Emission Spectra of a Two-level Atom Under the Presence of Another Two-level Atom

Abstract

We investigate the spectrum of light emitted by a two-level atom interacting with another two-level atom inside an ideal cavity within the frame of generalized Jaynes-Cummings model. The influence of various ratios of the coupling constants of the atoms to the field on the spectrum of the emitted light is studied in detail for the case when the atoms are supposed to be initially in the excited state and the field in a Fock state as well as their superposition.     

Spectrum of Scattered Light by an Ionized Two-level Atom

Abstract

The spectrum of scattered light by an ionized two-level atom is investigated. The ionization is considered as a damping out of the ordinary two-level system and its effect on the spectrum is extracted. Because of the ionization damping, the central peak in the spectrum changes significantly according to the parameters involved. For a large ionization damping, a central dip is observed; for a small ionization damping, an additional sharp peak appears on top of the central peak.     

Interaction of a Two-level Atom with Squeezed Light

The dynamic response of the inversion in a two-level atom to single-mode squeezed states of the radiation field is examined. Depending on the direction of squeezing, an increase or decrease in the collapse time is demonstrated. A number of additional departures from the response of the atom to a coherent field are noted. In particular, for certain squeezed states the response of the atom is similar to that expected for chaotic radiation.     

N-level Atom Interacting with Single-mode Radiation Field: An Exactly Solvable Model with Multiphoton Transitions and Intensity-dependent Coupling

Abstract

We study the dynamics of an N-level atom coupled in a lossless cavity to a single-mode near-resonant quantized field. The atomic levels are coupled by the multiphoton transitions and the coupling constants between the field and the atomic levels are supposed to be intensity dependent. We find the exact solution for the state vector describing the dynamics of the atom-plus-field system. As an illustration we use the model for studying (i) the time evolution of the atomic occupation probability with the initially coherent field and (ii) the light squeezing, when the cavity field is initially in the vacuum state and the atom is prepared in the atomic ‘coherent state’ (a superposition of atomic states).     

Entanglement Entropy in an Ising Chain with Alternating Field

The effects of alternating magnetic field on the bipartite entanglement in an opened Ising chain are studied. Entropy is used to evaluate bipartite entanglement in the system. All-values entropy decreases with the strength of alternating field increases. The method of density matrix renormalization-group is applied to obtain logarithmic behavior of entropy. It is found that the logarithmic behavior with a central charge c does not vary with the length of the subsystem.     

基于最大熵的两级逼近理想点的配送路线选择

供应链配送路线选择是多个节点企业共同决策的结果,对于供应链成员共同决策的评价指标,用最大熵的技术来确定初步的权重.但供应商和零售商对配送路线有不同的偏好与权重.用隶属度的方法来度量供应商对各指标确定的权重,并采用逼近理想点法对供应商的方案进行评判,形成接近度矩阵;在此基础之上,利用隶属度法来度量零售商对各配送路线确定的权重,并采用逼近理想点法对配送路线进行综合评判与选优.以某汽车制造业的供应链配送路线选择决策作为案例,进行了说明与分析.     

Describing the Properties of Chains of Segments Interacting Via Soft-Core Potentials of Variable Range with the SAFT-VR Approach

We present a general development for the equation of state (EOS) of chain molecules composed of tangent spherical segments interacting with a soft repulsive potential and an attractive well. The method is based on a recent version of the statistical associating fluid theory for chain molecules with interaction potentials of variable range (SAFT-VR). In this communication we focus our attention on the properties of Lennard–Jones chains (LJC), using SAFT-VR and a sample recipe for the evaluation of the chain free energy that requires only a knowledge of the contact value of the cavity function of a Sutherland-6 system. We study the liquid–vapor coexistence properties for different values of the chain length. The results obtained are of similar accuracy to other EOS for LJC, but our approach is simpler and more general. We show that standard perturbation theories developed for simple liquids can also be used for chain molecules.     

Interaction of a System of Initially Unexcited Two-level Atoms with a Weak Cavity Field

Abstract

Using a perturbation method, constructed in terms of SU(2) group representations, the interaction of N initially unexcited two-level atoms and a weak single-mode cavity field is studied. The field is assumed to be initially either in a Fock state with a number of photons equal to n or in a coherent state. In the case of the photon-number state with n  3, the pure phenomenon of collective collapses and revivals manifests itself. For the initially coherent field the phenomenon of collapses and revivals arising from the photon number distribution mechanism is additionally modulated by this collective mechanism. The problem of the interaction of excited atoms with an initially coherent field has already been solved numerically by Barnett and Knight. For n=1 2 and 3 the approximate solution is compared with the exact solutions also given in this paper and the limit of applicability of our approach is established.     

Phenomenological Equation of State and Density Profiles of Strongly Interacting Trapped Superfluid Fermi Gases with Arbitrary Atom Numbers

We present a phenomenological equation of state (EOS), derive a nonlinear quantum hydrodynamical equation and investigate the density profiles of a trapped superfluid Fermi gas with arbitrary number of particles in the BCS-BEC crossover regime. The asymptotic behavior of the EOS exactly matches with its expansions in three limiting regimes: BCS, unitarity and BEC. By using this EOS, the quantum hydrodynamical equation is beyond mean-field version, valid in all interacting regimes and used for the unitarity regime specially. We take a Fetter-like trial wave function in generalized Thomas-Fermi approximation, solve the hydrodynamical equation and calculate the energy, chemical potential, sizes and profiles of the ground-state condensate in the BCS-BEC crossover regime. Our results agree well with the theoretical and experimental results.     

Evolution of Rayleigh Equation in a Problem with Phase Transition

In the Rayleigh equation, physical effects are included such as the reaction of recoil of molecules of the gaseous phase on the interface and the time variation of the density of the gaseous phase during a process with phase transition. A simultaneous analysis is performed of the modified Rayleigh equation and asymptotic representation of the self-similar solution of the problem formulated on the basis of the energy model with a variable temperature of the interface. An equation is obtained that defines the dynamics of motion of a spherically shaped interface. A comparison of the calculation results obtained in solving this equation with experimental data on boiling of highly superheated water and the R-113 refrigerant reveals their good agreement.     

Phase Properties of a Strong Field Interacting with Many Atoms with and Without Initial Atomic Coherences

Abstract

The phase distributions of an initially strong, coherent, single-mode field interacting with one, two, three and four identical atoms with and without initial atomic coherences using the Pegg-Barnett Hermitian phase operator formalism have been examined. A number of interesting features of the phase distributions are revealed. A link between the coincidences of the peaks in the phase probability distribution and the revivals in the two-atom case is also shown.     

Quantum Phase Transition in the BCS-to-BEC Evolution of p-wave Fermi Gases

We discuss the possibility of a quantum phase transition in ultra-cold spin-polarized Fermi gases which exhibit a p-wave Feshbach resonance. We show that when fermionic atoms form a condensate that can be externally tuned between the BCS and BEC limits, the zero temperature compressibility and the spin susceptibility of the fermionic gas are non-analytic functions of the two-body bound state energy. This non-analyticity is due to a massive rearrangement of the momentum distribution in the ground state of the system. Furthermore, we show that the low temperature superfluid density is also non-analytic and exhibits a dramatic change in behavior when the critical value of the bound state energy is crossed.     

Polynomial Approximation-Based Optimal Design of Structures Interacting with an Aggressive Environment by the Random Search Method

Strength of Materials - The optimal design of structures that interact with an aggressive environment is considered on the example of a thin-walled shell exposed to the internal pressure of the...     

Response Functions of an Artificial Anderson Atom in the Atomic Limit

We consider the spin and pseudospin (charge) response functions of the exactly soluble Anderson atom model. We demonstrate, in particular, that a deviation from the magnetic Curie-law behaviour, appropriate for a free spin one-half, increases with increasing asymmetry and temperature. In general, oscillator strength is transferred from the spin degrees of freedom to the pseudospin modes. We also consider the negative-U Anderson atom and demonstrate that the pseudospin modes are the relevant low-energy excitations in this case. Especially, the roles of the spin and charge excitations are interchanged upon reversal of the intrasite Coulomb repulsion, U.     

激光与原子的相干性在计量测试领域中的应用进展

上世纪60年代激光刚被发现不久,其良好的相干性就被广泛用于测量设备的研制,在计量领域也以激光为工具建立了各类高水平计量标准,如米定义,几何量及运动量的基标准。半个世纪后的今天,冷原子技术使原子为代表的物质波具有良好的相干特性,它同样被立刻用于计量测试领域,法国计量院提供参与重力国际关键比对的冷原子重力仪就是最好的证明。本文以相干原理为主线,介绍了激光等电磁波在更高分辨力、更大空间范围以及更远物体的运动测量方面的进展,说明激光技术进展对动态测量领域开拓的重要引领作用,同时举例介绍了原子相干性在重力测量以及运动量动态测量中的重要作用。     

Local Electroelastic Field and Effective Electroelastic Moduli of Piezoelectric Nanocomposites with Interface Effect

Due to the large ratio of surface area to volume in nanoscale objects, the property of surfaces and interfaces likely becomes a prominent factor in controlling the behavior of nano-heterogeneous materials. In this work, based on the Gurtin-Murdoch surface/interface elastic theory, a distinct expression is derived for embedded nano-inclusion in an infinite piezoelectric matrix coupled with interface effect. For the problem of a spherical inclusion in transversely isotropic piezoelectric medium, we reach a conclusion that the elastic and electric field are uniform when eigen-strain and eigen-electric field imposed on the inclusion are uniform even in the presence of the interface influence. The electroelastic fields in the inclusion are related to both interface electroelastic parameters and the radius of the inclusion. Then overall properties of the composites are estimated by using the dilute distribution model. Numerical results reveal that the effective electroelastic moduli are function of the interface parameters and the size of the nano-inhomogeneities.     

Evolution of the Raman spectrum of graphene grown on copper upon oxidation of the substrate

Significant changes in the Raman spectrum of single-layer graphene grown on a copper film were observed after the spontaneous oxidation of the underlying substrate that occurred under ambient conditions. The frequencies of the graphene G and 2D Raman modes were found to undergo red shifts, while the intensities of the two bands change by more than an order of magnitude. To understand the origin of these effects, we further characterized the samples by scanning tunneling microscopy （STM）, scanning tunneling spectroscopy （STS）, and atomic force microscopy （AFM）. The oxidation of the substrate produced an appreciable corrugation in the substrate without disrupting the crystalline order of the graphene overlayer and/or changing the carrier doping level. We explain the red shifts of the Raman frequencies in terms of tensile strain induced by corrugation of the graphene layer. The changes in Raman intensity with oxidation arise from the influence of the thin cuprous oxide film on the efficiency of light coupling with the graphene layer in the Raman scattering process.