Linear Amplifier and Quasiprobability Distribution Functions for the Squeezed Displaced Fock States

The nondiagonal P-function (complex andpositive) for the output field with the squeezedcoherent state as an initial state to a linear amplifieris obtained. Moments of the field operators arecalculated. The Wigner distribution function for the outputof a linear amplifier is discussed. The input lightfield of the linear amplifier is assumed to be asqueezed displaced Fock state. Investigation of theWigner distribution functions at the output fields iscarried out, where it is found that the distributionspreads out as it rotates in the phase space with timedevelopment. For the case of a squeezed displaced Fock state input it is found that thedistribution disintegrates into two subdistributions.The phase distribution for the output light is discussedthrough the phase function associated with the Wigner function for different inputs.     

Linear amplifier via the displaced Fock states superposition

The linear amplifier with the superposition of displaced Fock states (DFS’s) as an input field is discussed. The s-parameterized characteristic function (CF) of linear amplifier for the superposition of two DFS’s is considered. Several quantum statistical expectation values for the output of linear amplifier are evaluated once the time dependent CF has been computed. The Glauber secondorder coherence function is calculated. The squeezing properties of the output field are studied. The s-ordered quasiprobability distribution function (QDF) for the output of linear amplifier driven by DFS’s superposition is investigated. The phase properties of the superposition of DFS’s are studied. The s-parameterized phase distribution, obtained by integrating the s-parameterized QDF over radial variable is illustrated.     

Nontrapping arrest of Langmuir wave damping near the threshold amplitude

Evolution of a Langmuir wave is studied numerically for finite amplitudes slightly above the threshold which separates damping from nondamping cases. Arrest of linear damping is found to be a second-order effect due to ballistic evolution of perturbations, resonant power transfer between field and particles, and organization of phase space into a positive slope for the average distribution function f(av) around the resonant wave phase speed nu(ph). Near the threshold trapping in the wave potential does not arrest damping or saturate the subsequent growth phase.     

Continuous-Variable Quantum Key Distribution Based on Heralded Hybrid Linear Amplifier with a Local Local Oscillator

An improved continuous variable quantum key distribution (CVQKD) approach based on a heralded hybrid linear amplifier (HLA) is proposed in this study, which includes an ideal deterministic linear amplifier and a probabilistic noiseless linear amplifier. The CVQKD, which is based on an amplifier, enhances the signal-to-noise ratio and provides for fine control between high gain and strong noise reduction. We focus on the impact of two types of optical amplifiers on system performance: phase sensitive amplifiers (PSA) and phase insensitive amplifiers (PIA). The results indicate that employing amplifiers, local local oscillation-based CVQKD systems can enhance key rates and communication distances. In addition, the PIA-based CVQKD system has a broader application than the PSA-based system.     

Zur Frage der Landau-Dämpfung im anisotropen Plasma

Starting from a wellknown form of the dispersion equation in quasistatic approximation some expressions for the Landau damping in anisotropic electron plasmas are derived. For special distribution functions they are of the form given by Jackson for a plasma without magnetic field. The essential part of the general stability criterion is derived. Using the Dawson model for Landau damping we obtain exactly the above expressions.     

相位损耗腔中TaVis-Cummings模型的熵特性

研究了Tavis—Cummings模型中光场存在相位损耗时,原子-光场系统线性熵、原子线性熵和光场线性熵的时间演化特性,讨论了光场的不同量子统计性质、不同的衰变常数和两原子的初始状态对各线性熵的影响。结果表明：光场的不同量子统计性质使得系统线性熵、原子线性熵和光场线性熵均发生明显改变。系统线性熵的演化与原子的初始状态无关,而原子线性熵的演化较强地依赖于原子的初始状态,但与腔场的相位损耗无关。     

A degenerate three-level laser with a parametric amplifier

The aim of this paper is to study the squeezing and statistical properties of the light produced by a degenerate three-level laser whose cavity contains a degenerate parametric amplifier. In this quantum optical system the top and bottom levels of the three-level atoms injected into the laser cavity are coupled by the pump mode emerging from the parametric amplifier. For a linear gain coefficient of 100 and for a cavity damping constant of 0.8, the maximum intracavity squeezing is found at steady state and at threshold to be 93%.     

耗散腔中简并Raman耦合系统中光场的相位特性

利用Pegg-Barnett相位理论,研究了耗散腔中两个A型原子与相干态光场在Raman相互作用下光场的相位特性,并讨论了光场平均光子数和腔场耗散系数对光场相位特性的影响.结果表明:当腔不存在损耗时,光场相位分布概率以π/λ作周期性振荡;且在t=nπ/λ时刻,光场和原子是退纠缠的,相位分布概率曲线在极坐标图中呈单叶型结构;但在演化周期内,由于光场与原子的相互作用相位分布概率曲线会劈裂为多叶型结构.当腔场存在损耗时,相位分布概率的叶型结构会向中心扩散最终变为一个圆,即表明在考虑腔场耗散时光场的相位最终会变为随机分布;而且腔的耗散系数越大,光场相位越快趋于随机分布.另外,随光场的平均光子数增大,光场相位分布趋于集中.光场相位涨落受到腔场耗散的影响呈现出衰减周期振荡最终达到稳定值,而且达稳定值所需时间随耗散系数的增大而缩短.     

Two-Photon Jaynes-Cummings Model Governed by Milburn Equation with Phase Damping

In this paper, we find an analytic solution of the master equation of a non-resonant two-photon JaynesCummings model (JCM) with phase damping with the help of the super-operator technique. We study the influence of phase damping on non-classical effects in the JCM, such as oscillations of the photon-number distribution, revivals of the atomic inversion, and sub-Possion photon statistics. It is demonstrated that the phase damping suppresses the revivals of the atomic inversion and non-classical effects of the cavity field in the JCM.     

Operatorenmethode zur Lösung der Vlasov-Gleichung mit BGK-Stoßglied und äußerem elektrischem Feld

Irreversible processes in a classical electron plasma are treated on the basis of a linearized Vlasov equation supplemented by Bhatnagar-Gross-Krook terms describing electron-electron and electron-ion collisions correctly. The infinitely extended plasma is under the action of a space- and time-dependent external electric field. A general method of solution with projection operator techniques is given which results in a system of two coupled Volterra integral equations of the convolution type for the internal electric field and the current density. From there follows the electron distribution function, the electric field in the plasma, the electrical conductivity and a very general dispersion relation including Landau and collision damping. The method given can be generalized f. i. for multicomponent plasmas and for strong external electric fields.     

利用分形法表征光学元件中高频相位畸变

针对神光Ⅲ主机装置使用的光学元件,基于分形理论,分析中高频相位畸变的统计分布特征,指出其满足分数布朗随机场,并利用结构函数法对分形维数进行计算,统计结果显示,大口径钕玻璃片的分形维数在2.34~2.43之间。利用局部稳态的随机中点位移法,提出一种新的表征光学元件相位的方法,将分形维数作为参数,可衡量中高频相位畸变,对高功率激光光学元件的评价有参考意义。     

Performance improvement of unidimensional continuous-variable quantum key distribution using heralded hybrid linear amplifier

We propose an improved scheme for unidimensional continuous-variable quantum key distribution (UCVQKD) using heralded hybrid linear amplifier, aiming to simplify the implementation and improve secret key rate. Different from the symmetrical continuous-variable quantum key distribution protocol (CVQKD), this scheme modulates one quadrature of the coherent state with security insurance. The heralded hybrid linear amplifier concatenates a deterministic linear amplifier (DLA) and a noiseless linear amplifier (NLA), which can tune between the high-gain or high noise-reduction for performance enhancement. Security analysis shows that the proposed scheme can be secured under the collective attacks. Compared with traditional UCVQKD involving noiseless amplifier, the security transmission distance of proposed protocol is increased by 24 kilometers. It not only simplifies the modulation process but also has approximate performance with symmetrical CVQKD in terms of maximal security transmission distance.     

双模光场与级联三能级原子相互作用系统中熵的演化

在大失谐的条件下，且腔场存在位相损耗时，研究了级联三能级原子与双模光场相互作用系统的线性熵、光场的线性熵和原子的线性熵随时间演化特性，分析了Stark位移和不同的初始双模光场对各线性熵的影响. 关键词： 位相损耗 双模光场 线性熵     

Recent results on hyperpolarized<Superscript>3</Superscript>He−<Superscript>4</Superscript>He liquid mixtures

Laser optical pumping in low magnetic field provides very high nuclear polarizations in gaseous helium mixtures, and is used to prepare polarized liquid. Wall relaxation in glass cells is effiently reduced using cesium coatings, and bulk longitudinal relaxation times are measured. In highly magnetized samples, dipolar fields control the spin dynamics in anisotropic volumes and weak external magnetic field inhomogeneities. Long lived magnetostatic modes are observed by pulsed NMR. Detailed analysis of their frequency and damping gives information on magnetization density and spin diffusion coefficient in polarized mixtures. Experiments are performed above 0.2 K on mixtures with³He concentrations of order a few percents or larger. When phase separation occurs, the³He-rich phase retains a high polarization.     

Weyl Ordering Symbol Method for Studying Wigner Function of the Damping Field

The symbolic method (including normal ordering. antinormal ordering and Weyl ordering symbol) is usually utilized to tackle miscellaneous operators which have different commutative relations. Considering the Weyl ordering symbol’s remarkable properties, we have efficiently and conveniently derived the Wigner distribution function for field damping in a squeezed bath and a vacuum bath respectively, and then examined the decoherence processes from the plots of Wigner function and its contour in quantum phase space. Alternatively, we can employ a general Wigner operator under phase space transform to calculate distribution function and discuss the damping process.     

相位损耗腔中大失谐Jaynes-Cummings模型中熵的演化

研究了一位于相位损耗腔中大失谐下二能级原子与相干态场相互作用系统中，光场线性熵、原子线性熵以及光场－原子系统线性熵的演化，讨论了原子初始状态和光场的平均光子数对各线性熵的影响，结果表明，光场线性熵和原子线性熵的演化都较强地依赖于原子初始状态，而系统线性熵的演化与原子初始状态无关。由于光场平均光子数的增加，光场、原子和系统的线性熵都会增加。     

非线性光学腔中的相位调制光机械动力学

研究了Fabry-Perot光学腔中包含一个光学参量放大器来增强腔场与机械振子之间的耦合的光机械动力学行为.在解析边带机制下用量子郞之万方程具体研究了振子的涨落光谱、光学多稳态行为、机械阻尼与修正共振频移和基态冷却.通过数值解讨论了辐射压力诱导机械振子和腔场的稳态振幅所展现的光学多稳态行为,同时也分析了辐射压力引起的修正共振频移和机械阻尼与参量增益、输入激光功率和参量相位这三个因素的关系.此外,随着调节泵浦场的参量相位,振子的涨落光谱呈现简正模式分裂.通过精确求解最终有效声子数论证了基态冷却.结果表明,机械振子的冷却由初始浴温度、机械品质因数和参量相位这个三个因素控制.参量相提供一个新的方法来操控非线性光机械动力学.     

Twisted electrostatic waves in a self‐gravitating dusty plasma

A generalized response (dielectric) function for twisted electrostatic waves is derived for an un‐magnetized self‐gravitating thermal dusty plasma, whose constituents are the Boltzmann‐distributed electrons and positive ions in the presence of negatively charged micrometre‐sized massive dust particulates. For this purpose, a set of Vlasov–Poisson coupled equations is solved along with the perturbed Laguerre–Gauss distribution function, as well as the electrostatic and gravitational potentials in the limit of paraxial approximation. For plane wave solution, the wavefronts of the dust‐acoustic (DA ) wave are assumed to have a constant phase with electric and gravitational field lines propagating straight along the propagation axis. On the other hand, non‐planar wave solutions show helical (twisted) wavefronts, in which field lines spiral around the propagation axis owing to the azimuthal velocity component to account for the finite orbital angular momentum (OAM ) states. The dispersion relation and damping rate for twisted DA waves are studied both analytically and numerically. It is shown that finite OAM states, the dust to electron temperature ratio, and dust self‐gravitation effects significantly affect the linear dispersion and Landau damping frequencies. In particular, the phase speed of twisted DA waves is reduced with the variation of the twist parameter η (= k /lq_ϕ ), dust concentration δ (= n_{d 0}/n_{i 0}), and dust self‐gravitation α (= ω_Jd /ω_pd ). The relevance of our findings to interstellar dust clouds is also discussed for micrometre‐sized massive dust grains.     

高功率激光驱动器中小尺度自聚焦和噪声模型

 建立了一套线性的近似分析方法，研究高功率激光驱动器中强激光传输的小尺度自聚焦效应和相位噪声对光束传输和光束质量的影响，给出了系统噪声强度、B积分值与光束近场调制对比度之间的定量关系。研究表明,为保证输出光束质量，即近场调制对比度小于给定值，系统内的噪声强度必须符合一定的谱分布。