Quantum Physics
Parallel algebraic surgery for qLDPC codes with constant shuttling depth
Tian-Gang Zhou, Boren Gu, Jens Eisert et al. (+1 more)
Reconfigurable atom arrays provide a promising platform for high-rate
quantum low-density parity-check codes, but their computational advantage depends on whether logical operations can be implemented without incurring prohibitive shuttling and space overheads. We introduce algebraic surgery for lifted product codes, co-designing the logical measurements, auxiliary codes, and atom shuttling to enable hardware-efficient Pauli-product measurements. These protocols provide flexible logical addressability subject to the cyclic-
symmetry constraint, enabling a broad class of parallel logical measurements, including canonical logical operators with heavily overlapping physical supports and joint measurements within or between code blocks even with different lift sizes, while achieving constant shuttling depth on neutral-atom processors under explicit layout assumptions. In a representative hardware-model
benchmark, a cycle supporting 33 parallel canonical logical measurements is about $2\times$ faster than the compared single-observable graph-based surgery schedules, with competitive
qubit overhead. These shuttling and
circuit-level simulations confirm that the algebraic structure of
quantum low-density parity-check codes can be used not only to reduce space overhead, but also to simplify physical implementation and expand the set of efficiently accessible logical operations on neutral-atom processors.
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All authors Tian-Gang Zhou, Boren Gu, Jens Eisert, Chen Zhao
Cosmology and Nongalactic Astrophysics
The Cosmological Correlation Dimension Beyond the Linear Regime: Analytical Approximation and Parameter Sensitivity
Miguel Aparicio Resco and Florencia A. Teppa Pannia
The correlation dimension ($D_2$) provides a scale-dependent characterization of the transition towards homogeneity and a complementary perspective on the clustering of large-scale structure. In this work, we study its full dependence on scales and
redshift connecting $D_2$ directly to the matter power spectrum of a given cosmological model, and derive an approximate analytical relation based on an effective cut-off representation of the filtering kernel. We further perform two complementary local (derivative-based) and global (variance-based) sensitivity analyses within the $w_0w_a$CDM model. In general, nonlinear
evolution lowers $D_2$ relative to the linear prediction at small scales, with the effect becoming more pronounced at low
redshift. Our cut-off approximation, with $k_{\rm cut}=\alpha/r$ and $\alpha\simeq 2.39$, reproduces the exact $D_2$ to better than 1% for the representative cases considered. The sensitivity analysis identifies $\Omega_m$ and $A_s$ as the dominant parameters for the linear correlation dimension and its nonlinear-to-linear ratio, respectively, while $w_0$ and $w_a$ induce scale- and
redshift-dependent changes in the nonlinear contribution. These results provide a framework for characterizing the cosmological scale- and
redshift-dependent features of $D_2$ and its nonlinear correction.
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Quantum Physics
Reducing the Entanglement Cost of Distributed Bipartite Quantum Computation with Constant Qubit Overhead
Kosuke Matsui, Jun-Yi Wu, Min-Hsiu Hsieh et al. (+1 more)
Distributed
quantum computation connects multiple
quantum processing units (QPUs) through
quantum communication to jointly perform large-scale
quantum computations. Since the number of
qubits available at each QPU is limited, it is important to reduce
quantum communication while keeping the
qubit overhead small. To this end, we study an
entanglement-assisted model, in which
entanglement consumption serves as a measure of
quantum communication cost. For exact deterministic implementations in this model, the operator Schmidt rank of the target bipartite
unitary provides a general lower bound on
entanglement cost when
qubit overhead is unrestricted. However, it has remained unclear how closely this bound can be approached with constant
qubit overhead. In this work, we show that this lower bound is attainable for every bipartite Clifford
unitary using at most two auxiliary
qubits per QPU. In addition, for non-Clifford
unitaries specified by exact Clifford+$T$ decompositions with $T$-count $t$, we construct implementations with the same
qubit overhead whose
entanglement cost is at most $2t$ Bell pairs above this lower bound.
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All authors Kosuke Matsui, Jun-Yi Wu, Min-Hsiu Hsieh, Mio Murao
General Relativity and Quantum Cosmology
Testing charged bumblebee black holes through high-frequency quasi-periodic oscillations in X-ray binaries
Qi-Qi Liang, De-Jiang Yin, Zi-Qiang Cai et al. (+1 more)
We investigate strong-field orbital dynamics for static spherically symmetric charged bumblebee black holes featuring spontaneous Lorentz-violating effects. Analysis of null and timelike circular geodesics yields the
photon-sphere radius, the innermost stable circular orbit (ISCO) radius, and characteristic orbital frequencies for test particles. Within the relativistic precession model for high-frequency quasi-periodic oscillations (HFQPOs), observed twin-peak frequencies are governed by the full set of fundamental parameters $M$, $X=r/M$, $l_1$, $l_2$, and $Q_0/M$. Among them, $l_1$, $l_2$, and $Q_0/M$ enter frequency expressions only in combined forms, giving rise to intrinsic parameter degeneracy. An effective-parameter set $\Theta=(M,X,C,\beta)$ is accordingly introduced to characterize these composite contributions.
Bayesian MCMC parameter inference is carried out using HFQPO observational data from three black-hole X-ray binaries: GRO J1655–40, XTE J1550–564, and GRS 1915+105. The 68% credible intervals of composite parameter $C$ all contain the Reissner–Nordström limit $C=1$, revealing no statistically significant net Lorentz-violating correction under our model assumptions. Distinct triples $(l_1,l_2,Q_0/M)$ yield identical QPO predictions, so HFQPO observations alone cannot disentangle Lorentz-violating and charge-related effects; precise constraints on these fundamental quantities require additional, more precise observational data.
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All authors Qi-Qi Liang, De-Jiang Yin, Zi-Qiang Cai, Zheng-Wen Long
Accelerator Physics
Beam Tracking I & II
Helga Timko
Longitudinal beam dynamics simulations are an essential tool for the design and operation of circular and linear accelerators alike, fundamentally supporting everything from RF system design to the interpretation of beam-based measurements. This paper gives a practical, self-contained introduction to longitudinal beam tracking, aimed at newcomers to the field who wish to build, or better understand, their simulation tools. Starting from the analogy between beam tracking and particle-in-
cell plasma simulations, the basic equations of motion, their discretisation, and the choice of phase-space coordinates are introduced, followed by the collective effects driven by the machine impedance. The modelling of the RF system and its associated control loops, and the generation and matching of realistic particle distributions are discussed thereafter. Selected topics that require a fully six-dimensional treatment are briefly touched upon, before closing with practical guidance on the design, optimisation, and benchmarking of longitudinal tracking codes.
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Quantum Physics
Reverse quantum state diffusion from differential geometry
Dinh-Long Vu and Patrick Rebentrost
Quantum state
diffusion unravels a Lindblad master equation into
stochastic trajectories of pure states. The ensemble of trajectories is described by a probability density on the
manifold of pure states, which contains much more information than the density
matrix, its first moment. We derive the time reversal of this
diffusion. Writing the reversal of a general
diffusion on a
manifold in Stratonovich form, and passing through the
manifold of pure states, we obtain a backward
stochastic differential equation for the state vector, valid for any
Hilbert space dimension and any Lindbladian. The backward
stochastic equation provides a physical, nonlinear unravelling of the inverse Lindbladian that holds only for the ensemble from which it was constructed. Following score-based generative models, we then use the backward equation to generate a new ensemble close to the original. For the depolarizing channel the unravelling is a Brownian motion on complex projective space, so the uniform distribution of pure states is its stationary law in any dimension. Starting the backward equation from that prior, we bound the error of the resulting distribution compared to the original one in different settings: exact and learned scores, continuous and discrete time.
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Physics and Society
Opinion dynamics under large-scale exogenous events
Gerard Argany Herrera, Lucila G. Alvarez-Zuzek and Oriol Artime
Large-scale events such as political scandals or misinformation campaigns can abruptly shift the collective opinion of a population and reshape the dynamics in ways that standard local-interaction models of sociophysics do not capture. Here, we investigate the dynamics of opinion formation when a group of interacting
agents is subjected to sudden, macroscopic exogenous shocks. Our framework is general and applies to arbitrary opinion dynamics models; to illustrate its scope, we consider the voter model and variations thereof. We verify that the mathematical description is excellent in describing the first-passage properties to consensus of the voter model on the complete graph and on complex networks. Remarkably, we identify the conditions under which shocks can be advantageous or detrimental to reach consensus. For the case of the all-to-all noisy voter model under exogenous events, we unveil a rich phase diagram characterized by novel trimodal and asymmetric bimodal states. Ultimately, this work provides a rigorous yet flexible
stochastic-process framework for understanding the out-of-
equilibrium behavior of opinion dynamics under recurrent exogenous stressors.
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Quantum Physics
Optical measurement is almost quantum: Quantum inspired universal optical bounds
Daniel Ish and Chase T. Ellis
Inspired by results in
quantum information, we report the development of a formalism for optical sensing which abstracts the details of specific optical systems and allows us to form general bounds on measurement based only on the quantity to be measured. We find a universal bound that controls the performance of any passive optical system regardless of the technology used to construct it and that this bound is attained by a unique measurement scheme for each quantity of interest. Shockingly, our optical formalism is nearly identical to the
quantum formalism, with essentially the same notions of the state to be measured and the operation of the measurement, along with an accompanying uncertainty principle.
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Quantum Physics · Cross-listed from cs.DC
EPR Count for Runtime Prediction in Distributed Quantum Computing
Fatih E. Bilgen and Ozgur B. Akan
EPR-pair consumption is commonly used as a communication-cost objective in distributed
quantum computing, but minimizing EPR cost does not necessarily minimize distributed execution time. Despite its widespread use, the reliability of EPR count as a runtime surrogate has received limited direct characterization across different workloads and communication conditions. This work addresses this gap by systematically evaluating the relationship between EPR cost and runtime over all balanced two-QPU mappings of QFT, QAOA, and CDKM
circuits. The results show that mappings with identical EPR cost can have substantially different execution times, lower-EPR mappings can be slower, and minimum-EPR mappings can be runtime-suboptimal. The reliability of EPR count is strongly workload dependent and also changes with the communication operating regime: increasing EPR-generation latency amplifies runtime differences hidden by equal EPR cost, while increased communication concurrency can reduce the ability of EPR count to preserve runtime ordering. These results show that EPR count and execution time are related but distinct optimization objectives, and identify regimes in which explicit communication-aware runtime modeling is necessary.
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Quantum Physics
Natural Barriers to Quantum Extraction: On the Post-Quantum (In)security of (O)EKE and Masny-Rindal OT
James Bartusek and Jake Januzelli
Encrypted key exchange (EKE), introduced by Bellovin and Merritt (IEEE S&P 1992), and Masny-Rindal OT, introduced by Masny and Rindal (ACM CCS 2019), are highly-efficient methods for compiling essentially any KEM into advanced cryptographic protocols, namely password-authenticated key exchange (PAKE) and oblivious transfer (OT), by relying only on idealized symmetric-key primitives. They have become leading candidates for practically-implementable PAKE and OT due to (1) their simplicity, (2) their plug-and-play nature, allowing for flexibility in the choice of KEM, and (3) existing proofs of UC-security (in the classical
adversarial model). Due to point (2) above, these compilers yield attractive candidates for efficient post-
quantum PAKE and OT, especially given the recent post-
quantum KEM standardization efforts. This motivates the question of whether the (UC-)security of these compilers translates to the
quantum adversarial model. In this work, we show that it does not. In particular, we prove that a general family of (O)EKE protocols, as well as Masny-Rindal OT, are not UC-secure against
quantum polynomial-time adversaries, even when instantiated with a post-
quantum KEM. To establish UC-insecurity, we devise an
adversarial strategy that provably thwarts any attempt by the simulator to extract its input (the password in the case of PAKE, and the receiver's choice bit in the case of OT). To complement these negative results, we establish that both compilers yield certain notions of game-based security. Along the way, we establish a novel “advantage-tight” one-way to hiding lemma that may be of independent interest.
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High Energy Astrophysical Phenomena
XRISM Resolve Spectroscopy of GX 5-1: Constraints on Iron Spectral Features in a Luminous Neutron-Star Binary
Tasuku Hayashi, Shinya Yamada, Shun Inoue et al. (+11 more)
GX 5-1 is one of the brightest persistent
neutron-
star low-mass X-ray binaries in the
Galaxy and one of the classical Z sources accreting at luminosities close to or above the Eddington limit. We present the first high-resolution X-ray spectroscopic study of GX 5-1 with the Resolve micro-calorimeter onboard the X-Ray Imaging and Spectroscopy Mission (XRISM), based on a 50 ks AO1 observation. With an energy resolution of approximately 5 eV at 6 keV, Resolve enables a sensitive non-dispersive search for weak and narrow spectral features in this luminous source. During the observation, GX 5-1 was located on the horizontal branch of the Z track. Although rapid spectral variability is detected on timescales of tens of ks, the variability is dominated by changes in the continuum spectral shape. No statistically significant emission or absorption features are detected in the time-averaged spectrum. Using matched-filter searches and time-resolved spectroscopy, we place stringent upper limits on the equivalent widths of low-ionization Fe K-alpha emission and highly ionized Fe XXV and Fe XXVI K-alpha transitions of $EW \lesssim$ a few eV. These results reinforce the picture that, in GX 5-1, classical Fe K diagnostics such as reflection- or wind-related features are either intrinsically weak, strongly ionized, geometrically diluted, or suppressed by rapid continuum variability. Placed in the context of the long observational history of GX 5-1 as a continuum-dominated Z source, the present XRISM result shows that this picture continues to hold even at calorimeter resolution. GX 5-1 therefore provides an important
benchmark for high-resolution studies of luminous
neutron-
star accretion flows and demonstrates the capability of XRISM to place meaningful constraints on line formation even when no significant features are detected.
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All authors Tasuku Hayashi, Shinya Yamada, Shun Inoue, Teruaki Enoto, Noriko Yamasaki, Shunji Kitamoto, Shogo Kobayashi, Yusuke Sakai, Shintaro Kaneko, Rin Ebisawa, Haruto Aoki, Kota Miyawaki, Misaki Mizumoto, Hiromitsu Takahashi
Quantum Physics
A self-tallying quantum anonymous voting protocol for multiple-selection elections
Guang-Bao Xu, Meng-Na Li, Yu-Guang Yang et al. (+1 more)
Self-tallying
quantum anonymous voting (SQAV) has drawn considerable
attention since it was proposed. However, constrained by design challenges, all existing protocols only accommodate single-selection voting and cannot support multi-selection voting. In this paper, we propose a SQAV protocol with multi-selection voting functionality. In our protocol, $nm$ $n$-particle entangled states are equally divided into $n$ groups, and the $n$ particles in each entangled state are delivered to $n$ voters, one particle per voter. Each voter obtains $n$ voting vectors by sequentially measuring all his (or her) particles that belong to $n$ different group, and then encodes his or her voting information into the vector corresponding to the secret index. Due to
entanglement correlation, each voter can verify whether his or her ballot is correct through computation, while any participant can obtain the vote count for each candidate through computation. Our protocol satisfies self-tallying, nonreusability, verifiability, and
fairness.
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All authors Guang-Bao Xu, Meng-Na Li, Yu-Guang Yang, Dong-Huan Jiang
Quantum Physics
All-Microwave Multiqubit Gates
Guanqi Wang, Yao Song, Peng-Bo Li et al. (+1 more)
Implementing high-fidelity multiqubit gates is critical for reducing
circuit depth in near-term
quantum processors and fault-tolerant architectures. However, realizing multiqubit interactions and
entanglement remains a critical challenge that limits the implementation of multiqubit gates. Here we propose an all-microwave scheme to realize single-step multiqubit gates incorporating n control and m target
qubits, tailored for frequency-tunable superconducting transmon networks. By leveraging cross-resonance (CR) drives, this approach induces effective two-body ZX interactions that are significantly stronger than those achieved in conventional resonant regimes, circumventing the need for tunable couplers. The system's effective
Hamiltonian is analytically derived using both quad frame rotation and rigorous block diagonalization. These combined theoretical methods facilitate the identification of optimal parameter regimes that simultaneously enhance desired target couplings and suppress parasitic higher-order terms, such as ZXX interactions. Through numerical simulations and gradient-based pulse-shape optimization, we demonstrate three-
qubit gates achieving fidelities exceeding 99.9% within a 60 ns gate duration. Furthermore, we evaluate the fundamental scalability of this framework by extending the optimization to a five-
qubit CXXXX architecture, confirming the physical viability of the multi-target driving scheme. Because these multiqubit operations naturally emulate stabilizer measurements, this architecture provides a hardware-efficient strategy for reducing the
circuit depth of stabilizer-type operations by replacing sequential two-
qubit gate decompositions with single-step multiqubit gates.
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All authors Guanqi Wang, Yao Song, Peng-Bo Li, Xiu-Hao Deng
Quantum Physics
Dynamic distributed quantum sensing of radio-frequency fields via time-bin entanglement
Vedansh Nehra, Richard Birrittella, Benjamin Malia et al. (+6 more)
We propose a novel framework for discrete-variable (DV) distributed
quantum sensing, wherein traditional polarization-based probes are replaced with time-bin entangled
qubits. We show that the intrinsic temporal structure of time-bin Bell states can be utilized as a tunable, built-in two-time differential sampling reference for sensing
radio-frequency (RF) fields. Unlike existing protocols based on polarization Bell states, which are limited to static measurements, our proposed architecture enables the coherent mapping of dynamic RF phase signals onto static
quantum optical phases. By matching the time-bin separation to the RF or intermediate frequency (IF) half-period (antipodal sampling), we theoretically demonstrate that our protocol provides a 6 dB sensitivity enhancement over one-sample static polarization encodings while preserving the 3 dB per-pair
entanglement advantage over the separable standard
quantum limit
benchmark. The performance enhancement is validated with Monte Carlo simulations. This approach provides a solution for RF sensing in DV photonic
quantum networks, offering a clear path toward
quantum-enhanced and frequency-agile distributed sensor arrays and broader utilization of time-domain
quantum probe encodings.
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All authors Vedansh Nehra, Richard Birrittella, Benjamin Malia, Nicholas J. Barton, Christopher Tison, James Schneeloch, David Hucul, Benjamin Kyle, Erin Sheridan
Fluid Dynamics
Is Vorticity Amplification Essential for Anomalous Dissipation and Intermittency in Turbulence?
Alessandro Chiarini
The distinct dynamical roles of vorticity amplification (VA) and
vortex tilting (VT) in three-dimensional homogeneous isotropic
turbulence are investigated using direct numerical simulations of a modified Navier–Stokes system. By selectively suppressing VA while retaining VT, we demonstrate that gradient amplification by VA is strictly required to sustain the classical forward energy cascade. Progressively suppressing VA weakens small-scale velocity gradients, heavily depletes extreme fluctuations, and entirely eliminates the classical energy dissipative anomaly, causing the normalized energy dissipation to decay as $Re_\lambda^{-1}$. In the limit of complete VA suppression, enstrophy emerges as the relevant inviscid invariant. Scale-by-scale budget analyses confirm that the dynamics transition to a purely forward enstrophy cascade, characterized by an anomalous enstrophy dissipation and a robust $E(k) \sim k^{-3}$ intermediate energy spectrum. We verify that these asymptotic scaling limits—including a $Re_\lambda^{-1/2}$ finite-Reynolds-number correction for the enstrophy anomalous dissipation—are universal properties of the VA-suppressed dynamics, independent of whether the large-scale forcing is helical or non-helical. Remarkably, despite the smoothing of the velocity field and the elimination of the energy dissipative anomaly, anomalous structural scaling and a broad multifractal spectrum persist. These results reveal a fundamental mechanistic separation: while VA is responsible for amplifying intense localized fluctuations,
geometric reorganization by VT alone is mechanically sufficient to sustain multifractal intermittency.
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Quantum Physics
Improved Quantum Random Self-Reduction for Linear Problems
Vahid R. Asadi, Shuichi Hirahara and Nobutaka Shimizu
We study
quantum random self-reductions for linear problems over finite fields. Let $M\in\mathbb{F}^{n\times n}$ be an arbitrary
matrix, and let $\mathcal{O}$ be an oracle that agrees with the linear map $x\mapsto Mx$ on an $\varepsilon$-fraction of inputs $x\sim\mathbb{F}^n$. Given coherent access to $\mathcal{O}$ and coherent entry access to $M$, we give a uniform
quantum reduction that computes $Mx$ on any prescribed input $x$ with probability at least $2/3$ in time $\widetilde{O}(nT^{1/3})$, for $n\le T\le n^{3/2}$ and constant field size and $\varepsilon$, where $T$ is the cost of one coherent query to $\mathcal{O}$. In particular, when $T=\widetilde{O}(n)$, the reduction runs in time $\widetilde{O}(n^{4/3})$, improving the $\widetilde{O}(n^{3/2}+T)$ reduction of Asadi, Golovnev, Gur, Shinkar, and Subramanian (SODA 2024). Our reduction uses the Bogolyubov–Ruzsa subspace guaranteed by additive combinatorics, but it avoids learning this subspace explicitly, which was computationally expensive for the previous reduction; in particular, it does not recover a basis for its orthogonal complement. The main technical step is to decompose the inputs into sparse pieces and find a vector that lies outside the Bogolyubov–Ruzsa subspace via a
quantum search based on amplitude amplification. This yields a tunable tradeoff between the cost of querying the average-case oracle and the cost of verifying
matrix-vector products.
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Quantum Physics
Learning Random Quantum Circuits and the Emergence of Pseudorandomness
Srinivasan Arunachalam, Qizhao Huang and Makrand Sinha
We give an efficient
algorithm for learning $k$-dimensional brickwork random
quantum circuits using only copies of the output state obtained by applying $U$ to the all-zero input. For a depth-$d$
circuit on $n$ sites with random $2\ell$-
qubit gates, the
algorithm learns the original
circuit $U$ with high probability in $\text{poly}(n,2^{\ell d})$ time for every constant dimensional
lattice. In particular, the
algorithm is
polynomial time as long as $\ell d = O(\log n)$. In one dimension, this reaches the natural boundary suggested by pseudorandomness: pseudorandom states require $\ell d=\omega(\log n)$, and structured cryptographic constructions suggest that this scale may be achievable from above. In higher dimensions, it remains plausible that the same $\ell d=\omega(\log n)$ scale remains the threshold for ancilla-free pseudorandomness, and our results help clarify the conditions under which pseudorandomness can arise in this setting. The main idea behind our
algorithm is a local correlation criterion that identifies gates in the final layer without learning their entire backward light cones, avoiding a bottleneck in the previous approaches. A key technical ingredient is a Carbery-Wright type anticoncentration inequality for low-degree
polynomials of Haar random
unitaries whose small-ball exponent is independent of the
matrix dimension. The dimension-independent exponent is crucial for handling gates of growing locality. This anticoncentration result may also be of independent interest.
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Materials Science
Phonon-mediated closing of topological Floquet gaps in graphene: Non-phenomenological analysis
Royi Ledermann, Rave Hanoch Saadon, Adam Herling et al. (+1 more)
Floquet band engineering has been intensively studied for its potential to control material properties via
laser driving. In particular, Floquet topological states have been measured on the surface of Bi$_2$Se$_3$. Nonetheless, the original prediction of Floquet topological bands in
graphene remains unobserved, with works only measuring non-topological Floquet-Bloch states or indirect features. Here, we theoretically explore
graphene irradiated by circular
lasers with non-phenomenological electron-
phonon (e-ph) coupling. We show that e-ph interactions substantially broaden Floquet bands due to
graphene's large zero-point motion, as expected from phenomenological treatments. However, we further find that larger displacement $\Gamma$ optical
phonons reduce Floquet gaps by about half, even in absence of instrumentation broadening, and can also induce additional features like flat bands. These
phonons "enter the gap" and blur photoemission signatures. Including non-$\Gamma$
phonons closes the gap and greatly reduces visibility. When these modes couple to reasonably expected instrumentation broadening, the effect is significantly exacerbated. Our results shed light on the missing Floquet topological gaps and also lead to possible mitigation strategies: (i) Pre-pumping coherent
phonons to counteract blurring, or (ii), transition to a Dirac system with more favorable
phonon statistics. Moreover, our real-space analysis proposes that Floquet topological physics is alive in localized regions, such that properties of interest like transport should be accessible. We expect this work to impact experimental analysis and lead to set-ups where
graphene Floquet
topology might finally be directly observed.
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All authors Royi Ledermann, Rave Hanoch Saadon, Adam Herling, Ofer Neufeld
Quantum Physics
Sharp Quantum Entropy Mixing Rates and the Operator Layer Cake Theorem
Alexander Stottmeister
At what rate does the von Neumann
entropy of an ensemble of
quantum states change under
Hamiltonian evolution of its constituents? Bravyi proposed the small incremental mixing
conjecture controlling the mixing rate of a binary ensemble $\{(1\!-\!p,\rho_1),(p,\rho_2)\}$ by $c\,\|{H}\|h_{2}(p)$ (with the binary
entropy $h_{2}$). The proof of Bravyi's
conjecture was subsequently reduced to the
matrix inequality $\|[A,\log B]\|_{1}\!\leq\! c\,h_{2}(p)$ for positive trace-class operators $A\!\leq\! B$ with $\text{Tr} A\!=\!p$ and $\text{Tr} B\!=\!1$ on separable
Hilbert spaces by Mariën, Audenaert, Van Acoleyen, and Verstraete, and they conjectured the optimal constant to be $c\!=\!1$. Here, I prove the latter
conjecture using an exact integral representation of the commutator $[A,\log B]$ obtained from the operator layer cake
theorem, due to Cheng and Liu. The result gives a sharp dimension-independent limit on how rapidly
unitary evolution of one component can change the
entropy of a binary
quantum ensemble. It follows that mixing rates satisfy small incremental mixing with the optimal constant, and entangling rates of bipartite
Hamiltonians are bounded by $(2\log d\!+\!1)\|H\|$. Moreover, the result corrects a
conjecture by Lieb and Vershynina for mixing rates of general ensembles.
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Mesoscale and Nanoscale Physics
Magnetization relaxation of interacting chains of nanomagnets
Denis Ledue, Renaud Patte, Francois Vernay et al. (+1 more)
We investigate the magnetization dynamics crossover from single-particle to collective behavior in a one-dimensional chain of dipolar-coupled nanomagnets with uniaxial anisotropy. Using both an intermediate-to-high damping (IHD) analytical approach based on Langer's theory and time-quantified Monte Carlo (TQMC) simulations, we derive and validate semi-analytical expressions for the relaxation rate and the magnetization relaxation curves. Our main results include: (i) a closed-form expression for the relaxation rate accounting for (weak) dipolar interactions, (ii) a two-exponential semi-analytical formula for the magnetization dynamics $m(t)$ of an interacting chain, and (iii) a systematic comparison with TQMC simulations, showing good agreement for a wide range of parameters. The analysis reveals a field-controlled crossover from uniform (macrospin-like) reversal to edge-nucleation propagation, driven by the spatial inhomogeneity of dipolar stabilization. The derived expressions provide a computationally efficient framework for predicting the relaxation behavior of dipolar-coupled nanomagnetic assemblies.
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All authors Denis Ledue, Renaud Patte, Francois Vernay, Hamid Kachkachi
Strongly Correlated Electrons
$\mu$SR measurements of 3D Ising ferromagnetism in bulk Fe$_3$GeTe$_2$ crystals
M. N. Wilson, J. Huang, T. J. Hicken et al. (+4 more)
Fe$_3$GeTe$_2$ is a quasi-two-dimensional itinerant ferromagnet with a van-der-Waals layered structure that exhibits substantial
magnetic anisotropy. In bulk samples, this material becomes magnetically ordered below 220~K, while in thin samples, the gate-tunability of the
ferromagnetic moment has attracted significant interest. Alongside high-temperature ferromagnetism, a low-temperature
magnetic state occurs whose nature has not been conclusively identified, with some studies suggesting a transition between ferromagnetism and antiferromagnetism with temperature. Here we present magnetometry and $\mu$SR data that demonstrate that Fe$_3$GeTe$_2$ exhibits three-dimenional Ising-like ferromagnetism over the entire temperature range between $T_{C}=220$~K and 2~K. The feature at 170~K that has previously been proposed to be a transition to antiferromagnetism is instead likely to represent a domain-freezing transition.
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All authors M. N. Wilson, J. Huang, T. J. Hicken, D. A. Mayoh, B. M. Huddart, G. Balakrishnan, T. Lancaster
Cosmology and Nongalactic Astrophysics
An improved standardization framework for Type II-P supernovae using a hierarchical Bayesian approach
A. Holas, S. Taubenberger, C. Vogl et al. (+41 more)
We use Type II-P
supernovae (SNe II-P) observed as part of the Nearby
Supernova Factory (SNfactory) experiment as standardizable candles to develop an improved standardization framework. The data consist of accurately flux-calibrated, host-subtracted spectrophotometry of low-
redshift SNe II-P in the wavelength range $3200 < \lambda < 10000$ ${\unicode{xC5}}$. We develop an improved method to determine the expansion velocities of SNe II-P based on Gaussian Process regression. We extend the conventional standardized candle method (SCM) by an additional correction term containing the H$_\alpha$ absorption-to-emission ratio and a hierarchical
Bayesian framework. We find that the additional correction improves the quality of the standardization, particularly around $30$ to $40$ days after the explosion. We are able to reduce the scatter of the Hubble-flow SNe II-P from $0.28$ mag down to $0.18$ mag compared to previous work. As an example application of this methodology we measure $H_0$ using a pre-existing calibrator sample of SNe~II having Cepheid- or TRGB-based distance
moduli. We find a value of $H_0 = 70.6^{+4.5}_{-4.3}$ km s$^{-1}$ Mpc$^{-1}$, including only statistical uncertainty, corresponding to a precision of $6.2$%. We find variations of $1.4$ km s$^{-1}$ Mpc$^{-1}$ between hierarchical model variations — well within our quoted statistical uncertainty. Without the additional correction term, we obtain $H_0 = 73.0^{+6.9}_{-6.1}$ km s$^{-1}$ Mpc$^{-1}$ ($8.9$% precision) highlighting the improved precision of our new methodology. We identify and discuss inconsistencies between the measured parent populations of the calibrator and Hubble-flow standardization characteristics — present in this and literature samples — that are not explained by a simple selection on magnitude and which will need to be improved upon as SN II-P samples grow.
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All authors A. Holas, S. Taubenberger, C. Vogl, D. Rubin, M. Vincenzi, W. Hillebrandt, G. Aldering, P. Antilogus, C. Aragon, S. Bailey, C. Baltay, S. Benitez-Herrera, S. Bongard, K. Boone, C. Buton, G. Csörnyei, Y. Copin, S. Dixon, M. Fink, D. Fouchez, E. Gangler, R. Gupta, B. Hayden, E. E. O. Ishida, A. G. Kim, M. Klauser, M. Kowalski, M. Kromer, D. K. Küsters, J. Nordin, R. Pain, E. Pecontal, R. Pereira, S. Perlmutter, K. A. Ponder, D. Rabinowitz, M. Rigault, K. Runge, M. Sasdelli, C. Saunders, G. Smadja, N. Suzuki, C. Tao, R. C. Thomas
Quantum Physics
Double Localization for Quantum Gibbs Sampler Gaps: From an Abstract Framework to Finite-Group Models
Ryu Hayakawa, Angus Southwell, Caesnan M. G. Leditto et al. (+2 more)
We introduce double localization, a framework for proving spectral gaps of
quantum Gibbs samplers through two complementary operations:
geometric localization, which selects updates supported in small spatial regions, and interface localization, which focuses on a model-defined subspace of observables while remaining geometrically global. Our abstract gap
theorem combines a global bound on this subspace, called the interface, with local
quantum gap estimates under quantitative coupling and
geometric assembly conditions. The resulting explicit lower bound controls the gap of the full dynamics without requiring the interface to be invariant under the generator. This separation allows global estimates, including classical comparison, to be combined with local control of the remaining
quantum directions. We apply the framework to
Hamiltonians built from the vertex terms of Kitaev's finite-group
quantum double construction, without plaquette terms, on finite simple three-regular graphs of girth at least six. For the specified local Davies dynamics, we prove an unconditional spectral-gap lower bound by a positive constant independent of graph size for every fixed nontrivial finite group and each fixed inverse temperature $\beta$ with $0\le\beta J<\log(5/3)$, where $J>0$ is the coupling strength. For the smallest non-Abelian group $S_3$, double localization yields a positive lower bound uniform in both graph size and the entire interval $0\le\beta J\le\log 3$, providing a guarantee that does not follow directly from existing results. This demonstrates how model-specific finite calculations can extend spectral-gap guarantees for the full
quantum dynamics.
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All authors Ryu Hayakawa, Angus Southwell, Caesnan M. G. Leditto, Kuo-Chin Chen, Min-Hsiu Hsieh
Cosmology and Nongalactic Astrophysics
Effects of a central dark matter core on time-delay cosmography with galaxy clusters
Yuting Liu and Masamune Oguri
The central dark matter distribution probes the nature of dark matter and
baryon physics, yet its impact on time-delay cosmography is not fully explored. We update previous analyses of the cluster-lensed
quasar SDSS J1004+4112 and the
supernova Refsdal in MACS J1149.5+2223 by replacing the main
halo density profile from an elliptical Navarro-Frenk-White (NFW) profile to a cored elliptical NFW profile and investigating the impact of the central dark matter core on the Hubble constant $H_0$. We jointly infer $H_0$ and the dimensionless core size parameter $\beta=r_{\rm c}/r_{\rm s}$, while the Brightest Cluster
Galaxy (BCG) is either tied to the scaling relation of cluster member
galaxies or modeled separately, with its mass left free or assigned a Gaussian prior from the
stellar mass estimate for a Chabrier or Salpeter initial mass function (IMF). For SDSS J1004+4112, constraints on both $\beta$ and $H_0$ strongly depend on the treatment of the BCG. A large core is implied when no prior is added to the BCG
stellar mass, while a reasonable assumption on the BCG mass prefers a nearly cuspy
halo with $\beta\sim 10^{-3}$. For MACS J1149.5+2223, a large core of $\beta\sim 0.5$ is obtained with no prior, while a modest core of $\beta=0.0410^{+0.0865}_{-0.0276}$ is preferred when the Salpeter IMF is assumed. The constraint on $H_0$ from MACS J1149.5+2223 is stable against the BCG treatment, supporting its robustness. For the Salpeter-prior case, we obtain $H_0=65.9^{+3.5}_{-3.4}\mathrm{~km~s^{-1}~Mpc^{-1}}$, and different BCG assumptions change the median $H_0$ by less than $1\sigma$. The core size constraints are translated into the self-interacting dark matter cross section, giving a 95% upper limit of $\sigma/m<0.035\,\mathrm{cm}^{2}\,\mathrm{g}^{-1}$ from SDSS J1004+4112 and the 68% range of $\sigma/m=0.071^{+0.15}_{-0.045}\,\mathrm{cm}^{2}\,\mathrm{g}^{-1}$ from MACS J1149.5+2223.
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Materials Science
A transferable full-band Monte Carlo framework for complex alloy avalanche photodiodes
Shafat Shahnewaz, Hannaneh Karimi, Joe C. Campbell et al. (+1 more)
We present a physics-based multiscale full-band Monte Carlo framework for modeling avalanche multiplication and excess noise in complex
alloy avalanche photodiodes (APDs), demonstrated on Al$_{0.7}$InAsSb as a representative quaternary system. The framework links atomistic material structure to device-level avalanche statistics: an environment-dependent $sp^3d^5s^\ast$ tight-binding calculation resolves the full conduction- and valence-band structure of the random- or digital-
alloy configuration – including $\Gamma$, X, and L valley ordering, non-parabolicity, anisotropy, and
spin-orbit-induced valence-band splitting – and supplies the band-structure inputs for
stochastic high-field transport. A central element of the framework is a physics-derived treatment of
alloy-disorder scattering, in which the quaternary disorder potential is constructed from atomic valence differences, covalent radii, and Thomas–
Fermi screening through a composition-weighted decomposition into binary contributions, complemented by composition-interpolated polar-optical, acoustic, intervalley-
phonon,
impurity, and impact-ionization models. Because every material-dependent input is generated from the atomic composition and configuration by the same well-defined procedure, the framework transfers without structural modification to arbitrary zinc-blende ternary and quaternary
alloys. Applied to a \SI{1}{\micro\meter} Al$_{0.7}$InAsSb p-i-n APD, the framework reproduces the measured gain and excess-noise characteristics with only the impact-ionization softness parameters calibrated. The approach provides a documented, reproducible route for analyzing and designing complex
alloy APDs in which band structure, disorder, and scattering physics jointly determine gain and ionization statistics.
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All authors Shafat Shahnewaz, Hannaneh Karimi, Joe C. Campbell, Avik W. Ghosh
Chaotic Dynamics · Cross-listed from cs.LG
TopTimeNet: Topologically-assisted time-series classification model
Sharareh Sayyad and Sophia Bazzi
Distinguishing periodic from chaotic dynamics in a time series is a fundamental challenge in both physics and engineering. Yet, end-to-end learned architectures must discover both a representation and a decision boundary from data, at substantial cost. We introduce TopTimeNet, which decouples these tasks: a fixed, non-learned stage extracts a $42$-dimensional
geometric and topological descriptor from Takens delay
embeddings and persistent homology, and a lightweight learnable stage performs classification. On a
benchmark of $49$ nonlinear dynamical systems, a $1{,}638$-parameter configuration matches the mean accuracy of one with $33\times$ more trainable parameters. Additionally, this approach delivers mean accuracy comparable to convolutional neural networks and surpasses the average performance of converged
Transformer models, while requiring three to four orders of magnitude fewer trainable parameters. Robustness also depends sharply on where noise is introduced: TopTimeNet degrades gracefully under perturbations to its precomputed features, but degrades sharply when noise is introduced into the raw signal and the full feature-extraction pipeline is recomputed, showing that robustness to perturbations of the precomputed features does not imply robustness of the complete raw-signal-to-prediction pipeline. These results show that decoupling fixed
geometric and topological feature construction from a lightweight discriminative stage can achieve comparable classification accuracy with substantially fewer trainable parameters.
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Optics
Topological Fermi-polaron Polaritons with Electrically Invertible Topology
Xin Xie, Chenxi Liu, Yuze Liu et al. (+8 more)
Topological polaritons provide a route to engineer optical Chern bands, but realizing large gaps or efficient electrical tunability remains challenging because time-reversal-
symmetry breaking in
semiconductor polariton systems is typically limited by weak Zeeman splittings. Here, we demonstrate a topological Bose-
Fermi mixture —
Fermi-polaron polaritons —where large gaps and electrically invertible
topology emerge from the interplay of
Fermi-polaron many-body interactions, photonic
symmetry, and strong light–matter coupling. Using a gate-controlled monolayer transition-metal dichalcogenide integrated with a
symmetry-engineered photonic
crystal, we create
Fermi-polaron polaritons with topological band structures. The direct coupling between band
topology and gate-tunable many-body interactions provides a mechanism for amplified time-reversal-
symmetry breaking beyond bare Zeeman splitting and enables electrical inversion of topological gaps, Berry
curvature, and Chern numbers. These results establish an electrically reconfigurable platform for interaction-driven topological states and programmable topological photonics.
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All authors Xin Xie, Chenxi Liu, Yuze Liu, Lingxiao Zhou, Chulwon Lee, Yuhan Zhang, Nathanial Lydick, Kenji Watanabe, Takashi Taniguchi, Kai Sun, Hui Deng
High Energy Physics (Phenomenology)
Gravitational waves in the complex-singlet-extended Manohar-Wise model
Benhong Mei, Yabo Dong, Jun Fan et al. (+1 more)
We investigate cosmological phase transitions and
stochastic gravitational-wave signals in the Manohar-Wise model extended by a complex scalar singlet. Spontaneous breaking of a discrete Z3
symmetry produces domain walls, whose subsequent annihilation is driven by a small explicit
symmetry-breaking bias. Subject to theoretical and experimental constraints, we study two thermal histories: a one-step strong first-order electroweak phase transition satisfying the
baryon-number preservation criterion, and a two-step history whose first transition is a first-order transition along the singlet direction, leaving electroweak
symmetry unbroken. We estimate the gravitational-wave contributions from sound waves, magnetohydrodynamic
turbulence, and domain-wall annihilation. Within the adopted approximations, the phase-transition signals of the selected
benchmarks peak at approximately 10^-3 -10^-2 Hz and overlap the projected sensitivity regions of space-based observatories such as LISA, TianQin, and BBO. Choosing the
vacuum-energy bias to fix the domain-wall peak at approximately 2x10^-9 Hz, we find that the larger domain-wall tensions of the two-step
benchmarks yield signals reaching the projected SKA sensitivity, whereas the one-step sample remains below the
pulsar-timing sensitivities considered. These results illustrate the complementarity of millihertz and nanohertz gravitational-wave observations in probing phase transitions and discrete-
symmetry breaking in this model.
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All authors Benhong Mei, Yabo Dong, Jun Fan, Jingya Zhu
Lattice Field Theory
Marco Garofalo, Tobias Hartung, Timo Jakobs et al. (+3 more)
Hamiltonian simulations of
lattice gauge theories promise new insights into the inner workings of QCD. The rapid development of
quantum computing hardware suggests that large scale simulations may soon become feasible. However, no efficient formulation suitable for simulations near the continuum limit is currently known for the non-Abelian case, and existing candidates typically feature long range interactions in the electric part of the
Hamiltonian. We prove that such non- localities are unavoidable when the gauge configuration is reparametrised while preserving both the number of degrees of freedom and the fundamental commutation relations. We then attempt to mitigate this by introducing additional gauge links alongside additional constraints. Although this approach is successful in U(1), we prove that the corresponding construction is inconsistent for non-Abelian
lattice gauge theories.
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All authors Marco Garofalo, Tobias Hartung, Timo Jakobs, Paul Ludwig, Johann Ostmeyer, Carsten Urbach
High Energy Physics (Phenomenology)
Enhancing Constraints on Ultralight Axion Dark Matter from Gravitational Capture
Pierce Giffin, Pankaj Munbodh and Elisa G. M. Ferreira
Ultralight
axions can be gravitationally captured by massive bodies such as the Sun, producing
solar-bound gravitational atom states that amplify the local dark matter density through Bose-enhanced capture. For
axion masses in the range $10^{-14}\text{eV}\lesssim m_a \lesssim 10^{-13}\text{eV}$, this mechanism becomes exponentially efficient. We show that, for a representative decay constant $f_a\sim 3.5\times10^7$ GeV, the local
axion dark matter density at Earth can grow to more than ten times the standard
Galactic value of $\rho_0 = 0.4 \text{ GeV/cm}^{3}$. Incorporating this overdensity, we derive updated limits on the
axion-
photon coupling from existing satellite and terrestrial measurements and present improved projections for upcoming experiments.
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