基于低Q腔光子Faraday旋转的远程态制备

基于低Q腔中单光子的输入与输出关系,提出了利用偏振光Faraday旋转分别遥远制备单原子态和两原子纠缠态的可行方案.研究结果表明,当初始原子态的系数为实数时,通过选择合适的偏振光、腔场与原子相互作用系统的参数,单原子态与两原子纠缠态的远程制备均可确定性地得以实现.与以前的原子态远程制备方案相比,本文方案采用光子作为飞行比特来传递量子信息,故原则上可实现原子态的真正长距离制备.由于原子态的信息编码在耗散单边腔囚禁的Λ型三能级原子的两个基态能级,且原子仅虚激发,因此本文方案对腔衰减和原子自发辐射不敏感.此外,本文所提出的两种方案不需要两体或多体正交测量,仅涉及单体直积态测量,而且两种方案都工作在低Q腔,不需要原子与光腔的强耦合,从而有效降低了实验难度.     

Efficient scheme for realizing quantum dense coding with GHZ state in separated low-Q cavities

We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in three spatial separated cavities. Meanwhile, with the assistance of a coherent optical pulse and X-quadrature homodyne measurement, we can implement quantum dense coding with three-particle GHZ state with a higher probability. Our scheme can also be generalized to realize N-particle quantum dense coding.     

Numerical simulation of mode interaction in 170 GHz/1 MW gyrotrons for iter

The paper presents an advanced method for and results of calculating main parameters of CW 170 GHz/1 MW gyrotrons operating at the TE_28.7 and TE_31.8 modes for ITER. Parameters are optimized to achieve maximum efficiency of the gyrotron with an acceptable Ohmic load on the cavity. Numerical modeling of starting up a gyrotron with an optimized cavity and processes of mode interaction are discussed.     

Numerical simulation and experimental study of magnetron injection guns of high-power shortwave gyrotrons

The results of numerical simulation and experimental study of magnetron injection guns for high-power gyrotrons that form intense helical electron beams are compared. Three types of beams are studied: those with regularly intersecting trajectories, laminar, and mixed (with irregularly intersecting trajectories). The corresponding guns differ in the angle of inclination of the emitting surface to the axis of axial symmetry. Numerical simulation was performed using the ÉPOS program, which takes into account the effect of the space-charge field on the velocity distribution. The experimental studies of the latter were performed by the retarding-field method. It is established that with allowance for temperature deformations of the electrode systems, the experimental data are in satisfactory agreement with the theoretical. It is shown that for a maximal beam current, the best velocity-distribution characteristics (velocity spread and pitch factor) are provided by guns that form laminar and boundary beams (an intermediate case between laminar and regularly intersecting beams).     

Dynamic processes in helical electron beams in gyrotrons

The results of theoretical and experimental studies of collective processes in helical electron beams in gyrotron-type devices are generalized. Main attention is paid to low-frequency oscillations associated with the development of instability in the space charge trapped between the cathode and the magnetic mirror. The mechanism of evolution of instability is substantiated and the effect of oscillations on the main parameters of the electron flow determining its quality is analyzed. Data on the suppression of low-frequency oscillations and resulting enhancement of the gyrotron efficiency are considered.     

Numerical simulation of transient processes in hydroturbines

A method for calculation of unsteady 3D turbulent flows in hydro turbines of power plants developed for simulation of the transient processes is presented herein. The method is based on joint solution to the Reynolds-averaged Navier—Stokes equations for incompressible fluid flow written for moving mesh, the equation of runner rotation and the system of 1D equations describing propagation of elastic hydraulic shock in the flow domain. The exchange in flow parameters between the penstock and hydro turbine regions is considered in this approach. Results of transient processes simulation are presented for several modes: start-up to the turbine regime, instantaneous load shedding, and output power decrease. Comparison with experimental data is performed.     

微通道板动态特性的数值模拟

对皮秒高压脉冲驱动下微通道板中电子的渡越时间特性和增益特性进行了数值模拟,在电压脉冲波形分别为高斯形、三角形和梯形时,得到了电子渡越时间与电压脉冲宽度、幅度的关系曲线。在考虑入射电子为一高斯电子脉冲的情况下,获得了增益曲线的半峰全宽和峰值随脉冲电压幅度、宽度的变化规律。分析结果表明：当微通道板两端所加电压为梯形波时,微通道板中电子的渡越时间特性和增益特性较加三角波和高斯波要好。     

Numerical simulation of chemical processes in atmospheric plasmas

A model is built to study chemical processes in atmospheric plasmas at low altitude (high pressure) and at high altitude (low pressure). The plasma lifetime and the temporal evolution of the main charged species are presented.The electron number density does not strictly obey the exponential damping law in a long period. The heavy charged species are dominant at low altitude in comparison with the light species at high altitude. Some species of small amount in natural air play an important role in the processes.     

一维大气等离子体化学过程数值模拟

用数值模拟方法研究了低空及高空环境下，大气等离子体的化学反应及一维扩散过程. 推导了三组分(电子和正负离子)的双极扩散公式，观察了扩散过程中不同组分的空间分离，以及扩散和化学反应对电子数密度演化的贡献. 关键词： 大气等离子体 化学过程 数值模拟     

喷气Z箍缩内爆动力学过程的数值模拟研究

在分析了喷气Z箍缩内爆等离子体物理过程的基础上，作了必要的假定和简化，给出了物理模型和相应的数学方程组.研制了一维三温辐射磁流体动力学的数值模拟程序，对氖喷气Z箍缩内爆产生高温高密度等离子体过程进行了总体数值模拟，得到了等离子体各参量在内爆过程中的时空分布，再现了该内爆动力学整体过程，并与GAMBLE-Ⅱ装置的实验结果进行了比较.计算结果表明，在对热传导系数和等离子体电阻率作适当调整后，得到的计算结果是自洽的，其中内爆到心时刻、x射线辐射脉冲的脉宽和总能量等宏观量与实验结果比较接近.同时对喷气Z箍缩内爆过 关键词： 喷气Z箍缩 x射线辐射 辐射磁流体动力学     

大气环境下氦气等离子体中化学过程数值模拟

建立一个大气化学程序用以模拟大气压下（地面附近）或低压（高空）情况下混合气体（氦气中混入少量空气）中产生等离子体后的化学过程。给出了电子寿命和主要带电粒子的随时间演化图。电子寿命在大气压下要长于大气等离子体，但在低压情况下这个结论不成立。电子数密度在一很长一段时间内不服从指数衰减规律。     

低温冷冻靶温度动态特性的数值模拟研究

惯性约束聚变点火成功的关键之一在于靶丸内形成均匀的氘氚冰层,靶丸周围的温度场对冰层质量有很大影响.首先通过实验靶系统实验验证了数值计算模型的可靠性,在此模型的基础上,对低温冷冻靶装置的热物理问题特别是温度动态特性问题展开了数值模拟,重点考察冷环温度波动时,温度传递衰减过程的规律以及各影响因素对于温度传递衰减过程的影响.结果显示:冷环温度一定时,填充气体压力降低、填充气体中氦气比例增大,靶丸表面温度均匀性提高;当冷环温度波动时,温度波动的周期减小、振幅减小、填充气体压力升高、填充气体中氦气比例降低有利于控制靶丸表面温度波动;冷环温度波动的周期适中、振幅减小、填充气体压力降低、填充气体中氦气比例提高有利于改善靶丸表面温度均匀性.研究结果对实验中冷冻靶合理配置各参数实现温度控制具有重要参考价值.     

强激光辐照下纳米铜动态拉伸型断裂的数值模拟

基于强激光辐照加载下纳米铜的层裂实验,采用含逾渗软化函数的损伤度函数模型对实验结果进行了数值模拟研究。强激光加载条件被简化为高斯分布脉冲压力施加在镍合金基体的前表面上。数值计算结果显示：损伤演化明显地改变了试样中波传播特性,无论是对微损伤还是完全层裂的试样,计算都较好地再现了实测自由面速度剖面,表明了含逾渗软化函数的损伤度函数模型在强激光加载条件下纳米铜层裂问题分析中具有较好适用性。     

Three-dimensional simulation of dynamic processes of formation of microclusters in a crystalline matrix

A discrete computer model of multistage processes of formation of porous clusters in a crystalline matrix is developed and constructed. A package of computer programs simulating dynamic processes of formation of a cluster in the bulk of crystals is developed taking into account the processes occurring at the surface, external fields, and chemical reactions accompanying these processes. The morphological pattern of formed pores is correlated with the regularities associated with the shape of the current-voltage characteristic of anodization.     

The simulation of XYZ-spin chain in coupled cavities

We simulated anisotropic XYZ-spin chain with an array of coupled cavities, each of which contains one 4-level atom. The anisotropic parameters of the effective Hamilton can be tuned by controlling the external lasers. The validity of our approximations is confirmed via a numerical simulation.     

Quantum dynamic behaviour in a coupled cavities system

The dynamic behaviour of the two-site coupled cavities model which is doped with ta wo-level system is investigated.The exact dynamic solutions in the general condition are obtained via Laplace transform.The simple analytical solutions are obtained in several particular cases,which demonstrate the clear and simple physical picture for the quantum state transition of the system.In the large detuning or hoppling case,the quantum states transferring between qubits follow a slow periodic oscillation induced by the very weak excitation of the cavity mode.In the large coupling case,the system can be interpreted as two Jaynes-Cummings model subsystems which interact through photon hop between the two cavities.In the case of λ≈△>> g,the quantum states transition of qubits is accompanied by the excitation of the cavity,and the cavity modes have the same dynamic behaviours and the amplitude of probability is equal to 0.25 which does not change with the variation of parameter.     

位错与溶质原子间动态相互作用的数值模拟研究

通过Cottrell-Bilby型溶质动力学模型，对位错线周围的溶质原子浓度随应变率的变化进行了研究，并得到了三种不同的位错-溶质相互作用方式：在低应变率时，位错被溶质原子气团充分钉扎，它上面的溶质浓度近似达到饱和；在高应变率时，脱钉作用占主导地位，位错运动几乎不受深质影响；而在中间应变率时，位错反复经历着钉扎和脱钉过程，动态应变时效发生.此外，通过对模型方程的推导，还自然地得到了平衡状态下率相关流动应力与应变率之间的N形关系曲线. 关键词： 位错 溶质原子 动态应变时效 数值模拟