ABSTRACT Multifunctional metasurfaces, a type of artificial two‐dimensional material, enable simultaneous or switchable modulation of electromagnetic radiation's multiple degrees of freedom through elaborate subwavelength periodic/aperiodic structure design, with applications in communications, imaging, and sensing. However, existing ones face difficulties in precisely modulating narrowband/broadband modes, both limited by low Q‐factors. Here, we present a polarization‐insensitive multifunctional switchable metasurface enabled by a vanadium dioxide (VO 2 )/graphene/diamond heterostructure. We demonstrate that flexible switching of the metasurface between narrowband and broadband modes can be achieved by precisely tuning the Fermi level of the upper graphene layer and the electrical conductivity of the lower VO 2 . The Q‐factors of two narrowband peaks reach 32.7 and 41.9, which are significantly higher than previously reported values. Furthermore, tailoring the gap between adjacent graphene disks can facilitate the achievement of BIC and quasi‐BIC within the system. In addition, we also demonstrate that systematic optimization of key parameters, including geometric structure, chemical potential, and carrier relaxation time, enables the multifunctional metasurface to achieve robust impedance matching with free space, coupled with a large angular tolerance and remarkable polarization insensitivity. This multifunctional metasurface holds considerable potential for applications in spectral sensing, terahertz filtering, and electromagnetic interference (EMI) shielding devices.
ABSTRACT We study the distribution of quantum imaginarity in Schwarzschild spacetime under Hawking radiation via imaginarity steering functionals. For bipartite systems, we analyze Werner states and general two‐qubit X‐states and find that the steering functional of physically accessible states decreases monotonically with Hawking temperature, shrinking the steerable region, whereas physically inaccessible states remain unsteerable for all temperatures. For multipartite systems, we consider general three‐qubit pure states up to local unitary equivalence and show that Hawking radiation induces a family of monogamy‐like steering inequalities with temperature‐independent bounds determined by subsystem accessibility. The corresponding maximal sum of imaginarity steering functionals decreases as the Hawking temperature increases when both subsystems are accessible, remains invariant when only one subsystem is inaccessible, and increases when both subsystems are inaccessible. These results reveal how Hawking radiation reshapes the distribution of imaginarity in relativistic spacetime.
ABSTRACT This work reports first‐principles studies of structural, electronic, elastic, mechanical, phononic and electron–phonon interaction properties for the simple tetragonal P4/mbm and P4 2 /mmc structures of (Ln = Y, Lu, and La) in comparison with a base‐centered orthorhombic Cmmm structure of . Extensive analysis establishes both the mechanical and dynamical stability of all studied compounds, evidenced by detailed calculations of elastic constants and phonon dispersion spectra. Calculated Vickers hardness values reach up to 18.77 GPa, identifying as a promising candidate for wear‐resistant coatings and cutting tools. The study further evaluates the polycrystalline bulk modulus, shear modulus, Young's modulus and Poisson's ratio, demonstrating significant anisotropy in these systems. Electronic structure calculations show that all the studied compounds are electrically conductive, and the contribution to the electrical conductivity comes from Ln d electrons as well as p electrons of B and C atoms. Finally, electron–phonon interaction calculations reveal for the first time that is a weakly coupled superconductor with a transition temperature of 1.25 K and a small electron–phonon coupling parameter of 0.429. Overall, the study provides the microscopic mechanisms governing mechanical and superconducting properties of and .
ABSTRACT The impact of the concurrent presence of Kerr nonlinearity and balanced gain/loss on picosecond pulse propagation in twin‐core AlGaAs waveguides is investigated under negligible dispersion using the Split‐Step Fourier Method. This dual influence establishes a mechanism for controlling the longitudinal length at which the excited pulse breaks, termed the breaking length. For a fixed input power, a reduction in the balanced gain/loss transforms a breaking pulse with a broad, noisy spectrum into a normal pulse with a narrow spectrum through intermediate states of simultaneous splitting in both cores and splitting confined to one core. Conversely, increasing the coupling coefficient at constant gain/loss and input power also drives this transition. Therefore, balanced gain/loss serves as a control parameter to regulate nonlinear effects at a fixed wavelength, providing the basis for a sensing strategy in non‐resonant non‐Hermitian coupler structures. Furthermore, increasing the wavelength at constant gain/loss and input power decreases the effective nonlinearity, and consistent sensing performance can be maintained by precise power adjustment across a range of central wavelengths. Overall, this non‐Hermitian control of nonlinear pulse dynamics opens new opportunities for device design with gain–loss and coupling regulation in integrated photonic platforms.
ABSTRACT This paper presents a reflective metasurface that enables simultaneous orbital angular momentum (OAM) mode division and polarization‐division multiplexing for high‐capacity wireless communication systems. Through a symmetric unit design, the metasurface is capable of generating four coaxial OAM beams with two orthogonal polarizations, thereby demonstrating high‐purity dual‐mode and dual‐polarization operation. The performance of the metasurface is verified via simulation and experimental approaches, which demonstrate interference‐free OAM multiplexing and excellent mode and polarization isolation within the 5G frequency band.Based on this metasurface, separate dual‐mode and dual‐polarization wireless communication experiments are demonstrated, verifying the independent transmission capability of the OAM‐mode and polarization channels. A projected aggregate raw throughput of 1.6008 Gbit/s can be expected if all four independent channels operate with 66.7‐Mbaud 64‐QAM signals.
ABSTRACT The Gamma Factory (GF) proposal is motivated by the recognition of a largely untapped potential of the CERN accelerator complex to enable a new research program at the intersection of particle, nuclear, atomic, fundamental, and applied physics. These fields could benefit from novel experimental tools made possible by a future GF facility. The central concept is to produce, accelerate, cool, and store atomic beams of highly relativistic partially stripped ions in the LHC, which would serve as an effective atomic trap. The internal degrees of freedom of these ions are then resonantly excited using laser photons. In the GF scheme, laser‐cooled atomic beams serve both as high‐precision probes and as low‐emittance beam sources for high‐luminosity LHC operation in the ion–ion collision mode. Interactions between laser pulses stored in Fabry–Perot cavities and circulating ion beams give rise to high‐energy, highly collimated, and polarized secondary photon beams. Their expected intensities exceed those of existing gamma‐ray sources by several orders of magnitude. These photon beams can further be used to generate unprecedented‐intensity, tertiary beams of polarized electrons, positrons, muons, neutrons, radioactive ions, and flavor‐ or CP‐tagged neutrinos. Furthermore, under a specific configuration, the same photon‐driven processes may be exploited in an energy‐production scheme generating the requisite plug‐power for LHC operation. Together, cold relativistic atomic beams, high‐intensity photon beams, and tertiary beams constitute a versatile experimental platform capable of opening a wide range of new scientific opportunities at CERN. By exploiting existing accelerator infrastructure and available state‐of‐the‐art laser technologies, the GF offers a path to a cost‐effective and timely program capable of sustaining experimental innovation and bridging the gap between the HL‐LHC era and the future high‐energy‐frontier collider era.
ABSTRACT Traditional quantum key distribution (QKD) protocols secure communications by trusting the source or the measurement device. Among these, measurement‐device‐independent quantum key distribution (MDI‐QKD) protocols remove the need to trust the measurement device by delegating it to an untrusted third party. We categorize the operations of the QKD protocol into three fundamental processes: realizing quantum sources, applying unitary operations, and performing measurements. Furthermore, we have designed an MDI‐QKD protocol utilizing third‐party quantum sources, which establishes connections with the BB84 protocol, the BBM92 protocol, and the first MDI‐QKD protocol. Specifically, the three protocols can be regarded as special cases of the proposed protocol under different equivalent implementations. Under the assumptions of the source's dimension and ideal operation devices, the proposed protocol can guarantee information‐theoretic security even if the quantum sources and measurement devices are controlled by an adversary. Moreover, we demonstrate that its security is equivalent to that of the BBM92 protocol, with a tolerable error rate of approximately . Finally, we give a generalization of the proposed protocol and a corresponding experimental setup framework. This work reveals certain inherent connections between different quantum key distribution protocols, enriching the research results of quantum key distribution.
ABSTRACT Ternary and quaternary hydride superconductors have been the focus of intensive experimental and first‐principles calculations studies in recent years. A primary approach in experimental synthesis of ternary and quaternary hydrides is to substitute La or Ce ions by other rare‐earth elements in LaH 10 and CeH 9 phases, respectively. The choice of CeH 9 as a matrix phase to synthesise ternary and quaternary hydrides is because this phase exhibits transition temperatures above 70 K at a relatively low‐pressure p = 90–130 GPa. One of the synthesized phases by this approach, where cerium is substituted by yttrium, is the ternary P6 3 /mmc ‐Y 0.5 Ce 0.5 H 9 hydride phase. This phase exhibits the onset of superconducting transition temperature T c = 100–140 K in the pressure range of p = 98–155 GPa. Here, based on the analysis of reported experimental data by Chen et al. ( https://doi.org/10.1038/s41467‐024‐46133‐x ), I found that the onset of the superconducting transition temperature in Ce 0.5 Y 0.5 H 9 obeys the parabolic dependence on pressure, T c,onset ( P )/ T c,onset,max = (1–95*( P ‐0.145) 2 ), where T c,max = 140 K, and P is in TPa. The revealed dependence of T c ( P ) is remarkably similar to that of T c ( p ) in cuprates, where p is the doping state. Furthermore, the evolution of the Einstein and Debye temperatures and the electron‐phonon coupling strength with pressure have been derived for the P6 3 /mmc ‐Y 0.5 Ce 0.5 H 9 phase.
This work proposes a terahertz metamaterial sensor featuring polarization-controllable high-Q Fano resonances and multi-parameter sensing capability. The proposed metasurface is based on an all liquid crystal polymer (LCP) material and consists of periodically arranged cylindrical tetramers. Under x-polarized incidence, the sensor exhibits a high-Q resonance of 2126 at 1.701 THz, with a sensitivity of 91 GHz/RIU and a figure of merit (FOM) of 113.75 RIU- 1. Under y-polarized incidence, a Q-factor of 1629 is achieved at 1.466 THz, together with a sensitivity of 54 GHz/RIU and a FOM of 60 RIU- 1. In addition, this platform is innovatively combined with a multi-parameter sensing strategy, integrating x-polarized frequency shift, transmission variation, and dual-polarization frequency difference to enhance analyte discrimination and suppress common-mode interference. Based on this strategy, the sensor can achieve accurate discrimination and quantitative thickness detection of glutamine and isoleucine, two biomolecules with overlapping THz absorption peaks. This design provides an innovative approach for the highly sensitive and accurate detection of biomarkers. It promotes the application of THz sensing technology in clinical diagnosis and wearable fields.
ABSTRACT Monolayer molybdenum disulfide (MoS 2 ) is a two‐dimensional semiconductor with a direct ∼1.8 eV band gap, making it promising for nano‐electronic devices. This work presents a theoretical study of electron transport in monolayer MoS 2 using a multi‐orbital tight‐binding (TB) model and the non‐equilibrium Green's function (NEGF) formalism. The TB Hamiltonian, fit to reproduce the first‐principles band structure, is implemented in a quantum transport code to simulate a two‐terminal MoS 2 device. The electronic band structure and density of states are calculated using the multi‐orbital tight‐binding framework, and the transport behavior is analysed through energy‐dependent transmission spectra, temperature‐dependent current–voltage characteristics, and field‐effect mobility. The NEGF method is further used to investigate how atomic defects affect conductance. Our results show a direct band gap at the K‐point, thermally activated transport behavior, mobility degradation at elevated temperatures, and a strong suppression of conductance by atomic vacancies. These findings provide insight into performance limits and design considerations for MoS 2 ‐based transistors.
ABSTRACT Two‐dimensional (2D) In 2 S 2 , In 2 Se 2 , and In 2 Te 2 monolayers were systematically investigated using density functional theory (DFT) calculations. Electronic structure calculations reveal indirect band gaps of 2.55 eV for In 2 S 2 , 2.44 eV for In 2 Se 2 , and 2.22 eV for In 2 Te 2 , demonstrating a systematic narrowing along the S→Se→Te sequence. Further, work functions decrease correspondingly from 6.334 to 6.047 to 5.575 eV across the S→Se→Te series. Optical analysis up to 15 eV reveals that In 2 Te 2 exhibits maximum reflectivity exceeding 0.35 at ∼4 eV, the highest refractive index (n ≈ 2.5), and the strongest plasmon‐loss peak at ∼9.5 eV, whereas In 2 S 2 achieves a maximum absorption peak at 6 eV with minimal optical losses. Elastic stiffness constants were found to decrease across the S→Se→Te order with corresponding Young's moduli of 61.90, 54.84, and 47.24 N/m, respectively. Pugh ratios of 1.61, 1.76, and 1.88, combined with Poisson's ratios of 0.23, 0.27, and 0.30, signify the brittle character of In 2 S 2, while In 2 Se 2 and In 2 Te 2 exhibit ductile behavior. In 2 S 2 , In 2 Se 2 , and In 2 Te 2 exhibit in‐plane mechanical isotropy arising from their hexagonal symmetry, confirming their suitability for flexible electronics and omnidirectional sensing applications.
ABSTRACT Environmental noise is harmful to quantum technologies, but structured environments can temporarily store and return information, producing useful memory effects. We study this mechanism in a microscopic qubit pseudomode model, where a qubit couples to a single damped mode. Although the enlarged qubit–pseudomode dynamics is Markovian, the reduced qubit channel crosses from CP‐divisible‐like to CP‐indivisible‐like regimes as the coupling , damping , and detuning are varied. Using a trace‐distance backflow proxy together with the amplitude‐damping CP‐divisibility criterion, equivalently Choi positivity of intermediate maps, we construct a finite‐window memory map. The backflow proxy is a restricted diagnostic based on selected state pairs, not a faithful estimate of the optimized BLP measure. This map organizes two task‐level benchmarks. In hybrid qubit–qutrit transmission, we use an established RHP‐type entanglement‐revival benchmark; the qutrit is only a passive embedded reference, and qubit–qubit checks confirm channel‐level revivals. In detuning metrology, the quantum Fisher information provides multiple interrogation windows under a time‐budgeted two‐time protocol with the same channel uses as a single‐time baseline. The protocol assumes ideal fresh environments with no reset‐time cost. Overall, the results link pseudomode memory to entanglement preservation and parameter estimation without claiming a full resource theory.
Quantum spin liquids (QSLs) are magnetically frustrated phases characterized by spin fractionalization, emergent gauge fields, and long‐range entanglement. Quantum spin–orbital liquids (QSOLs) form a subset of QSLs with fluctuating orbital degrees of freedom, normally adding a layer of complexity to an already involved research field. This topical review provides guidelines for understanding a specific type of QSOL in which the orbital operators facilitate the analysis of quantum liquids, thereby providing adequate starting points for /exploring these phases. Such models are extensions of the spin‐1/2 Kitaev honeycomb model (KHM), in the sense that their exact solutions depend on an extensive number of conserved quantities, combined with a mapping to a problem of Majorana fermions hopping on a static gauge field. The starting points to understand such models are classical Hamiltonians characterized by bond‐dependent Ising interactions. Such classical models are exactly solvable in spin basis thanks to their extensive symmetries and can be directly connected to classical spin ice (CSI) systems that satisfy a Gauss law. QSOLs are easily stabilized in these models by applying a transverse field or introducing other exchange mechanisms that preserve the conserved local operators. The theory of such Ising QSOLs bridges the KHM to specific types of CSIs, thus providing further insight into paradigmatic forms of spin liquids. Furthermore, bond‐dependent Ising models are related to minimal Hamiltonians describing Rydberg‐atom simulations, which provide experimental grounds for investigating them.
Superconductivity in compressed arises from the interplay between high‐frequency phonons and a pronounced van Hove singularity near the Fermi level. Using first‐principles calculations, we investigate the superconducting properties of and at 160 and 200 GPa, explicitly incorporating anharmonic lattice dynamics and first‐order vertex corrections to electron‐phonon (e‐ph) interactions, thereby going beyond the Migdal approximation underlying conventional Migdal‐Eliashberg theory. We find that both anharmonicity and nonadiabatic vertex corrections suppress the effective e‐ph coupling and reduce the superconducting critical temperature (). Calculations performed within the energy‐dependent full‐bandwidth Eliashberg formalism, including both anharmonic and vertex effects, yield values in close agreement with experimental measurements for at both pressures and for at 200 GPa.
The discovery of superconductivity in with a critical temperature of approximately has opened a new window toward room temperature superconductivity. In this work, we employ the lowest order constrained variational method to investigate the thermodynamic and magnetic properties of the structure, obtaining results in good agreement with experimental data. Based on the robustness of the LOCV approach for describing high‐ superconductors, we further extend our analysis to the gadolinium–yttrium–hydrogen system across various stoichiometries. The key finding of this study is the prediction of a superconducting phase transition at for under a critical pressure of approximately . This compound crystallizes in a tetragonal structure with space group . Moreover, the calculated gap ratio confirms that is a type‐II superconductor with a critical current density, although practical applications are currently limited by the requirement of high pressure.
High-performance terahertz (THz) polarization converters are critical for next-generation systems, yet conventional solutions often suffer from bulkiness or high losses. To address this, we present a numerically designed all-dielectric metasurface consisting of a single-layer array of silicon pillars. By leveraging form birefringence and Mie-resonant responses, the anisotropic geometry enables precise phase retardation control. The device demonstrates robust multifunctionality: it operates as a high-efficiency half-wave plate (HWP) at 1.09 THz with a polarization conversion ratio greater than 99%, and as a quarter-wave plate (QWP) at 0.9 and 1.22 THz. Notably, the metasurface maintains high transmittance (>84%) at all designated frequencies. This simple, single-layer architecture offers a highly integrated, efficient solution for multifunctional THz photonics.
The efficient implementation of quantum information processing relies on the reliable transfer of quantum states between specified vertices. This paper investigates the time required to achieve perfect state transfer (PST) on corona product graphs . To leverage the high symmetry of such graph structures, we employ a compression method to decompose their state space into several disjoint strata. By designing the coupling strengths between vertices, we analyze the time required for PST from a fixed vertex to vertices within each stratum. Furthermore, while keeping the number of vertices in the base graph fixed, we examine how the time required for PST on the corona product graph varies as the number of vertices in the other graph changes. Finally, we extend the obtained results to the general case where the base graph has an arbitrary number of vertices, thereby providing a complete characterization of the conditions for achieving PST.
Vlasov equation is a partial differential equation of Hamiltonian-Jacobi type. It combines with Maxwell equations and some special requirements to form a very fundamental model in plasma and beam physics. Even though these special requirements, such as macroscopic and microscopic non-negativity, microscopic relativistic boundary conditions, are favorable to obtain strict solutions of the model, they are rarely utilized in many related theoretical and computational investigations. The idea of utilizing these special requirements is analogous to that of the Galerkin-Ritz method, which refers to using a class of functions respecting special requirements to express test functions used in variational optimization of the "energy" functional associated with a partial differential equation. This work outlines a detailed procedure for achieving this method in Eulerian plasma kinetic simulation.
In fluid dynamics, particularly in research on soft matter, it is well known that surface tension gradients drive fluid flow, a phenomenon known as Marangoni flow. The effect is named after Carlo Marangoni, who described it in 1865 as part of his doctoral thesis on droplets and liquid films. While Marangoni's contribution is rightly recognized, this article examines three earlier scientific publications in which the same effect was described experimentally. Published between 1833 and 1855, these works are largely unknown to the modern soft matter research community, partly due to linguistic and disciplinary barriers. This work aims to trace the research history of this important phenomenon by briefly reviewing the history of Marangoni flow prior to Carlo Marangoni and highlighting the often fragmented nature of scientific discoveries across different eras and languages.
