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51.
We analyze the propagation of Laguerre–Gaussian (LG) beams in a cubic–quintic nonlinear medium by using the variational method. For low intensities, the results are in good agreement with the results of a numerical simulation. The characteristics of LG beams in the nonlinear medium are explored and the electric field distribution in the far field after passing through the nonlinear medium is calculated. 相似文献
53.
Quantum correlations in a family of states comprising any mixture of a pair of arbitrary bi-qubit product pure states are studied by employing geometric discord [Phys. Rev. Lett. 105(2010) 190502] as the quantifier. First, the inherent symmetry in the family of states about local unitary transformations is revealed. Then, the analytic expression of geometric discords in the states is worked out. Some concrete discussions and analyses on the captured geometric discords are made so that their distinct features are exposed. It is found that, the more averagely the two bi-qubit product states are mixed, the bigger geometric discord the mixed state owns. Moreover, the monotonic relationships of geometric discord with different parameters are revealed. 相似文献
54.
最小二乘支持向量机方法对冬小麦叶面积指数反演的普适性研究 总被引:5,自引:0,他引:5
冬小麦叶面积指数(leaf area index, LAI)是进行作物长势判断和产量估测的重要农学指标之一,高光谱遥感技术为大面积、快速监测植被LAI提供了有效途径。在探讨利用最小二乘支持向量机(least squares support vector machines, LS-SVM)方法和高光谱数据对不同条件下冬小麦LAI的估算能力。在用主成分分析法(principal component analysis, PCA)对PHI航空数据降维的基础上,利用实测LAI数据和高光谱反射率数据,构建LS-SVM模型,采用独立变量法,分别估算不同株型品种、不同生育时期、不同氮素和水分处理条件下的冬小麦LAI,并与传统NDVI模型反演结果对比。结果显示,每种条件下的LS-SVM 模型都具有比NDVI模型更高的决定系数和更低的均方根误差值, 即反演精度高于相应的NDVI模型。NDVI模型对不同株型品种、不同氮素和水分条件下冬小麦LAI估算精度不稳定,LS-SVM则表现出较好的稳定性。表明LS-SVM 方法利用高光谱反射率数据对于不同条件下的冬小麦LAI反演具有良好的学习能力和普适性。 相似文献
55.
采用射频反应磁控溅射技术在石英和Si衬底上制备了高度c轴择优取向的ZnO薄膜,样品的氧氩流量比分别为10:40,20:40,30:40,40:40.利用X射线衍射仪、表面轮廓仪、原子力显微镜和紫外-可见分光光度计研究了样品的微结构与光学特性.研究表明:氧氩流量比为30:40的样品结晶质量最好.所制备的ZnO薄膜的可见光平均透射率均大于87;.随着氧氩流量比的增大,薄膜的透射率呈非单调变化,氧氩流量比为30:40的样品在可见光范围的平均透射率可达93;.光学带隙随着氧氩流量比的增大,先增大后减小.与块材ZnO的带隙(3.37 eV)相比,ZnO薄膜的带隙均变窄. 相似文献
56.
According to Fan-Hu's formalism (Fan Hong-Yi and Hu Li-Yun 2009 Opt. Commun. bf282 3734) that the tomogram of quantum states can be considered as the module-square of the state wave function in the intermediate coordinate-momentum representation which is just the eigenvector of the Fresnel quadrature phase, we derive a new theorem for calculating quantum tomogram of density operator, i.e., the tomogram of a density operator ρ is equal to the marginal integration of the classical Weyl correspondence function of F+ρF, where F is the Fresnel operator. Applications of this theorem to evaluating the tomogram of optical chaotic field and squeezed chaotic optical field are presented. 相似文献
57.
58.
A generalized Collins formula derived by virtue of the displacement-squeezing related squeezed coherent state representation 下载免费PDF全文
Based on the displacement-squeezing related squeezed
coherent state representation ≤ft\vert z\right\rangle _{g} and
using the technique of integration within an ordered product of
operators, this paper finds a generalized Fresnel operator, whose
matrix element in the coordinate representation leads to a
generalized Collins formula (Huygens--Fresnel integration
transformation describing optical diffraction). The generalized
Fresnel operator is
derived by a quantum mechanical mapping from z to sz-rz^{\ast } in the %
≤ft\vert z\right\rangle _{g} representation, while ≤ft\vert
z\right\rangle _{g} in phase space is graphically denoted by an
ellipse. 相似文献
59.
In this paper, we propose a scheme for generating an arbitrary three-dimensional pure state of vibrational motion of a trapped ion. Our scheme is based on a sequence of laser pulses, which are tuned to the appropriate vibrational sidebands with respect to the appropriate electronic transition. 相似文献
60.
By swapping the entanglement of genuine four-particle entangled states, we propose a bidirectional quantum secure communication protocol. The biggest merit of this protocol is that the information leakage does not exist. In addition, the ideas of the ``two-step" transmission and the block transmission are employed in this protocol. In order to analyze the security of the second sequence transmission, decoy states are used. 相似文献