Quantum Physics
Higher-Order Magnus Corrections to Leakage Elimination Operator-Based Quantum Control Pulse Design in the Low-Frequency Regime
Hang Yu, Kai-Yu Yuan, Feng-Hua Ren et al. (+1 more)
Effective
quantum control is essential for
quantum computing and information processing, yet level leakage remains a bottleneck limiting control fidelity. The leakage elimination operator (LEO) approach is highly effective at suppressing leakage from a target subspace to other subspaces. Analytical control conditions under the high-frequency driving limit have been derived via the Feshbach PQ partitioning technique. However, the driving intensity is subject to fundamental physical bounds, and low-frequency driving is experimentally more feasible. In this work, we reformulate LEO within the Magnus framework and extend it beyond the high-frequency limit. We show that the analytical control conditions obtained from the Feshbach PQ partitioning technique are equivalent to the zeroth-order Magnus expansion. We then analyze the higher-order Magnus corrections. By minimizing the leakage, we obtain a modified pulse condition suitable for the low-frequency regime. As an illustrative example, we study near-perfect state transfer through a one-dimensional
spin chain under LEO control. We find that the second-order Magnus correction improves the transmission fidelity at low-frequency driving, while the improvement becomes negligible at high frequencies. Our results provide an effective route for designing control pulses in the low-frequency regime, with potential applications in superconducting
qubits, trapped ions, and solid-state
spin systems.
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All authors Hang Yu, Kai-Yu Yuan, Feng-Hua Ren, Zhao-Ming Wang
Fluid Dynamics
A second-order unified gas-kinetic wave-particle method with enhanced mesh independence for hypersonic flows
Junzhe Cao, Rui Zhang, Wenpei Long et al. (+2 more)
Benefiting from the direct modeling of physical laws in a discretized space and the automatic decomposition of the gas distribution function into hydrodynamic waves and particles, the UGKWP method offers significant advantages for multiscale flows such as hypersonic flows,
plasma transport, and radiation transport. In this study, the particle sampling accuracy in the UGKWP method is improved from first order to second order, so that the second-order spatial and temporal accuracy is preserved across the full scheme. Specifically, the modifications include second-order particle sampling based on local macroscopic gradients, a weighted least-squares gradient reconstruction that incorporates wall values, a revised Venkatakrishnan limiter for highly stretched
cells, and conservation corrections after particle sampling. Moreover, the first-order Chapman–Enskog term is considered in the free-transport part of the hydrodynamic wave flux, enabling better recovery of the GKS in the near-continuum regime. Based on these improvements, the mesh-independence behavior of the UGKWP method is notably enhanced, which is more consistent with the performance of the UGKS, validated by a detailed hypersonic cylinder flow test case. Furthermore, systematic comparisons with the single-scale DSMC method are performed for two-dimensional hypersonic flow over a cylinder and three-dimensional flow over a blunt cone. Wall pressure, shear stress, and heat flux coefficients (CP, CF, and CQ) are examined in the cylinder case, while the overall aerodynamic coefficients (CL, CD, and L/D) are assessed in the cone case. The multiscale UGKWP method exhibits significantly better mesh-independence performance than DSMC for mesh-sensitive quantities such as CF, CQ, CD, and L/D, which are critical for aerodynamic and thermal protection design of near-space hypersonic vehicles.
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All authors Junzhe Cao, Rui Zhang, Wenpei Long, Chengwen Zhong, Kun Xu
Optics
Hessian sparsity-constrained self-supervised network for near-infrared single-photon single-pixel imaging
Yao Wang, Muchen Zhu, Linjun Zhai et al. (+6 more)
Near-infrared (NIR) imaging has emerged as an important technology for night
vision, remote sensing, and biological imaging, yet conventional array-detector-based systems are often limited by insufficient sensitivity, high cost, and substantial dark noise. Single-pixel imaging (SPI) offers an attractive alternative, enabling single-
photon-level NIR imaging by using a cost-effective single-element detector. Nevertheless, SPI remains restricted by
photon noise, leading to degraded imaging quality and limited frame rate under extremely low
photon flux conditions. Here, we present a Hessian sparsity-constrained self-supervised network (HS3N) for single-
photon NIR SPI, which can suppress noise and enable high-fidelity and real-time imaging under ultra-low illumination conditions. The HS3N integrates the physical forward model of SPI with an untrained neural network regularized by both sparsity priors and Hessian-based structural constraints, enabling effective noise suppression while preserving structural fidelity and continuity. Both simulated and experimental results demonstrate that HS3N enables high-fidelity reconstructions under ultra-low NIR
photon levels down to ~0.01
photons per pixel. Furthermore, we demonstrate its dynamic capability by monitoring the dynamic
evolution and detachment of infrared-absorbing droplets, at a frame rate of ~20 Hz under ~0.19
photons per pixel, highlighting its potential for high-sensitivity infrared inspection. The proposed reconstruction framework paves the way for practical NIR imaging in extreme low light conditions, which can be extended to visible, mid-infrared or terahertz imaging, offering broad potential for
photon-efficient sensing across a wide spectral range.
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All authors Yao Wang, Muchen Zhu, Linjun Zhai, Huiyuan Zhang, Junnan Chen, Yiming Yu, Zhaohua Yang, Baolei Liu, Fan Wang
Quantum Physics
Quantum Eigenvalue Transformation via Linear Combination of Hamiltonian Simulation: A Weyl Calculus Approach
Hongkang Ni and Lexing Ying
Linear combination of
Hamiltonian simulation (LCHS) provides an efficient method for implementing
matrix exponentials $e^{-tA}$ on
quantum computers. In this paper, we develop LCHS formulas for computing general
matrix functions $f(A)$ when $f$ is analytic on the numerical range of $A$, with $A$ possibly non-normal. The essential technical tool is Weyl calculus, which reduces the construction of LCHS formulas for noncommuting operators to scalar
Fourier approximation problems. Our construction yields a
quantum eigenvalue transformation
algorithm with optimal $\mathcal{O}(\log\frac{1}{\epsilon})$ query complexity scaling. Furthermore, our Weyl-calculus-based theory gives rise to an ansatz-free convex optimization framework that directly produces discrete LCHS formulas. This circumvents the inefficiencies of traditional quadrature rules and yields formulas highly optimized for coherent implementation on
quantum computers. In addition, both our theory and optimization framework apply to the simulation of time-dependent dissipative ODE $\frac{\mathrm{d}}{\mathrm{d} t} \psi(t) = -A(t)\psi(t)$, for which we achieve a $2.1\times$ cost reduction over prior art.
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Fluid Dynamics
Gappy Reconstruction of Bubbly Flows by Guided Diffusion Models
Hridey Narula, Tianyi Li, Michele Buzzicotti et al. (+2 more)
Experiments in multiphase flows are often limited in their ability to simultaneously obtain velocity measurements in different phases. At the same time, flow reconstruction from phase-limited measurements is a challenging problem due to the substantially different velocity statistics across the phases. We address this problem for buoyancy-driven bubbly flows in the pseudo-
turbulence regime by using a guided
diffusion model. We train the model using two-dimensional slices of the velocity field extracted from fully resolved three-dimensional direct numerical simulations. The model generates physically realistic velocity fields both unconditionally and when conditioned on the surrounding
liquid flow. The reconstructed bubble-phase velocity field accurately reproduces key statistical features of the flow. We further show that a simple patching procedure for adjacent two-dimensional slices enables a reasonable reconstruction of the three-dimensional flow inside a bubble. These results establish the potential of
diffusion models to serve as generative priors for three-dimensional turbulent multiphase flows, opening a route toward the reconstruction of unobserved or experimentally inaccessible velocity fields from sparse, partial, or phase-limited measurements.
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All authors Hridey Narula, Tianyi Li, Michele Buzzicotti, Luca Biferale, Prasad Perlekar
Data Analysis and Statistics
The Squealer: Sensification of model exploration and model misfit
Andrew Gelman, Andrew H. Jaffe, Eliot Carlson et al. (+1 more)
We introduce a method for visual and auditory feedback when exploring the fit of a model to data. Starting with a best-fit curve fit to data, the user can drag the curve to a new position and the computer will emit a squeal, becoming louder and more unpleasant as the discrepancy between curve and data increases. We demonstrate with four examples: a two-parameter curve fit to golf putting data, a four-parameter curve fit to dilution assays, a fit to cosmological data sensitive to the parameters of the Big Bang model, and a nonparametric Gaussian process fit to temperature readings.
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All authors Andrew Gelman, Andrew H. Jaffe, Eliot Carlson, Philip Greengard
Statistical Mechanics
Poisson-shot-noise hybrid machines: efficiency and quasistatic divergence
Rita Majumdar, Costantino Di Bello, Ralf Metzler et al. (+2 more)
We study
stochastic models of a microscopic active heat engine, comprised of an overdamped Brownian particle trapped in a harmonic potential, and in simultaneous contact with thermal (passive) and athermal (active) baths. The interaction with the active bath is modeled as a
stochastic force described by Poisson shot-noise (PSN) having a specified amplitude distribution. With analytical calculations and numerical simulations, we study the thermodynamic performance of the machine to quasistatic cyclic protocols analogous to those running two-stroke and Stirling-like engines. For specific parameter ranges, the thermodynamic behavior is that of a $\textit{hybrid machine}$, simultaneously operating as a heat engine with respect to the passive/active baths and as a refrigerator with respect to the passive/active baths. Focusing on the parameter region where the overall performance is such of an engine, we show that the average total extracted work per cycle divided by average total heat intake from the cold baths per cycle may surpass the Carnot efficiency associated with the temperature of the passive baths. Applying the second law for active heat engines, we focus on a bona fide efficiency (bounded by Carnot's efficiency) that incorporates an information-theoretic metric $\mathcal{I}-$ which we call $\textit{quasistatic divergence}-$ quantifying how distinguishable are the engine's statistics in the quasistatic limit with respect to a continually changing
equilibrium distribution. We analyze, with theory and numerical simulations, how the PSN shot rate and the degree of non-Gaussianity in the particle position distribution influence the efficiency of the engine, and explore the correlation between non-Gaussianity and efficiency. Our findings reveal optimal PSN shot rates maximizing the engine's efficiency and an intriguing non-bijective relation between efficiency and kurtosis
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All authors Rita Majumdar, Costantino Di Bello, Ralf Metzler, Rahul Marathe, Édgar Roldán
Solar and Stellar Astrophysics
High Resolution Spectroscopic Analysis of Chromospheric Line Evolution during an Energetic Flare on AD Leo
Younghun Oh, Seo-Won Chang, Jongchul Chae et al. (+6 more)
Active M
dwarfs exhibit frequent and energetic
flares that provide a unique laboratory for studying chromospheric heating processes under extreme
magnetic activity. To probe the
flare process of M-
dwarfs, we present a high-resolution ($R\sim30{,}000$) spectroscopic case study of a superflare on AD Leo, detected on 2023 March 14 using the Bohyunsan Optical Echelle Spectrograph (BOES). Such high-energy events are rarely captured with simultaneous multi-line spectroscopy, allowing us to trace the energy partition and temporal
evolution of the chromospheric lines. Based on equivalent width variations, we found that the H$\alpha$ line radiated $8.8\times10^{30}$ erg, implying a total bolometric energy ($\sim10^{33}$ erg) comparable to the largest
solar flares. The Balmer series dominated the energy budget; the individual Ca II H and K lines contributed 47.5% and 26.2% of the H$\alpha$ energy, respectively, while each Ca II infrared triplet line emitted $\sim$17-19%. We confirm that the delayed peak emission, previously reported for Ca II H&K, also occurs in the Ca II triplet and Na I lines. These delays are consistent with the Neupert effect, suggesting that cumulative heating governs the gradual phase emission. While this superflare resembles
solar flares in general morphology, it also displayed systematic differences in chromospheric emission. It is likely that these differences reflect the distinct atmospheric structure and quiescent chromospheric conditions of M
dwarfs, rather than fundamentally different
flare physics.
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All authors Younghun Oh, Seo-Won Chang, Jongchul Chae, Juhyung Kang, Soosang Kang, Kyeore Lee, Kyoung-Sun Lee, Eun-Kyung Lim, Hyun-Il Sung
High Energy Astrophysical Phenomena
Constraints on Hadronic Emission from Microquasars Detected by LHAASO
V. Vecchiotti, E. Amato, G. Giacinti et al. (+2 more)
Recently, the LHAASO collaboration reported ultra-high-energy (UHE) gamma rays from six microquasars. For five of these sources, the emission extends beyond $100$ TeV, making microquasars promising candidates for
Galactic PeVatrons. We investigate whether gamma-rays around $100$ TeV originate from hadronic interactions of accelerated
cosmic rays (CRs) with the ambient medium, and we estimate the contribution of these sources to the measured CR spectrum around the knee. We also place upper limits on six LHAASO microquasars with no detected UHE emission. We assume
diffusion-dominated propagation of CR, with a
diffusion coefficient suppressed compared to the average
Galactic value near the source and equal to the
Galactic value at large distances. We assume continuous injection over timescales of $t_{\rm age}=0.1-1$ Myrs. Using available measurements of the gas density, we find that hadronic interactions alone cannot fully account for the observed emission for any of the detected sources. However, in the case of GRS 1915+105 and MAXI J1820+070, the hadronic scenario may still be valid when considering acceleration efficiency higher than $10\%$. We then derive upper limits on the hadronic contribution to the observed gamma-ray flux. We estimate that the detected sources contribute at most $\sim4\%$ of the
Galactic CR spectrum at $1$ PeV for an injection timescales of $0.1$ Myrs and a CR acceleration efficiency of $10 \%$. When adopting the maximum acceleration efficiency allowed by the gamma-ray observations the contribution rises to $37\%$. Longer injection timescales ($\sim 1$ Myrs) lead to contributions exceeding the observational constraints. For sources not detected at UHE, we obtained a maximum contribution of $\sim 17\%$, achieved assuming continuous injection over $1$ Myr.
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All authors V. Vecchiotti, E. Amato, G. Giacinti, G. Morlino, G. Peron
Mesoscale and Nanoscale Physics
Spin-1 Dirac dispersion and Chern insulating phases in 2D honeycomb Sierpiński fractal
Shneha Biswas, Shouya Yoshida, Katsunori Wakabayashi et al. (+1 more)
Graphene-based Sierpiński fractals host a zero-energy
chiral mode and
spin-1 Dirac dispersions within the nearest-neighbor tight-binding model. However, the presence of complex next-nearest neighbor hopping arising from the local flux and the staggered Semenoff mass terms, modeled within the Haldane
Hamiltonian, breaks the time-reversal and spatial inversion
symmetries, respectively, and makes these flat bands dispersive. Moreover, they introduce rich topological phases in this class of systems that can be characterized by Chern numbers up to $\pm 3$, i.e., beyond the conventional honeycomb
lattice. These observations pave the way for the exploration of 2D periodic fractals beyond
graphene, where topological phase transitions can be realized through externally applied fields.
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All authors Shneha Biswas, Shouya Yoshida, Katsunori Wakabayashi, Sudipta Dutta
General Relativity and Quantum Cosmology
Gravitational time advancement effect in Bumblebee gravity for Earth bound systems
G. Y. Tuleganova, R. Kh. Karimov, R. N. Izmailov et al. (+3 more)
This paper is a novel application of the new effect of gravitational time advancement or negative time delay, first predicted for static black holes (
spin $a=0$), that can be regarded as complementary to the well known effect of positive Shapiro time delay. We shall extend the Shapiro time delay formalism up to third PPN order using the recently proposed spinning ($a\neq 0$) black hole solution of the Lorentz
symmetry breaking (LSB) Bumblebee
gravity that is believed to reveal signatures of
quantum gravity at low energies. Adopting two practical examples of signal propagation along Earth-Moon and Earth-Satellite configurations, we shall calculate the influence of the Bumblebee parameter $\ell$ on time advancement using terms up to the second PPN order $\varpropto aM$ and $M^{2} $ as the Bumblebee solution is valid only upto first order in $a$. It is shown that there is a critical radial distance $r_{c}$ above the Earth, where the Shapiro delay vanishes, and beyond $r_{c}$ the delay becomes negative, i.e., time advancement begins to set in, leading to the intriguing consequence that the measured LLR distance to Moon or any Satellite becomes less than the zeroth order Euclidean distance. It is shown that the LSB correction arises from the conical geometry of the massless Bumblebee spacetime leading to upper bounds on the correction to the zeroth order Euclidean time interval as $\delta \tau _{\text{LSB}}^{\text{Eucl}}<0.8\times 10^{-4}$ (ns) and to time advancement as $\Delta \tau _{\text{LSB}}^{\text{adv}}<-4.5\times 10^{-13}$ (ns), both estimates based on the bound on $\ell $ corresponding to the Cassini spacecraft experiment. We shall also briefly touch upon the feasibility of direct experimental detection of the advancement effect.
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All authors G. Y. Tuleganova, R. Kh. Karimov, R. N. Izmailov, A. A. Potapov, A. Bhadra, K. K. Nandi
General Relativity and Quantum Cosmology
On a Class of Harko-Kovacs-Lobo Wormholes
R. Kh. Karimov, R. N. Izmailov and K. K. Nandi
The Harko, Kovács, and Lobo wormhole (HKLWH) metric contains two free parameters: one is the wormhole throat $r_{0}$, and the other is a dimensionless deviation parameter $\gamma$ with values $0<\gamma <1$, the latter ensuring the needed violation of the null energy condition at the throat. In this paper, we study the energetics of the HKLWH and the influence of $\gamma$ on the
tidal forces in the Lorentz-boosted frame. Finally, we apply\ a new concept, namely, the probabilistic identity of the object observed by different external observers in terms of the Fresnel coefficients derived by Tangherlini. The intriguing result is that observations can differ depending on the location of the observer, i.e., there is a nonzero probability that the HKLWH will be identified as a black hole even when $\gamma \neq 0$.
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Materials Science
Field-induced topological Hall effect and butterfly-shaped magnetoresistance in the centrosymmetric antiferromagnet EuAuAs
Yu Zhang, Junfa Lin, Huan Wang et al. (+6 more)
The coupling between
magnetic and electronic degrees of freedom gives rise to a variety of intriguing transport phenomena. Among them, the topological
Hall effect, originating from the real-space Berry phase associated with nontrivial
magnetic textures, has attracted considerable
attention. Here, we systematically investigate the
magnetic and transport properties of antiferromagnet EuAuAs.
Magnetic characterizations reveal
antiferromagnetic transition at 5.7 K and 6.3 K for $H \parallel ab$ and $H \parallel c$, accompanied by metamagnetic transition and small hysteresis for $H \parallel ab$. Electrical transport measurements reveal a pronounced topological
Hall effct in the
antiferromagnetic state with $H \parallel ab$ and $I \parallel c$, which may be attributed to finite scalar
spin chirality. Furthermore, the magnetoresistance exhibits butterfly-shaped hysteresis and strong angular dependence, which are likely associated with
spin-dependent electron scattering,
magnetic-domain
evolution, and domain-wall pinning. Our results suggest that field-induced
spin textures play an important role in the magnetotransport properties and provide insights into the interplay between
magnetic textures and electronic transport in centrosymmetric antiferromagnets.
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All authors Yu Zhang, Junfa Lin, Huan Wang, Kun Han, Yiting Wang, Xue Dong, Zhenfeng Guan, Shengdi Xi, Tian-Long Xia
High Energy Physics (Phenomenology)
Light Neutralino Dark Matter in a Supersymmetric Pati-Salam Framework
Ali Muhammad, Imtiaz Khan, Tianjun Li et al. (+2 more)
We investigate the low-energy phenomenology of the MSSM arising from the supersymmetric $SU(4)_C \times SU(2)_L \times SU(2)_R$ Pati-Salam framework, focusing on neutralino dark matter in bulk annihilation and
Higgs/Z-funnel regions. Using a comprehensive parameter scan consistent with radiative electroweak
symmetry breaking and a neutralino LSP, we analyze
collider,
flavor, and dark matter constraints for both signs of {\mu}. To isolate genuine bulk annihilation from coannihilation, we impose the mass-splitting condition $\mathcal{R}_{\tilde{\phi}} \equiv (m_{\tilde{\phi}}-m_{\tilde{\chi}_1^0})/m_{\tilde{\chi}_1^0}\gtrsim 10\%$. We identify a viable bulk region with a bino-like LSP and a light right-handed stau NLSP. These solutions satisfy all experimental constraints, including LHC searches,
flavor observables, and the Planck 2018 relic density, predicting upper bounds $m_{\tilde{\chi}_1^0}\lesssim 110~{\rm GeV}$ and $m_{\tilde{\tau}_1}\lesssim 120~{\rm GeV}$. This parameter space lies within the reach of future CEPC and FCC-ee
colliders. We also analyze
Higgs- and Z-funnel regions. Current direct-detection limits strongly constrain light Higgsino-assisted resonances for {\mu}>0. Conversely, for {\mu}<0, destructive interference in
Higgs-mediated scattering suppresses the direct-detection cross section, allowing a viable Z-funnel region to survive below the projected LZ 1000-day sensitivity. These results highlight the negative-{\mu} Pati-Salam framework as a predictive, testable scenario for upcoming dark matter and
lepton collider experiments
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All authors Ali Muhammad, Imtiaz Khan, Tianjun Li, Shabbar Raza, Mussawir Khan
Quantum Physics
Infrared Safety from ZX-Diagrams: A Categorical Proof of Soft-QED as Open Quantum System
Soo-Jong Rey
The discard ZX-calculus, a diagrammatic
language for mixed-state
quantum mechanics, is used to give a nonperturbative, categorical proof of the Bloch-Nordsieck cancellation of infrared divergences in QED. Soft
photons are treated as an open
quantum system: the resolved charged particles and hard
photons form the system, while
photons below a detector resolution form the environment. The reduced hard channel is a completely positive trace-preserving (CPTP) map, and the soft-
photon theorem replaces the full S-
matrix by a controlled displacement operator whose Feynman-Vernon influence functional satisfies the equal-history normalization ${\cal F}[J,J]=1 $. In the ZX-calculus, this normalization is a single diagrammatic identity: the doubled displacement diagram collapses to the bare wire under the unitarity, cyclicity, and discard rules. The proof therefore serves as a categorical consistency check on the open-system treatment of soft QED given in a companion paper; it confirms that the physical derivation is logically complete and free of hidden assumptions about the infrared limit. For off-diagonal hard-state elements, the same diagram yields the coherent-state overlap, giving a first-principles account of soft-cloud decoherence. The soft-shell coarse graining is then constructed as a CPTP Schur channel whose infinitesimal limit produces the exact Lindblad generator with jump operators determined by the eikonal emission amplitudes. Finally, a local CPTP-certification pipeline is developed for non-Markovian process tensors, enabling constant-time verification of trace preservation in open
quantum simulations. The framework bridges categorical
quantum semantics, non-
equilibrium field theory, and practical open-system compilation.
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Plasma Physics
Harnessing Toroidal Neutral Flows to Enhance Divertor Particle Exhaust
M. Moscheni, A. Herrmann, J.D. Lore et al. (+5 more)
In 1991 Reiter et al. (1991
Plasma Phys. Control. Fusion 33 1579) considered the onerous exhaust requirements of ITER, and wrote: "The
vacuum pumping problem of a fusion reactor will probably require some novel solution". Here we show that a toroidally oriented pump inlet can passively exploit intrinsic neutral flows to reduce back-flow, raise duct pressure, and ultimately improve particle-exhaust performance. Drawing on previous experimental observations and SOLPS-ITER edge-
plasma simulations, we consolidate the evidence for a
plasma-imprinted, multi-species toroidal neutral "wind" in detached tokamak divertors. We isolate the underlying mechanism in a prototypical divertor private-flux region using a database of two-dimensional direct simulation Monte Carlo (DSMC) calculations. The ordered neutral motion is recovered with a strong toroidal
alignment, kilometre-per-second velocities, and persistence up to several centimetres across slip-to-transitional rarefied regimes (Kn=0.02$-$2). We then assess the consequences of capturing this ordered motion using a second database of idealised proof-of-principle DSMC simulations. Compared to the traditional poloidal arrangement, a toroidally oriented pump inlet reduces back-flow by up to 20% for deuterium and up to 33% for helium at 10% concentration. Partial pressures in the toroidal exhaust path are enhanced across the database, nominally by a factor of 1.78$\pm$0.04 for deuterium and 2.00$\pm$0.05 for helium. For fixed throughput, this implies a reduction in the required effective pumping speed and corresponding hardware. More broadly, these results motivate explicit retention of toroidal neutral momentum in divertor and sub-divertor modelling, and dedicated studies of neutral aerodynamics, including in stellarators, where an analogous directional imprinting is expected to occur.
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All authors M. Moscheni, A. Herrmann, J.D. Lore, M. Kryjak, C. Soika, R. Kembleton, S. Lazerson, K. Revel
Cosmology and Nongalactic Astrophysics
Superhorizon curvature perturbations in hybrid inflation revisited
Shi Pi and Anxianyi Xiong
We revisit cosmological perturbations in multi-field inflation using the $\delta N$ formalism. By extending the analysis to directions transverse to the inflationary trajectory, we explicitly account for the geometry of the final hypersurface. Applying this framework to hybrid inflation, we identify an enhancement mechanism of the
curvature perturbation driven by the growing isocurvature perturbation due to the tachyonic instability of the waterfall field. This amplification occurs during the trajectory's turn in field space, a process qualitatively distinct from the non-attractor solution in single-field inflation models such as ultra-slow-roll. The resulting power spectrum features a broad peak with a characteristic $k^3$ infrared growth and a ultraviolet spectral tilt that uniquely determines the nonlinear parameter $f_\mathrm{NL}$ of a logarithmic non-Gaussianity, all of which are primarily governed by the waterfall dynamics. We found that in hybrid inflation, the sign of $f_{\rm NL}$ is fixed by tachyonic waterfall geometry and is always positive, leading to a generic enhancement of
primordial black hole formation. The enhanced
curvature perturbation can simultaneously account for
primordial black hole dark matter and a
stochastic gravitational wave background detectable by LISA, Taiji, and TianQin.
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Quantum Physics
Nonlocal effects via Local Quantum Fisher Information: Characterizations and Interpretations
R. Muthuganesan
We introduce a
quantum Fisher information based measurement-induced nonlocality (QFI-MIN), which quantifies the maximal statistical distinguishability induced by locally invariant
unitary dynamics. The proposed measure inherits desirable properties including positivity, local
unitary invariance, monotonicity under local operations, and immunity to the local ancilla problem. Analytical expressions are obtained for pure states, arbitrary two-
qubit states, and two-
qubit X states, revealing a direct connection with
entanglement for pure systems. We further establish clear operational interpretations of QFI-MIN in
quantum parameter estimation, local channel discrimination, and correlation-assisted communication. Its behavior under amplitude damping, depolarizing, and generalized amplitude damping channels demonstrates robustness against environmental noise. The proposed framework provides a physically consistent and operationally meaningful quantifier of
quantum correlations, linking nonlocality,
quantum metrology, and
quantum information processing
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Instrumentation and Methods for Astrophysics
Design Method of Quasi-Lumped Element Bandpass Filters Using Superconducting Coplanar Waveguide for Millimeter-Wave Multichroic Imaging
Shinsuke Uno, Kah Wuy Chin, Tai Oshima et al. (+6 more)
An on-chip band-defining filter coupled with a superconducting
photon detector is a promising technology for developing multi-band imaging cameras at millimeter and submillimeter wavelengths. In this paper, we present the design of on-chip bandpass filters based on coplanar waveguide geometry, which can be easily integrated into large-format multi-band detector arrays. A lumped element filter design is suitable not only for achieving a compact footprint but also for suppressing harmonics to reduce band-to-band crosstalk in a multiplexer. However, the coplanar waveguide geometry and the photolithography process rule limit the maximum available inductance and capacitance of lumped elements, which does not sufficiently meet the requirements of filter
circuits. To overcome this limitation, we have established a design method for quasi-lumped element filters, in which the maximum element size is relaxed to a quarter wavelength, exceeding the ideal lumped element size. We achieved design solutions for 150, 220, and 270 GHz 8th-order Chebyshev bandpass filters and a triplexer. We also report on the measurement results of a scaled model of the bandpass filter, demonstrating the validity of our proposed filter design.
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All authors Shinsuke Uno, Kah Wuy Chin, Tai Oshima, Satoshi Ono, Takeshi Sakai, Kazuki Watanabe, Shuhei Inoue, Tatsuya Takekoshi, Kotaro Kohno
Instrumentation and Methods for Astrophysics
Broadband anti-reflection coating for sub-terahertz optics using dielectric multilayers
Toyo Naganuma, Shinsuke Uno, Shuhei Inoue et al. (+4 more)
Sub-terahertz astronomy requires instruments capable of simultaneous observations across multiple spectral bands, motivating the development of broadband anti-reflection coatings (ARCs). We investigated low-loss dielectrics with refractive indices suitable for multilayer ARCs on polyethylene optical elements and identified candidates that partially meet the requirements. To address the remaining gaps in available refractive indices, we applied dielectric multilayer synthesis by combining newly identified thin materials with controlled bonding to realize the required effective refractive indices. As a result, the fabricated 5-layer ARC achieved reflection losses of 0.2% (average) and 3.2% (maximum) over 130-710 GHz.
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All authors Toyo Naganuma, Shinsuke Uno, Shuhei Inoue, Kazuki Watanabe, Tatsuya Takekoshi, Takeshi Sakai, Tai Oshima
Instrumentation and Methods for Astrophysics
GLTCAM: Concept of Multi-color Millimeter and Submillimeter Camera for the Greenland Telescope
Shuhei Inoue, Tatsuya Takekoshi, Shinsuke Uno et al. (+12 more)
To investigate the formation history of large-scale structure through the dynamics of
galaxy clusters, we are developing a multi-color millimeter and submillimeter-wave continuum camera (GLTCAM) for deployment on the Green-land
Telescope (GLT). GLTCAM will observe in six frequency bands - three in the millimeter range (150, 220, and 270 GHz) and three in the submillimeter range (350, 400, and 670 GHz). The optical design provides a compact configuration that fits within the GLT receiver cabin, while delivering diffraction-limited performance over an $18'$ field of view with minimal telecentricity error and distortion. A key advantage of this design is its uniform illumination footprint at the cold stop, which helps minimize thermal loading on both the detectors and the cryogenic stages. The focal plane module comprises a quasi-optical bandpass filter, a conical horn array coupled with planar ortho mode transducers (OMTs), and a superconducting multi-color microwave kinetic inductance detector (MKID) array. Current development efforts are focused on the three-color millimeter-wave module. The detector array employs a single-layer coplanar waveguide (CPW) architecture, which simplifies fabrication and enables scalability to large-format arrays. GLTCAM aims for the early realization of next-generation wide-field, multi-color observations as a pathfinder for future large submillimeter
telescopes.
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All authors Shuhei Inoue, Tatsuya Takekoshi, Shinsuke Uno, Kazuki Watanabe, Taiki Sato, Toshihiro Tsuzuki, Satoru Mima, Tohru Taino, Kazuyuki Fujita, Shunichi Nakatsubo, Yuki Kimura, Chiko Otani, Ryohei Kawabe, Kotaro Kohno, Tai Oshima
General Relativity and Quantum Cosmology
Optical Appearances of Accreting Ellis-Bronnikov Wormholes Observed from Both Sides of Throats
Yu-Hao Cui, Kai Lin, Sen Guo et al. (+2 more)
This study investigates the optical appearance of the Ellis-Bronnikov wormhole as viewed from both sides of its throat, under conditions of optically thick and thin
accretion. By solving the geodesic equation, we derive the relationship between the impact parameter and the aiming distance of
photons, and found that if the observer and the
accretion disk are located on both sides of the throat, these two quantities are not equal. The optical image of the wormhole observed from the other side of the throat is obtained through the ray-tracing method. For optically thick
accretion, increases in the parameter $n$ lead to an increase in the apparent size of the wormhole but a decrease in its brightness. For optically thin
accretion, the image is similar to the internal and external inversion of the image observed from the other side. Furthermore, for optically thin
accretion flows, the direct image does not block the emission from higher-order images, allowing radiation emitted from regions much closer to the event horizon to reach the observer. Our simulation results show that when the observer is on the $\mathcal{R}^+$ side, EB wormholes with small $n$ can mimic the images taken by the EHT to some extent, while wormholes with large $n$ or with the observer on the $\mathcal{R}^-$ side can be ruled out.
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All authors Yu-Hao Cui, Kai Lin, Sen Guo, Yu Liang, Tong Liu
Quantum Physics
Multipartite quantum resource distillation through local measurement programs
Yan Wang, Shao-Qi Lin, Xi-Nuo Tao et al. (+6 more)
Distributed
quantum resources in practical multi-user
quantum networks are inevitably degraded by environmental noise, channel loss, and device-induced imperfections. To address these issues,
quantum resource
distillation offers a fundamental approach to recovering stronger resources from imperfect states. However, conventional implementations often require additional copies, dedicated physical filtering elements, or restrict to bipartite systems, posing challenges for scalable multipartite networks. Here, we introduce the method of
quantum resource
distillation based on the local measurement program (LMP), which transfers completely positive maps into programmable measurement processes. We experimentally demonstrate the performance of resource
distillation through LMP in both bipartite and tripartite photonic systems, including the activation and enhancement of multipartite steering configurations. To demonstrate the flexibility and extensibility of the LMP framework, we also show that virtual resource
distillation can be naturally reformulated within it. Our results establish a programmable and experimentally economical approach for distilling
quantum resources in multipartite and higher-dimensional systems, thereby providing a practical route toward scalable
quantum networks.
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All authors Yan Wang, Shao-Qi Lin, Xi-Nuo Tao, Li-Jiong Shen, Yong-Nan Sun, Ze-Yan Hao, Kai Sun, Qi-Ping Su, Chui-Ping Yang
Quantum Physics
Krylov Complexity in Non-Inertial Quantum Systems
Ming-Qi Ma, Shi-Cheng Liu, Lei-Hua Liu et al. (+1 more)
This study formulates observer-dependent Krylov spreading for non-inertial
quantum systems driven by linear Bogoliubov transformations. Starting with the closed single Rindler-pair $SU(1,1)$ sector, we show that its Lanczos basis is identical to the Rindler pair-number basis. As a result, the Krylov spread complexity reduces exactly to the mean number of correlated Rindler pairs, $C_k=\vert\beta_k\vert^2$. Within this framework, we demonstrate that Krylov spreading dynamics are governed by the competition between the detuning parameter and the coupling constant, naturally dividing the dynamics into three distinct regimes. Notably, Krylov complexity becomes localized in the detuning-dominated regime. By extending this to a multimode, strictly quadratic Bogoliubov
Hamiltonian, we find that inequivalent Rindler wave-packet pairs violate the $C_k=\vert\beta_k\vert^2$ correspondence, thereby highlighting the single-pair $SU(1,1)$ model as an exactly solvable, observer-adapted
benchmark. In such multimode scenarios, the mean pair-number eigenstates no longer dictate Krylov complexity. Overall, our work provides a new perspective for analyzing Krylov complexity in non-inertial
quantum systems.
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All authors Ming-Qi Ma, Shi-Cheng Liu, Lei-Hua Liu, Hai-Qing Zhang
Quantum Physics
Quantum Circuit Realization of the PPT and CCNR Criteria
Jihui Mo and Yuanhong Tao
The efficient detection of
quantum entanglement is a central problem in
quantum information processing. This paper systematically proposes a
quantum circuit implementation scheme based on the Positive Partial Transpose (PPT) and the Computable Cross-Norm Realignment (CCNR) criteria, providing a complete
quantum algorithmic pathway for efficient and computable
entanglement detection. By encoding
quantum states into specific forms and utilizing SWAP operations, complex
matrix operations such as partial transpose and realignment are transformed into executable
quantum circuits. Furthermore, by integrating an improved variational
quantum singular value decomposition subroutine, the scheme enables the efficient estimation of the trace norm, thereby determining the existence of
entanglement. Designed to operate within a hybrid
quantum-classical framework, this scheme exhibits excellent scalability and practicality, offering a theoretical tool and methodological support for analyzing the
entanglement structure of complex
quantum systems on future intermediate-scale
quantum devices.
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Superconductivity
Unconventional Superconductivity in the Chiral Topological Semimetal Ag2Pd3S
Roshan Kumar Kushwaha, Dibyendu Samanta, Sudarshan Sharma et al. (+15 more)
Chiral crystals provide a unique setting where broken inversion
symmetry, strong
spin-orbit coupling, and electronic
topology intertwine, yet superconductivity in intrinsically
chiral materials remains rare. Here, we report unconventional superconductivity in the
chiral topological semimetal Ag$_2$Pd$_3$S, an enantiomorphic analog of natural mineral coldwellite, crystallizing in the right-handed space group $P4_132$. Bulk superconductivity with a transition temperature $T_C = 1.1(2)$ K is confirmed by electrical resistivity, magnetization, and specific-heat measurements.
Muon spin rotation and relaxation ($\mu$SR) experiments reveal a fully gapped superconducting state that spontaneously time-reversal
symmetry (TRS) breaking establishing Ag$_2$Pd$_3$S as the first
chiral topological semimetal
superconductor exhibiting intrinsic TRS breaking. First-principles calculations uncover multiple multifold band crossings near the
Fermi level, hosting Kramers-Weyl, double
spin-1, and
spin-3/2 quasiparticles with large topological charges. These unconventional
fermions generate
symmetry-protected topological surface states and underscore the nontrivial
topology of the normal state.
Symmetry analysis based on the Ginzburg-Landau theory suggests a loop-supercurrent-ordered superconducting state, yielding a full gap alongside spontaneous TRS breaking. The coexistence of TRS-breaking superconductivity and
chiral multifold
fermions identifies Ag$_2$Pd$_3$S as a platform for realizing intrinsic superconducting diode effects and chirality-induced
spin selectivity, offering a transformative pathway toward dissipationless topological
quantum technologies.
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All authors Roshan Kumar Kushwaha, Dibyendu Samanta, Sudarshan Sharma, Mathew Pula, Shashank Srivastava, Poulami Manna, Arushi, Sajilesh K. P., Suhani Sharma, Priya Mishra, Prabin Kumar Naik, James Beare, Yipeng Cai, Kenji M. Kojima, Amit Kanigel, Graeme M. Luke, Sudeep Kumar Ghosh, Ravi Prakash Singh
Materials Science
Ferron Hall effect: Transverse accumulation of polarization driven by thermal gradients in ferroelectrics
Daniel A. Bustamante Lopez, Verena Brehm and Dominik M. Juraschek
The
phonon Hall effect describes the generation of a transverse heat current in response to a longitudinal thermal gradient in a
magnetic field. Here, we theoretically demonstrate that, when the
lattice excitations deflected by the
Hall effect carry electric dipole moments, their transverse motion produces an accumulation of electric polarization in ferroelectric materials. This accumulation is driven by
lattice excitations that carry polarization, known as ferrons, and we therefore call the mechanism the ferron
Hall effect. Using atomistic
lattice dynamics with parameters obtained from density functional theory, we illustrate the effect in the prototypical ferroelectric BaTiO3. Our results identify ferrons as the electric-polarization analogues of
magnons in transverse transport and provide a route toward thermal and
magnetic manipulation of ferroic order.
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Quantum Physics
Coherent manipulation of the biphoton generation in cavity-QED system
Jia-Ni Yang, Xin-Yi Ling, Yuan Feng et al. (+2 more)
We theoretically investigate the coherent manipulation of biphoton generation via spontaneous four-wave mixing in a cavity-QED system with a single atom. The atom is driven by pumping, coupling, and driving fields, and the generation of the Stokes and anti-Stokes
photons are enhanced by two cavities. By solving the master equation in the steady state, we analyze the spectral brightness, as well as the degree of the auto-correlation and cross-correlation. Our results show that when the pumping and driving fields are in two-
photon resonance, the dark state established between the ground and Rydberg states. efficiently enhances the controllability of the driving field over the biphoton generation and the
quantum statistics. In contrast, under large two-
photon detuning, the control capability of the driving field is significantly reduced. The coupling field, which directly relates to the electromagnetically induced transparency, modifies the linewidth of the biphoton, while the atom-cavity coupling strength only changes the brightness without affecting the linewidth.
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All authors Jia-Ni Yang, Xin-Yi Ling, Yuan Feng, Xiao-Jun Zhang, Jin-Hui Wu
Cosmology and Nongalactic Astrophysics
Estimating Cosmological Parameters from Localized Fast Radio Bursts: A Method for Removing Milky Way Dispersion-Measure Contributions
Yuchen Zhang, Yang Liu, Hongwei Yu et al. (+1 more)
Fast
radio bursts (FRBs) are emerging as powerful probes for cosmology. However, cosmological inference based on FRB dispersion measures (DMs) is limited by uncertainties in the Milky Way contribution, including those from the
Galactic interstellar medium and the
Galactic halo. In this Letter, we propose a method that eliminates the Milky Way contribution by using DM differences between localized FRBs within the same sky region. The method removes the need to adopt a specific
Galactic electron-density model or a prior assumption for the
Galactic halo DM. We validate the reliability of the method using mock FRB samples and show that it successfully recovers the fiducial cosmological parameter. Applying the method to current localized FRB data, we obtain a constraint on $\Gamma \equiv \Omega_b H_0 f_{\rm d}$ that differs from that inferred using the conventional treatment of the Milky Way contribution. This difference highlights the importance of Milky Way DM systematics in FRB cosmology and demonstrates the potential of differential DM methods for future large samples of localized FRBs.
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All authors Yuchen Zhang, Yang Liu, Hongwei Yu, Puxun Wu
Statistical Mechanics
Finite-resolution exhaustive traversal of thermodynamic state spaces has divergent thermodynamic length
Satori Tsuzuki
Resolving a prescribed multidimensional control window by a single continuous, serial scan is a task distinct from driving between fixed endpoints. We formulate this task as metric coverage at resolution $\eps$. Classical covering estimates, applied to a compact regular $d$-dimensional Riemannian window, give a required length of order at least $\eps^{1-d}$; local grid traversals attain the same exponent. When a physical friction tensor uniformly dominates the coverage metric, this
geometric cost implies a necessary duration of order at least $\eps^{-2(d-1)}$ at fixed quadratic excess-work budget. Fixed-duration divergence refers to the slow-driving quadratic action and is not a claim about exact work outside that regime. A detailed-balance three-state process and an overdamped harmonic trap provide microscopic friction examples. For the trap, independently integrated Gaussian moment dynamics approach the quadratic prediction as the prescribed raster is slowed, while refinement at a controlled work budget increases scan duration. A quasi-uniform operational resolution floor cuts off the
geometric divergence. Landau-response and van der Waals proxy metrics serve separately as prescribed diagnostic geometries: independent quadrature tests their coordinate- and protocol-dependent critical prefactors without asserting universal critical dissipation. Morton ordering supplies an ordering/connector
benchmark with larger finite-resolution amplitudes. The resulting resource statements apply to exhaustive serial coverage, with metric, interpolation and driving assumptions specified explicitly.
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