TLS losses with the intrinsic properties of the superconducting metal and the dielectric edge smoothness is not well studied. In this work, we link the aluminum film grain size to non-TLS losses and the dielectric trimming profile and roughness to TLS loss; both loss mechanisms are subsequently mitigated. To reduce metal-related losses, we engineer the aluminum microstructure by heating during deposition, increasing grain size and reducing grain boundary density. Beyond mitigating metal losses, we introduce a two-step etching technique, Tropic etching, to suppress dielectric TLS loss by producing an ultra-smooth silicon surface with minimal defects and redeposition. These results lay out the fabrication pathway for aluminum resonators with lower loss, demonstrating two-orders-of-magnitude improvement in quality factor from $6\times10^{4}$ to $2.3\times10^{6}$. Since aluminum is the basis for most high-coherence Josephson junctions and dielectric edges are inherent to all common device geometries, the improvements in aluminum microstructure and edge profiling, presented here, can enhance the performance of superconducting
quantum devices.
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All authors Mahmoud Almansouri, Umar T. F. Alhuwaymel, Ibraheem AlYousef, Albaraa Shafi, Abdullah Albogime, Igor Getmanov, Ahmed Hajr, Atif Shamim
Materials Science
Composition Anisotropy Drives Large Bulk Photovoltaic Fields Along the Non-polar Vertical Direction in 2D Hybrid Perovskite Ferroelectrics
Yuzhong Hu, Andrii Shcherbakov, Jonathan Zerhoch et al. (+7 more)
The photovoltaic electric field of the bulk photovoltaic effect (BPE) reflects the intrinsic ability of ferroelectrics to separate photoexcited
excitons into electrons and holes, and are essential parameters for applications such as voltage-readout photodetectors. Because polarization defines the cation-anion displacement and noncentrosymmetric axis, the polar direction is generally one of the orientations exhibiting strong bulk photovoltaic field (EBPE). Here, we report emergent BPE behavior in 2D hybrid perovskite ferroelectrics (HPFs), where EBPE can be two orders of magnitude higher along the vertical nonpolar direction than along the polar in-plane direction. Its magnitude is up to orders of magnitude higher than that of
benchmark photoferroelectrics across different material systems and is the highest among 2D HPFs reported so far. This strong BPE response with emergent directional anisotropy originates from the unique coupling among the shift-current BPE mechanism, an efficient photocarrier-generating inorganic part, and an
insulator-like organic part, a combination that is conflicting or inaccessible in traditional photoferroelectrics. This composition and anisotropy also produce basic BPE behavior distinct from that of typical photoferroelectrics, including a
laser intensity dependent photovoltage and a nonlinear scaling of photovoltage with material dimension. We analyze and develop a series of formulas to describe the emergent photovoltage phenomena, which should be applicable to this novel 2D ferroelectrics family and to polar systems with similar anisotropy and robust photoelectric response.
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All authors Yuzhong Hu, Andrii Shcherbakov, Jonathan Zerhoch, Lars Schneider, Shangpu Liu, Xitao Liu, Fangping Zhuo, Lovro Fulanovic, Felix Deschler, Martijn Kemerink
Chemical Physics
Chiral vibrational modes and vibrational circular dichroism
Xuecheng Tao, Clàudia Climent, Ethan Abraham et al. (+2 more)
The recent interest in
chiral phonons in a variety of physical phenomena and their hypothesized role in the
chiral-induced
spin selectivity effect [Phys. Rev. Research, 5, L022039 (2023)] call for further investigation into the chirality of molecular vibrations. Although molecular chirality has conventionally been quantified using structural properties, recent work has highlighted the role of dynamical response properties as chirality metrics. In this work, we examine an inter-atom helicity pseudoscalar as a complementary measure of vibrational chirality, associated with the vibrational circular dichroism (VCD) intensity in the fixed partial charge (FPC) approximation. This pseudoscalar is translationally and rotationally invariant, can distinguish between opposite enantiomers, and unlike an atomic pseudoscalar measure considered in our earlier work [Phys. Rev. Lett., 133, 268001 (2024)] does not rely on a predefined
symmetry axis. For a twisted ethane model as well as several small molecules, this pseudoscalar correlates well with structural descriptors based on the continuous chirality measure. Overall, our results support response-based metrics as a physically meaningful and practically useful characterization of vibrational chirality. Importantly, while the FPC-based VCD estimate provides a useful quantifier of vibrational chirality, we show that it is a rather poor predictor of the actual molecular VCD response because the latter is strongly influenced by the (vibrational configuration-dependent) molecular electronic response.
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All authors Xuecheng Tao, Clàudia Climent, Ethan Abraham, Jichen Feng, Abraham Nitzan
Mathematical Physics · Cross-listed from cs.CV
From level set evolution to threshold optimization: A grayscale level set framework for image segmentation
Xingkai Li, Jiebao Sun, Fanghui Song et al. (+1 more)
The
segmentation of multiple degradations has been a challenging problem in the field of image
segmentation. Existing level set approaches commonly adopt a length regularization term to constrain the
geometric shape of the
segmentation contour. However, the introduction of the length term often results in numerical instability and high computational cost. In this paper, we show that the length term is not essential under certain smoothness constraints, and theoretically prove that the presence of the length term affects the property of $|\nabla \phi|=1$. Based on the finding, we define a class of smooth images, construct the grayscale level set, and propose a fast
segmentation framework for degraded images, such as heavily noisy images and intensity inhomogeneous images. The framework transforms PDE
evolution into one-dimensional threshold search, which has significant advantages in computational speed, especially on large-scale images. Experiments validate the
segmentation performance of the proposed framework on various degraded images.
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All authors Xingkai Li, Jiebao Sun, Fanghui Song, Zhichang Guo
Plasma Physics
Full 3D Maxwell solver for Inertial Electrostatic Confinement devices
Victor-Otto de Haan
Results of a full 3D electromagnetic
plasma fusion simulator are presented. It will enable investigations into the influence of structured electromagnetic potentials, anomalous
magnetic moments, or charge cluster structures on the fusion yield. The simulator calculates fusion yields similar to those found in real world fusors. In addition, the ion energy and density are accurately simulated. Given that the ion properties arise from a full Maxwell solver there is ample evidence that this part of the simulation is accurate. Concluded with a recommendation for continued research.
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General Relativity and Quantum Cosmology
Dynamical Baryogenesis in Rainbow Cosmology
Surendra Kumar Gour and Malay K. Nandy
We investigate baryogenesis in the framework of rainbow cosmology employing a complex scalar field with a softly broken global $U(1)$-
symmetry. The modified dispersion relation of rainbow cosmology leads to energy-dependent modification to the FLRW metric components, that modifies the Friedmann equation and the scalar field dynamics. We thereby obtain analytical solutions for the scalar field
evolution in the radiation-dominated epoch, and show that
baryon asymmetry is generated dynamically even from an initially
baryon-symmetric state. We find that the
baryon-to-
photon ratio asymptotically approaches a constant value in the long-time limit, which is proportional to the
symmetry-breaking coupling strength $\lambda$, and scales with the scalar field mass as $M^{-5/2}$. Our results demonstrate that requiring consistency with the observed
baryon asymmetry constrains the $\lambda$ and $M$ values within reasonable ranges, thus providing a viable dynamical mechanism for baryogenesis during the radiation-dominated era without invoking supersymmetry.
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Optics
Counterdirectional Exciton and Trion Motion in Applied Electric Field
Daniel Vaz, Yuanjun Guan, Qiaochu Wan et al. (+13 more)
Charged excitonic complexes are central to the optoelectronic and many-body properties of
semiconductors, yet their real-space transport dynamics remain largely unexplored. Here, we report the direct optical observation of trion motion under an applied electric field. The trions exhibit electrically driven drift with velocities approaching {$10^5~\mathrm{m/s}$}. Unexpectedly, the trion flow induces a pronounced back-action on coexisting neutral
excitons, driving them in the opposite direction and giving rise to counterpropagating
exciton-trion transport. Our results reveal an interaction-driven nonequilibrium transport regime of mixed excitonic fluids and establish a direct route for imaging the dynamics of more complex charged quasiparticles, including doubly charged
excitons.
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All authors Daniel Vaz, Yuanjun Guan, Qiaochu Wan, Bobby Bobby, Anshul Ramavath, Brandon Vargo, Juntong Ye, Jonathan Beaumariage, Om Patel, Kenji Watanabe, Takashi Taniguchi, Xiong Feng, James Hone, Nathan Youngblood, Zheng Sun, David W. Snoke
Quantum Physics
Lower bounds for the CNOT-complexity of linear reversible operators
Søren Fuglede Jørgensen
The CNOT-complexity of an invertible
matrix over $\mathbb{F}_2$ is the minimum number of CNOT gates needed to synthesize the corresponding linear reversible operator. While the maximum CNOT-complexity over all $n \times n$
matrices is known to be $\Theta(n^2 / \log n)$, no explicit family of
matrices requiring a superlinear number of CNOT gates is known, and until now the hardest explicitly known family has been the cyclic permutations, with CNOT-complexity $3(n-1)$. We show that lower bounds for the additive complexity of not-necessarily-reversible linear operators can be lifted to the reversible setting with only a small loss. As an application, we use this to describe an explicit family of
matrices, constructed from parity-check
matrices of error-correcting codes, with CNOT-complexity at least $4n - o(n)$, asymptotically surpassing the cyclic permutations. Moreover, this construction yields an explicit
matrix $A \in \mathrm{GL}_{n}(\mathbb{F}_2)$, $n = 17167$, whose CNOT-complexity exceeds that of the cyclic permutation on $n$ symbols.
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Fluid Dynamics
Critical assessment of RANS Models for Turbulent Heat Transfer in Low-Prandtl-Number Forced Convection
Luca Marocco, Jonathan Schmitt, Jonathan Neuhauser et al. (+2 more)
RANS modeling of turbulent heat transfer in
liquid metals remains challenging because the very low Prandtl number weakens the similarity between momentum and thermal transport. Several thermal
turbulence closures for forced convection in
liquid metals are assessed using OpenFOAM v2212. The combinations include the $k$–$\omega$ SST model with the Kays correlation for $\mathrm{Pr}_t$, the four-equation $k$–$\epsilon$–$k_\theta$–$\epsilon_\theta$ model, the logarithmic $k$–$\Omega$–$k_\theta$–$\Omega_\theta$ model, and two algebraic heat-flux formulations for $\overline{u_i'\theta'}$ coupled with either a low-Reynolds $k$–$\epsilon$ model or an
elliptic blending Reynolds-stress model (EBRSM). They are evaluated in channel flow, pipe flow, and heated backward-facing step flow against DNS data and results from the original publications, focusing on reproducibility, robustness, and accuracy. Only a limited subset of models proves reliable for low-$\mathrm{Pr}$ flows. The $k$–$\omega$ SST model with the Kays correlation gives the most robust performance and accurate temperature predictions in all cases. The $k$–$\epsilon$–$k_\theta$–$\epsilon_\theta$ model shows good reproducibility and satisfactory agreement with reference data, remaining the most consistent multi-equation alternative. The logarithmic four-equation model exhibits reduced numerical robustness, while the algebraic heat-flux model coupled with the $k$–$\epsilon$ closure fails to reproduce published thermal results despite correct prediction of the momentum field. The EBRSM-based algebraic heat-flux formulation reproduces selected reference results but suffers from significant robustness limitations. The study establishes a unified formulation of the examined closures, correcting inconsistencies in their published forms, and verifies their reproducibility and robustness.
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All authors Luca Marocco, Jonathan Schmitt, Jonathan Neuhauser, Bettina Frohnapfel, Davide Gatti
Strongly Correlated Electrons
Mizuki Urai, Hiraku Saito, Daisuke Nishio-Hamane et al. (+2 more)
We investigated the zero-field
magnetic structure of the
antiferromagnetic metal EuSnP through single-
crystal neutron diffraction experiments. The
magnetic propagation vector in the magnetically ordered phase was determined to be $(0,0,1/2)$, indicating that commensurate
antiferromagnetic ordering is realized in this material. The detailed
magnetic structure analysis revealed a collinear A-type
antiferromagnetic structure with
ferromagnetic alignment of Eu$^{2+}$ moments within the Eu–P layer. The present findings provide a microscopic basis for understanding the intriguing
magnetic behaviors of EuSnP, as exemplified by the multiple metamagnetic transitions in the
antiferromagnetic state and the strong pressure dependence of the
magnetic transition temperature.
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All authors Mizuki Urai, Hiraku Saito, Daisuke Nishio-Hamane, Taro Nakajima, Rina Takagi
Quantum Gases
Ashton S. Bradley, Tyler W. Neely, Xiaoquan Yu et al. (+1 more)
We review
turbulence in ultracold
quantum gases, using the scalar contact-interaction Bose-Einstein condensate as the reference system for quantized circulation, compressibility,
vortices, sound, and cascades. We focus on the quantitative diagnostics that connect helium and classical phenomenology to microscopic wave-function dynamics: incompressible and compressible kinetic-energy spectra, wave-occupation spectra, spectral fluxes,
vortex-resolved correlations, and velocity statistics. These diagnostics distinguish
equilibrium vortex organization, decaying turbulent relaxation, forced cascade dynamics, and weak-wave
turbulence, and show why power laws alone are insufficient evidence for a cascade. We survey experiments on two-dimensional Onsager clustering, three-dimensional
vortex-line
turbulence, box-trap wave cascades, engineered dissipation, and turbulent equations of state. We close by briefly placing the contact-interaction scalar superfluid system in a broader landscape of nonlocal, multicomponent, fermionic, and driven-dissipative
quantum fluids, where
turbulence concepts can be tested for universality.
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All authors Ashton S. Bradley, Tyler W. Neely, Xiaoquan Yu, Brian P. Anderson
Quantum Physics
Dark Polaron Theory for High Intensity Laser Cooling
Marcel Morillas-Rozas, Alberto López-García, Enamul Haque et al. (+2 more)
Conventional
laser control schemes for cooling and gate operation of trapped ions are limited to the regime of weak
laser intensities and small Lamb-Dicke parameters. To overcome this limitation, we present the concept of dark polarons: spatially extended states of pseudospin polarization that are fully decoupled from a lambda
laser configuration. In this picture, all high-order Lamb-Dicke terms collapse into a single linear coupling independent of
laser intensity. We apply it to definitively elucidate the reasons behind cooling rate limitations observed in recent experimental implementations of electromagnetically induced transparency with high-intensity
lasers.
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All authors Marcel Morillas-Rozas, Alberto López-García, Enamul Haque, Gonzalo Reina Rivero, Javier Cerrillo
Statistical Mechanics
Fermions on a 1D lattice: localized sources and sinks with dephasing
Elka Bhattacharya, Sushant Saryal, Soumya Ghosh et al. (+1 more)
We study a general one-dimensional spinless fermionic system subject to a localized source, sink, and bulk dephasing. Within the Lindblad framework, we compute the time
evolution of the density profile and spatial correlation functions. We find that the presence of bulk dephasing suppresses certain coherent
quantum features, such as the Friedel oscillations, and it alters the transport dynamics to exhibit two distinct dynamical regimes instead of three as observed in the absence of dephasing. This effect can be understood as the destruction of ballistic motion caused by the dephasing noise. Under strong dephasing, the density profile becomes similar to the one expected for a classical diffusive regime. We also investigate the system in the presence of both a localized source and sink, placed at a distance of $\Delta$. Interestingly,
quantum coherence generates secondary density peaks at integer multiples of the source-sink separation $\Delta$, which are systematically washed out as bulk dephasing drives the system toward the classical diffusive limit.
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All authors Elka Bhattacharya, Sushant Saryal, Soumya Ghosh, Kabir Ramola
General Relativity and Quantum Cosmology
Static vacuum metrics in (4 + 1) dimensions with {\Lambda} < 0 and squashed conformal infinity
Piotr T. Chruściel, Jiaxin Song, Raphaela Wutte et al. (+2 more)
We construct numerically two families of static five-dimensional Lorentzian metrics, solutions of
vacuum Einstein equations with a negative cosmological constant, one with and one without a black hole region, with a metric at sections of conformal infinity which is conformal to any squashed three-dimensional sphere.
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All authors Piotr T. Chruściel, Jiaxin Song, Raphaela Wutte, Maciej Maliborski, Klaus Kroencke
Mathematical Physics · Cross-listed from math.AP
A PDE approach to the 2D Yang-Mills measure
Ilya Chevyrev, Tom Klose and Abdulwahab Mohamed
We introduce the concept of rough additive functions, which extends rough paths theory to line integrals of distributional 1-forms. In the context of gauge theory, we use this notion to define controlled gauge transformations and holonomies via RDEs. One of our main results is a rough version of Uhlenbeck compactness for distributional connections based on rough additive functions. The main ingredient is a singular
elliptic PDE to obtain a Coulomb gauge. We solve this PDE using regularity structures and a method inspired by the implicit function
theorem. Surprisingly, the model needed to solve the equation is determined entirely from rough additive functions, which is a simpler and geometrically more natural object. We apply our results to the Yang-Mills measure on the unit square, showing that it has a gauge-fixed representation with optimal regularity. Although we focus on the unit square in this article, we expect our results to apply to more general surfaces.
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Mesoscale and Nanoscale Physics
Quantum transport in Cooper pair splitters using hierarchical equations of motion
Riya Baruah, Neill Lambert, Franco Nori et al. (+1 more)
We investigate charge transport in Cooper pair splitters beyond the weak-coupling and Markovian limits. To this end, we employ hierarchical equations of motion (HEOM), which can capture the combined effects of strong coupling to the leads, nonperturbative interactions, and finite voltage and temperature differences. Within this framework, we compute the electric currents as functions of the level positions of a Cooper pair splitter for various voltage and temperature configurations. In the large-bias regime, our results reduce to analytical expressions obtained from a Markovian Lindblad equation. However, recent experiments were conducted with finite voltage or temperature differences, where a Markovian description may not suffice. In this regime, HEOM yield quantitative agreement with the measured currents. We can also account for an experimentally observed thermoelectric effect in Cooper pair splitters. Our results show that HEOM provide a useful framework for describing nonequilibrium
quantum transport in Cooper pair splitters and related hybrid devices.
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All authors Riya Baruah, Neill Lambert, Franco Nori, Christian Flindt
Instrumentation and Methods for Astrophysics
HARMONI at ELT: LPOU calibrations for a micron-level pointing accuracy
Gonzalo José Carracedo Carballal, Irene Ferro Rodríguez, David L King et al. (+7 more)
HARMONI is the first light, adaptive optics assisted, near-IR integral field spectrograph for the ELT [1]. It covers a spectral range from 800 nm to 2450 nm with resolving powers from 3000 to 7000 and spatial sampling of 25 mas and 6mas. It can operate in two adaptive optics modes, SCAO (including a high contrast capability) and MCAO. The project is resuming its final design phase after a rescope design phase in 2025. To achieve its optimal image quality, HARMONI needs to perform pointing error measurement by means of three guide probes. Each guide probe is a robotic arm with a shoulder-elbow stage that is optically equivalent to two periscopes connected together. Since any systematic positioning error of the shoulder-elbow motors will result in a measurement error of the pointing error itself, an appropriate
geometric calibration reference is necessary. In previous designs, this calibration reference took the form of a deployable calibration mask that could be inserted in the
telescope's focal plane. However, this approach prevents the guiding sensors from distinguishing motor contributions from other effects caused by the instrument optics. In this work, we explore the possibility of inserting the calibration mask as close to the guide probes as possible, along with the addition of the necessary refocus optics in the light path of the guiding sensors. We discuss different variations of this idea, their effect on the image quality, and their ability to resolve positioning errors smaller than 1 {\mu}m. The results of these analyses were cross-validated by means of optical simulations in RayZaler, and will be used to put bounds to the expected calibration accuracy achievable by this design.
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All authors Gonzalo José Carracedo Carballal, Irene Ferro Rodríguez, David L King, Iago Funes Vecino, Guillermo Mercant Rubio, Alonso Álvarez Urueña, Laura García Moreno, Heribert Argelaguet Vilaseca, Javier Piqueras López, Chiara Cerruti
Instrumentation and Methods for Astrophysics
HARMONI at ELT: Design & Test on the current status of Low Order Wavefront Subsystem Pick Off Arm Engineering Model (LPOA-EM)
Iago Funes Vecino, Guillermo Mercant Rubio, Alonso Álvarez Urueña et al. (+5 more)
HARMONI is the first-light, adaptive-optics-assisted, near-infrared integral field spectrograph for the ELT, covering 800 to 2450 nm with resolving powers from 3000 to 7000. The Low Order Wavefront Sensor subsystem (LOWFS) provides field stabilisation by measuring the motion of the instrument focal plane relative to the
telescope wavefront sensors. Following a rescope process in 2025, LOWFS has been updated to operate three LOWFS Pick-Off Arms (LPOA) simultaneously within a shared volume. We present first results from the LPOA Engineering Model (EM) characterisation campaign on two rotary joints, shoulder and elbow, including measurements of angular resolution, discrete step tracking validated by independent metrology, rotation axis wobble, and radial and axial runout of the bearing assembly.
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All authors Iago Funes Vecino, Guillermo Mercant Rubio, Alonso Álvarez Urueña, Laura García Moreno, Gonzalo José Carracedo Carballal, Irene M. Ferro Rodríguez, Heribert Argelaguet Vilaseca, Javier Piqueras López
Soft Condensed Matter
Identifying the signatures of residual activity in harmonically bound active Brownian dynamics
Sanatan Halder and Manas Khan
A confined self-propelled particle exhibits a range of intriguing dynamical phenomena dictated by the interplay between the intrinsic activity of the particle and the imposed confinement. This competition manifests as a crossover in the steady-state position distribution of a harmonically bound active Brownian particle (HBABP) from Boltzmann-like to bimodal, commonly recognized as the passive and active regimes, respectively, upon variations in activity and confinement strength. We present a comprehensive analysis of the resultant dynamics of an HBABP employing analytical calculations and numerical simulations, examining the variations in the position distribution, residual or resultant velocity, mean square displacement, power spectral density, and effective harmonic confinement at varying activities in the characteristic regimes across the crossover. These analyses provide a reliable identification of the signature of residual or remnant activity in ABP dynamics after being impeded by the harmonic confinement. Our results show that the resultant HBABP dynamics in the regime with a Boltzmann-like position distribution is dominated by residual activity, and the motion in the other regime, with a bimodal position distribution, is similar to that of a harmonically bound Brownian particle–devoid of residual activity–at a displaced position, where the activity is balanced by the restoring force field.
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