自旋为j的粒子在旋转磁砀中的几何相位

用相干态的方法得到旋转磁场中自旋为j的粒子的态矢量的严格表达式，由此可计算相干态和叠加相干态的Abaronov－Anandan相位（AA相让）．并具有清楚的物理图象．     

合成孔径声呐分裂阵相位相干测高方法

利用合成孔径声呐可以获得高分辨力地貌或目标成像，在合成孔径基础上进一步采用分裂阵相位相干测高方法可以获得地貌或目标的三维成像。分析论证合成孔径中分裂阵相位相干测高的原理，在影响测高误差的诸多参数中着重针对相位差测量的因素进行了分析，并进行了仿真研究。仿真研究结果表明：利用小尺度合成孔径声呐进行三维成像的测高精度可达到目标水平距离的1％。     

全金属超表面在电磁波相位调控中的应用及进展

全金属超表面是由亚波长金属单元所组成的结构阵列,其在调控电磁波相位方面展现出了效率高、带宽大等特点,并且相较于金属-介质混合型超表面,全金属超表面具有优良的热学和机械性能,如耐高温、强度大、延展性好等,这使得其可以应用于高温高压等极端复杂环境中。本文对近年来全金属超表面取得的研究进展进行了简要的归纳总结,主要介绍了其在构建高效、多功能平面光学器件以及多频谱电磁隐身中的应用,并对其未来的发展方向进行了展望。

     

偏振无关的可变纯相位延迟器研究

提出了一种由快轴保持正交方位放置的两片相同的液晶可变相位延迟器构成的可变纯相位延迟器结构设计.利用琼斯矩阵,从理论上推导了该结构在任意偏振光入射条件下,出射光偏振态与入射光偏振态保持一致.实验上,在两片液晶可变相位延迟器所加电压分别为1.55V和1.49V时,分别测量了入射光和出射光的偏振态,表征偏振态的入射光和出射光的Stokes参教基本一致.上述两者结果都表明,该结构具有较好的纯相位调制特性,并给出了控制电压在1～2.7V范围时的相位变化.     

偏相干分析在客车降噪中的应用

车内低频噪声一直是汽车NVH研究关注的重点问题,常需要找到对噪声影响较大的振动结构进行改进,但是振动对场点的贡献并不能代表对整个声场噪声的贡献量。针对多峰值多场点的车内声场问题,引入"总相干系数"和"相干系数和"的概念对现有的偏相干分析方法进行改进。对某型客车的车内噪声进行小波包分解,得到车内声场的声学特性,确定研究的频率范围。通过对各板件振动与车内测点噪声信号进行偏相干分析,确定对车内声场影响较大的结构,并在实车上实施了改进措施。结果表明,车内噪声测点声压级降低0.5 d B~2 d B,为有效降低客车车内噪声提供了指导方向。     

浅海相干声场的单参数海底模型建构

海底反射性质在浅海声传播中起着决定性的影响。利用海底反射损失对掠射角的斜率可作为单个参数F dB来描述海底这一前提,对平面波入射液态半无限空间的情况进行推导,提出一种基于简单近似表示反射相位角关系的算法。将单参数F dB以及反射相变作为计算模型的边界条件输入参数,对浅海相干声场进行计算,将适用范围推广到复杂声速和水平变化情况。通过对三种类型海底进行仿真,比较基本参数海底模型及单参数海底模型计算所得传播损失曲线,验证了所提包含反射相变关系的单参数模型的有效性。     

干涉SAR相干系数估计的快速算法

在SAR干涉测量中,相干系数是干涉图像对相位稳定性的衡量标准。干涉基线距和地表地形都影响相干系数的计算,在通常的相干系数的计算中,需要补偿由基线和地形引起的干涉相位,造成相干系数计算中计算量的大大增加。本文应用了一种不需要进行相位补偿的相干系数计算方法,并与通常的相干系数的计算方法相比较。实验结果证明,本算法在保证一定的相干系数计算精确性的基础上,大大提高了相干系数的计算效率,可以应用于快速浏览相干图像对,以评价其用于相干测量时的质量好坏。     

几何布朗运动在股价模型中的应用

证券价格波动服从几何布朗运动是著名的Black—Scholes期权定价公式的基本前提假设，在金融定价领域具有十分重要的应用。本文用证券价格的随机游走模型对几何布朗运动进行了逼近，从而证明了股票价格过程可以用几何布朗运动来描述。本文在最后探讨了几何布朗运动刻画股价运动的合理性和局限性。     

相位补偿电路在有源滤波电路中的应用

针对有源滤波电路在滤波的同时会产生信号滞后的问题,提出一种带有相位补偿功能的电路.应用TL084集成运放组成的滤波器来实现滤波,设计了输出频率为0～100Hz的信号有源低通滤波电路.采用Multisim仿真软件对设计电路进行仿真分析,仿真结果与理论分析一致.结果表明,相位补偿电路对此滤波电路具有很好的相位补偿作用.     

一种采用相位补偿的线谱相干检测器

分析了加窗和实信号情况下相干线谱检测器的检测性能。从频谱泄漏现象出发,通过对实信号做加窗处理,有效地降低了信号傅里叶变换后频谱泄漏的旁瓣级,提升了弱信号的探测能力;针对分段处理时同一频率不同数据段出现的相位差,采用相位补偿的方法,实现了各段数据的相干叠加。理论分析和计算机仿真表明,相比于平均功率谱检测器(Average Power Processor,AVGPR),加窗相位补偿检测器(Window Phase-Compensated Processor,WPCPR)有10 lg L(L为分段数)信噪比的提高,从而拓宽了相干线谱检测的适用范围。此外,还从频域波束形成的角度,给出了WPCPR能提高信噪比的一种物理解释,并指出了仿真中信噪比增益与理论值存在差异的原因。     

Spatial Non-Cyclic Geometric Phase in Neutron Interferometry

We present a split-beam neutron interferometric experiment to test the non-cyclic geometric phase tied to the spatial evolution of the system: the subjacent two-dimensional Hilbert space is spanned by the two possible paths in the interferometer and the evolution of the state is controlled by phase shifters and absorbers. A related experiment was reported previously by some of the authors to verify the cyclic spatial geometric phase. The interpretation of this experiment, namely to ascribe a geometric phase to this particular state evolution, has met severe criticism. The extension to non-cyclic evolution manifests the correctness of the interpretation of the previous experiment by means of an explicit calculation of the non-cyclic geometric phase in terms of paths on the Bloch-sphere. The theoretical treatment comprises the cyclic geometric phase as a special case, which is confirmed by experiment.     

Measurement-device-independent quantum key distribution with odd coherent state

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all the detection attacks, thus when it is combined with the decoy-state method, the final key rate can be obtained by estimating the gain and quantum bit error rate for various input photon numbers. In this paper, we propose to perform MDI-QKD with odd coherent state (OCS) and compare the results with weak coherent source scenario. Our simulation indicates that both the secure key rate and transmission distance can be improved evidently with OCS owing to the lower probability of multi-photon events of the OCS. Furthermore, we apply the finite key analysis to the decoy-state MDI-QKD with OCS and obtain a practical key rate.     

Four-mode coherent entangled state as an entanglement of two bipartite coherent entangled states

By introducing a four-mode unitary operator U = exp[?iλ(X ₁ P ₂ + X ₂ P ₃ + X ₃ P ₄ + X ₄ P ₁)], we show how a four-mode coherent entangled state can be generated by entangling a two bipartite coherent entangled state. The corresponding squeezed vacuum state U|0000? in four-mode Fock space is derived by virtue of the technique of integration within ordered production of operators, which exhibits the standard squeezing for the four-mode quadratures. A new ideal quantum mechanical representation |α, β, γ? is constructed from U|0000? in the limit of infinite squeezing, which possesses the properties of both coherent and entangled states. The entanglement involved in |α, β, γ? is explained. A scheme for generating |α, β, γ? is presented.     

Optical protocol for quantum state sharing of superposed coherent state

We propose an optical protocol for quantum state sharing of superposed coherent state in terms optical elements. Our protocol can realize a near-complete quantum state sharing of a superposed coherent state with arbitrary coeficients. The realization of this protocol is appealing due to the fact that the quantum state of light is robust against the decoherence and photons are ideal carriers for transmitting quantum information over long distances. This protocol can also be generalized to the multiparty system.     

Time-dependent state populations with and without the rotating wave approximation: a model-based study

We present a benchmark study by comparing time-dependent electronic state populations calculated in the rotating wave approximation (RWA) to those obtained in numerical exact simulations without the application of the RWA. A wide range of laser intensities and energies are considered in order to explore the limits of the RWA. Our model system consists of a single electron confined to a finite potential well of atomic size so that there are five bound electronic states. The presented numerical study is carried out in the dipole approximation considering either two or all the five electronic states of the system.     

Why a Condensate Can Be Thought of as Having a Definite Phase

We present an argument for assigning a definite phase to an assembly of Bose-Einstein Condensed atoms. This relies on the demonstration that a coherent state of the condensed system is a robust state in the presence of interactions between the condensate and its environment.     

Quantum interference between an arbitrary-photon Fock state and a coherent state

Using the phase space method, we study the quantum interference through a Mach–Zehnder interferometer with an arbitrary-photon Fock state and a coherent state as two inputs. The statistical properties, in terms of the Wigner function, average photon number, photon number distribution and parity, are derived analytically for the field of the individual output port. These results indicate that the output state is actually a statistical mixture between a bunch of Fock state and coherent states. In addition, the phase sensitivity is also examined by using the detection scheme of intensity difference measurement.     

Entanglement of a new type of two-mode photon-added entangled coherent state

We introduce a new entangled state, which is composed of two photon-added coherent states. We discuss the entanglement of this state by using several sufficient entanglement criteria, such as higher-order entanglement criterion, EPR criterion, SU(1,1) algebra and Cauchy–Schwarz inequality. These criteria reflect some entanglement effects of this new state, but fail to find the degree of entanglement directly. Thus, we use the covariance to measure the entanglement in this state. Our findings show that the degree of entanglement decreases with the increasing of photon-number and the amplitude of the coherent states. One interesting result is that the new entangled state becomes a maximally entangled state when the photon-added number is 1 and the amplitude of the coherent states is zero, which is just one of the four Bell states.     

Analysis of rotating fields in magnetic bubble drive coils

Closed-form normalized expressions for the field components inside a single-layer rectangular solenoid are derived from a model in which the solenoid is approximated by finite length current sheets of infinitesimal thickness. The equations are extended by superposition to include the case of a multi-layered solenoid, and the effects of nearby magnetic materials are included by employing the method of images. Computer generated field plots compare favorably with measured data.