Optics
Compact Fully Integrated Alignment-Free and Linearly Polarized Ho$^{3+}$ Single-Frequency Waveguide Laser
Jeswin Jacob, T Toney Fernandez, Dale Otten et al. (+3 more)
We report, for the first time, a fully integrated Ho$^{3+}$-doped fluoride glass waveguide
laser incorporating a femtosecond
laser-inscribed waveguide and waveguide Bragg grating. A line-by-line inscription technique was employed to fabricate the Bragg gratings, yielding highly consistent and reproducible grating characteristics with precise control of the Bragg resonance wavelength. A compact 12.4 mm cavity achieves stable single-frequency lasing at 2062.21 nm with a linewidth of less than 5 MHz. The
laser exhibits intrinsically linearly polarized emission. This
alignment-free architecture provides a compact and robust platform for integrated mid-infrared single-frequency
laser sources.
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All authors Jeswin Jacob, T Toney Fernandez, Dale Otten, Ori Henderson-Sapir, Karen Privat, David Lancaster
Materials Science · Cross-listed from cs.LG
An extended deep energy method for thermo-mechanical crack propagation
Han Zhang, Mehrisadat Makki Alamdari, Babak Shahbodagh et al. (+4 more)
Thermo-mechanical fracture couples transient heat conduction on a cracked domain with a crack that grows as the temperature and the displacement evolve. Neural energy solvers have been proposed for phase-field fracture and later extended to represent a sharp crack through the network input, but heat conduction on the cracked domain and crack propagation under the resulting thermal stresses have not yet been treated together in these solvers. We present an extended deep energy method for thermo-mechanical crack propagation in which the crack remains a sharp polyline. Two networks represent the temperature and the displacement and receive the crack through a scalar
embedding function, discontinuous across the crack and smooth elsewhere, so that both fields can jump across it without a regularization length, and the displacement is enriched near the tip by the Williams expansion with trainable amplitudes. The two fields are obtained by minimizing an incremental conduction functional and the thermoelastic potential energy in a staggered sequence, with Monte Carlo integration on points stratified over background elements, densified near the tip and redrawn during training. The stress intensity factors are extracted by the interaction integral with the area term of Wilson and Yu and checked by a sweep of the contour radius, and the crack advances at the maximum hoop stress angle when the energy release rate of the kink reaches the critical value at the crack-tip temperature. On a stationary thermal edge crack the extracted stress intensity factor agrees with the published value to 0.11%, in a functionally graded shear test initiation agrees with an independent sharp-crack finite element solution to within one load step, and on a notched cruciform specimen the crack paths follow the published solutions under mechanical, thermal and combined loading.
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All authors Han Zhang, Mehrisadat Makki Alamdari, Babak Shahbodagh, Mohammad Vahab, Cosmin Anitescu, Timon Rabczuk, Elena Atroshchenko
General Relativity and Quantum Cosmology
Anisotropic Fluid Model for Massive Boson Stars: Spherically Symmetric Configurations
Ethan McKeever, Victor Guedes, Shu Yan Lau et al. (+1 more)
Boson stars are among the best-studied exotic compact objects and constitute one of the few black-hole mimickers for which both the formation mechanism and dynamical behavior can be investigated from first principles. Constructing
boson star solutions is generally more challenging than constructing
neutron star solutions, often requiring either extremely accurate initial guesses for the oscillation frequency or the use of computationally intensive relaxation methods to solve the field equations. In the strong-coupling limit, massive
boson stars can be described effectively as perfect- fluid configurations, enabling their construction using methods analogous to those developed for
neutron stars. In this paper, we relax the strong-coupling assumption and derive a phenomenological anisotropic-fluid model for spherically symmetric massive
boson stars that remains applicable over a broad range of model parameters. We provide ready-to-use fits for both the anisotropy profile and the effective equation of state in terms of the central scalar-field amplitude and the ratio of the self-interaction coupling constant to the squared scalar-field mass. To validate the model, we compute the masses and radii of
boson stars using a standard
neutron-
star construction approach and compare the results against full
boson-
star calculations. We find excellent agreement between the two methods, while the new approach reduces the computational cost by a factor of about 10. Our phenomenological fluid framework offers an efficient and accurate method for constructing spherically symmetric massive
boson stars and computing their observable properties. We provide a ready-to-use Python implementation of the Tolman-Oppenheimer-Volkoff solver, allowing users to construct
boson star configurations within the proposed framework.
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All authors Ethan McKeever, Victor Guedes, Shu Yan Lau, Kent Yagi
Quantum Gases
Quench dynamics and quantum flutter properties of one-dimensional attractive single-spin flipped Fermi gases
Xiangguo Yin and Shulong Zhao
Impurity nonequilibrium dynamics in
quantum many-body systems is a frontier subject in ultracold-atom physics, which helps uncover microscopic mechanisms of polaron and collective excitation phenomena. Although repulsive interacting systems have been extensively investigated, attractive-interaction dynamics lacks systematic studies owing to intricate couplings among different states. We study a one-dimensional ideal
Fermi gas containing an attractive
spin-down
impurity with initial momentum and analyze time
evolution of interspin two-body correlations and
impurity momentum. Using exact Bethe ansatz solutions, we simplify correlation
matrix elements to finite sums for efficient calculations of eigenstate occupations and long-time dynamical
evolution. In the weakly attractive regime, bound-state features appear when the total momentum is below or equal to the
Fermi momentum, while mixed oscillatory behaviors arise at larger total momentum. The strongly attractive regime shows locally bound-state dominated dynamics with localized correlation peaks and scattering-induced Friedel-like oscillations. We characterize
quantum flutter, the periodic oscillation of
impurity momentum, and obtain consistent critical chemical potential values of the
impurity via four independent Bethe ansatz approaches. This work clarifies quench dynamics and
quantum flutter under attractive interactions, improves the understanding of nonequilibrium
quantum many-body properties, and provides theoretical support for relevant ultracold-atom
impurity experiments.
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Quantum Physics · Cross-listed from cs.LG
What a Reporting Convention Hides: A Matched-Budget Audit of Quantum Natural Gradient with an Exactly Computed Metric
Lu Wei, Yufeng Wang and Haibin Ling
Several published comparisons of variational
quantum optimizers time only runs that reach a target loss, or read the verdict at a single target. Either convention could decide whether an optimizer's costlier steps pay off. We measure how much each convention changes verdicts among Adam, simultaneous perturbation
stochastic approximation (SPSA) and
quantum natural gradient (QNG), on initializations held out from the selection of settings. We compute the exact metric that preconditions QNG, price every step in
circuit evaluations and give every method the same budget. In a median pooled over
circuit widths, cost families and a sweep of settings with common misses, SPSA needs more than twice Adam's evaluations to reach a loose target. Dropping the censored runs that miss the target hides this gap. On the global-cost family we hold fixed the settings selected for a strict target. QNG then usually reaches the loose target after Adam but the strict target first. QNG's strict-target lead disappears when the metric's simulator price, linear in the number of parameters, is replaced by an assumed hardware count quadratic in that number. We recommend charging every miss the budget and reporting verdicts across targets.
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Quantum Physics
Non-Hermitian Cooperation Induced Chern Insulator
Weiwei Zhu, Bingbing Wang, Mengxiang Xie et al. (+5 more)
Conventional Chern
insulators rely on breaking time-reversal
symmetry via
magnetic fields or synthetic gauge fields. Here we introduce a fundamentally different paradigm: a static
lattice without any gauge field becomes a Chern
insulator solely through the cooperation of two non-Hermitian ingredients: on-site loss and non-reciprocal coupling. Neither effect alone suffices; only their synergy opens a topological gap and gives rise to robust
chiral edge states with a nonzero Chern number. The underlying mechanism originates from a non-Hermitian
chiral molecule formed by the lossy sites, whose dynamically dominant mode carries an orbital angular momentum that effectively generates a synthetic flux after the fast-decaying degrees of freedom are eliminated. Our results establish non-Hermitian cooperation as a versatile resource for inducing Chern
topology without external fields or temporal modulations, opening a new route to topological phases in open classical and
quantum systems.
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All authors Weiwei Zhu, Bingbing Wang, Mengxiang Xie, Hong-yu Zou, Yang Long, Hong-xiang Sun, Haoran Xue, Jie Ren
Mathematical Physics · Cross-listed from math.FA
Plunge bounds for Fourier concentration operators: geometry, smoothing, and wave packets
Ahmadreza Azimifard
We prove a single-logarithm bound for the
eigenvalues in the plunge region of
Fourier concentration operators, removing the extra logarithmic factor in the Kulikov–Dam Larsen bound for two general admissible sets throughout each fixed exponential window. For bounded spatial and frequency sets $A,B\subset\mathbb{R}^d$ of positive measure with finite upper codimension-one Minkowski boundary content, the number $\Lambda_\varepsilon(cA,B)$ of
eigenvalues in $(\varepsilon,1-\varepsilon)$ satisfies $\Lambda_\varepsilon(cA,B)\le C(d,A,B,\beta)c^{d-1}D(1+\log_+(c/D))$, where $D=\log(1/(\varepsilon(1-\varepsilon)))$, for every fixed $\beta>0$, $c\ge2$, $0<\varepsilon<1/2$, and $D\le\beta c$, with $\log_+t=\max(0,\log t)$. The argument uses positive band-limited smoothing and requires no
symmetry, convexity, or connectedness. In dimension two, the corresponding exponential-window estimate has a constant uniform in the window parameter. We also determine the optimal coordinate-Lipschitz constant $d-1$ for recursive decompositions of balls and standard simplices in every dimension, and obtain box-frequency estimates with explicit
geometric constants. For $C^1$ convex bodies in three dimensions, the optimal infimum of recursive coordinate slopes is $2$. Uniform real-order Bessel estimates give independent disk and ball bounds at every spectral threshold, including an explicit deep-tail term. For smooth strictly convex planar frequency bodies with positive
curvature, we prove correlation estimates for aligned Gaussian packets at arbitrary relative scales and quantitative lower bounds on the cost of estimating spatial blocks separately. Together these results connect the global spectral bound with sharp
geometric constructions and the cancellation retained by grouping boundary interactions.
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Statistical Mechanics
Heat Transport of the $\beta$-Fermi–Pasta–Ulam–Tsingou chain in the long-wave limit
Henrique Santos Lima, Matheus M. R. Poltronieri Martins and Lucas Reis e Silva
Resolving the anomalous conductivity exponent of the symmetric $\beta$-
Fermi–Pasta–Ulam–Tsingou chain by molecular dynamics can require very large systems because of long finite-size crossovers and thermal-contact resistance. Motivated by this computational challenge, we derive a long-wavelength continuum description and investigate whether the kinetic-theory scaling $\kappa\propto L^{2/5}$ becomes accessible with a moderate number of numerical degrees of freedom. The nonlinear elastic field retains the cubic stress of the microscopic interaction and exchanges heat with Langevin reservoirs. A flux-conservative spatial discretization constructs the force and energy current from the same stress, providing a consistent interior transport
estimator. For $L>8$, corresponding to approximately $10^3$ mesh nodes and above at the reference resolution, the fitted exponent is $0.399\pm0.004$. Mesh refinement supports the stability of this exponent between the two finer resolutions, although the conductivity amplitude remains resolution-dependent. The main result is thus an accessible finite-size regime near $2/5$, rather than convergence of the absolute conductivity as the mesh spacing vanishes. This formulation provides a practical route to studying anomalous transport in anharmonic systems and a conservative continuum framework for investigating energy flow in nonlinear elastic media.
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Atomic Physics
Genuine Molecular Effects in Bound-State Quantum Electrodynamics
Kjell Janke, Konstantin Gaul, I. Agustín Aucar et al. (+3 more)
Quantum electrodynamics (QED) currently features prominently at the precision frontier in describing the structure of atoms and molecules. Dominant QED effects are governed by the electronic structure in the vicinity of the
nucleus and are therefore generally regarded as atomic in origin, with molecular contributions largely arising from additive atomic contributions. By studying the
nuclear magnetic resonance shielding tensors of thallium in Tl$X$, we reveal genuinely molecular QED effects that strongly depend on the bonding partner ($X$ = F, Cl, Br, I, At) and are absent in the Tl$^+$ ion.
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All authors Kjell Janke, Konstantin Gaul, I. Agustín Aucar, Karol Kozioł, Gustavo A. Aucar, Robert Berger
Instrumentation and Methods for Astrophysics
The Fast Transient Foreground Fog of LSST
G. Megias Homar, S. R. Kulkarni, C. S. Lage et al. (+3 more)
Studies with 1-m class
telescopes have now established that glints from satellites and space debris are the main obstacles to searches for sub-minute optical transients. Here, we report a study of this foreground using observations from the Legacy Survey of Space and Time (LSST) with the Simonyi 8.4-m
telescope at the Vera C. Rubin Observatory. From 2,955 pairs of consecutive 30-s exposures, spanning 4,755 deg$^2$ of unique sky area and an area-time coverage of 472 deg$^2$ hr, we identified a population of faint, PSF-like, sub-minute events, including isolated events with no linear sequences of repeated flashes (tracklets) indicative of a tumbling satellite. We extended measurements of this population to the faintest magnitudes yet probed, finding a lower-bound to the occurrence rate of $(9.55 \pm 0.14) \times10^6\,$sky$^{-1}\,$day$^{-1}$ to $\sim23$ mag (median of $\sim22.3$ mag). The large aperture of the Simonyi 8.4-m
telescope provides an additional discriminator: orbital debris in low-Earth orbit are sufficiently out of focus that they are filtered out. We find that, for a $1^{\prime\prime}$ PSF, unresolved events are constrained to distances beyond 1,732 km, and identify a previously unreported population of glints consistent with medium-Earth-orbit altitudes with estimated sizes of order $\sim1$-3 mm. We also report two isolated events observed along sight lines deep within the Earth's shadow, for which a sunlit-debris origin is disfavored. The scant evidence is consistent with an eclipsing binary and a
stellar flare. The robust way forward for sub-minute transients is simultaneous observations of the same field by two (or more) widely separated
telescopes. The resulting measurement of parallax will cleanly eliminate local (primarily orbital) debris, clarifying the nature of this transient foreground. This understanding will help astronomers probe truly celestial optical bursts.
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All authors G. Megias Homar, S. R. Kulkarni, C. S. Lage, J. A. Tyson, S. M. Kahn, F. A. Harrison
Chemical Physics
Accelerating dynamic polarizability calculations of organic molecules using equivariant graph neural networks
Houssam Metni, Maria Kraus, Marie Louise Schubert et al. (+3 more)
Predicting the dynamic polarizability tensor of organic molecules is essential for simulating light-matter interactions in optoelectronic devices, yet conventional
quantum-chemical methods such as time-dependent density functional theory (TD-DFT) are computationally expensive and limit large-scale screening. We present an equivariant graph neural network architecture that predicts frequency-dependent, complex-valued dynamic polarizability tensors directly from readily available molecular information, such as 3D geometry and UV-vis spectra. The model learns to approximate the shape and magnitude of the dynamic polarizability tensor, capturing both dispersive and absorptive features that define the molecular optical response. We evaluate the model on molecules from both the QM9
dataset and the Harvard organic photovoltaic
dataset using various metrics, including the earth mover's distance, which is suitable for comparing spectral quantities. For both
datasets, the model successfully reproduces the main features of the dynamic polarizability tensor and generalizes across diverse molecules. To assess the applicability, we further validated the model using a downstream workflow to calculate the optical properties of organic photovoltaic devices. We used the model-predicted polarizabilities to perform device-level optical simulations, yielding charge carrier generation rates in agreement with TD-DFT-based results ($R^2 = 0.94$). Our approach offers a promising complement, or even an alternative, to conventional methods such as TD-DFT, enabling faster and more efficient screening of photoactive organic molecules for optoelectronic applications.
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All authors Houssam Metni, Maria Kraus, Marie Louise Schubert, Marjan Krstic, Carsten Rockstuhl, Pascal Friederich
Materials Science
Bottom-Up Prediction of Amorphous Poly(1,3-dioxolane) using Ab Initio Reactive Machine-Learning Force Fields
Yizhi Song, Bharatha K. Gunawardana, Kriti Alam et al. (+3 more)
Poly(1,3-dioxolane) (pDXL) is a chemically recyclable polyether that can be synthesized by living cationic ring-opening polymerization with precise control of chain length into the ultra-high-molecular-weight (UHMW) regime, where it acquires enhanced mechanical properties. Like most
polymers, however, it has amorphous condensed-phase structure, and diffraction measurements alone cannot resolve the atomistic microstructure that underlies them. In this work, we predict the ensemble of the pDXL microstructures by applying a recently developed AI-accelerated ab initio bottom-up
polymer structure prediction (AI$^{2}$-BPSP) framework that simulates the living polymerization of pDXL under experimental synthetic conditions with machine-learning force fields trained within van der Waals-corrected hybrid density functional theory. Partitioning the predicted X-ray and
neutron diffraction signal between the growing chain and the surrounding monomer resolves its dominant feature into two counteracting modes: a monomer contribution near $q \approx 1.5$ Å$^{-1}$ that decays as monomer is consumed, and a
polymer contribution near $q \approx 1.6$ Å$^{-1}$ that is absent in oligomers and grows with chain length. This work paves the way to direct accuracy validation of these statistically significant, first-principles, and chain-length resolved diffraction predictions against experiments.
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All authors Yizhi Song, Bharatha K. Gunawardana, Kriti Alam, Teresa Shah, Deepa Ranabhat, Hsin-Yu Ko
Quantum Physics
Distance Structure of Insertion Kernels and Local Port Response in Non-Reciprocal Su–Schrieffer–Heeger Chains
Xudong Zhang and Bin Guo
Non-reciprocal
lattices offer a flexible setting for directional wave transport, raising the question of how enhanced internal scattering translates into transmission between fixed external ports. We address this question for non-reciprocal Su–Schrieffer–Heeger (SSH) chains with staggered gain and loss by relating the reference-dependent insertion kernel $K_p=VG_pV$ to the coherent transmission intensity $T$. On a fixed finite graph, a strong-insertion expansion gives a contribution proportional to $\gamma^{1-d}$, whose coefficient is the signed sum of shortest directed paths of length $d$. When this sum is nonzero, it sets the leading behavior independently of fixed diagonal losses; when it cancels, those losses can enter the first surviving higher-order term. For a fixed cross-sublattice endpoint channel, transmission has a strictly negative slope at every nonzero differentiable stationary point of the kernel magnitude. In the weak-insertion regime, the reference-system coefficient $\chi=-\mathrm{Re}\,\mathrm{Tr}[(G_{0p}Z)^2]$ predicts the initial transmission change for symmetric SSH ports, and $\chi>0$ together with a strictly stable baseline guarantees local stable enhancement. Finite-chain calculations and driven dynamics connect these results to observable response and distinguish asymptotic convergence from transient settling. A strictly dissipative short-chain example exhibits local enhancement without net power gain. Together, these results separate graph-path structure, coherent port response, and dynamical establishment, providing channel-specific criteria for interpreting internal scattering.
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Quantum Physics
Particle-Number-Preserving Quantum Signal Processing for Thermal Properties: Canonical-Ensemble Estimation and Grand-Canonical Reconstruction
Taehee Ko, Sungbin Lim and Sangkook Choi
We develop an end-to-end framework for estimating canonical thermal properties of particle-number-conserving second-quantized
Hamiltonians using
quantum simulations. The framework integrates initial state preparation with mixed Dicke states, particle-number-preserving Trotterized simulation, and generalized
quantum signal processing to estimate canonical partition functions and observables. Building on this canonical scheme, we introduce a grand-canonical reconstruction scheme in which the same
quantum measurement data can be reused for arbitrary chemical potentials through classical reweighting, thereby avoiding repeated
quantum circuit executions as the chemical potential is varied. We prove the existence of system-size-independent temperature regimes in which both the canonical and reconstructed grand-canonical schemes have lower asymptotic time complexity than classical Lanczos methods, up to
polynomial factors, for physically relevant
Hamiltonians. We numerically validate our theoretical results for the two-dimensional Hubbard model in both weak- and intermediate-coupling regimes.
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Optics
Electromagnetically Transmissive and Thermally Opaque Engineered Microwave Interconnect
Md. Jawad Ul Islam, Ishrat Jahan, Abdelrahman Omar et al. (+3 more)
In a standard two-conductor microwave transmission line, both the signal trace and the wide ground plane act as parasitic heat leakage paths along the propagation direction. To prevent this heat leakage, we devised a single-conductor microwave interconnect: the ground plane is removed entirely and the remaining signal trace is periodically fragmented into physically isolated metallic islands. We show that despite the galvanic isolation between adjacent metal islands, a surface confined mode of specific
symmetry, the odd-symmetric spoof surface plasmon polariton, propagates through this periodic, single-conductor medium. This odd
symmetry imposes an electromagnetic field null at the waveguide centerline, allowing complete removal of the metal at periodic intervals along the single-conductor waveguide without impacting EM propagation. Measurements on fabricated prototypes confirm the transmission response despite the physical fragmentation of the conductor, with de-embedded propagation loss of ~0.0031 dB/mm across a 5-6.5 GHz passband. Time-domain characterization verifies 1 Gbps amplitude-modulated data transmission with less than 145 ps group delay variation. Coupled electro-thermal simulation yields an effective thermal conductivity of 0.336 W/m*K, a 40x reduction relative to a continuous microstrip line of identical footprint.
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All authors Md. Jawad Ul Islam, Ishrat Jahan, Abdelrahman Omar, Md. Omar Faruk Noman, Md Zunaid Baten, Soumitra R. Joy
Quantum Physics
Non-Orthogonal Amplitude Amplification for Hybrid CV-DV Quantum Processors
Jiyuan Liu, Joel Bierman and Yuan Liu
We introduce a non-orthogonal amplitude amplification (NOAA) method for hybrid continuous-variable- discrete-variable (CV-DV)
quantum processors, where the available CV-assisted projector is not perfectly se- lective for the target state. We establish a bound on the achievable target-state fidelity, which is determined by the initial target-state amplitude and the selectivity of the accessible reflection operator. This bound limits the performance of NOAA in hybrid CV-DV systems. To mitigate this limitation, we propose using a squeezed CV ancilla to reduce the overlap between relevant CV states and a hybrid
quantum signal processing (HQSP) filter to suppress errors arising from imperfect knowledge of the target eigenenergy. Numerical simulations show that, for small initial target-state amplitudes, our protocol achieves higher fidelity and efficiency than the repeat-until-success (RUS) method despite the presence of non-orthogonality. For large initial amplitudes, RUS is already efficient, and amplitude amplification provides little additional advantage.
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Strongly Correlated Electrons
Polarized neutron diffraction with ex-situ $^3$He neutron spin filter and two-dimensional detector for noncollinear incommensurate magnetic order
Shingo Takahashi, Yuta Osawa, Ryuju Kobayashi et al. (+11 more)
Polarized
neutron scattering has been widely used for studying
magnetic orders in condensed matter. A typical setup for this technique is a triple-axis spectrometer with a
ferromagnetic single-
crystal monochromator and analyzer, which is suited for point-by-point measurements within the horizontal scattering plane. However, this setup cannot fully meet the demands of recent studies on complex
magnetic orders with emergent cross-correlated phenomena. For instance, multiferroics,
magnetic skyrmions, and other topologically nontrivial
magnetic orders tend to have incommensurate
magnetic modulation vectors running along various directions in reciprocal space, which cannot be captured by measurements restricted to the horizontal scattering plane. To overcome these limitations, we have developed an experimental setup combining a $^3$He
neutron spin filter ($^3$He-NSF) and a two-dimensional (2D) detector, which enables us to analyze the polarization of
neutrons scattered away from the horizontal plane. We also establish a data reduction procedure to convert the 2D intensity maps into three-dimensional intensity distributions in reciprocal space, correcting for the effect of imperfect $^3$He polarization. This method is applied to single-
crystal diffraction measurements on the multiferroic material Mn$_3$WO$_6$, which exhibits complex incommensurate
magnetic orders. We have successfully observed polarization-dependent intensities of out-of-plane incommensurate
magnetic reflections, demonstrating the effectiveness of the present method for analyzing complex
magnetic structures.
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All authors Shingo Takahashi, Yuta Osawa, Ryuju Kobayashi, Takashi Ino, Hiraku Saito, Takuro Kawasaki, Takayuki Oku, Tatsuya Nakamura, Yoichi Ikeda, Masaki Fujita, Daisuke Koto, Yusuke Tokunaga, Taka-hisa Arima, Taro Nakajima
Quantum Physics
Building codes with transversal CCZ using projective geometry and SAT solvers
Bohan Lu and Kenneth R. Brown
We construct CSS codes with three logical
qubits whose logical CCZ gate is implemented by transversal physical $T/T^\dagger$ gates and whose distance is at least 3. These codes start with 8-divisible $X$-stabilizers defined by projective geometry, which guarantees $d_Z \geq 3$. A SAT solver then finds three $X$-logical operators compatible with the transversal CCZ. We build codes at thirteen block lengths from $n=48$ to $n=496$, with $d_Z=3$ or 4, and illustrate the method with the [[48,3,3]] code $Q_{48}$. Additionally, we prove that no CSS code with three logical
qubits, $Z$-distance at least 3, and a quasi-transversal CCZ gate (transversal $T$ with a diagonal Clifford correction) exists below $n=39$. The [[47,3,3]] code of Jacinto et al. attains the minimum length in this class, as established by the classification of Wills, Jain, and Singh.
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General Relativity and Quantum Cosmology
Collisions of Multiple Black Holes: A Numerical Relativity Study
Chen-Kai Qiao and Shu-Yuan Liu
Numerical relativity has a profound impact on gravitational theory and gravitational wave astronomy. In this work, we present a systematic study of the head-on collisions of multipule black hole systems within the framework of numerical relativity using the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation. The numerical simulations of the dynamical
evolution of gravitational fields are computed using the AMSS-NCKU code. We report numerical results for black hole collisions in several symmetric and non-symmetric configurations, in which the black holes are initially at rest and are described by Bowen-York type initial data. Our results suggest that black hole systems with perfectly symmetric configurations (e.g., black holes located at the vertices of a regular polygon or a regular polyhedron) impose strong constraints on the emitted gravitational waves, and no gravitational kick arises in these symmetric systems. For regular polygonal configurations, the radiation is dominated by the plus polarization of the $l=2$, $m=0$ mode. For regular polyhedral configurations, all the quadrupole modes with $l=2$ nearly vanish, and gravitational wave amplitudes are strongly suppressed to the order of $10^{-4}$ or below, which is in accordance with an analysis based on the quadrupole approximation. Gravitational radiations from $m \ne 0$ modes become non-negligible only when non-symmetric configurations are encountered. Keywords: Numerical Relativity, Black Holes, Gravitational Waves, N-Body Systems
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Cosmology and Nongalactic Astrophysics
Scalar Perturbations and Induced Gravitational Waves from First-Order Phase Transitions in Lattice Simulations
Yuan-Jie Li, Jing Liu, Zhuan Ning et al. (+2 more)
Cosmological first-order phase transitions can generate
curvature perturbations through inhomogeneous
quantum tunneling, as studied previously on superhorizon scales. In this work, we for the first time conduct three-dimensional
lattice simulations that incorporate scalar metric perturbations and radiation perturbations, covering a range from bubble wall scales to super-horizon scales. We obtain the precise scalar perturbation power spectrum and the probability density function of energy density perturbations. Furthermore, we simulate the gravitational-wave energy spectra generated by each source during the first-order phase transition, including the scalar field itself, scalar metric perturbations, and the energy density and velocity perturbations of radiation. For gravitational waves, the contribution from other sources can exceed $1/3$ of that from the scalar field at superhorizon scales. Additionally, we compare the effects of different values of the transition strength and rate on the results. This paper provides more accurate numerical results for research aimed at detecting or constraining first-order phase transitions via gravitational waves and
curvature perturbations.
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All authors Yuan-Jie Li, Jing Liu, Zhuan Ning, Xiang-Xi Zeng, Zong-Kuan Guo
Instrumentation and Methods for Astrophysics
Constrained Diffusion for Data-Scarce Orbital Monte Carlo in Constellation Tasking
Omar Ramadan, Sam Siavoshian, Amir Kashif Saeed et al. (+3 more)
Constellation Monte Carlo results depend on the orbital population used to evaluate a tasking policy. With scarce reference trajectories, replay limits
geometric diversity, while independent orbital-element jitter can violate physical constraints. We study constrained
diffusion for orbital-population augmentation. A force-conditioned
diffusion model learns a 13-dimensional orbital prior, recovering semimajor axis from perigee altitude and eccentricity; Basilisk propagates each sample under one of five force-model tiers. Using 800 reference trajectories, we compare
diffusion with jittered bootstrap, per-tier Gaussian mixtures, and a conditional variational autoencoder, and evaluate distributional fidelity, support shift, classical astrodynamics diagnostics, and 4,000 paired GoDSAT-compatible campaigns. The largest
diffusion model achieves held-out trajectory MMD of 0.0171 +/- 0.0239, similar to bootstrap (0.0170) and the mixture (0.0198), but samples farther from training priors (median nearest-training distance 2.7 versus 0.10 standardized units). All generators fail to match the shifted-blind population (classifier AUC 0.991-0.998). Endpoint-conditioned samples satisfy Lambert boundaries but have greater interior error than the matched Lambert reference (29.2 versus 5.7 km mean RMSE). Residual
diffusion improves selected sparse forecasts and catalog-mode recall but does not outperform classical
estimators on custody ranking. In a fixed 16-satellite configuration,
diffusion yields similar mean custody to replay and bootstrap, while the force-tier mixture shifts custody by about 5.5 percentage points. Constrained
diffusion supports local, in-support augmentation but cannot replace orbital dynamics or serve as an operational posterior. Orbital-population construction is a consequential source of uncertainty in constellation analysis.
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All authors Omar Ramadan, Sam Siavoshian, Amir Kashif Saeed, Benjamin A. Johnson, Amin M. E.-A. Diab, Benjamin M. Rodriguez
Quantum Physics
Cross-Validation of Open-Source Quantum Network Simulators
Joaquin Chung, Michal Hajdušek, Naphan Benchasattabuse et al. (+9 more)
We present a comparative analysis of two open-source
quantum network simulators, QuISP and SeQUeNCe, focusing on cross-validation of basic networking tasks to ensure consistency and accuracy in simulation outputs. Although both simulators are designed to study
quantum network management policies and their dynamics under complex noise models, their differing underlying assumptions can lead to variations in simulation results. We highlight the discrepancies in how the two simulators handle connections, internal network node processing time, and classical communication, resulting in significant quantitative and qualitative differences in the time required to perform basic network tasks such as
entanglement generation, purification, and swapping. We simulate common scenarios between the simulators to compare both the latency of resource distribution and the fidelity of the distributed resources. Our findings indicate that while the simulators differ in the time required to complete network tasks—a constant factor difference attributable to their respective connection models—they agree on the fidelity of the distributed resources under identical error parameters. This work demonstrates a crucial first step towards enhancing the reliability and reproducibility of
quantum network simulations, as well as leading to full protocol development. Furthermore, our benchmarking methodology establishes a foundational set of tasks for the cross-validation of simulators to study future
quantum networks.
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All authors Joaquin Chung, Michal Hajdušek, Naphan Benchasattabuse, Robert J. Hayek, Alexander Kolar, Ansh Singal, Kento Samuel Soon, Kentaro Teramoto, Allen Zang, Caitao Zhan, Raj Kettimuthu, Rodney Van Meter
High Energy Physics (Phenomenology)
Tianji Cai and Hancheng Li
By defining notions of similarity between
collider events, metrics give rise to event
manifolds with nontrivial
geometric structure. Understanding these structures and their relation to the underlying physics remains largely unexplored, partly due to the challenge of systematically comparing spaces endowed with distinct metrics. We introduce the multi-reference relative representation (M3R) framework, which provides a unified coordinate system for analyzing different spaces on equal footing. Applying M3R to three physically motivated event metrics—the phase space, spectral 2-Wasserstein, and energy-flow 2-Wasserstein metrics—we study individual event
manifolds and the decision boundaries separating different physical processes. We find that these metrics resolve distinct yet partially shared structures, while intra- and inter-
manifold geometries exhibit qualitatively different properties. Combining multiple metrics further reveals complementary information that can be exploited within a unified representation. More broadly, M3R provides a general
language for comparing and composing different notions of event similarity, opening a path toward a systematic
geometric description of
collider event space.
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Superconductivity
Delamination in Large REBCO Coils
Jun Lu, Yan Xin, Iain Dixon et al. (+6 more)
REBCO coated conductors have been used in ultrahigh field magnets for condensed matter physics research,
nuclear fusion, particle accelerators, and NMR applications. It is well known, however, that they are not mechanically strong against delamination due to their intrinsic layered structures. As a result, the delamination issue has become one of the major design challenges of REBCO magnet coils. As a part of the development of the 40 T all-superconducting magnet at the National High
Magnetic Field Laboratory, USA, large-scale coils wound by two-in-hand REBCO conductor with turn-to-turn insulation was designed and tested at 4.2 K in an 11.4 T background
magnetic field. We found REBCO degradations within the windings and at the crossover joints during the tests. The postmortem inspection found that the degradation was caused by delamination. The delamination appears on the surface of the conductor as bubbles which were subsequently studied by microscopy. Additionally, a similar bubble was found on a short sample by torque magnetometry. This supports the inference that the delamination bubbles found in coils are due to electromagnetic stress. In this paper, we present these findings. The implication of these findings for future magnet designs and the method of mitigation will be discussed.
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All authors Jun Lu, Yan Xin, Iain Dixon, Brent Jarvis, Kwangmin Kim, Yu Suetomi, Jeremy Levitan, Jan Jaroszynski, Hongyu Bai
Quantum Physics
Witnessing Quantum Bayesian Inference beyond Classical Learning
Francesco Buscemi
Can an
agent's predictions reveal whether its
reasoning is based on a classical or a
quantum model? Using known results on
matrix factorizations, here we show that
quantum Bayesian retrodiction can produce one-step-ahead forecasts incompatible with every classical
Bayesian explanation based on learning about a fixed but unknown sampling law from conditionally independent observations. The separation has a sharp threshold in the number of outcomes: for any measurement with at most four outcomes, the
quantum predictions admit a classical realization, irrespective of the prior state and the finite
Hilbert-space dimension, whereas a five-outcome measurement on a single
qubit already violates an explicit classical bound. This bound holds for arbitrary classical latent states, prior probabilities, and sampling laws, and involves only the
agent's initial and updated predictions. Thus, in this setting,
quantum Bayesian retrodiction is strictly more expressive than classical
Bayesian learning, and this difference can be witnessed without observing or specifying the
agent's internal description.
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Geophysics
Bridge Vibrations as Persistent Seismic Sources for Time-lapse Imaging of River Corridors with Distributed Acoustic Sensing
Haipeng Li, Jingxiao Liu, Doyun Hwang et al. (+2 more)
Fluvial corridors mediate dynamic river-groundwater exchanges and support major transportation infrastructure, yet continuous subsurface monitoring remains limited by sparse point sensors and infrequent time-lapse surveys. Addressing this observational gap is critical during extreme flood events, when transient saturation, pore-pressure buildup, and structural scour drive complex hydro-mechanical changes that threaten both riparian slope stability and bridge foundations. Here, we demonstrate that traffic-excited highway bridges act as persistent, spatially fixed seismic sources; their vibrations, recorded on roadside telecommunication fiber with Distributed Acoustic Sensing (DAS), enable time-lapse imaging of river corridors. We evaluate this approach using dark fiber recordings along South Korea's Gyeongbu Expressway during a record monsoon flood in July 2025, targeting a 430 m multi-span bridge crossing the Miho River. Vehicle impacts excite flexural resonances of the bridge deck, generating a discrete spectral comb of fundamental-mode Rayleigh waves in the surrounding ground; these 3-6 Hz waves propagate beyond 400 m across both riverbanks to image the alluvial section down to bedrock. Because bridge-structure geometry constrains the source location and dominant modal frequencies, virtual source gathers achieve rapid convergence within 5 min of ballistic wave stacking with high waveform repeatability over the recording period. Relative seismic velocity (dv/v) monitoring resolves velocity drops up to 1.0% during flood passage associated with heavy precipitation and river stage rise, consistent with hydrological softening of the riparian sediments. These results demonstrate that traffic-excited bridges provide persistent, repeatable seismic illumination, turning roadside telecommunication cables into dense arrays for both hydrogeophysical and civil infrastructure applications.
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All authors Haipeng Li, Jingxiao Liu, Doyun Hwang, Hae Young Noh, Biondo Biondi
Geophysics · Cross-listed from cs.LG
Self-attention summary networks for subsurface velocity-model building from common-image gathers
Shiqin Zeng, Yunlin Zeng, Abhinav Prakash Gahlot et al. (+2 more)
Common-image gathers (CIGs) contain physically meaningful information about velocity-model errors through reflector focusing and residual moveout, but in conventional imaging workflows they are typically used only as diagnostic tools. In this work, we propose a multiscale self-
attention summary network that maps high-dimensional 3D CIG volumes into compact conditioning
embeddings for probabilistic subsurface velocity inversion. These learned
embeddings preserve offset-dependent kinematic structure and spatial coherence while reducing variability caused by background-velocity mismatch. Conditioned on these summary
embeddings, a flow-matching model learns a transport from a Gaussian source distribution to the posterior distribution of plausible velocity fields. Numerical experiments show that, compared with direct conditioning on raw CIGs, the proposed summary network improves posterior velocity inference. In particular, the multiscale
attention design provides greater robustness to background-model mismatch, yielding more accurate posterior reconstructions and lower predictive uncertainty.
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All authors Shiqin Zeng, Yunlin Zeng, Abhinav Prakash Gahlot, Zijun Deng, Felix J. Herrmann
Geophysics · Cross-listed from cs.LG
Twist Flow for Inverse Problems
Shiqin Zeng, Zijun Deng and Felix J. Herrmann
In
Bayesian inverse problems, posterior sampling requires generating samples that are consistent with given observations while capturing the range of plausible solutions. Direct conditional generative models introduce latent noise to model this ambiguity, but paired inverse-problem training can still encourage an almost deterministic map from the observation to the target. As a result, generated samples may be observation-consistent while under-representing posterior variability, especially when the posterior is
multimodal, leading to undercoverage, mode distortion, or artificial transitions between distinct feasible solutions. We propose joint twist-flow, an augmented flow-matching formulation that learns a continuous transport from the augmented source state $(z_x, y)$ to the augmented terminal state $(x, z_y)$. Here x is the target variable, $y$ is the observation, $z_x$ is the Gaussian reference coordinate for posterior sampling, and $z_y$ is a Gaussian likelihood-side coordinate associated with the observation branch. Under a Gaussian observation model, $z_y$ is motivated by the normalized observation residual associated with observation compatibility. Its role is not to replace uncertainty in $x$, but to couple generated samples of x to observation consistency, helping reduce likelihood-inconsistent variation while preserving variability in weakly constrained directions. We validate the method on low-dimensional inverse problems with reference posterior samples, where joint twist-flow better preserves
multimodal posterior support than a direct conditional-flow baseline. We further evaluate the method on image restoration and seismic subsurface velocity-model inversion, showing increased posterior variability while maintaining observation consistency.
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Atomic Physics
Full molecular dynamics simulations of a single trapped ion in a neutral bath
Saajid Chowdhury, Ruiren Shi and Jesús Pérez-Ríos
We present full molecular dynamics simulations that explicitly incorporate the simultaneous interactions between a trapped ion and a bath of neutral atoms. In contrast to conventional molecular dynamics treatments, this framework enables a systematic assessment of how the atomic-gas density influences both the ion's cooling dynamics and its steady-state mean kinetic energy. Our results show that the gas density measurably modifies the ion's average kinetic energy, albeit only weakly, in qualitative disagreement with predictions obtained from standard molecular dynamics simulations. In addition, the calculations indicate that short-range features of the atom-ion interaction potential become increasingly consequential as the atomic density increases. Simulations including many atoms yield higher mean kinetic energies than standard molecular dynamics, a trend we attribute to the transient formation of molecular-ion complexes. Finally, we observe that for a fixed ion, lighter atomic baths lead to a smaller final ion average kinetic energy than heavier atomic baths.
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Chemical Physics
Resolving molecular biexcited states using classical leading-order triples corrections to quantum equation-of-motion UCCSD
Zachary W. Windom, Prince Kwao, Luke Bertels et al. (+3 more)
Excited electronic states are difficult to accurately and tractably model, particularly those exhibiting multiexcitonic character. Scalable single-reference excited state methods typically fail to describe such states as they suffer from the defects of the mean-field approximation and/or neglect higher-rank excitation operators. To address this, we derive the [T] perturbative correction to the
quantum self-consistent equation-of-motion
unitary coupled cluster singles and doubles (q-sc-EOM-UCCSD) method. The method captures triple excitation effects through a classical step of second-order in many-body perturbation theory following a q-sc-EOM-UCCSD calculation on a
quantum computer. The perturbative correction developed has a $\mathcal{O}(N^7)$ classical computational time scaling. We incorporate [T] into a hybrid compute strategy wherein eigenvectors of the effective
Hamiltonian from the hybrid
quantum-classical q-sc-EOM-UCCSD
algorithm are relayed to a classical computer which performs the postprocessing required for the [T] correction. The benefits of [T] are quantified in a
benchmark covering a variety of electronically excited states of the isoelectronic CH$^+$ and BH molecules. We find that the addition of the [T] correction to both trotterized and full operator variants of q-sc-EOM-CCSD can offer dramatic improvements over baseline q-sc-EOM-UCCSD. Our assessment clearly demonstrates the importance of considering higher-rank excitation operators in q-sc-EOM-UCCSD, quantifies the overall success of the [T] correction, and discusses some of its limitations.
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All authors Zachary W. Windom, Prince Kwao, Luke Bertels, Daniel Claudino, Ayush Asthana, Rodney J. Bartlett