Axions are hypothetical particles that could address both the strong charge-parity problem in quantum chromodynamics and the enigmatic nature of dark matter. However, if axions exist, their mass remains unknown, and they are expected to interact very weakly with the electromagnetic field, which explains why they have not been detected yet. This study proposes a way to substantially augment the axion-photon interaction by confining the photons within high-quality-factor dielectric resonators, increasing their intensity and lifetime, and thus the possibility of interacting with axions in the background. In view of this, we study resonant axion-mediated photonic transitions in millimeter-sized spherical dielectric resonators, based on fully analytical calculations to the first order in perturbation theory. Such resonators exhibit high-lifetime Mie resonances in the microwave part of the spectrum, with a separation that can be tailored with the radius of the sphere to match the expected axion frequency, allowing axion-mediated photonic transitions when particular selection rules are fulfilled. We predict experimentally accessible axion mass regimes where such triply resonant transitions can be realized with standard dielectric resonators. We propose an experiment for probing such interactions named DARK-ROSE.

The theoretical understanding of conventional superconductivity as the phonon-assisted formation and condensation of two-electron Cooper pairs is a significant triumph in condensed matter physics. Here, we propose many-electron characterizations of higher-charge superconductivity with Cooper pairs consisting of more than two electrons, by implementing translation symmetrization on parent pair-density-wave-ordered states. In particular, we demonstrate many-electron constructions with vanishing charge-$2e$ sectors, but with sharp signatures in charge-$4e$ or charge-$6e$ expectation values instead. Such characterizations are consistent with previous phenomenology of vestigial order and Ginzburg-Landau theory. Furthermore, we demonstrate that at the microscopic level, momentum conservation alone may be vital and sufficient for the robust emergence of higher-charge superconductivity. Our study thus offers a general and microscopic route to understand and characterize higher-charge superconductivity, including nontrivial experimental signatures such as fractional magnetic flux and period in interferometry, as well as localized Cooper pairs at lattice topological defects.

A classical-limit formula is derived for matrix elements between bound states of distinct one-dimensional potentials. We leave open the physical interpretation of the potentials, but generally envision them to be Born-Oppenheimer-type potentials with the position variable $x$ identifying with a slowly evolving degree of freedom of the system. For instance, $x$ could represent the internuclear separation in a diatomic molecule, with the potentials being potential energy curves for different electronic states. In this scenario, the matrix elements could be, e.g., conventional Franck-Condon factors. To test the derived formula, we assume functional forms for the potentials and operator that afford analytical solutions for the matrix elements. As the classical limit is approached, the computed matrix elements exhibit a clear tendency toward the classical-limit formula, providing strong validation for the formula. In future work, we anticipate using the formula to model inhomogeneous excitation spectra of atoms in one-dimensional optical lattices, with an eye toward improved optical lattice clock performance.

Topological quantum computing promises intrinsic fault tolerance by encoding quantum information in non-Abelian anyons, where quantum gates are implemented via braiding. While braiding operations are robust against local perturbations, a critical yet often overlooked challenge arises when scaling beyond two qubits: the naive extension of braiding-based gates fails to support even the full Clifford group. To overcome this limitation, we incorporate projective measurements that enable transitions between different qubit encodings, thus restoring computational universality. We perform many-body simulations of braiding dynamics augmented with measurement-based switching, explicitly preparing the Bell state and Greenberger–Horne–Zeilinger state for systems of two and five qubits, respectively. Furthermore, we execute a random unitary circuit on five qubits, achieving a fidelity exceeding 99%. We analyze the circuit's robustness by studying its fidelity dependence on total braid duration and static potential disorder. Our results show that the fidelity remains above 99% for moderate disorder, underscoring the intrinsic fault tolerance of the architecture. Finally, we demonstrate a random circuit on a ten-qubit system to showcase the scalability of our techniques.

Photon-number-resolved detection with superconducting nanowire single-photon detectors (SNSPDs) attracts increasing interest, often focusing on the rising edge of the electrical signal as the main source of photon-number-resolving information. It remains unclear whether additional photon-number information is contained in the rest of the detector response and how this can be optimally extracted and interpreted. In this work, we combine principal component analysis (PCA) with readout at relatively low sampling rates to explore the photon-number-resolving capabilities of SNSPDs. We find that the information of the photon number is captured by a single principal component that closely resembles the time derivative of the average response trace. Using the time derivative of the average response trace provides an agnostic method to obtain the photon number from SNSPD traces without the necessity of performing PCA, making this method simple and quick to calibrate. As an auxiliary diagnostic, we use a distinguishability metric based on the Bhattacharyya coefficient [Indian J. Statistics 7, 401 (1946)] to quantify and compare the photon-number-resolving capabilities of different detector systems. Our analysis and interpretation of the principal components imply that photon-number resolution in SNSPDs can be achieved with moderate hardware requirements in terms of both sample rate (5 GS ${\mathrm{s}}^{-1}$) and analog bandwidth (3 GHz) and could be implemented in a field-programmable gate array, giving a highly scalable solution for real-time photon counting.

We develop a one-class, deep-learning framework to detect the phase transition and recover critical behavior of the three-dimensional (3D) Ising model. A 3D convolutional autoencoder (CAE) is trained on ground-state configurations only, without prior knowledge of the critical temperature, the Hamiltonian, or the order parameter. After training, the model is applied to Monte Carlo configurations across a wide temperature range and different lattice sizes. The mean-square reconstruction error is shown to be sensitive to the transition. Finite-size scaling of the peak location for the reconstruction error susceptibility yields the critical temperature $T_c=4.5128\left(58\right)$, in excellent agreement with the known value. Additionally, we obtain an estimate of the correlation-length critical exponent, $\nu =0.63\left(27\right)$, also consistent with results from the literature. Our results show that a one-class CAE, trained on zero-temperature configurations only, can recover nontrivial critical behavior of the 3D Ising model.

A metric is called universal if every symmetric conserved rank-two tensor constructed locally from the metric, the curvature, and covariant derivatives of the curvature is proportional to the metric. Such a metric solves arbitrary metric-based higher-curvature field equations after, at most, a change in the effective cosmological constant. A metric is called almost universal if the same field equations reduce instead to a finite set of algebraic conditions and a single linear scalar equation for a profile function. Universal and almost universal metrics are useful because they keep higher-curvature gravity under analytic control. Plane waves are a well-known example of universal metrics, while the Kerr-Schild-Kundt class of metrics including the $pp$ waves is almost universal. Here, we add a member to this class of metrics and show that nonzero constant curvature $pp$-wave metrics are also almost universal. They reduce the generic gravity field equations to those of cosmological Einstein-Maxwell theory with null dust. The background of the $pp$ waves has the topology ${\mathbb{R}}^{1,1}\times S^2$ and provides the missing partner to the Nariai metric with ${\mathrm{dS}}^2\times S^2$ and the Bertotti-Robinson metric with ${\mathrm{AdS}}^2\times S^2$ topologies. These quantum-protected metrics are of clear interest. We exemplify our results by using the quadratic and cubic gravity theories.

We study the spectral statistics and wave-function properties of a one-dimensional quantum system subject to a Cantor-type fractal potential. By analyzing the nearest-neighbor level spacings, inverse participation ratio (IPR), and the scaling behavior of the integrated density of states (IDS), we demonstrate how the self-similar geometry of the potential is imprinted on the quantum spectrum. The energy-resolved level spacings form a hierarchical, filamentary structure, in sharp contrast to those of periodic and random systems. The normalized level-spacing distribution exhibits a bimodal structure, reflecting the deterministic recurrence of spectral gaps. A multifractal analysis of eigenstates reveals critical behavior: The generalized fractal dimensions $D_q$ lie strictly between the limits of extended and localized states, exhibiting a distinct $q$ dependence. Consistently, the IPR indicates the coexistence of quasiextended and localized features, characteristic of critical wave functions. The IDS shows anomalous power-law scaling at low energies, with an exponent close to the Hausdorff dimension of the underlying Cantor set, indicating that the geometric fractality governs the spectral dimensionality. At higher energies, this scaling crosses over to the semiclassical Weyl law. Our results establish a direct connection between deterministic fractal geometry, hierarchical spectral statistics, and quantum criticality.

The impact of disorder on collective phenomena depends crucially on whether it is quenched or annealed. In synchronization problems, quenched disorder in higher-dimensional Kuramoto models is known to produce unconventional dimensional effects, including a striking odd-even dichotomy: Synchronization transitions are continuous in even dimensions and discontinuous in odd dimensions. In contrast, the impact of annealed disorder has received comparatively little attention. Here, we study a $D$-dimensional Kuramoto model with both fundamental and higher-harmonic interactions under annealed disorder, and develop an arbitrary-dimensional center-manifold framework to analyze the nonlinear dynamics near the onset of collective behavior. We show that annealed disorder fundamentally alters the role of dimensionality. With fundamental coupling alone, it completely removes the odd-even dichotomy, yielding continuous synchronization transitions with universal mean-field scaling in all dimensions. Higher-harmonic interactions preserve this universality while rendering the synchronization transition tunable between continuous and discontinuous. At the same time, they give rise to a correlation-driven transition between a symmetry-protected incoherent phase and a symmetry-broken state lacking global synchronization, which is therefore invisible to the conventional Kuramoto order parameter. This transition is continuous in two dimensions but discontinuous in higher dimensions, revealing an emergent and previously unrecognized special role of two dimensions.

We examine the mechanical and statistical-mechanical structure of interacting particle systems composed of zero-thickness rigid rods with fixed orientations. Despite strong geometric interactions imposed by nonintersection constraints, such systems are expected to exhibit ideal-gas equilibrium behavior, a fact that has not been established on rigorous grounds. We show that the collision dynamics defines a symplectic mapping on the reduced phase space of translational degrees of freedom, implying an impulsive Hamiltonian system that preserves Liouville measure and samples the standard equilibrium ensemble without invoking Dirac-type formulations. We further demonstrate that the virial contribution from collisions vanishes identically at the level of individual events, as a direct consequence of the collision geometry, so that the equation of state coincides exactly with that of an ideal gas, independently of density. These results place on firm theoretical footing assumptions made in earlier numerical studies and clarify how constrained collision dynamics can remain consistent with equilibrium statistical mechanics.

Conventional acoustic waveguides rely on sound-hard cladding layers to suppress crosstalk and radiation loss, raising fundamental limitations for integration. Here, we demonstrate that such constraints can be released by exploiting boundary-selective wave transport in a glide-symmetry-induced double-zero-index acoustic metamaterial. Waves incident on different boundaries perceive the same metamaterial as fundamentally distinct effective media: Along the glide-symmetric direction, it behaves as a double-zero-index medium that supports near-unity transmission, whereas waves incident on lateral boundaries meet a band-gap material due to the anisotropic equal-frequency contour. Such a media duality enables efficient forward transport and intrinsic lateral isolation between adjacent channels. Based on this mechanism, we demonstrate acoustic waveguides without sound-hard claddings and zero-spacing multichannel waveguide arrays with tiny crosstalk. Furthermore, compact waveguide configurations with sharp bends are achieved by combining metamaterial and air channels. Our results establish a general strategy for wave manipulation and may facilitate the development of integrated acoustic platforms.

Superpositions of orbital angular momentum (OAM) eigenstates form a continuous state space characterized by the complex coefficients of the constituent modes. When such OAM superposition states propagate through a random medium, they produce speckle patterns. The random granular speckle patterns encode the complete information of the original superposition states. This work demonstrates that the complex coefficients of an arbitrary OAM superposition can be retrieved from a single-shot speckle image. The extraction is performed using custom-designed regression model and is validated through both experimental measurements and numerical simulations. The method remains effective for superpositions of high-dimensional OAM eigenstates, including intensity-degenerate states, demonstrating that speckle can serve as a robust information carrier for state characterization.

Cooperative magnetic behavior in nanomagnet networks is governed by the interplay between exchange interactions and topology, offering routes for information transmission without charge flow. We show that a magnetic field can drive deterministic domain-wall propagation in a hierarchical, loop-free network, proceeding through a ladder of configurations. In a Cayley tree, an effective longitudinal field drives a competition between Zeeman energy and exchange frustration that reshapes the energy landscape, causing magnetization reversal to nucleate at the central node and propagate outward in quantized, layer-by-layer radial steps. This topology-controlled mechanism produces robust domain-wall motion that rapidly resynchronizes after local exchange inhomogeneities. The loop-free geometry precludes closed paths for circulating currents and magnetostatic feedback, enabling direct analysis of domain-wall nucleation and depinning energetics. The propagation reported here is thresholded and state based, with the field magnitude selecting when and whether the wall advances, stops, or reverses. These results establish hierarchical spin networks as minimal surrogate platforms for studying field-controlled propagation of discrete spin interfaces, and identify topology and boundary pinning as control parameters for thresholded magnetic information routing.

Atomic interactions play an important role in the properties of ultracold atomic gases. In single-component bosonic systems, its effect is already present at the critical point for the Bose-Einstein condensate phase transition by shifting it to lower temperatures as a consequence of effective repulsion between the atoms. When considering atomic bosonic mixtures, interesting effects arise from the competition between intra- and interspecies interactions such as the miscible-immiscible phase transition and the particular case of self-bounded quantum droplets. In such a scenario, it is natural to expect that these interactions will also affect the critical point of each species composing the mixture. In this paper, we obtain semianalytical expressions for the critical temperature shift of the phase transition to a Bose-Einstein condensate in the presence of a second species considering the mean-field framework. We treat differently the cases in which the second species is above or below its own critical temperature and apply the obtained relations to the case of a ${}^{23}\mathrm{Na}\text{−}{}^{39}\mathrm{K}$ bosonic mixture that can be realized in current running experimental setups. Our findings can be easily extended to other atomic mixtures.

We examine the interaction between floating cylindrical objects and surface waves in the gravity regime. Since the impact of resonance phenomena associated with floating bodies, particularly at laboratory scales, remains underexplored, we focus on the influence of the floats’ resonance frequency on wave emission. First, we study the response of floating rigid cylinders to external mechanical perturbations. Using an optical reconstruction technique to measure surface wave fields in both space and time, we study the natural resonance frequency of floats with different sizes. The results indicate that the resonance frequency is influenced by the interplay between the cylinder geometry and the solid-to-fluid density ratio. Second, these floating objects are placed in an incoming wave field. These experiments demonstrate that floats diffract incoming waves, while radiating secondary waves that interfere with the incident wave field. Minimal wave generation is observed at resonance frequencies. These findings can provide insights for elucidating the behavior of larger structures, such as sea ice floes, in natural wave fields.