Effects of the Binomial Field Distribution on Collapse and Revival Phenomena in the Jaynes-Cummings Model

Abstract

The dynamical properties of a two-level atom interacting with a single non-decaying mode of an electromagnetic field in a binomial state are studied. The statistical aspects of the field, such as intensity-intensity correlation and squeezing, are also investigated. The binomial state reduces to a pure number state and a pure coherent state in different limits. Hence it enables us to study how the sinusoidal Rabi oscillations in a pure number state develop to give rise to the phenomenon of collapse and revival which has been studied extensively in the coherent-state field. In addition, the binomial state exhibits squeezing for certain values of parameters, but it is not a minimum-uncertainty-product state.     

Statistical Properties of the Even Binomial State

Abstract

In this paper we introduce the even binomal state, which interpolates between the even number state and the even coherent state. We consider the effect of this state on the Glauber second order correlation function. Both squeezing phenomena are discussed, i.e., normal squeezing and amplitude squared squeezing. The quasiprobability distribution functions (Wigner function and Q function) for such a state are also examined.     

Quantum Electrodynamics of a Rydberg Atom Making Two-photon Transitions in the Binomial State of the Field in a Lossless Cavity

Abstract

The dynamic and statistical properties of a system of an effective two-level atom making two-photon transitions in the binomial state of the field in a lossless cavity are discussed. The binomial state enables the study of the development of the phenomenon of collapses and revivals of the Rabi oscillations as the field state is changed from a pure number state to a coherent state. This is because the binomial state, which is a pure number state in one limit, develops into a coherent state as some parameters are changed appropriately. The effect of Stark shifts arising due to the transitions to virtual levels are also investigated.     

Effects of Magnetic Field on the Coherence Time of a Parabolic Quantum Dot Qubit

We obtain the eigenenergies and eigenfunctions (EE) of the ground and first excited states of an electron strongly coupled to LO-phonon in a parabolic quantum dot. The effect of an applied magnetic field is considered by using variational method of Pekar type. This system may be regarded as a two-level qubit. Spontaneous phonon emission arouses the qubit’s decoherence. Relations between the coherence time (CT) and the magnetic field, the effective confinement length (ECL) and the polaron radius (PR) are numerically calculated. It is found that the CT is an increasing function of the ECL, whereas it is a decreasing one of the cyclotron frequency and PR. We can extend the CT by changing these parameters in the correlated quantum functional devices.     

Effects of a Moving Mass Centre on Atomic Dynamics in Locally Inhomogeneous Quantized Cavity Field

Abstract

By invoking an exactly solvable model as the generalization of the Jaynes-Cummings model, the influence of spatial motion of atomic centre on the dynamics of a single-mode cavity-two-level atom system are studied for various initial conditions. These investigations show that the Doppler effect exercised by the motion of atom in a locally inhomogeneous cavity field can lead to the phenomenon of oscillation collapse and revival in the transition probability and the atomic population inversion.     

Four-point Field Coherence Function in a Turbulent Medium

The paper presents the results of the theoretical and experimental studies of the four-point field coherence function o ₄ of a wave propagating in a turbulent medium. On the basis of the asymptotic method, expressions for the complex value of o ₄ in the region of strong intensity fluctuations are obtained. The theoretical and experimental results for the real and imaginary parts of o ₄ and for different configurations of receiving points are compared.     

小波谱在舰船地震波场分析中的应用

舰船地震波信号是一个非平稳过程,以傅里叶变换为基础的传统谱分析方法已经难以发挥作用.小波变换因其在时-频域都具有表征信号局部特征的能力而成为非平稳信号分析的有力工具.提出了小波谱、小波相干系数用于舰船地震波信号的处理方法.由于Morlet小波所具有的优势,选用Morlet小波作为母小波进行小波分析,得到舰船地震波信号的时频特征.通过对实验数据的分析对比体现出小波谱良好的时频定位能力,表明小波谱适于信号特征的提取,并优于传统谱分析.     

基于二项分布的装备状态质量诊断试验评估指标研究

提出了通过诊断方法获取装备状态质量特性指标值的思想,解决了统计特性不明显的小样本集装备获取状态质量特性指标的难题;规范了装备状态质量诊断试验的条件;在装备质量评估领域首次提出了评价装．备诊断试验效果的确诊率、负确诊率、误诊率、漏诊率、故障预测指标、正常预测指标等单指标体系以及符合率、综合指数、比数积、故障似然比、正常似然比等综合指标体系,并进一步提出了提高装备状态质量诊断试验效率的平行诊断试验方法和系列诊断试验方法。     

Atomic Dipole Dynamics in the Thermal Quantized Cavity Field

Abstract

We consider the resonant interaction of a two-level atom with a thermal state of the quantized field in a lossless cavity. Non-trivial dynamics of the atomic dipole moment and the field quadrature components arise if the atom is initially prepared in a coherent superposition of its upper and lower states. In particular, the initial thermal field state acquires a well defined phase that corresponds to the initial phase of the superposition atomic state. Population trapping occurs when the intensity grows.     

Lateral Heterostructures of Graphene and h-BN with Atomic Lattice Coherence and Tunable Rotational Order

In-plane heterostructures of graphene and hexagonal boron nitride (h-BN) exhibit exceptional properties, which are highly sensitive to the structure of the alternating domains. Nevertheless, achieving accurate control over their structural properties, while keeping a high perfection at the graphene-h-BN boundaries, still remains a challenge. Here, the growth of lateral heterostructures of graphene and h-BN on Rh(110) surfaces is reported. The choice of the 2D material, grown firstly, determines the structural properties of the whole heterostructure layer, allowing to have control over the rotational order of the domains. The atomic-scale observation of the boundaries demonstrates a perfect lateral matching. In-plane heterostructures floating over an oxygen layer have been successfully obtained, enabling to observe intervalley scattering processes in graphene regions. The high tuning capabilities of these heterostructures, along with their good structural quality, even around the boundaries, suggest their usage as test beds for fundamental studies aiming at the development of novel nanomaterials with tailored properties.     

Some Effects of Spatial and Temporal Coherence in Holography

The following two problems have been investigated theoretically: systematic treatment of image formation in two-beam Fresnel holography from the viewpoint of spatial coherence, and influence of temporal coherence in two-beam Fraunhofer holography.     

原子束在光驻波场中的运动研究

介绍了光力的来源,对平行原子束在与其垂直的一维光驻波场中的运动进行了详细的理论分析,模拟失谐量对原子束空间运动轨迹的影响并进行讨论。根据模拟结果得到一些有重要意义的结论。     

Effects of Noise-Induced Coherence on the Performance of Quantum Absorption Refrigerators

We study two models of quantum absorption refrigerators with the main focus on discerning the role of noise-induced coherence on their thermodynamic performance. Analogously to the previous studies on quantum heat engines, we find the increase in the cooling power due to the mechanism of noise-induced coherence. We formulate conditions imposed on the microscopic parameters of the models under which they can be equivalently described by classical stochastic processes and compare the performance of the two classes of fridges (effectively classical vs. truly quantum). We find that the enhanced performance is observed already for the effectively classical systems, with no significant qualitative change in the quantum cases, which suggests that the noise-induced-coherence-enhancement mechanism is caused by static interference phenomena.     

浅海风成海洋环境噪声场宽带垂直相干特性研究

本文对浅海风成海洋环境噪声场两接收点宽带垂直相干特性作以研究.首先给出了宽带垂直相干的简正模式展开形式,然后讨论了宽带垂直相干与海底各参数、海面噪声源深度、海水声速剖面、两接收器的深度和间距等因素之间的关系.计算结果发现,海底各参数和海面噪声源深度对宽带垂直相干的影响以不同的方式体现,这为宽带垂直相干进一步应用于海面环境的监测以及海底多参数的反演奠定了基础.     

Cold Binary Atomic Collisions in a Light Field

The rate coefficients are calculated for trap loss due to excited state formation during s-wave collisions of two atoms in a light field in a cold atomic gas near conditions for formation of a Bose-Einstein condensate. Blue detuning from the allowed atomic resonance transition causes excitation of a replusive molecular potential, whereas red detuning causes excitation when the light is tuned near a bound vibrational energy level of an attractive molecular potential. In either case, when the light intensity is low and the detuning is large compared to the natural linewidth of the atomic transition, the rate coefficient for the collisional loss rate is proportional to a molecular Franck-Condon factor. A simple reflection approximation formula is derived which permits the rate coefficient to be given analytically in either case. The Franck-Condon factor is equal to |Ψ_g(R_C)²|/D_C, where Ψ_g(R_C) is the ground state scattering wavefunction at the Condon point R_C, where the quasimolecule is in resonance with the exciting light, and D_C is the slope difference between ground and excited potentials at R_C. The analytic reflection approximation formula, as well as a simple phase-amplitude formula for the intermediate range wavefunction, give excellent agreement with the results of numerical quantum mechanical calculations. The trap loss rates due to binary collisions are comparable to or exceed those due to atomic recoil heating for a wide range of detunings to the blue of atomic resonance and near the peaks of photoassociation resonances for the case of red detuning.     

Some Effects of Temporal Coherence on the First Order Statistics of Speckle

Moments and the first order probability density function of the intensity in a speckle pattern are considered as a function of the spectral bandwidth of the incident light. It is shown that the standard deviation of the intensity generally depends on the surface roughness of the diffuser, and on the position of measurement in the far field. Numerical results are given for a diffuser with a Gaussian distribution of surface height limited by a circular aperture. Exact and approximate forms of the probability density function are discussed. The analysis applies when the fluctuations in optical path are greater than the maximum wavelength incident.     

Influence of Magnetic Field and LO Phonon Effects on the Spin Polarization State Energy of Strong-Coupling Bipolaron in a Quantum Dot

On the basis of Lee–Low–Pines unitary transformation, the influence of magnetic field and LO phonon effects on the energy of spin polarization states of strong-coupling bipolarons in a quantum dot (QD) is studied by using the variational method of Pekar type. The variations of the ground state energy $E_0$ and the first excited state the energy $E_1$ of bipolarons in a two-dimensional QD with the confinement strength of QDs $\omega _0$ , dielectric constant ratio $\eta $ , electron–phonon coupling strength $\alpha $ and cyclotron resonance frequency of the magnetic field $\omega _{c}$ are derived when the influence of the spin and external magnetic field is taken into account. The results show that both energies of the ground and first excited states ( $E_0$ and $E_1)$ consist of four parts: the single-particle energy of electrons $E_\mathrm{e}$ , Coulomb interaction energy between two electrons $E_\mathrm{c}$ , interaction energy between the electron spin and magnetic field $E_\mathrm{S}$ and interaction energy between the electron and phonon $E_{\mathrm{e-ph}}$ ; the energy level of the first excited state $E_1$ splits into two lines as $E_1^{(1+1)}$ and $E_1^{(1-1)}$ due to the interaction between the single-particle “orbital” motion and magnetic field, and each energy level of the ground and first excited states splits into three “fine structures” caused by the interaction between the electron spin and magnetic field; the value of $E_{\mathrm{e-ph}}$ is always less than zero and its absolute value increases with increasing $\omega _0$ , $\alpha $ and $\omega _c$ ; the effect of the interaction between the electron and phonon is favorable to forming the binding bipolaron, but the existence of the confinement potential and Coulomb repulsive energy between electrons goes against that; the bipolaron with energy $E_1^{(1-1)}$ is easier and more stable in the binding state than that with $E_1^{(1+1)}$ .     

Properties of Squeezed Binomial States and Squeezed Negative Binomial States

Abstract

The effect of squeezing on binomial states and on negative binomial states is studied in terms of second-order correlation functions and quasi-probabilities of Wigner and Q-functions. The photon number distribution of these states is also discussed. The results presented for squeezed binomial (negative binomial) states may be useful for studying a transition from squeezed coherent states to squeezed number (quasi-thermal) states.