Klein tunneling, a counterintuitive phenomenon where relativistic particles transmit through potential barriers with near-unity probability, has sparked extensive attention. In this work we demonstrate the anomalous Klein tunneling in the classical system of photonics in a T-graphene-like photonic crystal (TGPC), which is enabled by the triple-degenerate point (TDP) formed by a pair of Dirac-like linear branches and an additional quadratic branch in the TGPC. Unlike conventional Klein tunneling in Dirac system, the TGPC heterojunction not only exhibits broadband near-unity transmission, but also presents a robust and sharp dip at the TDP. Our theoretical model based on the multiple scattering theory accounts well for the phenomenon. In addition, TGPC exhibits unconventional refraction characteristics, which simultaneously shows positive and negative refraction at the interface with air. These findings enable alternative applications in tunable filtering and tailored optical waveguides and bridging quantum-inspired physics with photonic engineering.

In this paper, we will provide a complete derivation of the decoherence rate for a magnetic nanoparticle in quantum superposition in the presence of the fluctuating electromagnetic field in a thermal background by using the fluctuation-dissipation theorem in the long-wavelength limit. The long-wavelength limit assumes that the superposition size is much smaller than the wavelength of the electromagnetic-field fluctuations. We will extend this computation to two diamagnetic nanoparticles kept in quantum superposition adjacent to each other. We will also show how the drag force on a single nanoparticle arises from external electromagnetic-field fluctuations and compare our results with those for the nanoparticle's dielectric properties.

I develop a straightforward analytical framework for the propagation of spatial light modes through a turbulent atmosphere. Built upon the split-step approach with the mode-based optical field representation, it directly assesses how turbulence-induced phase fluctuations deplete the optical power in the original mode and redistribute it into neighboring spatial modes. Importantly, this power transfer is effectively a discrete diffusion process on a set of transverse modes, with the propagation distance serving as the evolution variable, yielding a simple solution for arbitrary distances in uniform channels in the form of a matrix exponential. The transfer rate is determined by the spatial spectral overlap between the turbulence spectrum and the acceptance spectrum for a pair of interacting spatial modes. The model predicts the average power in each spatial mode and is exact when a single mode strongly dominates all others. Our predictions show reasonably good agreement with simulations up to medium-to-strong turbulence levels. The model also confirms the scalings with mode order previously known from empirical observations.

We present a theoretical framework for the derivation of the $z$-directed total angular momentum density of a Bessel wave and of the corresponding intercepted angular momentum flux in an ideal perfectly absorbing disk model. Exact expressions for these quantities are obtained in both paraxial and nonparaxial regimes. We then analyze several experimentally relevant setups in the large-argument asymptotic of the Bessel functions. By varying the beam wavelength, polarization, and cone angle, we identify several distinct regimes of the intercepted angular momentum flux. Within the ideal absorber model, this intercepted flux may be identified with the corresponding mechanical torque. The results suggest potential applications for size-sensitive probing and controlled flux manipulation within the idealized macroscopic model.

Accurate quantum channel parameter estimation is essential for effective information reconciliation in continuous-variable quantum key distribution (CV-QKD). However, conventional maximum likelihood (ML) estimators rely on a large amount of disclosed data, leading to a significant loss in symbol efficiency. Moreover, the separation between the estimation and reconciliation phases can introduce error propagation. In this paper, we propose a joint message-passing scheme that unifies channel parameter estimation and information reconciliation within a Bayesian framework. By leveraging the expectation-maximization algorithm, the proposed method simultaneously estimates unknown parameters during decoding, eliminating the need for separate ML estimation. Furthermore, we introduce a hybrid multidimensional rotation scheme that removes the requirement for norm feedback, significantly reducing classical channel overhead. This work unifies multidimensional reconciliation and channel parameter estimation in CV-QKD, providing a practical solution for high-efficiency reconciliation with minimal information disclosure.

We study the Fano effect in dissipative cavity quantum electrodynamics (QED), which originates from the interference between the emitter's direct radiation and that mediated by a cavity mode. Starting from a two-level system coupled to a structured reservoir, we show that a quantum master equation previously derived within the Born-Markov approximation can be rederived by introducing a single auxiliary mode through the pseudomode approach. We identify the corresponding spectral function of the system-environment interaction and show that it consists of a constant contribution and a non-Lorentzian contribution, whose interplay gives rise to a spectral profile of the Fano form. The constant contribution represents a Markovian background and is essential for obtaining a Lindblad master equation. Furthermore, by applying Fano diagonalization to an atom-cavity system coupled to common and independent reservoirs, we independently derive the same spectral function and clarify its physical origin. Our results provide a unified description of the Fano effect in single-mode cavity QED systems and reveal its non-Markovian origin encoded in the spectral function of the structured reservoir.

Tripartite interactions have recently garnered significant interest owing to their potential in quantum information processing and quantum computation. In this work, we present a scheme for realizing a hybrid tripartite interaction between an atom and two cavities in the strong-driving regime. This tripartite interaction enables the deterministic generation of hybrid tripartite Greenberger-Horne-Zeilinger (GHZ) entangled states, the transfer of the atomic state to a two-cavity entangled state, and the construction of a controlled-phase gate between the two cavities. Our scheme requires only a single two-level coupler atom and a single-step operation, making the system architecture and protocol notably simple. As no auxiliary atomic levels are involved, decoherence caused by higher energy levels can be avoided. As an example, we investigate the experimental feasibility of generating the proposed hybrid GHZ state within a circuit QED system. The approach is broadly applicable and can be implemented in a wide range of physical systems, such as a two-level natural or artificial atom coupled to two optical or microwave cavities.

Identifying when observed statistics cannot be explained by any reasonable classical model is a central problem in quantum foundations. A principled and universally applicable approach to defining and identifying nonclassicality is given by the notion of generalized noncontextuality. Here, we study the typicality of contextuality, namely, the likelihood that randomly chosen quantum preparations and measurements produce nonclassical statistics. Using numerical linear programs to test for the existence of a generalized-noncontextual model, we find that contextuality is fairly common: even in experiments with only a modest number of random preparations and measurements, contextuality arises with probability over $99\%$. We also show that while typicality of contextuality decreases as the purity (sharpness) of the preparations (measurements) decreases, this dependence is not especially pronounced, so contextuality is fairly typical even in settings with realistic noise. Finally, we show that although nonzero contextuality is quite typical, quantitatively high degrees of contextuality are not as typical, and so large quantum advantages (like for parity-oblivious multiplexing, which we take as a case study) are not as typical. We provide an open-source toolbox that outputs the typicality of contextuality as a function of tunable parameters (such as lower and upper bounds on purity and other constraints on states and measurements). This toolbox can inform the design of experiments that achieve the desired typicality of contextuality for specified experimental constraints.

Searching for degenerate ground spaces in quantum many-body systems is central to understanding spontaneous symmetry breaking and topological order. Although existing numerical methods can approximate individual ground states with high accuracy, recovering the full degenerate space remains a substantial challenge. Here, we address this problem using a hybrid generative quantum circuit that combines a classical generative model with an expressive parametrized quantum circuit (PQC). The classical model learns a distribution over PQC parameters, enabling the generation of an ensemble of ground states, while the PQC ensures compatibility with quantum hardware. To promote both low energy and state diversity, we define an energy-diversity objective composed of an energy-minimization term and cosine-similarity penalties derived from local observable correlators. These local descriptors provide a scalable, measurement-efficient means of distinguishing different ground-state directions. We benchmark the framework on the Majumdar-Ghosh model, the Affleck-Kennedy-Lieb-Tasaki model, and the spin-1 XXZ chain, which realize distinct mechanisms of degeneracy. In all cases the method produces diverse ensembles whose linear spans accurately reproduce the target ground spaces, and in some instances it identifies approximately orthogonal bases within the learned ensembles. Finite-shot simulations on small MG chains further show that the training protocol remains stable under sampling noise, preserving the recovered ground-space span.

We study quantum controllability under finite control resources using a multiobjective optimization perspective. By numerically constructing the feasibility boundary (Pareto front) in the resource space spanned by pulse energy and control duration, we identify the physical factors that determine this boundary. In particular, we examine the shortest control duration $T^{*}$ extracted from the boundary, below which the target fidelity cannot be achieved even with unbounded pulse energy. Using representative two- and three-level examples, we show that a finite $T^{*}$ can originate from diagonal coupling terms, small energy gaps, and relative-phase requirements in wavepacket formation, and that these limitations are not necessarily captured by conventional quantum-speed-limit arguments.

Vibrational excitations of the CH molecule are critical for understanding the kinetics of the interstellar medium, stellar atmospheres, and plasma-assisted combustion. Building upon previous $R$-matrix calculations—which characterized the $X{}^2\mathrm{\Pi }$ and $a{}^4{\mathrm{\Sigma }}^{-}$ electronic states of CH and the ${}^1{\mathrm{\Sigma }}^{+}, {}^3\mathrm{\Pi }$, and ${}^5{\mathrm{\Sigma }}^{-}$ resonant states of ${\mathrm{CH}}^{-}$—this study evaluates cross sections and rate coefficients for electron-impact vibrational excitation using the local complex potential method. State-to-state formalism is used to analyze electron-vibration energy exchange. Our results demonstrate that electron-driven processes provide non-negligible contributions to nonequilibrium kinetic modeling.

The sensitivity of experiments searching for the electron electric-dipole moment ($e\mathrm{EDM}$) using the symmetric top molecules can be greatly enhanced by laser cooling. A detailed understanding of the Zeeman structure of the $e\mathrm{EDM}$-sensitive levels is crucial for controlling systematic effects. We develop a method for calculating the $g$ factors of $K$-doublet levels in symmetric top molecules and apply it to ${\mathrm{RaOCH}}_3$. The electric-field-dependent $g$ factors of the first excited rotational level of ${\mathrm{RaOCH}}_3$ are calculated. We find that the $K$ doublet with a total angular momentum projection $M_F=2$ has a ratio $\mathrm{\Delta }g/g\sim {10}^{-6}$ for an electric field in the range from 500 mV/cm to 1 V/cm, where $\mathrm{\Delta }g$ is the difference in the $g$ factors for the $K$-doublet components.

We investigate the nonadiabatic quantum dynamics of ultralong-range Rydberg molecules using a vibronically coupled two-channel treatment. The two channels are composed of coupled trilobite and butterfly electronic states, formed as a result of $S$-wave and $P$-wave scattering of high angular momentum Rydberg electrons with perturbing ground state atoms. Within the Born-Oppenheimer treatment, the $P$-wave scattering channel introduces an adiabatic decay pathway that affects the stability and lifetimes of trilobite states. Our numerical results show that the vibronic coupling is dependent on the principal quantum number $n$, and for certain $n$ there is nonadiabatic stabilization against internal molecular decay, facilitating previously studied dynamical effects in pure trilobite molecules. Apart from the internal diffraction effect caused by the backscattering of vibrational wavepackets from the trilobite potential, we also observe interesting multiwell tunneling effects during low-energy oscillations for a range of $n$ values. Our work serves to highlight the fact that the unique vibrational coordinate dependent electronic structure of these polar molecules, along with high-level densities, promises many exciting dynamical effects.

Photoassociation of $5snd {}^1{D}_2-5s^2 {}^1{S}_0$ ultralong-range Rydberg dimers from an ultracold ${}^{84}\mathrm{Sr}$ atomic gas in a magnetic field is studied. In the absence of magnetic fields, the electronic wave function is aligned along the rotating molecular axis through electron-atom scattering. With increasing magnetic field strength, the symmetry axis of the electron wave function becomes determined by the applied field. While the ground-state atom has no spin or net charge to interact directly with the magnetic field, the dimer wave function in the limit of strong magnetic field becomes aligned along the applied field. Photoassociation spectra show that with increasing field, an increasing number of rovibrational states are excited, indicating strong coupling between rotational states within the Rydberg dimer.

Neutral-atom quantum simulation is susceptible to entanglement between the atom's internal electronic state and its center-of-mass position. In many alkali Rydberg platforms, the ‘‘spin-motion coupling’’ is exacerbated by the free expansion required to avoid ponderomotive antitrapping from optical fields. A recent proposal [Phys. Rev. A 111, 053120 (2025)] claims sufficiently excited Rydberg states could be trapped in a monochromatic, far-detuned, circularly polarized optical field via a large vector polarizability. We disprove the proposal through analytic calculation and measurement of the vector polarizability of the $54S, 54P$, and $53D$ orbitals of Cesium. We analytically derive that the real scalar, vector, and tensor polarizabilities scale with optical angular frequency $\omega$ as ${\omega }^{-2}, {\omega }^{-3}$, and ${\omega }^{-4}$, not the proposed scaling of ${\omega }^{-2}, {\omega }^{-1}$, and ${\omega }^{-2}$. We refine the sum-over-states expression to be numerically stable for optical frequencies and predict negligible vector and tensor polarizabilities far detuned from resonances, in agreement with our measurements. However, we find that vector polarizability can enhance near-detuned attractive trapping [Phys. Rev. A 112, L041101 (2025)]. Furthermore, we evaluate the breakdown of the electric-dipole approximation and derive no effect stronger than ponderomotive repulsion. We conclude that an attractive, monochromatic, far-detuned optical trap for alkali Rydberg states is not possible, regardless of the beam geometry.

Decoherence and dissipation in open quantum systems generally drive quantum batteries toward passive states, thereby reducing their extractable work (ergotropy). Here, we study a driven qubit quantum battery coherently coupled to an auxiliary harmonic oscillator in the presence of dephasing and dissipation. Using the differential formulation of the first law of open quantum thermodynamics, we analyze the local energy-flow dynamics during the charging process. We find that the auxiliary oscillator induces a transient negative local energy current into the qubit subsystem, corresponding to a temporary inward energy backflow. This transient energy redistribution is accompanied by an enhancement of the qubit ergotropy and a partial suppression of decoherence-induced passivation. Moreover, the parameter regime exhibiting a more pronounced negative-current interval is consistently correlated with larger ergotropy enhancement. Our results suggest that transient inward energy flow provides a useful thermodynamic signature associated with enhanced energy storage in open quantum batteries.

Dipole condensates, formed from particle-hole pairs, represent a unique class of charge-neutral quantum fluids that evade conventional vector gauge fields, making their electrodynamic responses difficult to probe in natural materials. Here, we propose a tunable platform using strongly interacting two-component ultracold atoms to realize dipole condensates and probe their coupling to rank-2 electric fields. By applying spin-dependent forces and treating spin as a synthetic dimension, we engineer a synthetic rank-2 electric field that induces measurable electrodynamic responses. We identify the atomic analog of perfect Coulomb drag: increasing intercomponent interactions leads to equal and opposite displacements of the centers of mass of the two spin components. Furthermore, a rank-2 electric field imprints a phase twist in the dipole condensate and generates a supercurrent of dipoles that obeys the dipolar Josephson relation—a smoking gun for dipole condensation. Our results establish a powerful platform for exploring dipolar superfluidity under tensor gauge fields.

The skin effect is a phenomenon characterized by the exponential localization of wave functions at a boundary in non-Hermitian topological systems, demonstrating potential applications in the field of quantum information. Here we explore its application in optimizing the performance of quantum energy-storage devices. We employ the Hatano-Nelson chain as a non-Hermitian topological charger to concentrate energy on one side of the coupled quantum energy-storage devices via the skin effect. Numerical results indicate that compared to the ordinary charger, the non-Hermitian topological charger surpasses the thermal mean photon number limit, leading to a significant increase in both the charging power and steady-state stored energy of the quantum energy-storage device. By enhancing the asymmetric coupling strength within the non-Hermitian topological charger, the stored energy of quantum energy-storage devices can be elevated. As the number of harmonic oscillators in the charger increases, the storage energy rises accordingly. In particular, under a purely rightward coupling configuration in the non-Hermitian topological charger, the stored energy in the quantum energy-storage device scales linearly with the number of harmonic oscillators. Additionally, since the composite system formed by the non-Hermitian topological charger and the quantum energy-storage device is itself a non-Hermitian topological system, it exhibits strong robustness against parameter disorder during the charging process. The proposed model can be implemented on various quantum platforms and holds enlightening significance for the research on high-performance quantum energy-storage devices.

While ideal lattice models have been widely used to study giant-atom systems, fabrication-induced imperfections inevitably introduce disorder in realistic platforms. Here, we study the non-Markovian dynamics of a giant atom coupled to a discrete photonic lattice with static on-site frequency disorder. Using time-domain and spectral analyses, we find that the overall population-decay envelope and global photon-transport patterns remain qualitatively robust within the explored disorder range, while the accumulated non-Markovianity shows a modest overall increasing trend with disorder. We characterize the information backflow using a cumulative normalized geometrical non-Markovianity measure and show that the coupling-point separation primarily determines the feedback delay timescale, whereas the disorder strength provides a weaker modulation of the accumulated backflow. The overall spectral structure remains qualitatively similar in the ordered and disordered lattices, with only small disorder-induced shifts in some of the out-of-band branches. The representative real-space profiles of the selected out-of-band states also remain qualitatively similar, with only minor quantitative changes. These observations are consistent with the relatively small disorder-induced changes in the delayed-revival dynamics. Our results provide a disorder-aware description of non-Markovian giant-atom dynamics in structured reservoirs.