Atomic Physics
Trap-Quenched Matter-Wave Optics in Space
Gabriel Müller, Timothé Estrampes, Claudia Puertas González et al. (+12 more)
Dual-species atomic sources in space promise to be the testbed for a multitude of searches in
quantum gas physics such as a precise test of the Universality of Free Fall (UFF), few-body physics, cold molecules and
quantum bubbles. These experiments demand exquisite control over the expansion energies of both condensed ensembles as well as over their differential center-of-mass dynamics. We propose a trap-quenched collimation technique featuring in-trap excitations of collective modes compatible with state-of-the-art atom-chip setups. Using NASA's Cold Atom Laboratory aboard the International Space Station, we demonstrate it on a single-species $^{87}$Rb condensate. By controlling the center-of-mass release dynamics, we observe free expansion times up to 700 ms and measure a two-dimensional expansion energy of $k_B \cdot 78\pm 9 \;\mathrm{pK}$ in the imaging plane. A detailed model of the magnetically-induced dynamics indicates that this corresponds to a two-dimensional expansion energy of about $k_B \cdot 15^{+12}_{-5}\; \mathrm{pK}$ along two of the condensate's eigenaxes. Finally, we theoretically study this trap-quenched collimation scheme for a $^{41}$K-$^{87}$Rb mixture, predicting a simultaneous collimation that meets the expansion energy requirements for a state-of-the-art UFF test at the $10^{-15}$ accuracy level.
Read the full abstract ▾
All authors Gabriel Müller, Timothé Estrampes, Claudia Puertas González, Jannik Ströhle, David B. Reinhardt, Dana Codruta Marinica, Ethan R. Elliott, Jason R. Williams, Nathan Lundblad, Eric Charron, Ernst M. Rasel, Matthias Meister, Wolfgang P. Schleich, Naceur Gaaloul, Nicholas P. Bigelow
High Energy Physics (Theory)
A Supernova Constraint on F-theory
Sebastian Vander Ploeg Fallon, James Halverson, Liam McAllister et al. (+1 more)
We study constraints on the
quantum chromodynamics (QCD)
axion in F-theory, a strongly coupled limit of string theory. We build models of QCD from compactifications to four dimensions on
elliptic fibrations over toric threefolds $B_3$, characterized by an integer $N=h^{1,1}(B_3)$. The QCD
axion mass increases with $N$, and we find that models with sufficiently high $N$ are inconsistent with observations of the
neutrino burst from
supernova 1987A, disfavoring large regions of the
moduli space. Specifically, at least $95\%$ of models with $N \ge 8,791$ – a regime that arguably contains the vast majority of known F-theory
topologies – have a QCD
axion mass $m_{QCD}>15~meV$ and are thus constrained. This limit is independent of cosmology. We only consider weakly-curved threefolds, where $\alpha'$ corrections are plausibly negligible.
Read the full abstract ▾
All authors Sebastian Vander Ploeg Fallon, James Halverson, Liam McAllister, David J. E. Marsh
High Energy Physics (Theory)
Heavenly equations in de Sitter space
Maciej Dunajski and Timothy Moy
We demonstrate that all anti-self-dual Einstein metrics with non–zero cosmological constant $\Lambda$ locally arise from solutions of a single second order PDE introduced by Lipstein and Nagy. We show how this equation fits into the heavenly formalism of Plebański, and establish a Lax pair. Finally we show how Plebański's second heavenly equation arises in the limit as $\Lambda\rightarrow 0$.
Read the full abstract ▾
Atmospheric and Oceanic Physics
Regional Climate Model Emulation with Diffusion Approaches: What is the Added Value of Generative Machine Learning?
Mikel N. Legasa, Antoine Doury, Achille Gellens et al. (+4 more)
Emulators provide a cost-effective alternative to regional
climate models (RCMs) by capturing their dynamical downscaling function. They link large-scale predictors simulated by global
climate models (GCMs) to RCM-simulated high-resolution fields of the target variable, here precipitation. Machine learning methods, typically deep learning, are cheaper than running RCMs in computation time and energy. Among them, generative models are appealing because they can simulate ensembles of local high-resolution fields consistent with the predictors. This ensemble, which we call the uncertainty envelope, remains to be properly assessed for added value. Here, we make three contributions. First, we introduce ParamDiffusion, a new two-stage
diffusion-based framework, and compare it with a state-of-the-art
diffusion approach. Second, we expand standard validation through a comprehensive framework aligned with
climate-science needs, examining specific precipitation events, including extremes. Third, within this framework, we assess the added value of
diffusion approaches relative to deterministic methods. We intercompare four deep-learning models: a deterministic model designed to capture the precipitation tail; a parametric probabilistic model based on it; a recently proposed
diffusion approach; and ParamDiffusion, which couples the parametric model with a
diffusion model. Our results show that
diffusion-based approaches reproduce climatological precipitation statistics with high skill, including distributional tails and spatially compounded extremes, while generating spatially detailed fields. However, none of the assessed models consistently accounts for the most extreme RCM-simulated events within its uncertainty envelope.
Diffusion models are therefore promising for probabilistic RCM emulation, but progress is still required before they can reliably represent high-impact precipitation extremes.
Read the full abstract ▾
All authors Mikel N. Legasa, Antoine Doury, Achille Gellens, Redouane Lguensat, Clara Naldesi, Soulivanh Thao, Mathieu Vrac
Solar and Stellar Astrophysics
Research on the Flat Field Measurement Method of Coronagraph
Yulong Feng, Xuefei Zhang, Hongfei Liang et al. (+4 more)
The
solar corona has an extremely low density, and its brightness is only about one millionth of that of the photosphere. High-dynamic-range imaging of its faint structure is therefore essential for studying coronal heating, coronal mass ejections, and space weather. Quantitative coronagraph imaging requires flat-field measurement and calibration, which underpin intensity calibration, small-scale feature detection, and long-term cyclic analysis. This paper analyzes the coronagraph imaging chain and the origins of flat-field errors, including optical aberrations, stray light, and pixel-response non-uniformity, and summarizes the resulting calibration requirements of next-generation coronagraphs. On this basis, ground-based and space-based flat-fielding methods are systematically reviewed: the ground-based methods include integrating-sphere uniform light sources, opal glass/diffuser plates, clear-sky and thin-cloud backgrounds, and
solar-disk scanning, while the space-based methods include internal light sources and diffuser plates, attitude-roll and off-corona offset observations, and multi-phase statistical self-consistent flat-fielding. Their accuracy, resource cost, and applicability are compared. The review shows that no single method is simultaneously high-precision, easy to update, and engineer-friendly; a hierarchical, multi-method calibration framework is therefore recommended. Finally, a new method is proposed in which lithographically generated structured light fields, combined with
Fourier-optics and machine-learning inversion, are used to estimate the pixel-response function. Preliminary experiments show that this method achieves a lower residual error than the integrating-sphere and opal-glass methods, providing a high-precision reference for future wide-band, high-resolution coronagraph calibration.
Read the full abstract ▾
All authors Yulong Feng, Xuefei Zhang, Hongfei Liang, Yu Liu, Mingzhe Sun, Tengfei Song, Mingyu Zhao
Fluid Dynamics
Scale-Separated Collective Bubble Nucleation and Departure
Rameez Iqbal, Gautier Rouaze, Gio Bellone et al. (+3 more)
Nucleation is classically treated as a local process, yet whether coupling between neighboring sites governs activation and stability remains unexplored. Here we show bubble nucleation is fundamentally collective: sites separated by the hydrodynamic-boundary-layer scale activate more readily and resist deactivation under changing thermal loads, consistent with a non-local hydrodynamic shielding mechanism, whereby neighboring bubbles slow the intervening flow, suppress convective heat removal, and stabilize vapor embryos. Using surfaces with two independently tunable length scales, we isolate this near-wall coupling from a second collective process, coalescence between departing bubble clusters, which transitions through isolated, promotive, and excessive regimes as the departure diameter grows with heat flux. The dominant length scale thus shifts with operating conditions, from boundary-layer coupling near activation to departure-scale coupling once nucleation is established. These results establish a scale-dependent framework for collective nucleation and departure, broadly related to phase change processes on structured surfaces.
Read the full abstract ▾
All authors Rameez Iqbal, Gautier Rouaze, Gio Bellone, Francesco Minola, Lenan Zhang, Zhengmao Lu
Computational Physics · Cross-listed from cs.CE
CANN-EUCLID: unsupervised constitutive artificial neural network model discovery from full-field data
Benjamin Alheit, Siddhant Kumar and Mathias Peirlinck
Constitutive artificial neural networks (CANNs) provide interpretable material model discovery, but have so far been used in stress-supervised settings based on apparent stress-strain data from homogeneous tests. Because each test samples only a narrow loading path and provides homogenized rather than local stress information, robust discovery typically requires multiple loading modes to constrain the multidimensional response. This is challenging for soft biological tissues, where repeated testing, damage, and sample variability limit reliable information from a single specimen. Here, we combine CANNs with the stress-unsupervised full-field discovery framework EUCLID to identify sparse hyperelastic laws directly from displacement fields and reaction forces in one heterogeneity-inducing loading case. CANN-EUCLID minimizes
equilibrium imbalance with sparsity-promoting regularization selecting compact active terms, without local stress measurements or a prescribed law. We evaluate the approach on isotropic and anisotropic
benchmarks with prescribed ground-truth laws. When the ground truth is representable by the chosen CANN basis, our method recovers the correct terms with near-exact accuracy, including exponential terms with embedded parameters. When it is not contained in the basis, the method retains shared terms and approximates missing contributions using available basis functions. Generalization depends strongly on sampled deformation states: exponential strain-stiffening terms can be recovered accurately when sufficiently probed, but can produce large extrapolation errors when the stiffening regime lies outside the sampled domain. Forward FE validation simulations show that the discovered behavior accurately replicates the ground truth. These results establish stress-unsupervised CANN discovery as a promising framework for interpretable full-field constitutive model identification.
Read the full abstract ▾
Pattern Formation and Solitons
Benjamin-Ono dynamics of internal waves with currents
Lyudmila Ivanova
Internal water waves arise when there is a change in density stratification in a fluid, which may occur in an oceanographical context due to variations in temperature, salinity, or other fluctuations in the equations of state. We present a derivation of nonlinear integrable models for the propagation of interfacial internal waves arising between two fluid layers of different densities (at the so called pycnocline). We examine the integrable Benjamin-Ono (BO) equation as an internal wave model, incorporating underlying currents by permitting a sheared current in both fluid layers. The BO equation arises for a specific small-amplitude asymptotic regime. We show that the BO
soliton characteristics are strongly affected by the shear current parameters.
Read the full abstract ▾
Nuclear Theory
Noemi Rocco, Carlo Graziani, Alessandro Lovato et al. (+2 more)
We carry out continuum
quantum Monte Carlo calculations of the
quantum-mechanical Wigner distribution functions of selected
nuclei, up to $^{16}$O. These distributions provide a form of
quantum tomography of the spatial and momentum structure of the system. They also help identify the location of high-momentum regions in atomic
nuclei and provide insight into the onset of alpha clustering. Besides their intrinsic interest, these distributions will be useful for
neutrino event generators, as they correlate the positions and momenta of nucleons in the initial target state. To facilitate their application, we address the need to store them compactly by developing an accurate Gaussian Process emulator that automatically preserves their normalization.
Read the full abstract ▾
All authors Noemi Rocco, Carlo Graziani, Alessandro Lovato, Anthony J. Tropiano, Robert B. Wiringa
Quantum Physics
Scaling native entanglement generation in layered semiconductors with quasi-phase matching
Benjamin Braun, Andrea Alessandrini, Josip Bajo et al. (+10 more)
Efficient generation of entangled
photons typically relies on spontaneous parametric down-conversion (SPDC) in phase-matched macroscopic nonlinear media. However, generating
entanglement under phase-matching constraints requires additional bulk optics or interferometers. In contrast, ultrathin van der Waals
semiconductors - such as transition metal dichalcogenides (TMDs) - exhibit strong enough optical nonlinearities for SPDC to be observed from subwavelength-thick media, thereby bypassing conventional phase-matching constraints. In this microscopic domain, the intrinsic
crystal symmetry governs the nonlinear optical response, enabling the native generation of polarization-entangled
photon pairs. However, generating these states efficiently has been fundamentally restricted by the material's coherence length ($L_c$), which limits the attainable conversion efficiency. Here, we investigate periodically-poled TMDs (PPTMDs) designed to scale up this interaction via quasi-phase matching. We demonstrate that mechanically flipping the sign of the nonlinearity at precise intervals of $L_c$ introduces quasi-phase matching, that scales the pair-production rate while preserving the pristine,
symmetry-generated polarization
entanglement, with fidelities exceeding 99%. Backed by a rigorous theoretical model, our work clarifies the interplay between
crystal symmetry and propagation effects in thin nonlinear media, providing a new avenue for engineering
quantum light in nanophotonic systems.
Read the full abstract ▾
All authors Benjamin Braun, Andrea Alessandrini, Josip Bajo, Philipp K. Jenke, Leone di Mauro Villari, Birui Yang, Zhi Hao Peng, P. James Schuck, Cory R. Dean, Andrea Marini, Philip Walther, Chiara Trovatello, Lee A. Rozema
General Relativity and Quantum Cosmology
Searching for Extra Dimensions with Gravitational Waves: Dark-Siren Constraints from GWTC-4
Anson Chen and Jun Zhang
Higher-dimensional theories of
gravity predict that gravitational waves (GWs) can propagate into extra spatial dimensions, leading to modified amplitude damping over cosmological distances. Measurements of GW luminosity distances therefore provide a unique probe of the dimensionality of spacetime. In this work, we constrain higher-dimensional GW propagation using the dark-siren method with the Gravitational-Wave Transient Catalog 4.0 (GWTC-4). We adopt a phenomenological parameterization motivated by braneworld scenarios, in which deviations from General Relativity are characterized by the spacetime dimension number $D$ and a crossover scale $R_c$ governing the transition between four- and higher-dimensional
gravity. We perform a hierarchical
Bayesian analysis combining 141 compact binary coalescences from GWTC-4 with line-of-sight
galaxy information from the GLADE+ catalog. For a prior $H_0 \in [65,77]\ {\rm km~s^{-1}Mpc^{-1}}$ and $\log(R_c/{\rm Mpc}) \in [2.7,4.0]$, we obtain $D = 4.38^{+1.91}_{-1.01}$ (68% credible interval). We also find that the inferred posterior distribution of $R_c$ accumulates near the upper prior boundary, indicating that the crossover scale remains poorly constrained by current observations. We further show that the inferred constraint on $D$ depends sensitively on the assumed prior range of $R_c$, which determines the characteristic distance scale at which deviations from General Relativity become significant. Our results provide the first GWTC-4 dark-siren constraints on higher-dimensional GW propagation and demonstrate that current observations remain consistent with four-dimensional General Relativity.
Read the full abstract ▾
Soft Condensed Matter
On the physical meaning of latent track boundaries in swift heavy ion irradiated polymers
Adil Tuleushev, Fiona Harrison and Maxim Zdorovets
A large body of experimental studies of swift heavy ion latent tracks in dielectric materials has produced a wide range of estimates of track size. We investigate the physical meaning of these estimates by examining the different criteria of track boundary probed by various experimental techniques, including SAXS, XRD, chemical etching and conductometry. We show that different methods probe different physical aspects of ion induced modification, such as electron density redistribution, molecular ordering, chemical reactivity and charge separation, resulting in different determinations of effective track boundaries. Particular
attention is paid to
polymer films with electret-like properties, where post irradiation redistribution of weakly bound electrons may play an important role in the
evolution of latent track structure.
Read the full abstract ▾
Lattice Field Theory
Resonant scattering in two-flavored Sp(4) lattice gauge theories
Ed Bennett, Yannick Dengler, Deog Ki Hong et al. (+8 more)
We apply Lüscher's method to the vector channel of the scattering amplitude of Pseudo-Nambu-Goldstone-
Bosons (PNGBs), in the $Sp(4)$
lattice gauge theory coupled to $N_f=2$
flavors of Wilson-Dirac fundamental
fermions. We generalize existing
algorithms and numerical implementations of the method, to adapt them to this prominent candidate for the completion of proposed extensions of the Standard Model (SM). We present the first ab initio measurements of key properties of the vector resonances in the theory, including the coupling to the PNGBs, that are relevant to direct and indirect new physics searches, both for composite
Higgs models (CHMs), as well as for strongly interacting massive particle (SIMP) realizations of dark matter. We also present a global update of the spectroscopy of the
mesons in the theory, improving both the statistics and analysis systematics in respect to previous
lattice measurements reported in the literature.
Read the full abstract ▾
All authors Ed Bennett, Yannick Dengler, Deog Ki Hong, Ho Hsiao, Jong-Wan Lee, C.-J. David Lin, Biagio Lucini, Axel Maas, Maurizio Piai, Davide Vadacchino, Fabian Zierler
Materials Science
First-principles calculations of internal conversion processes in spin defects
Stefano Paolo Villani, Yu Jin and Giulia Galli
Optically active
spin defects are foundational for
quantum technologies, yet common approximations underestimate their internal conversion (IC) rates by orders of magnitude. We propose a broad, predictive framework to compute IC rates that incorporates multi-configurational effects via many-body wavefunctions in TDDFT, and includes all-
phonon-mode contributions via analytical non-adiabatic couplings. Our approach resolves discrepancies with experiment, achieving quantitative agreement for the NV$^-$ center in diamond, and identifying a previously overlooked non-radiative channel in the divacancy triplet lifetime in SiC.
Read the full abstract ▾
Soft Condensed Matter
Bacterial adhesion to curved surfaces in fluid flow
Edwina F. Yeo, Benjamin J. Walker, Philip Pearce et al. (+1 more)
Minimising bacterial surface adhesion and subsequent biofilm formation in industrial and medical settings requires understanding how bacteria are transported and adhere to complex surface geometries in the presence of non-uniform flow. In this paper, we consider the transport of a dilute suspension of motile bacteria through a corrugated two-dimensional channel with perfectly adhesive walls. We asymptotically analyse the diffusive boundary layer that forms in high velocity flows using a curvilinear coordinate system based on the fluid streamfunction, presenting a similarity solution to the diffusivity-varying
diffusion-type equation that arises. From this solution, we derive an analytical expression for the bacterial adhesion rate as a function of surface arclength and the spatially varying wall shear rate. Our model predicts that bacterial adhesion becomes localised on curved surfaces, with bacteria showing preferential adhesion to wall `peaks' at lower shear rates and preferential adhesion to wall `valleys' at higher shear rates. More broadly, our results highlight how spatially varying flows generated by complex geometries can lead to localised bacterial adhesion, with potential implications for both enhancing and minimising biofilm formation.
Read the full abstract ▾
All authors Edwina F. Yeo, Benjamin J. Walker, Philip Pearce, Mohit P. Dalwadi
Statistical Mechanics
Boltzmann-like occupation of nonequilibrium steady states on dense disordered networks
Jacob Calvert
A central problem in statistical physics is to extend the Boltzmann distribution to nonequilibrium steady states (NESS). We prove that NESS on large dense disordered networks have Boltzmann-like occupation despite extensive
entropy production. One consequence is that such NESS can conceal their nonequilibrium nature from measurements of static response to energy perturbations. We further prove that the active-matter heuristic of "low rattling" is asymptotically exact for these NESS. Intuitively, they spend a greater fraction of their time in states they leave more slowly. We show that rattling effectively extends the Boltzmann distribution to such NESS, as well as the broader class of "equiaccessible" steady states, which play a role in our analysis akin to that of
equilibrium in linear response.
Read the full abstract ▾
High Energy Physics (Theory)
Yang-Baxter symmetries of Type II supergravity
Igor Bogatyrev, Edvard T. Musaev and Timophey Petrov
We provide a complete proof that Yang–Baxter bi-vector deformations are solution generating transformations in Type II supergravity. The proof does not rely on the assumption that the vielbein is invariant under Lie derivative along all Killing vectors entering the bi-vector. We analyse transformation of boundary terms and derive a simple expression for the case, when the boundary does not change its geometrical locus.
Read the full abstract ▾
General Relativity and Quantum Cosmology
Modeling dark matter as self-bound quantum liquid droplets
Abdelaali Boudjemaa
The Bose-Einstein condensate dark matter model, where dark matter can be thought of as a non-relativistic, Newtonian gravitational condensate, has recently attracted a great deal of interest. In the present study, we explore the possibility that the dark matter could exist in the form of a self-bound
quantum droplet formed by ultradilute
quantum Bose mixtures under the action of Lee-Huang-Yang corrections at zero temperature. To this end, we derive an extended equation of state by using the nonrelativistic self-consistent Hartree-Fock-Bogoliubov theory and the hydrodynamic approach. The solutions of the obtained equations of state show that the key parameters of the dark matter
halos such as the density, mass, and radius are sensitive to the interspecies interaction and to the
quantum fluctuation strength. The stability and the dynamical
evolution of the droplet
Galactic halos are analyzed by considering small perturbations of the
quantum hydrodynamical equations. In order to increase the reliability of our predictions we compare them with some observed data for the
Galactic rotation curves.
Read the full abstract ▾
Physics and Society
Modeling inhomogeneous spatial point configurations with applications to replicated patterns in real-life waiting crowds
Lars Sickert Karam, Rui M. Castro, Maarten Schoukens et al. (+1 more)
In this article, we connect statistical inference for spatial point processes with the analysis of waiting pedestrian crowds through two interconnected contributions. First, on the methodological side we develop an inference procedure for semiparametric spatial point process models leveraging replicated spatial patterns, i.e., multiple approximately independent realizations from the same process. Second, we show that spatial point processes provide a suitable modeling framework for waiting pedestrians, capturing two key aspects: spatial inhomogeneity driven by location attractiveness and repulsive interactions between pedestrians. These two components are central to the inference problem itself, since spatial point process modeling hinges on disentangling background intensity from interaction. Although replicated spatial patterns are rare in point process literature, they are available here through a unique real-life pedestrian
dataset, thereby directly linking the methodological development to the physical application. We use the proposed methods to fit and evaluate determinantal and Gibbs point processes in a simulation study and a real-world case study. Despite persistent challenges in decoupling the influences of inhomogeneity from interaction, these models are able to reproduce key empirical features of waiting pedestrians.
Read the full abstract ▾
All authors Lars Sickert Karam, Rui M. Castro, Maarten Schoukens, Alessandro Corbetta
Optics
Extreme-ultraviolet optical response of atomically-thin molybdenum disulfide
G. Fiorentini, N. Di Palo, G. Inzani et al. (+18 more)
We report multi-angle reflectivity measurements in the extreme-ultraviolet (XUV) range for mono- and
bilayer MoS$_2$ on a Si$_3$N$_4$ substrate. Using a single-sheet 2D conductivity model, we extract the complex optical response of the MoS$_2$
bilayer between 25 and 90 eV and derive an effective refractive index by introducing a thickness equal to the interlayer spacing. The MoS$_2$ monolayer response is consistently reproduced either by halving the 2D conductivity or the effective thickness, indicating a robust scaling with layer number. The resulting optical constants display a broad resonance at the Mo N$_{2,3}$ edge with no signatures of sharp core-
exciton features despite the reduced dimensionality. First-principles calculations reproduce the experimental results and show that local-field (Hartree) effects dominate the XUV response, while screened-exchange (SEX) contributions remain weak and mainly induce spectral shifts. Our analysis demonstrates that excitonic effects play a minor role in the XUV optical response of atomically thin MoS$_2$, highlighting key differences with respect to the visible and infrared regimes, and calling for a reassessment of the use of Mo-based transition metal dichalcogenides in attosecond spectroscopy and XUV excitonics.
Read the full abstract ▾
All authors G. Fiorentini, N. Di Palo, G. Inzani, G. L. Dolso, S. Bonetti, Q. Li, F. Liu, X. Zhu, A. Giglia, N. Mahne, L. Pasquali, M. D'Alessandro, M. Malakhov, M. Camarasa-Gómez, J. J. Esteve-Paredes, J. J. Palacios, R. Borrego-Varillas, M. Nisoli, A. Picón, D. Sangalli, M. Lucchini
Quantum Physics
Dissipation-induced superradiance in matter coupled to a self-interacting cavity
Sebastian Schmid, Matteo Soriente, Oded Zilberberg et al. (+1 more)
Light-matter interactions are often modeled via the Dicke model, namely, by two-level systems coupled to a cavity mode. Alas, the threshold for superradiance is often experimentally inaccessible or hindered by light's diamagnetic term. Here, within the Dicke setting, we consider self-interacting light in a cavity, modeled by a photonic Kerr nonlinearity. We show that negative Kerr nonlinearity gives rise to a low-threshold superradiant phase with
spin inversion. While unstable in a closed system, cavity dissipation stabilizes this lit phase, opening avenues for lasing and bath-engineered phases.
Read the full abstract ▾
All authors Sebastian Schmid, Matteo Soriente, Oded Zilberberg, Javier del Pino
Quantum Physics
Quantum gates with parametrically driven multi-qubit couplers
Verena Feulner, Marjan Fani, Lukas Heunisch et al. (+2 more)
Superconducting
quantum processors could significantly profit from enhanced connectivity together with precise control of interactions and gates between
qubits. Here we investigate plaquettes of four
qubits that are coupled via a central tunable coupling
circuit, so that not only gates between
qubits connected by an edge of the plaquette can be executed but also between
qubits across the diagonal. By numerically and analytically analyzing parametrically driven processes, we explore $\sqrt{\text{iSWAP}}$-gates between any pair of
qubits, also across the diagonal, as well as three-
qubit interactions and gates. For experimentally available
circuit parameters, we for example find $\sqrt{\text{iSWAP}}$-gates with a gate time of 50 ns and 99.9% fidelity, which is decreased to 99.4% if two such gates are executed in parallel on disjoint
qubit pairs in the plaquette. For three-
qubit gates we find fidelities of 95% fidelity at a gate time of 200 ns.
Read the full abstract ▾
All authors Verena Feulner, Marjan Fani, Lukas Heunisch, Stephan Tasler, Michael J. Hartmann
Cellular Automata and Lattice Gases
Exact Lyapunov spectra of affine cellular automata and the parity rule on networks
Michiel Rollier and Jan M. Baetens
The Lyapunov exponent quantifies the sensitivity of a dynamical system to perturbations, and the full Lyapunov spectrum extends this to every orthogonal direction in tangent space. For cellular automata the spectrum is almost always approximated numerically, and the approximation is delicate. We show that the affine rules, those whose update is an XOR of a subset of the inputs together with a constant, admit an exact Lyapunov spectrum. An affine rule has a configuration-independent Boolean Jacobian, so the spectrum reduces to the logarithms of the
eigenvalue moduli of a single constant
matrix, with no simulation and no limit involved. Two cases are shown to carry a closed form. For an affine cellular automaton on a periodic
lattice the Jacobian is a multilevel circulant
matrix, and its
eigenvalues are given by the discrete
Fourier transform of the rule's gradient stencil, valid in any spatial dimension. For the parity rule on an arbitrary graph the Jacobian is the adjacency
matrix, plus the identity in the self-inclusive case, so the spectrum is the logarithm of the absolute spectrum of that
matrix, and the maximal exponent the logarithm of its spectral radius. In both cases the exact spectra serve as
benchmarks: they expose errors in previously reported spectra, and turn the informal correspondence between spectral radius and tangent-space sensitivity into an exact identity.
Read the full abstract ▾
Atmospheric and Oceanic Physics
Wind vector retrieval from miniaturized wave-enabled sea-surface drifters
Alexey S. Mironov
Open-ocean in situ winds are sparse, limiting the calibration and validation of satellite wind products. We evaluate wind-vector
retrieval from MELODI (Miniaturized Electronics Lagrangian Oceanographic DrIfter), a compact freely drifting GNSS/IMU wave buoy. Wind speed is inferred from the shape of the measured wave acceleration spectrum. A regularized regression with a gated nonlinear correction (Wind Inversion using Tikhonov Regularization, WITR), trained on scatterometer winds and evaluated by leave-one-buoy-out cross-validation against ASCAT MetOp-B/C and HY-2B/C, gives a root-mean-square difference (RMSD) of 0.91 m/s. Symbolic regression distills the trained model into compact spectrum-only and motion-enhanced equations suitable for onboard use; the reduced drag law gives 0.93-0.94 m/s. Wind direction is estimated, without any fitted reference-wind regression, from IMU-derived directional wave moments in the 0.60-0.90 Hz wind-sea band, with a circular mean absolute angular difference (MAAD) of 9.4 degrees against ASCAT. These differences are comparable to published scatterometer-moored-buoy comparisons and improve substantially on the traditional single-band Toba inversion. Validation is strongest from 4 to 14 m/s and sparse above approximately 16 m/s; stronger winds are assigned low confidence. The results show that small wave-sensing drifters, calibrated to the well-established scatterometer wind scale, can provide useful wind-vector observations for validating satellite wind products and for atmospheric and wave modeling; stronger-wind sampling remains a priority.
Read the full abstract ▾
Statistical Mechanics
Extending Covariant Fluctuation Theorems into Quantum Regime through Quasiprobability Approach
Ji-Hui Pei, Tingzhang Shi, Jin-Fu Chen et al. (+1 more)
The covariant formulation of
stochastic thermodynamics requires treating the
stochastic work as a 4-vector, posing significant challenges for
quantum systems due to the non-commutativity. We introduce a new quasiprobability distribution for the work 4-vector, which combines the Wigner and Margenau-Hill quasiprobabilities. This extends the covariant fluctuation
theorems from classical to
quantum regime. We illustrate our findings with a scalar field driven by classical particles with a generalized version of trace formula. Our work establishes a quasiprobability approach to studying relativistic
quantum thermodynamics in a covariant way.
Read the full abstract ▾
All authors Ji-Hui Pei, Tingzhang Shi, Jin-Fu Chen, H. T. Quan
General Relativity and Quantum Cosmology
Spinning test particles in the spacetime of a global monopole
Morteza Mohseni and Saurya Das
We investigate the motion of spinning test particles in the spacetime of a global monopole in the framework of the Mathisson-Papapetrou-Dixon equations. By making use of the
symmetries of the spacetime, we obtain a general exact solution to the equations of motion. We show that the particle's trajectories, momenta, and
spin can be expressed in terms of three specific functions of the polar and azimuthal angles. We also show that the system is completely integrable. We obtain the general non-geodesic trajectory of the particle, and also examine the particular cases of radial and planar motion. We compare the non-geodesic trajectories of a spinning particle with a non-spinning particle.
Read the full abstract ▾
Earth and Planetary Astrophysics
Tidal locking as a negative feedback on Earth-like planetary dynamos: Consequences for magnetic shielding and habitability
J. P. Hidalgo and D. R. G Schleicher
We investigate how
tidal locking affects the
magnetic field generation and magnetospheric protection of Earth-like
planets orbiting the habitable zone of M
dwarfs. While the role of
stellar activity has been widely studied, the impact of
tidal locking on the planetary dynamo remains largely unexplored. We develop a framework that couples the
stellar wind with two distinct dynamo paradigms: direct rotational scaling of a dipolar field, and energy-flux scaling where the local Rossby number governs the
magnetic geometry, capturing a rapid transition from a dipolar to a multipolar configuration. We employ a Constant Time Lag model to capture the continuous
tidal spin-down of the
planets, evaluating two distinct planetary interiors: a highly dissipative Modern Earth and a less dissipative, rapidly rotating Early Earth. We find that
tidal locking acts as a severe negative feedback on planetary magnetism across both paradigms, where the dipolar field frequently collapses before full
tidal synchronization is reached. At the inner boundary, nearly all the
planets are rapidly locked and the intrinsic
magnetic fields are significantly attenuated. The outer boundary provides a favorable environment only for early M
dwarfs ($M_\star \gtrsim 0.32~M_\odot$) hosting Early Earth. Here, the combination of non-synchronous rotation and residence outside the sub-Alfvénic regime provides atmospheric protection likelihoods of $97-100\%$. For mid-to-late M
dwarfs, the combination of inevitable
tidal locking and a sub-Alfvénic environment results in a total collapse of the
magnetic shield, reducing the likelihood of atmospheric protection to essentially zero across the entire habitable zone.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Spectral Softenings, Composition Bump, and Anisotropy Transition: A Consistent Picture of Cosmic-Ray Origin Below the Knee
Xulin Dong, Yuhua Yao, Shuwang Cui et al. (+1 more)
Recent DAMPE measurements of individual
cosmic-ray components, including carbon, oxygen, and iron, reveal distinct spectral softenings below the knee. The energy spectrum, mass composition, and anisotropy together provide key probes of
cosmic-ray origin and propagation. By incorporating the individual elemental spectra reported by DAMPE, we derive a more complete $\langle \ln A\rangle$ distribution, which smoothly connects to the higher-energy $\langle \ln A\rangle$ measurements from LHAASO and exhibits a pronounced bump-like feature. This feature indicates a transition from the conventional
Galactic cosmic ray source population to a nearby-source-dominated regime. We show that a spatially dependent propagation model with a nearby-source contribution can consistently reproduce the observed spectra, mass composition, and anisotropy. This suggests a unified picture in which
Galactic cosmic rays below the knee arise from multiple source populations jointly constrained by these observables. Leveraging the precise component-resolved spectra from DAMPE, we further predict the transition energies in the anisotropy phase and amplitude for different mass components. Future component-resolved anisotropy measurements by LHAASO will provide a crucial test of this scenario.
Read the full abstract ▾
All authors Xulin Dong, Yuhua Yao, Shuwang Cui, Yiqing Guo
Chemical Physics
A Fixed-Point Neural Operator for Size- and Functional-Transferable Hamiltonian Prediction
Yunhong Lou, Xihang Yue, Xinran Wei et al. (+2 more)
Predicting the Kohn-Sham
Hamiltonian with machine learning can accelerate density functional theory while retaining access to molecular orbitals, energy levels, and electronic-structure observables that energy-only surrogates cannot resolve. Yet element-wise agreement with the converged
Hamiltonian, an implicit fixed point of the self-consistent field iteration, does not determine the occupied subspace that governs orbital energies and densities. Here we present HamEvo, a neural operator that learns the single-step self-consistent update and returns the converged
Hamiltonian as its fixed point. HamEvo is pre-trained on intermediate self-consistent trajectories and calibrated at
equilibrium with density-
matrix supervision. Across
benchmarks from MD17 to drug-like QMugs, HamEvo lowers
Hamiltonian errors by 35-49% over direct-regression and deep-
equilibrium baselines, and predicts QMugs HOMO and LUMO energies with mean absolute errors of 0.036 and 0.053 eV, near the 1 kcal/mol chemical-accuracy scale. Few-shot fine-tuning with only 20 reference conformations extends HamEvo to molecules of up to 122 atoms, well beyond the size range covered by pre-training. With thermal molecular-dynamics sampling, HamEvo captures temperature-dependent HOMO-LUMO gap renormalization beyond the harmonic approximation. Inference is up to 242 times faster than conventional DFT.
Read the full abstract ▾
All authors Yunhong Lou, Xihang Yue, Xinran Wei, Tianqi Deng, Linchao Zhu
Atomic Physics
Ultra-broadband Anti-Jamming Communication via a Rydberg Atomic Receiver
Jia-Dou Nan, Jun-Rong Chen, Bang Liu et al. (+11 more)
Ultra-broadband anti-jamming communication represents a promising approach to secure and robust information transfer through spread-spectrum techniques, effectively combatting malicious interference and eavesdropping. Rydberg atoms, enhanced by waveguide coupling, facilitate ultra-broadband spectrum sensing without traditional RF components. This framework provides an experimental platform for ultra-wide anti-jamming communication. Here, we demonstrate real-time signal demodulation based on frequency-hopping spread spectrum (FHSS) in a waveguide-coupled Rydberg receiver, achieving ultra-broad frequency-hopping covering 100 kHz to 20 GHz and a hopping rate of 100 khop/s. When confined to a standard operational band (e.g., the 2.4 GHz ISM band), our system achieves a high channel density of 8 channels per MHz. Beyond this, by leveraging its ultra-broad and continuous bandwidth, the system supports over 150,000 channels. Experimental results reveal a 51 dB enhancement in narrowband interference tolerance compared with single-frequency systems, confirming its outstanding anti-jamming capability. The reported system demonstrates significant potential for secure communications based on
quantum technology, especially communication in complex electromagnetic environments.
Read the full abstract ▾
All authors Jia-Dou Nan, Jun-Rong Chen, Bang Liu, Qi-Feng Wang, Yu Ma, Yi-Ming Yin, Tian-Yu Han, Guang-Can Guo, Hao Tian, Li-Hua Zhang, Bo Du, Bin-Bin Wei, Dong-Sheng Ding, Bao-Sen Shi