高Q光学微球腔角速度传感效应验证

根据角速度传感的基本原理,搭建了以高Q光学微球腔为核心敏感部件的角速度传感实验测试系统。实验中通过调制、解调技术得到了光学微球腔的谐振曲线及其相对应的解调曲线,并采用PID反馈控制电路实现了微球腔谐振点的实时跟踪锁定,谐振点锁定精度约为10 kHz。通过对系统提供低、高2组不同的旋转角速度进行实验测试,并对数据进行处理分析,得到系统输出信号幅度的变化趋势与测试转台提供的旋转角速度变化情况相对应的结果。初步验证了高Q光学微球腔的角速度传感效应,为后续深入研究高Q光学微谐振腔角速度传感器件奠定了基础。     

THE OSCILLATION MODE OF INCOMPRESSIBLE CAVITY FLOW

采用二维大涡模拟方法进行了空腔水流场的数值计算, 考察空腔前缘动量损失厚度及来流速度等因素如何影响空腔流的振荡, 同时考察了空腔长深比与空腔流振荡模式的关系. 用空腔水流场的粒子图像测速测量结果验证了数值计算的可信性.结果表明, 空腔水流是否发生振荡取决于壁面摩擦速度.瞬时涡结构和空腔阻力系数2个方面的特征显示空腔水流场有2种典型的振荡模式, 剪切层模式与尾流模式, 确定振荡模式的关键因素是空腔长深比.     

Escape of Particles from an Open Square-Shaped Cavity

The escape of particles in an open square-shaped cavity has been examined. We consider a family of trajectories launched from the left bottom lead of the square cavity and escaped from the right boundary. For each escaping trajectories, we record the propagation time and the detector position. We find that the escape time graph exhibits a regular sawtooth structure. For a set of detector points, we search for the classical trajectories from the source point to the detector points. Then we use semiclassical theory to construct the wave function at different given points. The calculation results suggest that the escape probability density depends on the detector position and the momentum of the particle sensitively. The Fourier transform of the semiclassical wave function gives the path length spectrum. Each peak in the path length spectrum corresponds to the length of one escape trajectory of the particle. We hope that our results will be useful in understanding the escape and transport process of particles inside a microcavity.     

Scheme for Implementing Controlled Dense Coding with Six-Atom Cluster State in Cavity QED

We propose an experimentally feasible protocol for implementing controlled dense coding with a six-atom cluster state in cavity QED. In the scheme, we investigate that the atoms interact simultaneously with the highly detuned single-mode cavity and the strong classical driving field, and thus our scheme is not sensitive to both the cavity decay and the thermal field. In addition, the four-atom entangled states can be exactly distinguished by performing the single-atom measurements in cavity QED, therefore our scheme might be implemented in a simple way.     

非定常空泡闭合区域最大压力的理论研究

当物体在流体中高速运动产生空泡时,空泡通常以回射流的形式闭合在物体表面上,并在闭合位置对物体表面产生流体超压. 在物体表面上的空泡闭合位置一般不是固定的,其位置根据物体运动速度的变化、空泡压力的变化及重力场中的位置等因素而在物体表面发 生快速移动,在非对称情况下,这种移动超压会极大影响运动物体的稳定性. 基于势流理论研究了重力场中非定常垂直空泡闭合区域中最大压力的存在位置,推导了最大压力的理论公式,揭示了最大压力与空泡发 展速度之间的关系,证明了最大压力点的两个特殊流体性质. 最后设计了测量空泡闭合区域最大压力的验证性试验,并将理论计算结果与试 验测量结果进行了对比,验证了理论研究结果.     

Evolution of three-dimensional cavitation following water entry of an inclined cylinder

The water entry of an inclined cylinder is firstly studied experimentally for low Froude number. The cylinder is 50 mm in diameter and 200 mm in length, with a moderate length to diameter ratio. As it is submerged below the water surface, the cavity is fully three-dimensional. Due to the rotation of the cylinder caused by the initial inclined impact, the cavity evolution is quite complicated and a new phenomenon is revealed. The cylinder moves along a curved trajectory in water, which greatly affects the evolution of the cavities. The cavity breaks up into two sub-cavities, and finally collapses because of hydrostatic pressure.     

Mechanical effects of light on the Ξ-type three-level atom in a high-finesse optical cavity

A theoretical study is carried out for the modification and implication of the effect on the Ξ-type three level atom in a high-finesse optical cavity driven by light field including spontaneous emission and the cavity decay. Analytic expressions for the dipole force, the friction force, the optical potentials and the friction coefficient are obtained. Then the numerical and graphical methods are used to investigate the friction coefficient with the controlling parameters. It is shown that the friction coefficient is strongly dependent on the controlling parameters. The cooling rate can increase by one order of magnitude more than that of a two-level atomic system. The reason can be given using the dressed states and the Sisyphus cooling mechanism, which would stimulate further experimental investigations.     

Nonlocal quantum cloning via quantum dots trapped in distant cavities

A scheme for implementing nonlocal quantum cloning via quantum dots trapped in cavities is proposed.By modulating the parameters of the system,the optimal 1 → 2 universal quantum cloning machine,1 → 2 phase-covariant cloning machine,and 1 → 3 economical phase-covariant cloning machine are constructed.The present scheme,which is attainable with current technology,saves two qubits compared with previous cloning machines.     

Analysis of radiometer effect on proof mass in purely gravitational orbit

Spacecrafts with the pure gravity environment are of great significance in precision navigation,gravity field measurement for celestial bodies,and basic physics experiments.The radiometer effect is one of the important interfering factors on the proof mass in a purely gravitational orbit.For the gravity field measurement system based on the inner-formation flying,the relationship between the radiometer effect on the innersatellite and the system parameters is studied by analytical and numerical methods.An approximate function of the radiometer effect suitable for the engineering computation and the correction factor are obtained.The analytic results show that the radiometer effect on the inner-satellite is proportional to the average pressure while inversely proportional to the average temperature in the outer-satellite cavity.The radiometer effect increases with the temperature difference in the cavity,and its minimum exists when the cavity radius increases.When the minimum of the radiometer effect arrives,the ratio of the cavity radius to the inner-satellite radius is 1.189 4.This constant is determined by the spherical cavity configuration and independent of the temperature and pressure distributions.When the ratio of the cavity radius to the inner-satellite radius is more than 10,it is believed that the cavity is large enough,the radiometer effect is approximately proportional to the square of the inner-satellite radius,and the influence of the outer-satellite cavity radius on the radiometer effect can be ignored.     

Strong Coupling Optomechanics Mediated by a Qubit in the Dispersive Regime

Cavity optomechanics represents a flexible platform for the implementation of quantum technologies, useful in particular for the realization of quantum interfaces, quantum sensors and quantum information processing. However, the dispersive, radiation–pressure interaction between the mechanical and the electromagnetic modes is typically very weak, harnessing up to now the demonstration of interesting nonlinear dynamics and quantum control at the single photon level. It has already been shown both theoretically and experimentally that if the interaction is mediated by a Josephson circuit, one can have an effective dynamics corresponding to a huge enhancement of the single-photon optomechanical coupling. Here we analyze in detail this phenomenon in the general case when the cavity mode and the mechanical mode interact via an off-resonant qubit. Using a Schrieffer–Wolff approximation treatment, we determine the regime where this tripartite hybrid system behaves as an effective cavity optomechanical system in the strong coupling regime.