Tailoring light beams in terms of intensity, phase, and polarization distribution has recently garnered significant attention. This work considers vector beams obtained by the natural conical diffraction phenomenon, occurring when a focused light beam travels along one of the optic axes of a biaxial crystal. If a cascade of several aligned biaxial crystals is used, in its sharpest plane this phenomenon usually gives rise to a concentric ring pattern with spatially varying linear polarization, thus covering the equator of the Poincaré sphere. Here, we propose smart arrangements of conical diffraction cascades based on Fibonacci and degenerate sequences leading to vectorial beams addressing multiple areas of the Poincaré sphere. The present approach is based on the concept of path interference and enables a clear spatial separation between regions exhibiting distinct polarization states (linear, elliptical, circular).

The high-extinction cross-polarization measurement of a paraxial laser beam results in a Hermite-Gaussian (${\text{HG}}_{11}$)-like four lobes with a dark-centered cross pattern. The azimuthally spin-separated mode pattern is understood to result from the spin-orbit interaction of light. The perfect dark region at the beam center, due to extreme cross-polarization extinction (EXE), is used here to accurately determine the on-axis residual polarization of the laser beam and, using it, the residual elliptical birefringence of optical crystals. By propagating the laser beam through uniaxial optical crystals with their optic axis cut either parallel or perpendicular to the beam propagation direction and performing the EXE measurement, we demonstrate a simple approach to precisely quantify the residual elliptical birefringence of crystals, which are otherwise assumed to be absent, to a high degree of extinction of 1 part in ${10}^{-8}$. The experimental results are interpreted using Jones-matrix-based calculations for a paraxial laser beam and upon its propagation through the optical crystals. The high sensitivity and high accuracy of the EXE technique make it well suited for measuring and characterizing anisotropy and its dispersion of monolayers, ultrathin films, and two-dimensional materials.

In an open quantum ring (OQR), an asymmetric ring-to-electrode configuration, where the upper and lower arms have unequal lengths, generates antiresonances in the junction transmission spectrum around the doubly degenerate eigenenergies of the isolated ring Hamiltonian. The asymmetric OQR also gives rise to a net circular current transmission within the ring, specifically around these doubly degenerate eigenenergies. We investigate the system-size scaling properties of the transmission within the ring and the overall junction transmission of an OQR. Ballistic transport refers to the unhindered flow of charge carriers within a conductor, where transmission is independent of the system size. Here, we find beyond-ballistic behavior, characterized by an anomalous increase of the transmission with increasing system size, near both the degenerate and nondegenerate eigenenergies of the ring Hamiltonian, depending on the ring-to-electrode configuration. This phenomenon is unique to OQRs and is associated with the quantum interference effect between two counterpropagating electronic waves with nearly equal and opposite momenta. Consequently, there is no equivalent phenomenon in open quantum junctions with linear conductors.

By systematically introducing small symmetry-violating terms into quantum gates, we examine whether such perturbations can reproduce the tomographic noise patterns observed on actual quantum hardware. This study fits into the broader context of quantum computing and quantum information processing, where realistic noise modeling remains essential for understanding device behavior. Our analytical framework mirrors Qiskit's tomography procedures and shot model, using transparent noise control. Our results show that weak generator perturbations can reproduce average deviations in Pauli transfer matrices (PTMs) with high fidelity (given the recorded hardware noise characteristics). These findings suggest that symmetry-violating generators provide a phenomenological model for relevant classes of hardware noise. This approach offers a reproducible analytic baseline for testing noise hypotheses and calibrating simplified models against experimental data. Beyond this descriptive role, the appearance of stable symmetry-violating perturbations in the fitted models supports their use as a phenomenological description. Because the analytical framework isolates these violations at the generator level, it links native-generator perturbations to reconstructed PTM signatures. As a result, the model not only reproduces experimental process tomography data but also tests which PTM structures can be reproduced and at what perturbation magnitude, providing information for calibration, simulation, and the development of symmetry-sensitive mitigation and error-correction strategies. The present analysis is restricted to single-qubit gates.

We investigate magnetotransport in a time-reversal symmetry-broken, untilted Weyl semimetal in the simultaneous presence of momentum-space Berry curvature and skyrmion-induced emergent magnetic fields ${\mathbf{B}}_{\mathrm{emer}}$. Using a semiclassical Boltzmann approach incorporating Berry-curvature corrections and intervalley scattering, we analyze the longitudinal magnetoconductivity and planar Hall conductivity in this mixed-topology regime. In the absence of ${\mathbf{B}}_{\mathrm{emer}}$, increasing intervalley scattering drives a strong sign reversal of the longitudinal magnetoconductivity. A finite ${\mathbf{B}}_{\mathrm{emer}}$ introduces an additional shift of the parabolic magnetic-field dependence, leading to a weak sign-reversal regime without altering the curvature. The coexistence of these effects naturally produces a strong-and-weak sign-reversal regime, demonstrating that intervalley scattering and real-space topology control distinct geometric features of the response. The emergent field further induces asymmetry in the angular dependence of both longitudinal and planar Hall conductivities. We show that a finite planar Hall response can arise solely from ${\mathbf{B}}_{\mathrm{emer}}$ when its direction is varied, providing a transport signature of real-space topology. Our results establish that the skyrmion-induced emergent field acts as an independent topological tuning parameter, revealing measurable consequences of the interplay between real- and momentum-space Berry curvature in Weyl systems.

On the grounds of nonadditive entropies—appropriate for complex systems—we investigate the electroencephalogram amplitudes of typical and attention-deficit hyperactivity disorder (ADHD) children. The corresponding probability distributions are $q$-Gaussians, i.e., $\rho \left(x\right)\propto e_q^{-\beta x^2}\equiv {[1+(q-1)\beta x^2]}^{1/(1-q)}$, where $(q,\beta )$ are, respectively, the entropic index characterizing complexity and the inverse width. We show that $q$ tends to monotonically vary with $\beta$ for both typical and ADHD subjects, thus strongly suggesting a scalinglike organization of electroencephalogram amplitude statistics compatible with nearly critical or multiscale brain dynamics. Moreover, we verify that ADHD subjects have a higher complexity than the typical ones. Consistently, biomarkers for objective psychiatric diagnosis could emerge along this path.

We analyze decoherence in a one-loop Stern-Gerlach-type matter-wave interferometer for a massive nanoparticle embedded with a nitrogen-vacancy-centered nanodiamond evolving under an effective harmonic-oscillator dynamics in a magnetic-field gradient. We assume that the Stern-Gerlach interferometer is subjected to an acceleration $\vec{a}$ external to the system, which is at an angle ${\theta }_0$ with respect to the direction of the superposition. For a one-loop interferometer, we quantify dephasing from two noise channels: fluctuations in the external acceleration $\delta a\left(t\right)$ and fluctuations in the tilt angle $\delta \theta \left(t\right)$. At the level of the action, we treat these two external sources of noise as stochastic inputs, compute the resulting stochastic phase difference between the interferometer arms, and obtain the dephasing rate $\mathrm{\Gamma }$. We obtain the transfer function of the interferometer for each of the noise sources. We also show explicit results of constraints on the power spectral density of the noise sources for an interferometer that produces a superposition size of $\mathrm{\Delta }x\sim 1\mathrm{nm}$ of a nanodiamond of mass $m={10}^{-15}\mathrm{kg}$ by considering white-noise statistics and imposing a coherence target $\mathrm{\Gamma }\tau \le 1$, where $\tau \simeq 0.015\mathrm{s}$. We find $\sqrt{{\mathcal{S}}_{aa}}\lesssim \mathcal{O}\left({10}^{-11}\right)\mathrm{m}{\mathrm{s}}^{-2}{\mathrm{Hz}}^{-1/2}$ if we take the external acceleration, $a=0\mathrm{m}{\mathrm{s}}^{-2}$ and ${\theta }_0=0^{\circ }$ (along the direction of the superposition), and $\sqrt{{\mathcal{S}}_{\theta \theta }}\lesssim \mathcal{O}\left({10}^{-10}\right)\mathrm{rad}{\mathrm{Hz}}^{-1/2}$ for $a=g=9.81\mathrm{m}{\mathrm{s}}^{-2}$ and ${\theta }_0={90}^{\circ }$ (superposition direction is perpendicular to the Earth’s gravity). We have also found an operating regime where the acceleration noise can be minimized by either varying ${\theta }_0$ or $a$ for a fixed set of other experimental parameters.

Labyrinthine structures are ubiquitous in pattern-forming systems arising from a wide variety of physical, chemical, and biological processes. Yet, their characterization remains challenging due to the lack of long-range order and the resultant complicated morphologies. Here, we present an approach for characterizing labyrinthine patterns based on the identification and the correlation analysis of their topological defects. We employ advanced machine-learning-based-pattern-recognition techniques to identify the types and locations of topological defects of the local stripe ordering. Applying this method to single-crystal Bi-substituted yttrium iron garnet films, we uncover a distinct morphological transition between two zero-field labyrinthine structures. Crucially, the pair distribution functions of the topological defects reveal subtle differences between labyrinthine structures, which are not discernible from conventional global analysis. By systematically analyzing the spatial correlations and geometric properties of these defects, we provide insights into the athermal dynamics that govern the observed morphological transitions. Our work demonstrates that machine-learning-based recognition techniques enable systematic studies of rich and complex labyrinthine-type structures universal to many pattern-formation systems.

A quantum network enables the execution of advanced protocols, such as distributed quantum computing, quantum metrology, quantum cryptography, and long-distance quantum communication. Anomalous nodes pose significant threats to these protocols, as they are notoriously difficult to detect and can cause severe disruption. In this work, we introduce a quantum-walk-based protocol for detecting such anomalies. The protocol exploits the sensitivity of coherent quantum transport to local perturbations of the network Hamiltonian. In particular, anomalous on-site potentials or modified hopping amplitudes alter the quantum walker's interference pattern, thereby shifting the time-averaged arrival probability between two trusted end points and offering the detection signal. We develop the protocol for one-dimensional quantum networks, derive spectral criteria for detectability, and discuss how the resulting ideas may extend to more general graph topologies.

Local material inhomogeneities can strongly influence magnetization dynamics and macroscopic magnetic properties, yet detecting such defects from magnetic imaging data remains challenging when thermal fluctuations and experimental noise obscure static contrast. Here, we investigate defect detection in strongly fluctuating magnetization regimes, where signatures of inhomogeneities largely average out in time-resolved measurements. Using finite-temperature micromagnetic simulations with randomly distributed defects and material parameters representative of ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$, we compute per-pixel temporal mean, temporal standard deviation, and latent entropy and use them as inputs for U-Net-based semantic segmentation models. We find that the most effective descriptor depends on the noise level and, importantly, that robust detection requires training data that reflect the expected noise statistics. These results provide practical guidance toward designing noise-robust defect-detection workflows in magnetic imaging.

We consider highly inaccurate measurements made on classical stochastic and quantum systems. In the quantum case, such a “weak” measurement preserves coherence between the system's alternatives. We demonstrate that in both classically and quantally the information about the scenario realized in each individual trial is lost. However, ensemble parameters such as classical path probabilities and quantum quasiprobabilities can be extracted from the obtained statistics. Both classically and quantally, causality ensures that additional postselection only redistributes individual outcomes between the system's final states. Quantum quasiprobabilities may change sign, which allows for anomalously large meter's (pointer's) reading for some final states. These, we show, result from mere “reshaping” of a broad distribution obtained earlier and provide no “experimental evidence” of quantum variables taking, albeit on rare occasions, exceptionally large or otherwise anomalous values.

We construct a series of graphene-based superconducting quantum circuits and integrate them into three-dimensional (3D) cavities. For a device exhibiting single-qubit behavior, we demonstrate flux-tunable qubit transition, with a relaxation time $T_1\approx 48\mathrm{ns}$ measured in one cooldown at a reduced qubit frequency of $3.65\mathrm{GHz}$, and a separate power-broadening-based lower bound $T_2^{*}\gtrsim 17.63\mathrm{ns}$ at the sweet spot in an earlier cooldown at $f_q\approx 8.07\mathrm{GHz}$. By coupling the device to cavities with different resonant frequencies, we access multiple qubit-cavity coupling regimes, enabling the observation of vacuum Rabi splitting and flux-dependent spectral linewidths. In a two-circuit device consisting of a superconducting quantum interference device (SQUID) and a single junction, power-dependent measurements reveal a two-stage dispersive shift. By flux tuning the cavity frequency at different readout powers, we attribute the first shift to the fixed qubit and the second to the SQUID qubit, indicating successful coupling between the two circuits and a single cavity mode. Our study demonstrates the flexible coupling achievable between two-dimensional (2D)-material-based flux-tunable superconducting circuits and 3D cavities, and paves the way toward constructing multicircuit 3D transmonlike devices from 2D materials.

A linear stability analysis is conducted to decipher how the thermal and surfactant Marangoni numbers affect primary instabilities when a two-dimensional incompressible viscous film flows down a uniformly heated flexible substrate under gravity. Since the viscous film is nonisothermal and a soluble surfactant is dissolved in it, we require additional heat- and mass-transfer equations along with the Navier-Stokes equations for describing this film flow. To explore linear stability, we formulate the Orr-Sommerfeld-type boundary value problem (OS BVP). The analytical long-wave series expansion and the numerical Chebyshev spectral collocation method are applied to solve the OS BVP. The long-wave results disclose that surface mode instability intensifies in the presence of the thermal Marangoni number but weakens as the surfactant Marangoni number rises, creating a surfactant-free isothermal film flowing over a flexible substrate when these two opposing impacts balance each other. Moreover, we identify a range of the inclination angle for which the surface mode becomes linearly stable, primarily because the stabilizing effects of the surfactant Marangoni stress and depthwise gravitational force dominate over the destabilizing effects of the thermal Marangoni stress and spring stiffness coefficient $C_K$. In the arbitrary wave-number regime, the numerical results reveal that surface mode, S-mode, and P-mode instabilities are amplified with rising values of the thermal Marangoni number but are weakened with rising values of the surfactant Marangoni number. Moreover, we observe a modal coalescence between the surface mode and the S-mode in the long-wave regime as the thermal Marangoni number increases. The base surface surfactant concentration parameter, ${\mathrm{\Gamma }}_E$, exhibits both stabilizing and destabilizing influences on all the surface mode, S-mode, and P-mode instabilities. However, the surfactant solubility parameter, ${\xi }_s$, shows only a stabilizing influence on all instability modes. If the magnitudes of the spring stiffness coefficient $C_K$, the longitudinal tension parameter $C_T$, and the flexural rigidity parameter $C_B$ are significantly lowered, unstable domains of the P-mode and the wall mode, which emerged separately in the finite wave-number regimes, coalesce at higher values of ${\mathrm{\Gamma }}_E$. Additionally, we observe a competition between the surface mode and the wall mode. When the damping coefficient, $C_D$, is equal to 0.32, the wall mode controls the primary instability in the finite wavelength regime. As soon as $C_D$ increases to 0.35, the surface mode governs the primary instability in the long-wave regime at low values of the surfactant Marangoni number. On the other hand, we see the existence of the unstable shear mode in the high Reynolds number regime when the inclination angle is small enough. The initiation of shear mode instability can be quickened by raising the thermal Marangoni number, while its initiation will be delayed if the surfactant Marangoni number goes up. Finally, we demonstrate that the primary instabilities induced by the surface mode and the wall mode may also appear in different ranges of $C_D$ due to the destabilizing impact of the thermal Marangoni number even when the Reynolds number approaches zero.

Two-level systems (TLS) are widely recognized as a dominant source of energy relaxation in superconducting qubits, limiting coherence times and device performance. While TLS-induced dissipation is often modeled as independent channels, interacting TLS can form finite many-body environments whose dynamical role in qubit relaxation remains insufficiently understood. Building on the information-erasure-based framework for irreversible thermalization developed in our previous work, we present a microscopic model and numerical simulations of a superconducting qubit coupled to a finite interacting many-body TLS environment as a concrete physical realization of this mechanism. We show that effective irreversible energy relaxation can emerge from intrinsic many-body dynamics without invoking external baths or phenomenological dissipation. The introduction of information erasure drives a transition from coherent oscillatory energy exchange to nonoscillatory exponential relaxation of the qubit. The relaxation times exhibit the scaling $T_1,T_2\propto J_{q,\tau }^{-2}$ with respect to the qubit-TLS coupling strength, consistent with Fermi's golden rule and Lindblad-type descriptions. Importantly, both exponential decay and its scaling behavior arise directly from microscopic many-body dynamics. These results provide quantitative insight into TLS-induced decoherence mechanisms and establish a microscopic link between information erasure, many-body thermalization, and irreversible relaxation in superconducting quantum systems.

Vacuum electron-positron pair production is investigated using the Dirac-Heisenberg-Wigner formalism in spatially inhomogeneous electric fields. The external field, given by $E(x,t){\mathbf{e}}_x$, exhibits a strong positional dependence and a strict spatial antisymmetry—i.e., $E(-x)=-E\left(x\right)$. Our results demonstrate that this antisymmetry fundamentally reshapes the pair-creation dynamics, yielding results that differ qualitatively and quantitatively from those obtained under spatially symmetric or fully asymmetric field configurations. We further analyze multipulse field profiles with systematically varied field separations and show that the separation distance exerts a decisive influence on both the integrated pair yield and the detailed structure of the momentum spectrum. Crucially, precise control over the relative spatial positioning of the fields proves essential for engineering desired features in the pair momentum spectrum. We also find that numerical results are in excellent agreement with the analytical approximation for both small and large separation distances. These findings provide robust theoretical guidance for optimizing vacuum pair production in experimentally accessible spatiotemporal field configurations and reveal dynamical effects arising specifically from spatial field antisymmetry.

Artificial spin ice provides a versatile setting for emergent gauge fields and magnetic monopole excitations. Here, we propose a driven-dissipative polariton realization of artificial spin ice, in which the circular polarization of each link mode plays the role of an Ising degree of freedom, while an auxiliary lossy vertex mode dynamically enforces a local ice-rule constraint. Adiabatic elimination of the vertex mode yields an effective spin ice penalty, favoring the two-in two-out manifold in the steady state. We show that local polarization flips generate monopole-antimonopole defects, and that sequential flips transport these defects across the lattice while defining a Dirac string. In an extended spin ice geometry, the vertex charges and their dynamics can be directly reconstructed from polarization-resolved real-space imaging. Our results establish polariton lattices as a controllable driven-dissipative platform in which local ice-rule constraints and monopolelike vertex defects can be generated, manipulated, and reconstructed through polarization-resolved optical measurements.

The fluctuations in the phonon vacuum state can lead to zero point density fluctuations in a material, which in turn lead to local zero point fluctuations of the dielectric properties of the material. We argue that the density fluctuations lead to a fluctuating force on a test charge, such as an electron, located a short distance outside of the material. This force is due to fluctuating dipole moments inside the material and produces Brownian motion of the electron. We calculate the mean squared velocity of the electron in both the normal and transverse directions relative to the boundary of the material. The result is nonzero in both directions, but larger in the normal case. We estimate the magnitude of this quantum Brownian motion and find that, in some cases, it can exceed the effects of both thermal motion and quantum momentum uncertainty. This suggests that the effect may be observable and could constitute a source of quantum noise in nanoscale devices. It also potentially offers a means to remotely sense zero point density fluctuations in a material.

Quantum networks enable forms of nonlocality beyond the standard Bell scenario, with a multitude of potential applications. Continuous-variable (CV) platforms are particularly attractive for large-scale networks, offering deterministic entanglement generation and favorable prospects for long-distance distribution. Here, we present a formalism to study CV network nonlocality using pseudospin measurements. Considering the linear chain and star configurations, we derive the maximal violations of the corresponding network locality inequalities for arbitrary two-mode states. Using two-mode squeezed vacuum states, we show that the strength of nonlocality in the star configuration remains independent of the network size. Moreover, the nonlocal correlations persist even at arbitrarily high temperatures provided the squeezing exceeds a critical threshold. Further, we demonstrate non-Gaussianity as an enhancer of network nonlocality through illustrations of various classes of non-Gaussian resources. Remarkably, a coherent superposition of single-photon subtractions across modes achieves maximal violation for arbitrarily small squeezing. Finally, we provide schematics of an experimentally feasible implementation of CV network nonlocality based on the isomorphism between pseudospin and spatial parity observables.

To overcome the fast oscillatory behavior of correlation functions for extracting scattering phase shift in real-time quantum simulations encountered in the work of Guo et al. [Phys. Rev. D 113, 054512 (2026)], we propose and test two solutions in the present work. One is to simulate Hermitian systems in imaginary time, and the other is to simulate non-Hermitian systems in real time. We demonstrate that both approaches lead to the problem of nonunitary quantum evolution that can be solved by combining two quantum algorithms: block encoding and Hadamard test. The combined quantum algorithm does not require midcircuit measurements or adjustment of the input parameters of the Hamiltonian and can be easily implemented on quantum computers. Numerical tests on quantum simulators show that both approaches agree with exact solutions for a sufficiently long time before the signal is lost in statistical fluctuations. The results bode well for using non-Hermitian and imaginary-time simulations to circumvent oscillations inherent in real-time simulation of other quantum systems. In particular, the non-Hermitian approach shows a decisive advantage over the imaginary-time one on the number of required ancillary qubits, and hence is more practical to scale up.

Quantum batteries can be charged by performing a work “instantaneously” in the limit of a large number of cells, achieving a so-called quantum advantage. In general, the work exhibits statistics that can be represented by a quasiprobability in the presence of initial quantum coherence in the energy basis. Here, we show that these two concepts of quantum thermodynamics, which apparently appear disconnected, can show a simple relation. Specifically, if a certain work distribution shows negativity asymptotically in the limit of a large number of cells and in a certain time interval, then we surely get a quantum advantage in the charging process. In particular, we prove this for a direct charging protocol performed with a class of charging Hamiltonian operators.