- 标题
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Ring modes supported by concentrated cubic nonlinearity
摘要： We consider the one-dimensional Schr?dinger equation on a ring, with the cubic term, of either self-attractive or repulsive sign, con?ned to a narrow segment. This setting can be realized in optics and Bose-Einstein condensates. For the nonlinearity coef?cient represented by the δ function, all stationary states are obtained in an exact analytical form. The states with positive chemical potentials are found in alternating bands for the cases of the self-repulsion and attraction, while solutions with negative chemical potentials exist only in the latter case. These results provide a possibility to obtain exact solutions for band-gap states in the nonlinear system. Approximating the δ function by a narrow Gaussian, stability of the stationary modes is addressed through numerical computation of eigenvalues for small perturbations, and veri?ed by simulations of the perturbed evolution. For positive chemical potentials, the stability is investigated in three lowest bands. In the case of the self-attraction, each band contains a stable subband, the transition to instability occurring with the increase of the total norm. As a result, multipeak states may be stable in higher bands. In the case of the self-repulsion, a single-peak ground state is stable in the ?rst band, while the two higher ones are populated by weakly unstable two- and four-peak excited states. In the case of the self-attraction and negative chemical potentials, single-peak modes feature instability which transforms them into persistently oscillating states.
关键词： cubic nonlinearity,Bose-Einstein condensates,stationary states,optics,Schr?dinger equation,stability analysis
更新于2025-09-23 15:21:01
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Prominent radiative contributions from multiply-excited states in laser-produced tin plasma for nanolithography
摘要： Extreme ultraviolet (EUV) lithography is currently entering high-volume manufacturing to enable the continued miniaturization of semiconductor devices. The required EUV light, at 13.5 nm wavelength, is produced in a hot and dense laser-driven tin plasma. The atomic origins of this light are demonstrably poorly understood. Here we calculate detailed tin opacity spectra using the Los Alamos atomic physics suite ATOMIC and validate these calculations with experimental comparisons. Our key finding is that EUV light largely originates from transitions between multiply-excited states, and not from the singly-excited states decaying to the ground state as is the current paradigm. Moreover, we find that transitions between these multiply-excited states also contribute in the same narrow window around 13.5 nm as those originating from singly-excited states, and this striking property holds over a wide range of charge states. We thus reveal the doubly magic behavior of tin and the origins of the EUV light.
关键词： multiply-excited states,tin plasma,EUV lithography,atomic physics,opacity spectra
更新于2025-09-23 15:21:01
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Third-Order Unitary Coupled Cluster (UCC3) for Excited Electronic States: Efficient Implementation and Benchmarking
摘要： The efficient implementation of the third-order unitary coupled-cluster scheme (UCC3) for the calculation of excited electronic states is reported. The UCC3 scheme and its second-order UCC2 variant have been benchmarked and compared to Jacquemin’s recently introduced as well as Thiel’s well-established benchmark sets for excitation energies and oscillator strengths. For the latter, the calculation of 134 excited singlet and 71 excited triplet states of 28 small to medium-sized organic molecules has revealed that UCC2 exhibits a mean error and standard deviation of 0.36 ± 0.41 eV for singlet states and 0.22 ± 0.21 eV for triplet states, whereas UCC3 revealed an accuracy of 0.06 ± 0.27 eV for singlet and ?0.22 ± 0.15 eV for triplet states. Additionally, the oscillator strengths obtained with effective transition moments correct through second order in perturbation theory are in very good agreement with literature data.
关键词： perturbation theory,unitary coupled-cluster,oscillator strengths,excited electronic states,benchmarking
更新于2025-09-23 15:21:01
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Automated Tuning of Double Quantum Dots into Specific Charge States Using Neural Networks
摘要： While quantum dots are at the forefront of quantum-device technology, the tuning of multidot systems requires a lengthy experimental process as multiple parameters need to be accurately controlled. This process becomes increasingly time-consuming and difficult to perform manually as the devices become more complex and the number of tuning parameters grows. In this work, we present a crucial step toward automated tuning of quantum-dot qubits. We introduce an algorithm driven by machine learning that uses a small number of coarse-grained measurements as its input and tunes the quantum-dot system into a preselected charge state. We train and test our algorithm on a GaAs double-quantum-dot device and we consistently arrive at the desired state or its immediate neighborhood.
关键词： neural networks,automated tuning,charge states,machine learning,quantum dots
更新于2025-09-23 15:21:01
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Numerical simulation of multilayer organic light-emitting diodes with hosta??guest emissive layer: the role of defect states
摘要： In this study, a comprehensive model for the numerical simulation of electrical and optical characteristics of multilayer organic light-emitting devices (OLED) is presented. The model consists of three parts: charge carrier transport model, exciton model, and a post-processing part for calculating luminance. The defect states in the organic layers are modeled and are introduced into the equations. For demonstrating the rule of the defect states in such devices, a multilayer OLED is considered consisting of a host–guest emissive layer sandwiched between electron and hole transport layers. The current density and luminance results of the analyzed device are compared with the experimental data. We have found that by considering the defect states, there is good accordance between the simulation results and the experimental data.
关键词： Host–guest emissive layer,Luminance,Current density,OLED,Numerical simulation,Defect states
更新于2025-09-23 15:21:01
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Pathways to excitation of atoms with bicircular laser pulses
摘要： We study the excitation of the hydrogen atom by bichromatic circularly polarized laser pulses using numerical solutions of the time-dependent Schr?dinger equation. The results are in agreement with the selection rules for multiphoton processes in such fields, namely, excited states are populated in which orbital angular momentum and magnetic quantum numbers are either both odd or both even, independent of the relative helicity, peak intensity, and pulse duration of the pulses. For co-rotating pulses the results show that excitation predominantly proceeds to states with magnetic quantum number of the same helicity as the laser pulses. Besides pathways via direct photon absorption from the ground state our results indicate that a transfer of population among the Rydberg states occurs via (cid:2)-type transitions. In the case of counter-rotating pulses the largest excitation probability is found for Rydberg states that differ in magnetic quantum number by (cid:3)m = ±3. This pattern allows us to estimate how many photons from each of the two bichromatic fields have been absorbed. Finally, we confirm that a population in Rydberg states beyond a maximum orbital angular quantum number is unlikely.
关键词： Rydberg states,hydrogen atom,bichromatic circularly polarized laser pulses,time-dependent Schr?dinger equation,multiphoton processes
更新于2025-09-23 15:21:01
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Clocks without a??Timea?? in Entangled-State Experiments
摘要： Entangled states of light exhibit measurable correlations between light detections at separated locations. These correlations are exploited in entangled-state quantum key distribution. To do so involves setting up and maintaining a rhythm of communication among clocks at separated locations. Here, we try to disentangle our thinking about clocks as used in actual experiments from theories of time, such as special relativity or general relativity, which already differ between each other. Special relativity intertwines the concept of time with a particular de?nition of the synchronization of clocks, which precludes synchronizing every clock to every other clock. General relativity imposes additional barriers to synchronization, barriers that invite seeking an alternative depending on any global concept of time. To this end, we focus on how clocks are actually used in some experimental situations. We show how working with clocks without worrying about time makes it possible to generalize some designs for quantum key distribution and also clari?es the need for alternatives to the special-relativistic de?nition of synchronization.
关键词： agent,entangled light states,unpredictability,synchronization
更新于2025-09-23 15:21:01
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Strong angular dependence of resonant states in 2D dielectric cylinder rings
摘要： We investigate collective resonators made of dielectric cylinders assembled as two-dimensional regular octagons and decagons. These structures exhibit collective resonance states that change their intensity with the incident radiation angle. While most parts of the spectra present small or even null variation, one of these resonances presents high-sensitivity to the incidence angle. This strong variation is well characterized in terms of the electric field intensity distribution of a resonant state where all the cylinders show the lowest order Mie resonance and the neighbors alternate their polarities. The collective state is optimally excited when radiation impinges on a vertex of the polygonal arrangement of cylinders, while the response decreases to its minimum when the incident field hits an edge (two cylinders at the same time). The resonant state and its high dependence on the excitation incidence angle have been found in both octagonal and decagonal configurations for different dielectric permittivity values. In addition, the scalability of Maxwell equations warranties the same behavior if the whole system is downscaled to terahertz or optic frequencies. The study was performed by finite integration time domain calculations of scattering and transmission for different incidence angles. Experimental measures in the microwave range were taken from photonic molecule prototypes made of centimeter-scale glass cylinders (ε = 4.5). We find an overall excellent agreement between measurements and simulations. We propose that photonic molecules made of polygonal rings of dielectric cylinders are an ideal structure to build angle sensors using the strongly varying state that they present.
关键词： resonance states,angle sensors,incident radiation angle,collective resonators,photonic molecules,dielectric cylinders
更新于2025-09-23 15:21:01
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A general approach for the calculation and characterization of x-ray absorption spectra
摘要： We present a general approach for the calculation and assignment of X-ray absorption spectra based on electronic wavepacket propagations performed using explicitly time-dependent electronic structure calculations. Such calculations have the appeal of yielding the entire absorption spectrum for the cost of a single set of electronic wavepacket propagations, obviating the need to explicitly calculate large numbers of core-excited states. The spectrum can either be calculated from the Fourier transform of the time-dependent dipole moment or from the Fourier transform of the wavepacket autocorrelation function. We propose that calculating the absorption spectrum using the latter approach will generally be the preferred option. This method has two important advantages. First, the autocorrelation functions can be obtained for twice the propagation time, resulting in a halving of the computational effort required to calculate the spectrum relative to the time-dependent dipole moment approach. Second, using the tools of filter diagonalisation, the autocorrelation functions may be used to determine the time-independent final core-excited states underlying the peaks of interest in the spectrum. The proposed scheme is validated by calculating and characterizing the X-ray absorption spectra of benzene and trifluoroacetonitrile at the time-dependent second-order algebraic diagrammatic construction level of theory.
关键词： time-dependent electronic structure calculations,X-ray absorption spectra,core-excited states,electronic wavepacket propagations,filter diagonalisation
更新于2025-09-23 15:21:01
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On the role of magnesium in LiF:Mg,Ti thermoluminescent dosimeter
摘要： LiF doped with Mg and Ti is the most widely used thermoluminescent (TL) dosimeter for a large variety of applications. It has been argued that the Mg dopant is the most important defect in the TL process. Besides the common F-centre defects in LiF, optical absorption measurements have suggested the presence of Mg-related absorption bands at 380 nm (3.26 eV), and 310 nm (4.0 eV) when LiF:Mg is exposed to ionizing radiation, whose origin is not yet well understood. This work presents an investigation of the role of defects induced by Mg in LiF through electronic structure calculations. The calculations show that Mg interstitials induce a local lattice distortion characterized by the displacement of two opposite fluorine atoms, adjacent to the magnesium, away from their original sites by an average distance of 0.6 ? each, while the closest Li atoms are displaced by 0.1 ?. This defect introduces electronic states in the band-gap that can trap excess electrons produced during irradiation, thus enhancing the efficiency of the detector. Holes, on the other hand, are created and trapped in orbitals of mainly Mg-3s character. Additionally, the results suggest that irradiation can simultaneously remove a Li atom nearby a Mg interstitial; substitute a Li by a Mg atom or create a Li vacancy plus a Mg substitutional, giving rise to defects within the LiF gap that are more stable thermodynamically than the Mg interstitial itself.
关键词： magnesium dopant,LiF:Mg,Ti,thermoluminescent dosimeter,electronic structure calculations,defect states
更新于2025-09-23 15:21:01