Multimode squeezing and entanglement are important resources in quantum metrology and sensing. For spin-1/2 Bose-Einstein condensates subject to spin-orbit coupling (SOC), previous studies on spin squeezing have been limited to two-mode systems. In this work, we demonstrate that such a system can naturally construct a four-mode model spanning an $\text{su}\left(4\right)$ algebra with six SU(2) subspaces. Using spin squeezing parameters and quantum Fisher information matrices, we analyze the dynamical evolution of coherent spin states. The results show that, beyond two-mode models, the SOC-induced four-mode couplings give rise to richer entanglement-enhanced sensing approaching the Heisenberg limit across various SU(2) subspaces. Additionally, by tuning a single system parameter (the Raman Rabi frequency), one can selectively control the optimal measurement across different subspaces.

This paper predicts the spiral-like beams based on the effective mass tensor by extending the diametric drive acceleration mechanism to a two-dimensional local photonic lattice. Such spiral-like beams differ from conventional optical rotation mechanisms that rely on orbital angular momentum, spin-orbit coupling, or exotic materials. Instead, they arise from the combined effects of anisotropic effective mass properties and the optical Kerr effect, without requiring conventional angular momentum or chiral media. Numerical simulations show that the specific beam combinations, such as $\mathrm{\Gamma }\text{−}X$ and $M\text{−}X$, can induce spiral-like motion under both self-focusing or self-defocusing conditions. This study breaks through the physical constraints of existing optical rotation mechanisms, highlighting the crucial role of effective mass in optical field dynamics.

This report presents a theoretical demonstration of a bistable quartic soliton (BQS) in saturable nonlinear media, specifically within a realistic dispersion-engineered ridge waveguide made of lithium niobate (${\text{LiNbO}}_3$). The study employs the variational method to establish the amplitude-width relationship, indicating the coexistence of stable solitons with the same duration but differing amplitudes. The impact of shock on the bistable soliton is examined through perturbative variational analysis, supported by numerical results. Additionally, we examine the interaction of BQS in different regimes and analyze the formation of the bound state. The robustness of the BQS under perturbations is further investigated via linear stability analysis.

We report stable composite vortex solitons in the model of a three-dimensional photonic crystal with the third-harmonic (TH) generation provided by the quasi-phase-matched quadratic nonlinearity. The photonic crystal is designed with a checkerboard structure in the $\left(x\text{,}y\right)$ plane, while the second-order nonlinear susceptibility, $d\left(z\right)$, is modulated along the propagation direction as a chain of rectangles with two different periods. This structure can be fabricated by means of available technologies. The composite vortex solitons are built of fundamental-frequency (FF), second-harmonic (SH), and TH components, exhibiting spatial patterns which correspond, respectively, to a vortex with topological charges $s=1$, a quadrupole emulating $s=2$, and an antivortex with $s=-1$ in these components (due to the system's symmetry, the latter value is actually tantamount to $s=3$). Soliton profiles feature rhombic or square patterns, corresponding to phase-matching conditions ${\phi }_d(x,y)=0$ or $\pi$, respectively, the rhombic solitons possessing a broader stability region. From the perspective of the experimental feasibility, we show that both the rhombic and square-shaped composite vortex solitons may stably propagate in the photonic crystals over distances of up to 1 m. The TH component of the soliton with $s=\mp 1$ is produced by cascaded nonlinear interactions, starting from the FF vortex component with $s=\pm 1$ and proceeding through the quadrupole SH one. These findings offer a previously unexplored approach to the creation of stable vortex solitons in nonlinear optics.

We propose a reconfigurable polaritonic platform based on a liquid-crystal (LC)-filled microcavity with embedded excitonic layers, enabling selective control over multiple polariton field distributions within a single structure. In earlier work we used a similar LC geometry for polarization-encoded confinement of two polariton modes [Sedov and Kavokin, Phys. Rev. A 112, 013504 (2025)]. Whereas the previous scheme was limited to two polarization-selected modes, the present approach harnesses the LC's externally tunable birefringence to program spatial potentials for multiple modes. The system leverages LC-induced anisotropy to tune the photonic component and spatially structured excitonic layers to modulate light-matter interaction. Using topology optimization, we design stationary potentials that reshape the spatial profiles of distinct polariton modes depending on the orientation of the LC molecules. Our approach allows for mode-selective control and supports versatile polariton field reconfiguration in a single compact structure, highlighting a pathway toward programmable polaritonic architectures.

Although pure-quartic fiber lasers exhibit diverse soliton dynamics, the multistage evolution and controllability of vector dissipative pure-quartic solitons remain underexplored. We show that increasing the saturable energy enhances the spectral group delay near the frequency edges via positive fourth-order dispersion, breaking phase equilibrium and triggering a cross-phase-modulation-induced energy imbalance between polarization components. This, combined with modulation instability, leads to spectral collapse and transition into noise-like pulses. Remarkably, precise tuning of the polarization controller enables reversible switching back to the vector dissipative pure-quartic soliton state. We further employ mutual information and Pearson correlation analysis to quantify spectral coherence and verify deterministic chaos in noise-like pulses via Poincaré sections and Grassberger-Procaccia dimensions. These results offer insight into nonlinear dynamics and controllable state transitions in high-order-dispersion fiber lasers.

An ongoing debate surrounding the intrinsic transverse orbital angular momentum (OAM) attributed to spatiotemporal optical vortex (STOV) light pulses has raised the energy and photon-density centroids as two alternative frameworks to define the center of a free electromagnetic wave packet. We herein derive, within a single formalism, lowest-order expressions for the positions and velocities of both centroids, directly applicable to an arbitrary scalar, near-paraxial, and quasimonochromatic pulse envelope formulated in space-time. Examining pulses with structures including temporal chirp, wavefront rotation, Gaussian-type STOVs, and tilted lobulated profiles, we illustrate general principles underlying the shifts and propagation dynamics of the two centroids and discuss how these properties underpin the value and conservation of intrinsic OAM referenced to either centroid. Finally, despite widespread use of the notion of intrinsic OAM per photon, we argue that in neither framework could individual STOV photons be said to carry a well-defined quantum of intrinsic transverse OAM, as such quantities do not read as expectation values of a single operator for which STOV states could form a basis of orthogonal eigenmodes. This contrasts with the well-established quantization scheme for the total longitudinal OAM of light in spatial vortex beams, bearing implications for the interpretation of future experiments involving STOV pulses in quantum optics, nonlinear wave-mixing, or light-matter interactions.

Bipartite and multipartite quantum steerings are significant resources for various quantum tasks such as ultrasecure multiuser quantum networks, one-site-trusted quantum communication, and high-fidelity quantum computation. A flexible steering manipulation scheme of five down-converted Hermitian Gaussian modes generated from an optical parametric oscillator using a spatial structured pump is presented. In our scheme, not only the direction and types of the bipartite steering, but also different situations of multipartite steering can be manipulated effectively, by adjusting the pump proportions with a spatial light modulator. In addition, stricter genuine pentapartite steering (only one site is trusted) can also be achieved by making the pump proportions as balanced as possible. Our scheme is versatile and experimentally feasible and offers new insights into the manipulation of steering, especially multipartite steering, which is valuable in many special quantum tasks.

We study the modification to the energy level shifts of an atom induced by the quenched monopolar charge disorder inside the bulk of neighboring dielectric slabs as well as their surfaces. By assuming that the charge disorder follows Gaussian statistics with a zero mean, we find that the disorder generally results in a downward shift of the energy levels, which corresponds to an attractive force that can compete with and overcome the nonresonant Casimir-Polder force for sufficiently large atom-surface separations $z_0$. For an atom near a single semi-infinite slab with bulk (surface) charge disorder, the shift decays as $z_0^{-1}$ $\left(z_0^{-2}\right)$. For both surface and bulk disorder, the shift is proportional to the variance of the charge disorder density. In addition, we investigate the behavior of the charge disorder-induced energy level shift for an atom confined to a vacuum gap between two coplanar and semi-infinite slabs of the same dielectric material, finding that the position of net zero disorder-induced force occurs closer to the surface of the slab with the smaller charge disorder variance.

Achieving a high population of antihydrogen and hydrogen atoms in the $2S$ level is essential for spectroscopy measurements testing similarities between matter and antimatter. We propose and examine the efficiency of applying the STIRAP (stimulated Raman adiabatic passage) process in achieving high population transfer from the $1S$ to the $2S$ levels. We utilized a circularly polarized Lyman alpha (Ly-$\alpha$) pulse to couple the $1S$ state to the $2P$ state and a microwave pulse to couple the $2P$ state and the $2S$ state. We calculate the efficiency of the STIRAP process for transferring the population between the stretched states $(1S_d,2S_d)$ as a function of experimental parameters such as Rabi frequencies and pulse durations. We find that a Ly-$\alpha$ pulse with an energy of a few nanojoules could produce nearly perfect transfer at zero detunings for atoms on the laser beam axis. We extended the analysis to a thermal ensemble of atoms, where Doppler detuning affects the velocity distribution of the hydrogen atoms produced in the $2S$ level. We found that the width of such velocity distribution is controlled by the Rabi frequency. We show that the peak velocity of the hydrogen atoms in the $2S$ level after STIRAP can be controlled by the Ly-$\alpha$ pulse detuning. The efficiency of STIRAP in transferring population increases at low temperature ($T\sim 1\mathrm{mK}$). Finally, we show that a background magnetic field improves the transfer rates between the other trappable states $(1S_c,2S_c)$.

In one-dimensional waveguide quantum electrodynamics systems, quantum emitters interact through infinite-range, dispersive, and dissipative dipole-dipole interactions mediated by guided photonic modes. These long-range periodic interactions give rise to rich many-body physics absent in free space. In this work, we construct a set of symmetrized multiexcitation dark states and derive analytic expressions for their time-evolution projections. This framework captures the essential dynamics of excitation transport and storage while significantly reducing computational complexity compared to full master equation simulations. Our analysis reveals a fundamental bound on energy redistribution governed by the structure of dark states and collective dissipation and discovers that optimal excitation transfer between emitter ensembles converges toward an initial pumped fraction of $N_{\text{p}}/N\approx 0.55$ for large system sizes. We further examine the robustness of this mechanism under realistic imperfections, including positional disorder, nonradiative decay, and dephasing. These results highlight the role of many-body dark states in enabling efficient and controllable energy transfer, offering new insights into dissipative many-body dynamics in integrated quantum platforms.

We construct a pairwise measurement-based code on eight qubits that is error-correcting for circuit noise, with fault distance 3. The code can be implemented on a subset of a rectangular array of qubits with nearest-neighbor connectivity of pairwise Pauli measurements, with a syndrome extraction circuit of depth 28. We describe fault-tolerant logical operations on patches of this eight-qubit code that generate the full Clifford group. We estimate the performance under circuit noise both during logical idle and during a logical two-qubit measurement. We estimate the pseudothreshold to be between ${10}^{-5}$ and $2\times {10}^{-4}$, depending on the amount of noise on idle physical qubits. The use of postselection in addition to error correction (correcting all degree-one faults and rejecting a subset of the higher degree faults) can improve the pseudothreshold by up to an order of magnitude.

Only a few states in high-dimensional systems can be identified as (un)steerable using existing theoretical or experimental methods. We utilize semidefinite programming (SDP) to construct a dataset for steerability detection in qutrit-qutrit systems. For the full-information feature $F_1$, artificial neural networks achieve high classification accuracy and generalization, and perform better than the support vector machine. As feature engineering plays a pivotal role, we introduce a steering ellipsoidlike feature, $F_2$, which significantly enhances the performance of each of our models. To address quantum steering detection in isotropic states, partially entangled states, and random states, we explore, respectively, the most tailored feature and classifier. Given that the SDP method provides only a sufficient condition for steerability detection, we establish the first rigorously constructed, accurately labeled dataset based on theoretical foundations. This dataset enables models to exhibit outstanding accuracy and generalization capabilities, independent of the choice of features. As applications, we investigate the steerability boundaries of isotropic states and partially entangled states, discover new steerable states, and determine their parameter ranges. This work not only advances the application of machine learning for probing quantum steerability in high-dimensional systems but also deepens the theoretical understanding of quantum steerability itself.

Precise estimation of the atomic resonance frequency is fundamental for the characterization and control of quantum systems. The resonance experiment is a standard method for this measurement, wherein the drive field frequency is swept to invert the system population. We analyze the classical and quantum Fisher information for the resonance experiment driven by hyperbolic-secant-shaped $\pi$ pulses, setting a fundamental limit on the precision obtainable using the resonance method. We show that measurements using sequences of pulses with alternating phases nearly saturate the quantum Cramér-Rao bound, improving the precision of atomic resonance frequency measurements.

We report on a precision measurement of the ${\left(5p\right)}^{5}6p{[1/2]}_0\leftarrow {\left(5p\right)}^6{}^{1}S_0$ transition wave number of Xe by Doppler-free two-photon spectroscopy using near-Fourier-transform-limited long pulses of UV-laser radiation. The measurements led to absolute uncertainties of 750 kHz in the two-photon transition wave numbers for the five dominant isotopes of Xe, e.g., 80 118.982 918(27) ${\mathrm{cm}}^{-1}$ for ${}^{136}\mathrm{Xe}$. These values were combined with other precision measurements in Xe to resolve an $\sim 1\text{−}\mathrm{GHz}$ discrepancy between the ionization energy of Xe obtained in recent measurements from the $\left(6s\right){[3/2]}_2$ metastable state [Herburger et al., Phys. Rev. A 109, 032816 (2024)] and the ionization energy listed in the NIST atomic database. The analysis indicates that the natural-abundance-weighted ionization energy of Xe should be revised by $-0.023{\mathrm{cm}}^{-1}$ to 97 833.7641(20) ${\mathrm{cm}}^{-1}$. Large fluctuations in the UV-laser pulse intensities were exploited to characterize intensity-dependent shifts of the observed two-photon transition frequencies. Shifts of up to $-20\mathrm{MHz}$ were observed and attributed to frequency shifts arising from chirps in the amplification and up-conversion of the laser radiation rather than to the ac-Stark effect.

Barium monofluoride (BaF) is a promising molecular species for precision tests of fundamental symmetries and interactions. We present a combined theoretical and experimental study of BaF spectra and isotope shifts, focusing in particular on the poorly understood odd isotopologues ${}^{137}\mathrm{BaF}$ and ${}^{135}\mathrm{BaF}$. By comparing state-of-the-art ab initio calculations with high-resolution fluorescence and absorption spectroscopy data, we provide a benchmark for electronic structure theory and disentangle the hyperfine and rovibrational spectra of the five most abundant isotopologues, from ${}^{138}\mathrm{BaF}$ to ${}^{134}\mathrm{BaF}$. The comprehensive knowledge gained enables a King plot analysis of the isotope shifts that reveals the odd-even staggering of the barium nuclear charge radii. It also paths the way for improved laser cooling of rare BaF isotopologues and crucially supports future measurements of nuclear anapole and Schiff moments.

High-precision molecular experiments testing the Standard Model of particle physics require an accurate understanding of the molecular structure at the hyperfine level, both for the control of the molecules and for the interpretation of the results. In this work, we calculate the hyperfine structure constants for the excited states ${}^2\mathrm{\Pi }_{1/2}$ and ${}^2\mathrm{\Pi }_{3/2}$ of ${}^{137}\mathrm{BaF}$ due to the ${}^{137}\mathrm{Ba}$ nucleus. We use the four-component relativistic Fock-space coupled-cluster method, extrapolating our results to the complete basis set limit. We investigate the effect of the basis sets and electron correlation, and estimate the uncertainty in our final results. Our results are used in the interpretation of the experimental spectroscopy of the hyperfine and rovibrational spectra of BaF, and the planning of laser-cooling schemes for future parity-violating anapole moment measurements [Kogel et al., Phys. Rev. A 112, 042807 (2025)].

Combined experimental and theoretical studies are performed on the elastic scattering and electron-impact ionization of ammonia $\left({\mathrm{NH}}_3\right)$ in the energy range of $30\mathrm{eV}$ to $1\mathrm{keV}$. Differential elastic scattering cross sections are measured across an angular range of $5^{\circ }$ to ${150}^{\circ }$, while doubly differential ionization cross sections were measured in the angular range of ${30}^{\circ }$ to ${135}^{\circ }$, with secondary electron energies ranging from $5\mathrm{eV}$ up to about half the primary electron energy. In parallel with the measurements, theoretical calculations of differential elastic scattering and doubly differential ionization cross sections of ${\mathrm{NH}}_3$ are performed using the $\mathrm{IAM}\text{−}\mathrm{SCAR}+\mathrm{I}$ approach, the polydcs code, and the distorted wave Born approximation. Reasonably good agreement is observed between the present experimental results and theoretical predictions. Total ionization cross sections, derived by integrating the experimental doubly differential ionization cross sections over the emission angle and secondary electron energies, show excellent agreement with theoretical values obtained using the Binary-Encounter-Bethe model with rescaled orbital binding and mean kinetic energies, and are consistent with experimental data measured by another group using a different method. As a final validation, the sum of the total elastic and ionization cross sections is compared with the recommended total electron scattering cross sections, confirming the consistency of the present experimental results.

We have applied a semiclassical impact-parameter close-coupling method to calculate the state-resolved excitation cross sections in proton collisions with the ground state of helium. Using both correlation-configuration and frozen-core two-electron basis functions, we construct a large number of helium pseudostates to use in the expansion of the total scattering wave function. Extensive convergence studies show that the present results are accurate to within a few percent. The present cross sections for transitions from the ground state into all $n\le 5$ states for the ${}^{1}S,{}^{1}P,{}^{1}D,{}^{1}F$, and ${}^{1}G$ symmetries agree very well with experimental data where available. This work serves to provide a comprehensive set of excitation cross sections that were previously available only in narrow energy regions and for some channels. Furthermore, we present elastic-scattering, total excitation, and total electron-loss cross sections from 2 to $2000\mathrm{keV}$. We conclude that with modern supercomputer technology, a single-center method can accurately model ${\mathrm{p}}^{+}+\mathrm{He}$ collisions through implicit inclusion of the electron-capture process via coupling to the large number of positive-energy pseudostates representing the continuum.