Quantum Harmonic Oscillator and Nonstationary Casimir Effect

We consider the relations between the theory of quantum nonstationary damped oscillator and nonstationary Casimir effect in view of the problem of photon creation from vacuum inside the cavity with periodical time-dependent conductivity of a thin semiconductor boundary layer, which simulates periodical displacements of the cavity boundaries. We develop a consistent model of quantum damped harmonic oscillator with arbitrary time-dependent frequency and damping coefficients within the framework of Heisenberg-Langevin equations with two noncommuting delta-correlated noise operators. For the minimum noise set of correlation functions, whose time dependence follows that of the damping coefficient, we obtain the exact solution, which is a generalization of the Husimi solution for undamped nonstationary oscillator. It yields the general formula for the photon-generation rate under the resonance condition in the presence of dissipation. We obtain a simple approximate formula for a time-dependent shift of the complex resonance frequency. It depends only on the total energy of a short laser pulse (which creates an effective time-dependent electron-hole “plasma mirror” on the semiconductor-slab surface) and the recombination time. We show that damping due to a finite conductivity of the material significantly diminishes the photon-generation rate in the selected field mode of the cavity. Nonetheless, we have found optimum values of the parameters (laser pulse power, recombination time, and cavity dimensions), for which the effect of photon generation from vacuum could be observed in the experimental set-up proposed in the University of Padua. We also provide with a list of publications from 2001 to 2005 devoted to the study on quantum-field interactions with moving boundaries (mirrors). Dedicated to Prof. Vladimir I. Man'ko on the occasion of his 65th birthday.     

Attracting cavities for docking. Replacing the rough energy landscape of the protein by a smooth attracting landscape

Molecular docking is a computational approach for predicting the most probable position of ligands in the binding sites of macromolecules and constitutes the cornerstone of structure‐based computer‐aided drug design. Here, we present a new algorithm called Attracting Cavities that allows molecular docking to be performed by simple energy minimizations only. The approach consists in transiently replacing the rough potential energy hypersurface of the protein by a smooth attracting potential driving the ligands into protein cavities. The actual protein energy landscape is reintroduced in a second step to refine the ligand position. The scoring function of Attracting Cavities is based on the CHARMM force field and the FACTS solvation model. The approach was tested on the 85 experimental ligand–protein structures included in the Astex diverse set and achieved a success rate of 80% in reproducing the experimental binding mode starting from a completely randomized ligand conformer. The algorithm thus compares favorably with current state‐of‐the‐art docking programs. © 2015 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.     

Entanglement of two Jaynes-Cummings atoms in single-excitation space

We study the entanglement dynamics of two atoms coupled to their own Jaynes-Cummings cavities in single-excitation space.Here,we use concurrence to measure atomic entanglement,and consider the Bell-like states to be initial states.Our analysis suggests that collapse and revival take place in entanglement dynamics.The physical mechanism behind entanglement dynamics is periodic information and energy exchange between atoms and light fields.For the initial Bell-like states,evolutionary periodicity of the atomic entanglement can only be found if the ratio of the two atom-cavity coupling strengths is a rational number.Also,whether there is a time translation between two kinds of initial Bel-like state depends on odd versus even numbers of the coupling strength ratio.     

High-frequency gravitational waves having large spectral densities and their electromagnetic response

Various cosmology models, brane oscillation scenarios, interaction of interstellar plasma with intense electromagnetic radiation, and even high-energy physics experiments （e.g., Large Hadron Collider （LHC）） all predict high frequency gravitational waves （HFGWs, i.e., high-energy gravitons） in the microwave band and higher frequency region, and some of them have large energy densities. Electromagnetic （EM） detection to such HFGWs would be suitable due to very high frequencies and large energy densities of the HFGWs. We review several typical EM detection schemes, i.e., inverse Gertsenshtein effect （G-effect）, coupling of the inverse G effect with a coherent EM wave, coupling of planar superconducting open cavity with a static magnetic field, cylindrical superconducting closed cavity, and the EM sychro-resonance system, and discuss related minimal detectable amplitudes and sensitivities. Furthermore, we give some new ideas and improvement ways enhancing the possibility of measuring the HFGWs. It is shown that there is still a large room for improvement for those schemes to approach and even reach up the requirement of detection of HFGWs expected by the cosmological models and high-energy astrophysical process.     

Hydrophobic interactions and clustering in a porous capsule: option to remove hydrophobic materials from water

The investigation of hydrophobic interactions under confined conditions is of tremendous interdisciplinary interest. It is shown that based on porous capsules of the type {(pentagon)}(12){(linker)}(30) ≡ {(Mo)Mo(5)(12){Mo(2)(ligand)}(30), which exhibit different hydrophobic interiors-achieved by coordinating related ligands to the internal sites of the 30 {Mo(2)} type linkers-there is the option to study systematically interactions with different uptaken/encapsulated hydrophobic molecules like long-chain alcohols as well as to prove the important correlation between the sizes of the related hydrophobic cavities and the option of water encapsulations. The measurements of 1D- and 2D-NMR spectra (e.g. ROESY, NOESY and HSQC) allowed the study of the interactions especially between encapsulated n-hexanol molecules and the hydrophobic interior formed by propionate ligands present in a new synthesized capsule. Future detailed studies will focus on interactions of a variety of hydrophobic species with different deliberately constructed hydrophobic capsule interiors.     

Dynamically tunable multiband plasmon-induced transparency effect based on graphene nanoribbon waveguide coupled with rectangle cavities system

A dynamically tunable multiband plasmon-induced transparency (PIT) effect in a series of rectangle cavities coupled with a graphene nanoribbon waveguide system is investigated theoretically and numerically by tuning the Fermi level of the graphene rectangle cavity. A single-PIT effect is realized using two different methods: one is the direct destructive interference between bright and dark modes, and the other is the indirect coupling through a graphene nanoribbon waveguide. Moreover, dual-PIT effect is obtained by three rectangle cavities side-coupled with a graphene nanoribbon waveguide. Results show that the magnitude of the dual-PIT window can be controlled between 0.21 and 0.74, and the corresponding group index is controlled between 143.2 and 108.6. Furthermore, the triple-PIT effect is achieved by the combination of bright-dark mode coupling and the cavities side-coupled with waveguide mechanism. Thus, sharp PIT windows can be formed, a high transmission is maintained between 0.51 and 0.74, and the corresponding group index is controlled between 161.4 and 115.8. Compared with previously proposed graphene-based PIT effects, the size of the introduced structure is less than 0.5 μm². Particularly, the slow light effect is crucial in the current research. Therefore, a novel approach is introduced toward the realization of optical sensors, optical filters, and slow light and light storage devices with ultra-compact, multiband, and dynamic tunable.     

基于天线辐射理论构建微波混沌腔的随机耦合模型

为了能够快速有效地求解电大复杂腔体(微波混沌腔)的电磁耦合问题, 文中采用统计电磁学方法研究了该类腔体电磁散射的统计特征. 首先, 根据天线辐射理论, 利用电磁场的本征模展开式建立了腔体耦合输入阻抗表达式. 其次, 利用波动混沌理论和概率统计方法进一步推导出了微波混沌腔的随机耦合模型. 该方法简单并且可以直接推导出三维模型. 最后, 构建了一个三维Sinai微波混沌腔并进行数值仿真实验, 其仿真实验结果与随机耦合模型计算结果的统计特征基本一致. 重要的是, 该模型与复杂腔体的细节特征无关, 能够快速有效地预测微波混沌腔的敏感耦合问题. 关键词： 统计电磁学 微波混沌腔 输入阻抗 随机耦合模型     

双光子过程耦合腔系统中的纠缠特性

研究了双光子过程原子与耦合腔相互作用系统,给出了系统总激发数等于2时态矢的演化。采用负本征值来描述两个子系统间的纠缠,利用数值计算方法研究了系统中原子与原子间、腔场与腔场间和原子与腔场间的纠缠特性。讨论了腔场间的耦合强度变化对纠缠特性的影响。研究结果表明:随着腔场间耦合的增强,两原子间的纠缠增强,但原子与腔场间和两腔场间的纠缠却减弱。     

双光子过程耦合腔系统中光场的量子特性

本文研究了双光子过程原子与耦合腔相互作用系统中腔场的压缩效应和反聚束效应.考虑系统总激发数等于2的情况,利用数值计算方法讨论了腔场间的耦合强度变化和原子与腔场间耦合强度变化对反聚束效应的影响.研究结果表明:腔场不呈现出压缩效应;腔场的反聚束效应与原子与腔场的耦合系数之间,以及与腔场间的耦合系数之间都存在着非线性关系,     

A Confined Hydrogen Atom in Higher Space Dimensions

We compute ground state energies for the N-dimensional hydrogen atom confined in an impenetrable spherical cavity. The obtained results show their dependence on the size of the cavity and the space dimension N. We also examine the value of the critical radius of the cavity in different dimensions. Furthermore, the number of bound states was found for a given radius S, in different space dimensions. .