Deterministic Quantum Key Distribution Using Two Non-orthogonal Entangled States

A deterministic quantum key distribution scheme using two non-orthogonal entangled states is proposed.In the proposed scheme,communicators share key information by exchanging one travelling photon with two random and secret polarization angles.The security of the distributed key is guaranteed by three checking phases in three-way channel and the communicators' secret polarization angles.     

General formulation of spin rotations in neutron interferometry

Starting from the fact, that different rotations can lead to states with the same polarization but different phases the expressions of intensity and polarization of the forward diffracted beam after a Laue-case single crystal neutron interferometer are derived for the general case of phase shifts and spin rotations in both beam paths of the interferometer. A basic and instructive experiment where the polarization of the emerging beam is rotated by phase shift is discussed.     

Polarized spin transport in mesoscopic quantum rings with electron--phonon and Rashba spin--orbit coupling

The influence of electron--phonon (EP) scattering on spin polarization of current output from a mesoscopic ring with Rashba spin--orbit (SO) interaction is numerically investigated. There are three leads connecting to the ring at different positions; unpolarized current is injected to one of them, and the other two are output channels with different bias voltages. The spin polarization of current in the outgoing leads shows oscillations as a function of EP coupling strength owing to the quantum interference of EP states in the ring region. As temperature increases, the oscillations are evidently suppressed, implying decoherence of the EP states. The simulation shows that the magnitude of polarized current is sensitive to the location of the lead. The polarized current depends on the connecting position of the lead in a complicated way due to the spin-sensitive quantum interference effects caused by different phases accumulated by transmitting electrons with opposite spin states along different paths.     

Influence of electronic correlations on orbital polarizations in the parent and doped iron pnictides

Orbital polarization and electronic correlation are two essential aspects in understanding the normal-state and superconducting properties of multi-orbital FeAs-based superconductors. In this paper, we present a systematic study on the orbital polarization of iron pnictides from weak to strong Coulomb correlations within the Kotliar-Ruckenstein slave boson approach. The magnetic phase diagram of the two-orbital model for LaFeAsO clearly shows that a striped antiferromagnetic metallic phase with orbital polarization exists over a wide doping range, in addition to the Slater-type insulator, Mott insulator and paramagnetic phases. A reversal of the orbital polarization occurs in the intermediate correlation regime in the absence of the crystal field splitting; however, a small crystal field splitting considerably enhances the orbital polarization, and stabilizes the xz-type orbital order. We argue that the ferro-orbital polarization is characteristic of a density wave, and leads to a pseudogap-like behavior in the density of states.     

Measurement of geometric phase for mixed states using single photon interferometry

Geometric phase may enable inherently fault-tolerant quantum computation. However, due to potential decoherence effects, it is important to understand how such phases arise for mixed input states. We report the first experiment to measure mixed-state geometric phases in optics, using a Mach-Zehnder interferometer, and polarization mixed states that are produced in two different ways: decohering pure states with birefringent elements; and producing a nonmaximally entangled state of two photons and tracing over one of them, a form of remote state preparation.     

Accurate Jones matrix expansion for all orders of polarization mode dispersion

I present a simple method for extracting the dispersive elements from a general unitary Jones matrix in such a way that the parts comprising the phase delays and higher-order dispersion in the two principal states of polarization are separated from those describing the frequency-dependent coupling between them. I then rigorously expand these two parts into power series in relative optical frequency, wherein the coefficients are explicit functions of the polarization mode dispersion vectors of various orders. This accurate expansion of the Jones matrix reveals in particular the amplitudes and phases of the cross-coupled components of the principal states of polarization, which are incorrectly described in most polarization mode dispersion models.     

Theoretical study of the intensity of chemically induce dynamic electron polarization of radical-triplet pairs

Considering the interaction between encited triplet molecule and cloublet radical,based on the second-order perturbation theroy and the motion equation of density matrix,the polarzation intersity of RTPM were theoretically calculated with the overpopulated doublet spin states and quartet spin states of radical0triplet paris as initial conditions the radical result from the zero-field-splitting(zfs)and the multiplet A/E and E/A polarization result from hyperfine (hf) interactions of the triplet molcule,The hyperfine ralated A A/E or E E/A CIDEP on the radical were the overpopulation of the net abscrptive or emissive polarization and multiple A/E or E/A polarization.     

Evidence for particle-shape sensitivity in the correlation between polarization states of light scattering

The cross correlation between polarization states of scattered laser speckle as a function of scattering angle is observed for a range of spherical and nonspherical particle suspensions. A variation in the degree of correlation between polarization states is observed, and this information is indicative of the particle shape. A comparison with a theoretical model for small particles is made, suggesting that variations in polarization correlation with angle originate from the nonisotropic polarizability of nonspheres. Experiments are also performed on large spheroids and random-shaped polydispersions, and the results indicate that the measurement method has significant potential for nonsphere detection and characterization.     

Pairing of spin excitations in lateral quantum dots

We demonstrate the existence of correlated electronic states as paired spin excitations of lateral quantum dots in the integer quantum Hall regime. Starting from the spin-singlet filling-factor nu=2 droplet, by increasing the magnetic field we force the electrons to flip spins and increase the spin polarization. We identify the second spin-flip process as one accompanied by correlated, spin depolarized phases, interpreted as pairs of spin excitons. The correlated states are identified experimentally in few-electron lateral quantum dots using high source-drain voltage spectroscopy.     

Comparison of three kinds of polarized Bessel vortex beams propagating through uniaxial anisotropic media

A comparison of differently polarized Bessel vortex beams propagating through a uniaxial anisotropic slab is discussed in terms of the vector wave function expansions.The magnitude profiles of electric field components, the transformation of polarization modes, and the distributions of orbital angular momentum(OAM) states of the reflected and transmitted beams for different incident angles are numerically simulated.The results indicate that the magnitude profiles of electric field components for different polarization modes are distinct from each other and have a great dependence on the incident angle,thus the transformation of polarization modes which reflects the change of energy can be affected largely.As compared to the x and circular polarization incidences, the reflected and transmitted beams for the radial polarization incidence suffer the fewest transformation of polarization modes, showing a better energy invariance.The distributions of OAM states of the reflected and transmitted beams for different polarization modes are diverse as well, and the derived OAM states of the transmitted beam for radial polarization present a focusing effect, concentrating on the state between two predominant OAM states.     

Polarization configuration recognition based on analysis of torsion and curvature

A novel method to recognize polarization configuration is proposed. The method is based on analysis of torsion and curvature of three-dimensional curve segments. The three-dimensional curve segments is defined by series of points represent states of polarization. The obtained results indicate that the analysis of torsion and curvature permits to identify the polarization configuration consisting of four or more states of polarization.     

High-speed fiber based polarization-sensitive optical coherence tomography of in vivo human skin

A high-speed single-mode fiber-based polarization-sensitive optical coherence tomography (PS OCT) system was developed. With a polarization modulator, Stokes parameters of reflected flight for four input polarization states are measured as a function of depth. A phase modulator in the reference arm of a Michelson interferometer permits independent control of the axial scan rate and carrier frequency. In vivo PS OCT images of human skin are presented, showing subsurface structures that are not discernible in conventional OCT images. A phase retardation image in tissue is calculated based on the reflected Stokes parameters of the four input polarization states.     

Microscopic insight into temperature-graded ferroelectrics

A microscopic approach based on the first-principles effective Hamiltonian is developed to study the polarization response in temperature-graded ferroelectrics. This approach has been applied to the case of (Ba(0.75)Sr(0.25))TiO? alloy. A comparison of the computational results with available experimental data attests to the remarkable accuracy of the present approach. Our computations reveal a strong anisotropy in the response of polarization to the temperature gradient (TG). In particular, the polarization offset along the direction of TG is an order of magnitude lower than in the perpendicular direction. The large as well as the small TGs are considered and found to yield qualitatively different polarization field responses. Among other striking findings are (i) the coexistence of different phases in chemically homogeneous regions, (ii) formation of low-symmetry phases, and (iii) thermally controlled polarization rotation.     

在保偏光纤上制作光纤光栅的应用研究

提出一种在保偏光纤上计算光纤拍长的方法，即在保偏光纤上制作光纤光栅，利用光纤光栅的特性可以方便地求得光纤的拍长，同时，发现在保偏光纤上写入光纤光栅，其过程等效于在两个主轴上分别写入了一个光纤光栅，并且这两个光栅对于光的偏振态具有选择性，它们分别作用的偏振态是相互正交的。利用此特性，可以得到偏振消光比比较高的偏振分束器。     

多阶有序钙钛矿多铁性材料的高压制备与物性

钙钛矿是研究磁电多铁性最重要的材料体系之一.由于高的结构对称性,在以往的立方钙钛矿晶格中尚未发现多铁现象.另外,现有的单相多铁性材料很难兼容大电极化和强磁电耦合,严重制约多铁性材料的潜在应用.本文简单综述了利用高压高温条件制备的两个多阶有序钙钛矿氧化物的磁电多铁性质.在具有立方晶格的多阶钙钛矿LaMn_3Cr_4O_(12)中,观察到自旋诱导的铁电极化,表明该材料是第一个被发现的具有多铁性的立方钙钛矿体系.在另一个多阶有序钙钛矿BiMn_3Cr_4O_(12)中,随温度降低该材料依次经历了I类多铁相和II类多铁相.正因为这两类不同多铁相的同时出现,BiMn_3Cr_4O_(12)同时展示了大的电极化强度和强的磁电耦合效应,并且通过不同的电场调控可实现四重铁电极化态,为开发多功能自旋电子学器件与多态存储提供了先进的材料基础.     

基于数字全息及复用技术的全场偏振态测试方法

提出了一种在数字全息记录系统中利用偏振和角分复用技术对光场进行偏振态检测的方法. 将全息系统中的一束参考光分为偏振方向相互正交、初相位相同的两束光, 并分别与物光相同偏振方向的两个分量干涉, 形成两幅子全息图, 同时记录在一帧画面中. 为了分开记录到的物光两个分量, 系统中利用了角分复用技术, 即在两束参考光中引入不同载频, 使物光两分量的频谱位于全息图频谱面的不同区域. 通过滤波、逆傅里叶变换和衍射计算, 获取距离全息图不同位置处物光两正交分量复振幅信息. 利用复振幅信息, 可以构建被测物光的斯托克斯参量和琼斯矢量, 从而表征物光的偏振态. 实验中, 通过对一束椭圆偏振光进行偏振态测量以及对该光束在不同空间位置处的偏振态进行表征, 表明该方法可以实现光束偏振态全场测试, 并且具有较高的可靠性. 关键词： 数字全息 偏振态 琼斯矢量 斯托克斯参量     

相位-偏振编码的量子保密通信系统的研究

提出了一种新型的量子信息编码和解码新方法，并用全量子力学方法，对这种量子信息编码 技术进行了系统的理论分析.根据态叠加原理，可以用两个正交的偏振态，通过偏振干涉方 法合成一个新的偏振态.这个合成的偏振态由两个正交偏振态的相位差决定.改变相位差，就 可以合成各种不同的偏振态.而相位差的改变可以通过相位调制器来实现，从而可以用相位调制方法，实现对光子偏振态的编码和解码.这种方法可以随机地制备各种非正交偏振态， 也可以随机地产生各种非正交偏振态测量基，对各种非正交偏振态的光子进行检测和解码. 这种编码方法既具有相位编码方法传输距离大的优点，同时又克服了该方法信息损失过半的 缺点，还可以对光子的位相和偏振态进行精确补偿，有效地降低误码率. 关键词： 量子密钥分配 相位编码 偏振编码     

Tuning the polarization states of optical spots at the nanoscale on the Poincaré sphere using a plasmonic nanoantenna

It is shown that the polarization states of optical spots at the nanoscale can be manipulated to various points on the Poincaré sphere using a plasmonic nanoantenna. Linearly, circularly, and elliptically polarized near-field optical spots at the nanoscale are achieved with various polarization states on the Poincaré sphere using a plasmonic nanoantenna. A novel plasmonic nanoantenna is illuminated with diffraction-limited linearly polarized light. It is demonstrated that the plasmonic resonances of perpendicular and longitudinal components of the nanoantenna and the angle of incident polarization can be tuned to obtain optical spots beyond the diffraction limit with a desired polarization and handedness.     

Vectorial Pauli algebraic approach in polarization optics. II. Interaction of light with the canonical polarization devices

A theoretical approach to the interaction between polarized light and polarization devices, based on the vectorial and pure operatorial form of the Pauli algebra, is presented. In the first part of the paper we have established the vectorial Pauli-algebraic forms of the operators corresponding to various polarization devices and states of light polarization. In this second part we give the vectorial Pauli-algebraic treatment of the interaction between the canonical polarization devices and the various forms of light polarization. Unlike the standard (Jones and Mueller) approaches, this formalism does not appeal to any matrix representation of the involved operators. This approach establishes a bridge between the Hilbert space of the density operators of the polarization states and the Poincaré space of their geometric representations and gives a rigorous justification of the handling of the interactions between the polarization states and polarization systems on the Poincaré sphere and in the Poincaré ball. In such an approach, unlike the standard ones, the three relevant quantities that characterize the interaction - the gain, the Poincaré vector of the outgoing light and its degree of polarization - result straightforwardly, in block. A generalized form of Malus’ law, for any dichroic device and partially polarized light is also obtained this way.     

基于半导体光放大器偏振旋转的全光缓存器

全光缓存器可实现数据包在光域内的缓存,是全光路由、伞光计算以及全光交换的关键部件之一.提出了一种基于半导体光放大器(SOA)中非线性偏振旋转(PR)的光纤环型全光缓仃器结构;提出了一种利用偏振主态(PSP)寻找两个正交线偏振态以及在线实时测量光纤中偏振态的方法.通过改变SOA的注入电流,实现了对两个正交偏振态转化的控制,利用这两个正交的线偏振态,实现了信号的"写"人和"读"出.利用该结构的缓存器,实现了2.5 Gb/s的1024 bits数据包6圈的缓存.缓存后的信号波形良好.