Papers

We give a closed-form finite-dimensional construction of quantum channels with real algebraic entries exhibiting arbitrarily large violations of minimum-output Rényi entropy additivity uniformly above any prescribed positive Rényi order, using a different finite realization based on direct products of free groups and fixed-field high-girth graphs. More precisely, for every $p_0>0$ and $g>0$, we construct one channel and one Bell input for which the additivity gap is greater than $g$ simultaneously for all $p\in[p_0,\infty]$. With $r=\lceil2g\rceil$, the construction uses $15r$ output qubits and $O(r2^{30r}+r^2(1+p_0^{-1}))$ input qubits. Compared with the stated parameters of Shou and Gorshkov \cite{ShouGorshkov2026}, our construction uses fewer output qubits for every target gap and has a smaller asymptotic input-qubit bound as the gap grows with the positive cutoff fixed. At the von Neumann order, a separate specialization gives an explicit channel with gap greater than $1/1024$ using $37608898$ input qubits and $8$ output qubits.

We show that the familiar Cherenkov burst from a finite superluminal charge track can be understood as a pair of interfering electromagnetic memory transitions. Endpoint accelerations of the track produce opposite memory steps in the transverse vector potential, such that the corresponding finite-frequency radiation is universally fixed, below the endpoint-acceleration-scale, by the memory amplitude and the time for which the temporary memory offset persists. As the Cherenkov direction is approached, the memory amplitudes grow while their separation in observer time shrinks, until the two vector-potential steps overlap and their divergent contributions cancel into a finite Cherenkov burst. This perspective opens the door to using the Askaryan effect as a setting in which individual macroscopic memory transitions may be resolved, providing a new experimental arena for memory-linked infrared physics.

Photon loss makes Gaussian boson sampling easier to simulate classically. A standard approach replaces the lossy input by classical light, and it stays accurate while the mean number of surviving photons grows no faster than the square root of the number $N$ of squeezed inputs at fixed squeezing and accuracy. We prove that this scale is a limit of replacement by classical light. For explicit interferometers, no state with a nonnegative Glauber–Sudarshan $P$ representation, Gaussian or not and however correlated, keeps the error in the photon count distribution small beyond this scale. We then surpass this limit by approximating the detection instead of the input. The sampler evolves the state exactly between detections and, after each detection, replaces the conditional state by a Gaussian with the same covariance. For every interferometer its total variation error is $O(N\eta^3)$ at polynomial expected cost, where $\eta$ is the photon survival probability. The mean surviving photon number can therefore grow as $N^{2/3}$ at fixed accuracy. A separate pair construction reaches $N^{3/4}$ when every input mode is equally squeezed.

Rotational transitions of SiC$_6$ with $j=26$–$40$ have been detected in IRC+10216, but collisional rate coefficients for SiC$_6$ with He or H$_2$ were previously unavailable. We present rate coefficients for SiC$_6$ rotational excitation by He, calculated using a two-dimensional potential energy surface (PES) at the RCCSD(T)-F12 level under the rigid-rotor approximation. Close-coupling (CC) calculations were performed for low rotational levels, while the coupled-states (CS) method was used for higher levels. Convergence tests were conducted, and CC and CS scattering cross sections were compared. The CS rate coefficients cover rotational levels up to $j=40$ and temperatures of 3–60\,K. Although CC and CS rate coefficients differ by up to a factor of $\sim 2$ for some transitions, particularly those affected by weak coupling and resonances, they yield nearly identical excitation and brightness temperatures for the high-$j$ transitions examined, including $19\rightarrow18$. These results support the reliability of the CS method for non-LTE modelling of the high-$j$ transitions considered, for which CC calculations are computationally impractical. We use reduced-mass scaling of the SiC$_6$–He rate coefficients to estimate those for SiC$_6$–H$_2$ and model the observed transitions. A $\chi^2$ analysis of the observed line fluxes, excluding heavily blended features, yields a best-fitting of $n(\mathrm{H_2})=4.33\times10^5$\,cm$^{-3}$ and $N(\mathrm{SiC_6})=8.11\times10^{11}$\,cm$^{-2}$. The latter agrees excellently with the previous observational estimate of $(7.9\pm1.5)\times10^{11}$\,cm$^{-2}$, supporting the consistency of our non-LTE modelling with observational constraints.

Magnetic reconnection is a fundamental mechanism underlying the heating and a wide variety of eruptive phenomena in the solar atmosphere; however, characterizing its 3D aspects remains challenging. Our aim is to understand how 3D magnetic reconnection in unipolar regions drives localized heating and plasma ejections. To this end, we used a self-consistent 3D radiation-MHD simulation of a coronal bright point (CBP) performed with the Bifrost code. We focused on localized, intense heating events and upflows near a unipolar CBP footpoint associated with its parasitic polarity. 3D reconnection diagnostics were carried out using the parallel electric field and its integral along magnetic field lines. We then compared the resulting upflows with spectroscopic observations from Hinode/EIS. We find recurrent episodes of 3D magnetic reconnection without nulls at the footpoints of loops rooted near the CBP's parasitic polarity. A detailed analysis of one representative event places the reconnection region at heights z=[1.0,2.5] Mm, within a predominantly vertical magnetic field with localized concentrations of electric current. The dissipation of these currents efficiently heats the plasma to about 2 MK and produces strong gas-pressure gradients that drive upflows of a few tens of km/s. Blueshifts observed with Hinode/EIS near the parasitic polarity of an observed CBP are consistent with this scenario. The recurrence of these reconnection events are essential for heating CBP loops to million-degree temperatures. This form of 3D reconnection may operate more generally in the solar atmosphere, dissipating magnetic stress around strong flux concentrations and contributing to heating in apparently unipolar regions. The resulting pressure-driven upflows offer an indirect spectroscopic diagnostic of localized reconnection heating, which future observations with MUSE and Solar-C will be able to test.

In this work, we present the Simpson-Visser black-bounce (SV-BB) spacetime with both electric and magnetic charges (the dyonic SV-BB) as an exact solution of general relativity coupled to Maxwell electrodynamics and an anisotropic fluid with vanishing radial pressure. We assume the anisotropic fluid represents an Einstein cluster, which consists of a dense system of particles moving in circular orbits that generate only tangential pressure and zero radial pressure. We show that the dyonic SV-BB metric, which provides a regular black hole spacetime, can be obtained as an exact solution to the Einstein field equations sourced by a combination of an Einstein cluster (which is responsible for providing the exotic matter required to keep a black-bounce throat open) and an electromagnetic field in the framework of Maxwell electrodynamics.

What makes one quantum process more complex than another? We adopt an operational approach inspired by classical complexity science, which characterises structure through the memory required for causal generation. We develop a fully-quantum extension of computational mechanics for quantum space series: Correlated sequences of quantum outputs that do not return to interact with their generator. For stationary, memoryful quantum space series admitting finite-dimensional, primitive causal models, we show that any memory-minimal causal generator can be chosen to produce outputs isometrically, without a discarded environment. The resulting canonical matrix product state representation uniquely determines the irreducible memory required for generation. In particular, the minimum memory entropy is exactly the entanglement entropy across the past-future bipartition, giving entanglement a direct operational interpretation as irreducible memory for causal generation. The same structure determines the minimum memory dimension through the corresponding Schmidt rank. Within this class, we further show that the fundamental entropy rate vanishes, that causal generation is symmetric under time reversal, and that all memoryful processes possess infinite quantum Markov order with respect to arbitrary sharp measurements. These results establish an operational framework for quantifying intrinsic quantum structure, revealing deep connections between causal generation, complexity, memory, entropy, and entanglement.

We identify a structural mechanism by which perfect play in a nonlocal game requires and self-tests a specific non-maximally entangled state. To this end, we construct a Flagged Magic-Square game by extending the standard Magic-Square game with an additional “flag” outcome and two additional questions for each player. The game admits a perfect strategy using a state with Schmidt coefficients proportional to $(1,\sqrt{2},\sqrt{2},\sqrt{2},\sqrt{2})$. We give a direct algebraic proof that maximally entangled strategies have winning probability bounded away from one, independently of dimension. Moreover, the game self-tests this state, providing an example of a two-party pseudo-telepathy game that certifies a specific non-maximally entangled state. Our construction illustrates how adding suitable constraints to a rigid measurement geometry can enforce specific Schmidt ratios and provides a modular route to further self-tests based on other rigid pseudo-telepathy games. We establish a general game-to-channel reduction that transfers separations in the game model to one-shot zero-error communication over classical channels. Applied to the Flagged Magic-Square game, it yields a classical channel for which entanglement permits the zero-error transmission of ten messages in a single use, whereas any finite-dimensional maximally entangled resource permits at most nine. Thus, maximally entangled states are not a universally optimal entanglement resource for zero-error communication over classical noisy channels.

Deep learning has revolutionised weather forecasting in recent years, especially through atmospheric foundation models, which offer competitive skill for a fraction of the computational costs of classic physics-based models. However, most existing foundation models are deterministic, limiting the generation of large ensembles for accurate uncertainty quantification, extreme weather risk assessment, and long-range weather forecasting. Furthermore, these models incur a large, often prohibitive, computational overhead to train from scratch. To address these shortcomings, we turn a pretrained deterministic prior model, namely the Aurora foundation model, into a generative ensemble-prediction model. To that end, we introduce a novel generative method, Denoising Stochastic Interpolants, combined with a replay buffer for Stochastic Differential Equation (SDE) rollout, enabling probabilistic training of SDE trajectories. Our stochastic foundation model, Xaurora, is finetuned from the small Aurora version, yet it approaches the state-of-the-art on global ensemble metrics and is competitive with the large version of Aurora. Our method is parameter and sample efficient, and generates skilful 15-day forecasts in 13 minutes. Our results demonstrate that deterministic foundation models can be efficiently extended into even stronger stochastic models.

Plastic scintillators remain attractive for large-area particle detectors because of their fast response, mechanical flexibility, and relatively simple fabrication. Motivated by future applications including the ALICE~3 Muon Identifier (MID) and the upgrade of the ALICE Fast Interaction Trigger (FIT), this work investigates polyurethane (PU)-based plastic scintillators doped with 2,5-diphenyloxazole (PPO) and 1,4-bis(5-phenyloxazol-2-yl)benzene (POPOP). Systematic information on the optimization and radiation response of this material system remains limited. A series of compositions was therefore fabricated and characterized using minimum-ionizing particles (MIP), optical spectroscopy, and time-correlated single-photon counting. The measurements show that the scintillation response is governed primarily by the PPO concentration, while POPOP mainly modifies the spectral response, and fast effective decay times of approximately 1.6–1.75~ns are maintained across the doped samples. The best-performing formulation was subsequently scaled to 20-$cm$ and 1-m scintillator bars and successfully operated with a single embedded wavelength-shifting fiber and SiPM readout, demonstrating its suitability for meter-scale light collection. Proton-irradiation measurements at the CERN IRRAD facility further revealed systematic degradation of the optical and scintillation responses with increasing exposure, together with substantial recovery after approximately two months. These results demonstrate that optimized PU–PPO–POPOP scintillators can combine fast timing, high light output, scalable detector geometry, and recoverable radiation response, supporting their further development for future large-area particle-detector systems.

Topological entanglements are central to understanding and predicting the properties of polymer melts. Yet, they make equilibrium sampling computationally challenging, as decorrelation times grow rapidly with chain length. Here, we introduce a Monte Carlo scheme that bypasses typical computational bottlenecks by working in a self-assembly ensemble rather than at fixed composition. Strictly local moves efficiently propagate backbone reconnections across scales while conserving the number of linear chains, achieving near-linear scaling of decorrelation time with system size, $\tau_{\rm eq}\sim V^{1.0}$. With this method, formulated for a fully-packed lattice, we equilibrate periodic systems totalling up to $\simeq 1.1\times 10^9$ monomers, accessing a universal melt regime insensitive to lattice details. We analyze intra- and inter-chain entanglements for chains of up to $N\simeq 5 \times 10^5$ monomers, revealing that they manifest as localized knots and links rather than as global tangles. Finally, we show that the magnitude of the Gauss linking integral between neighbouring chains grows only as $N^{1/4}$.

We study upper large deviations of the free energy of mixed $p$-spin Ising spin glasses through the generalized TAP free energy $F_{\mathrm{TAP}}$ of Chen, Panchenko and Subag. For every mixture with radius of convergence greater than one, $\max F_{\mathrm{TAP}}$ and $\log Z_N$ have the same large deviations at speed $N$; the proof combines their band theorem with Ramsey's theorem. For convex mixtures with $\sum_p 2^p\beta_p^2<\infty$, upper deviations at level $f$ are carried by generalized TAP critical points, which exist at the free-energy rate without Boursier's strict Plefka condition. Outside an event of smaller exponential order, near-maximizers at level $f$ lie near the contact set of a constrained Parisi obstacle, follow the Auffinger-Chen field law, and have Hessian bulk near a reflected Pastur law whose edge is nonpositive and vanishes exactly at contacts where the obstacle is flat to second order. Where every contact is of this kind, a fixed stability margin costs rate.

We present boundary conditions for the quasiclassical Green's functions describing spin active interfaces between two materials, at least one of which is in the diffusive regime. These boundary conditions are developed with the help of the action formalism, and provide clean and easily tractable expressions. We connect our expressions to previous literature in limiting cases and describe normal transport, magneto-resistance transport and spin-precession through the bound ary. By using the Keldysh-Nambu-spin formalism, our equations are valid both in the normal and superconducting state. The construction through the action formalism also allows us to derive the corresponding full counting statistics for charge currents, thermal currents and spin currents. We use this boundary condition to consider the anomalous proximity effect, and to study the Josephson coupling between triplet and spin-split superconductors through a magnetic interface. We find an analytic expression for the zero bias conductance in junctions with a p-wave superconductor and a spin-filter, and show how it depends on the relative orientation of the exchange field and d-vector. For Josephson junctions, we show that, in agreement with time-reversal symmetry, the conditions on the relative orientations of the spins in the materials for the appearance of anomalous Josephson currents, are distinctly different for two spin-split superconductors and a spin-split superconductor with a triplet superconductor. Moreover, we show that the anomalous Josephson currents are only accompanied by a diode effect if both transparencies for spin up and down are nonzero and distinct.

We investigate the longitudinal momentum distributions (LMDs) of the deuteron using a relativistic deuteron wave function derived from a realistic nucleon-nucleon (NN) interaction within the light-front framework. By convoluting the deuteron LMDs with the nucleon parton distribution functions (PDFs), we analyze the unpolarized, longitudinally polarized, and tensor-polarized structure functions of the deuteron. In addition, we also study the EMC effect in the weakly bound deuteron through the structure function ratio $F_{2}^{D}/(F_{2}^{p}+F_{2}^{n})$, which deviates from unity due to nuclear binding and Fermi motion effects.

Let $Z_N$ be the partition function of the Sherrington-Kirkpatrick model at inverse temperature $\beta>1$. Replica theory (Kondor near the critical temperature, Parisi and Rizzo at all temperatures) predicts that the probability that $N^{-1}\log Z_N$ exceeds its typical value by $\delta$ decays like $\exp(-Na\delta^{6/5})$ with an explicit $a$; Aronow and Lopatto recently proved bounds of this order. The exponent is the Legendre transform of the Parisi problem constrained to carry an atom $\theta$ at zero. We show that the constrained minimum exceeds the equilibrium free energy by $c_\beta\theta^5(1+o(1))$, where $c_\beta=\frac{9}{640}\beta^3\rho_\beta(0)^{-3}$ and $\rho_\beta(0)>0$ is the density at zero of the Parisi measure. With the fractional-moment formula this gives the exponent $\frac56(6c_\beta)^{-1/5}\delta^{6/5}(1+o(1))$ as $N\to\infty$ and then $\delta\to0$. The constrained minimizer has a marginal first positive contact, to leading order at $3\theta/(2\rho_\beta(0))$ with an atom $\theta/2$. This plateau calculus applies to every mixture with $\xi'''(0)=0$ whose Parisi measure accumulates at zero; a small field $h$ opens a gap of order $|h|^{2/3}$, and an atom of the Parisi measure at zero, present in every pure $p$-spin model with $p\ge3$, makes the rate leave zero linearly. Near criticality the constant tends to Kondor's value $9/5120$ and the marginal regime ends at a de Almeida-Thouless threshold. For the Sherrington-Kirkpatrick model at every $\beta>1$, a finite-step curvature inequality from an unrefereed preprint shows that every constrained minimizer either has an interval of positive contacts, all marginal, or has exactly two atoms, and that the marginal regime ends at a unique de Almeida-Thouless threshold $\theta_c(\beta)$. The laws at every $\beta>1$ use that the Parisi measure accumulates at zero, a theorem of Lopatto also proved in earlier work of the author.

We report an implementation of continuous-wave (CW) vacuum-ultraviolet (VUV) generation at 148.4 nm by single-pass second-harmonic generation of 296.8 nm light in strontium tetraborate (SBO). At an incident fundamental power of approximately 580~mW, we estimate a VUV output power of approximately 1.7 nW at the crystal exit. The crystal is grown by the top-seeded solution growth method and operated in a helium-filled chamber. The quadratic power dependence observed under vacuum, together with its strong suppression in air, supports the identification of the generated second harmonic. We further characterize the dependence of the VUV signal on beam position, incidence angle, polarization, and crystal temperature, providing practical guidance for SBO-based CW VUV sources for nuclear spectroscopy and clock applications.

A Direct Numerical Simulation (DNS) investigates transonic flow over a NACA0012 airfoil coupled with single-DOF structural dynamics. Analysis is performed for angle of attack ({\alpha}) 8{\deg} with varying reduced velocity (U*) from 2 to 8, reduced mass (m*) 5.0, Reynolds number (Re_\infty) of 3 \times 10^6, and Mach number (M_\infty) 0.8. The speed of sound in air is calculated as a = sqrt({\gamma}RT_\infty). It is noted that the magnitude of the aerodynamic loads and moments increased with higher reduced velocity. The Fast Fourier Transform (FFT) of the moment coefficient (C_M) in the fixed-airfoil condition is carried out to extract the non-dimensional dominant frequency, referred to as the Strouhal number (St), along with the coupled oscillation frequency of the airfoil (Stc). The FFT analysis for the stationary case at {\alpha} = 8{\deg} yields a value of St = 1.3161. The presence of high-frequency components indicates the onset of instability associated with shock-boundary layer interaction. The computed values of the coupled oscillation frequency (Stc ) are 0.0762 and 0.1716 for the cases with angle of attack (AoA) 8{\deg} and reduced velocities U* = 2.0 and 8.0, respectively. The corresponding natural aeroelastic frequencies (Stn) are taken as 1/U*, yielding values of 0.5 and 0.125. It is observed that for U* = 2, the coupled frequency (Stc) aligns with the subharmonic of shock-buffet frequency, indicating flow-dominated dynamics. In contrast, for U* = 8, Stc coincides with the natural pitching frequency, indicating a dominant influence of the structural mode. Pressure fluctuation contours are examined to analyze the characteristics of acoustic radiation. Vorticity and schlieren visualizations are employed to identify the nature of vortex structures, the strength of the shock, and its spatial location, respectively.

The large-$D$ membrane paradigm provides a perturbative, non-gravitational description of black hole dynamics. While the local second law of thermodynamics has been established for neutral membranes, the explicit determination of the local entropy production equation within the charged large-$D$ membrane framework remains unsolved. In this paper, we compute the subleading-order correction to the divergence of the membrane velocity for a charged black hole in a flat background. We evaluate the corresponding scalar Einstein-Maxwell constraint equation at the physical event horizon via the non-affine null Raychaudhuri equation, and relate the physical horizon expressions to the auxiliary membrane kinematics, demonstrating that the membrane velocity produces a non-negative divergence at the first non-vanishing order in the membrane worldvolume, which is driven by two quadratic forms: the membrane shear and a novel contribution generated purely by the Maxwell field. Using this result, we construct the membrane entropy current and prove that its divergence is non-negative through this order, thereby establishing the local second law for the charged large-$D$ membrane paradigm.

Understanding phase stability and navigating vast compositional spaces in multicomponent solids remain central challenges in solid-state chemistry. Here, we develop a quantum spectral thermodynamic framework connecting interaction-induced phonon spectral broadening to free energy, alongside an uncertainty-guided active-learning workflow that explores 7.7 million high-entropy ceramic configurations at density-functional-theory fidelity, achieving a $10^5$-fold acceleration. We show that phonon self-energy effects arising from chemical disorder provide an intrinsic vibrational contribution to thermodynamic stabilization beyond ideal configurational entropy, compensating unfavorable mixing enthalpies and suppressing phase separation. Across the chemical space, we uncover a robust ~12 at.% solute threshold separating strengthening and softening regimes, associated with the filling of metal-carbon antibonding states. Chemical disorder further enables an unusual combination of high-temperature mechanical stiffness and low thermal conductivity, together with anomalous temperature-dependent lattice heat transport. This work establishes a quantum spectral foundation for connecting many-body interactions to thermodynamics and phase stability, while providing a scalable framework for exploring previously inaccessible multicomponent chemical spaces.

Our previous work [Y.~Li, D.~Xu, and Y.~Hao, Phys. Rev. Accel. Beams 28, 074001 (2025)] introduced a square-matrix method for constructing approximate invariants recursively, order by order, from the one-turn map of non-integrable Hamiltonian systems. At fourth and higher even orders, the recursive construction is intrinsically non-unique because rotationally invariant polynomials generate a null space in the corresponding homological equations. In the resonant regime, this ambiguity can lead to an incorrect description of the resonance-island topology and is therefore particularly relevant to accelerator applications that rely on stable resonance islands. In this work, we select the null-space contributions by explicitly incorporating the null-space basis vectors and determining their coefficients through an averaging procedure over a prescribed region of interest. The method is demonstrated using the Kobayashi map near a third-order resonance, extending the square-matrix construction to resonant Hamiltonian dynamics.

Designing custom Cerrobend collimators for linac-based preclinical electron irradiation is labor intensive and susceptible to design inconsistencies. We developed Collimator Creator (CC), an open source parametric workflow that converts aperture dimensions and jig offsets into printable STL models for a collimator mold, collimator shell, Cerrobend holder, and beam degrader. Two designs were fabricated and characterized: a 4.0 x 1.5 cm$^2$ bilateral lung collimator centered on the central axis and a 1.5 x 1.5 cm$^2$ unilateral lung collimator with a 7.5 mm jig offset, each with a 15 mm thick Cerrobend collimator and a 10 mm PLA degrader. Kilovoltage planar images were used to assess aperture geometry and casting uniformity. Radiochromic film was used to measure full width at half maximum (FWHM) and 80%-20% penumbra under conventional and ultra high dose rate (UHDR) electron delivery on a Varian TrueBeam, and off axis leakage was measured with an ionization chamber at conventional dose rate. The cast Cerrobend apertures deviated by less than 0.2 mm from their specified designs. FWHM values were within 3% of the nominal field dimensions, and penumbra ranged from 0.73 to 1.05 mm under conventional and UHDR delivery. Crossline leakage 2 cm beyond the collimator edge was below 2% for both collimators at conventional dose rate. Parametric collimator generation standardized digital design inputs for the two evaluated rectangular linac-based electron fields. Further work will assess specimen-level dosimetry, additional aperture geometries, and Monte Carlo integration.

Photonic quantum technologies require the integration of high-quality quantum light sources with programmable photonic circuitry to enable on-chip quantum information processing. Semiconductor quantum dots have emerged as a leading platform for quantum light generation, yet their monolithic integration with cryogenic-compatible, programmable photonic circuitry remains challenging. Here we demonstrate a programmable quantum photonic platform that enables simultaneous control of highly coherent quantum dot-based single photon emitters and reconfigurable optical elements at cryogenic temperatures. System-level integration enables individual electrical and optical addressing of active components on a single chip, allowing their concurrent operation while preserving coherent non-classical light emission. We demonstrate multiple quantum-photonic functionalities, including pure single-photon generation, two-photon interference, and resonant transmission and reflection measurements of integrated emitters. These results mark a step from isolated quantum-optical devices towards programmable quantum-photonic hardware platforms capable of combining coherent quantum emitters with large-scale photonic functionality.

Does any integer survive in the shift current, and does the Chern number control its sign? We show that the shift vector is a singular field on the Brillouin torus. Its curl has two sources: the interband Berry curvature and quantised point charges at the zeros of the transition dipole. Inverting this relation gives an exact decomposition of the shift conductivity, valid at every frequency, into one sector linear in the integer charges and three continuous sectors. As a testing ground, we take a graphene-Haldane bilayer: a model that lets us sweep the interband Chern number through five values at fixed gap to isolate its role. We also test the formalism against the time-reversal-symmetric biased AB bilayer. Whenever a charge sits at the band edge, and trigonal warping is present, the integer sector alone accounts for the band-edge peak. The relevant integer is not the Chern number but the winding of that single charge. Its sign, combined with a valley-dependent profile, sets the sign of the photocurrent. In these bilayers, sign reversals across topological transitions follow this winding; the invariant changes with it only when the same gap closing does both. A band-edge charge needs no invariant. It only requires that the two band-edge sublattices not be connected by the nearest-neighbour hopping, and trigonal warping makes it visible.

The Variational Quantum Eigensolver (VQE) has become a central hybrid quantum-classical method for addressing electronic structure and materials science problems on near-term quantum hardware. As researchers across physics, chemistry, and quantum information engage with VQE, they encounter a wide range of algorithmic choices, including problem encoding, ansatz construction, classical optimization, and measurement strategies to choose from. This article provides a structured overview of these components and discusses practical factors that influence VQE performance in real settings, such as noise characteristics, available error-mitigation techniques, and hardware-dependent circuit considerations. Drawing partly on our early experiences, we highlight aspects that may be especially relevant for newcomers and outline common challenges observed in practical workflows. Our aim is to offer an accessible entry point for researchers approaching VQE-based quantum simulation and to support informed decision-making as the method and underlying hardware continue to evolve, which we support by discussion of examples from physics and quantum chemistry.

We present deep, narrowband Gemini North/GMOS images of the Pa 30 nebula that reveal rich small-scale structure in the ejecta filaments. In [S II], the number of detected filaments increases by about an order of magnitude compared to previous studies. The imaging further reveals that the filaments are not smooth radial streaks, but instead are composed of cascades of knots or clumps. The images in [O III] yield the first confirmation that previously detected diffuse [O III] emission in fact originates from the same [S II] filaments. We measure a nebula center consistent with the position of the central star, indicating that the remnant has not received a large transverse kick. The 3$\sigma$ upper limit on the velocity of the stellar kick is $\lesssim$100 km/s. Cross-sectional profiles of the filaments in [S II] and [O III] show a central peak on top of a nebular background, the latter being likely due to diffuse emission or unresolved filaments. The median [S II] width of 0.7” is slightly broader than the 0.50” seeing, providing some evidence of partially resolved filaments and implying a characteristic knot diameter of ${\sim}10^{16}$ cm. The $\approx$1” widths measured in [O III] are consistent with the poorer seeing of the oxygen images. The discovery of this clumpy substructure provides a new observational constraint on models for the origin and evolution of the remarkable filamentary ejecta of Pa 30.

We derive a quantum master equation in Lindblad form for the open quantum Rabi model in the perturbative deep strong coupling regime, where the spectrum is close to degenerate and harmonic. The Lindblad form is obtained by combining secular and singular-coupling approximations, working in a Schrieffer-Wolff transformed frame. We benchmark our equation against a Bloch-Redfield one, analyzing the time-evolution and steady state properties of several observables and find excellent agreement. Analytical results are obtained in limiting cases.

Motivated by the peculiar features of the trans-Neptunian object (TNO) Máni and the discovery of ring systems around Centaurs and trans-Neptunian bodies, we investigate the stability of particles around a small irregular body hosting a deep equatorial crater. This study is the third contribution in a sequence devoted to the dynamics around non-spherically symmetric bodies. Using Máni as a reference model, whose crater depth exceeds 10% of its radius, we map the system stability through complementary methods: Poincaré surfaces of section (PSS), survival maps, and the finite-time Lyapunov exponent (FTLE). In the nominal case, the $1\!:\!1$, $2\!:\!1$, $3\!:\!1$, and $4\!:\!1$ spin-orbit resonances (SORs) are consistently identified by all techniques. The prominent $3\!:\!1$ SOR exhibits a bifurcated structure at high eccentricities, matching structural transitions observed at lower Jacobi constant values in the PSSs. Increasing the rotation rate ($\lambda$) and crater mass ratio ($\mu$) enlarges resonance widths and promotes overlap, making the $2\!:\!1$ and $4\!:\!1$ SORs progressively dominant. Lower rotation rates allow stable trajectories to persist at higher eccentricities, whereas the $1\!:\!1$ SOR is highly sensitive to stronger perturbations and disappears in the most extreme cases. In contrast to mass-anomaly models, which can clear the region interior to the $2\!:\!1$ SOR, the crater configuration considered here preserves stable regions in this vicinity, suggesting alternative scenarios for the formation and maintenance of debris structures around irregular minor bodies.

Traditional technosignature and transient searches commonly operate on beamformed time–frequency products. Interferometric imaging adds spatial context and allows time-domain searches to be performed across many image pixels simultaneously. We report the development and testing of a GPU-accelerated interferometric imaging and image-domain dispersion-measure (DM) search pipeline for Allen Telescope Array (ATA) post-correlation UVH5 visibility data, integrated with the CyberEther streaming framework to replay recorded visibility data and work toward real-time operation. The pipeline forms Stokes-I dirty images from correlated visibilities, incorporates Inter-Quartile Range Mitigation (IQRM) flags into the imaging weights, images 48 frequency subbands spanning 287.5\,MHz, subtracts a temporal mean over the full observation from each subband and pixel, applies IQRM-informed subband masking, and performs a blind trial-DM search using a short-history image ring buffer. On a controlled 10-minute three-spectral-window test observation containing a periodic dispersed pulsed injection (DM\,$\approx$\,150\,pc\,cm$^{-3}$), the pipeline recovers the injected source at the phase centre with a best-fit DM\,$=$\,150\,pc\,cm$^{-3}$, with individual dispersed pulses reaching a median image-plane S/N of $\approx$52. When integrated into CyberEther, the core processing requires approximately 63\,ms per integration compared with a native integration time of approximately 98\,ms, demonstrating that the core science-processing operations can be completed within the available integration time. The present implementation operates on recorded visibility data and relies on a temporal mean and MAD noise estimate precomputed over the full observation. For live operation, these quantities will instead need to be estimated from data available up to the current integration.

The Davey-Stewartson (DS) system is a canonical model for a weakly nonlinear wave packet in two spatial dimensions that is resonantly coupled to the slowly varying mean flow it generates, and as such it governs modulated wave trains in settings as different as finite-depth water waves, quadratic optical media and magnetic films. Here we develop the Whitham modulation theory for the DS system and use it to study the stability of its periodic traveling wave solutions. Specifically: 1. We perform a detailed study of the parametric dependence of the periodic solutions of all four variants of the DS system, including their harmonic and soliton limits. 2. We present the formulation of Whitham modulation theory for the DS system and write down the resulting Whitham modulation equations for all four variants of the DS system. 3. We use the resulting modulation equations to study the stability of the periodic traveling wave solutions of all four variants of the DS system. 4. We validate the theoretical predictions by comparing them with a direct linearization of the DS system as well as with the direct numerical simulations of the DS system, showing excellent agreement. The results indicate that the periodic solutions of the defocusing DSII system are linearly stable, whereas those of all other variants of the DS system are unstable. The calculations also evidence many structural features (non-evolutionary modulation equations, constraints on the admissible initial data, and auxiliary mean-field constants absent from the traveling wave solutions yet indispensable to the modulation system) are expected to recur in any two-dimensional envelope equation with mean-field coupling.

We study semi-Clifford and generalized semi-Clifford structures in the Clifford hierarchy as a function of hierarchy level $k$ and qubit number $n$. We show that $\mathcal{C}_k(n)$ is semi-Clifford if and only if $k\le2$, $n\le2$, or $k=3$ and $n\le6$. We also establish that $\mathcal{C}_k(n)$ is generalized semi-Clifford when $k\le4$ or $n\le3$ and construct counterexamples when $k,n \geq 5$. For $n=4$ and $k\ge5$, we show that every gate defined over $\mathbb{Q}(i)$ up to a scalar is generalized semi-Clifford, reduce the general case to a single level, and propose a strategy to prove our conjecture that $\mathcal{C}_k(n)$ is generalized semi-Clifford if and only if $k\le4$ or $n\le4$. Lastly, we go beyond this structure by introducing $n_c$-generalized semi-Clifford gates, which we show are exactly the gates of the form $\sum_x|\pi(x)\rangle\langle x|\otimes V_x$ up to Clifford gates on both sides, where $\pi$ permutes the computational basis states of $n_c$ control qubits. We conjecture that for $k\ge3$ every gate in $\mathcal{C}_k(n)$ has this form for some $n_c\ge1$ with every $V_x\in\mathcal{C}_{k-3}(n-n_c)$, refining the conjecture of Zeng, Chen, and Chuang.