依赖强度耦合双模Jaynes-Cummings 模型的纠缠和场熵演化

应用von Neumann熵研究了依赖强度耦合双模Jaynes-Cummings模型中原子与光场的纠缠度。给出了两模初始场均处于相干态和双模压缩真空态两种情况下熵演化的数值结果。讨论了初始场强度对原子―场纠缠度的影响。发现在强场条件下，原子与光场基本稳定在最大纠缠态但伴随着周期性的脉冲式解纠缠。     

双模相干光场与原子依赖强度耦合双光子过程的纠缠演化

分别应用量子约化熵和量子相对熵研究了双模相干光场与原子依赖强度耦合双光子过程中原子与光场之间及光场的模之间纠缠演化.结果表明,通过选择系统初态参数、控制原子与光场的作用时间,可以调控原子与光场间的纠缠和光场的模间纠缠.可增加或减弱双模相干光场间纠缠,但无法使双模相干光场完全退纠缠.强场条件下,可周期性获得光场与原子的EPR态和可分离态.     

双模相干光场与原子依赖强度耦合双光子过程的纠缠演化

分别应用量子约化熵和量子相对熵研究了双模相干光场与原子依赖强度耦合双光子过程中原子与光场之间及光场的双模之间纠缠演化.结果表明,通过选择系统初态参数、控制原子与光场的作用时间,可以调控原子与光场间的纠缠和光场的模间纠缠.可增加或减弱双模相干光场间纠缠,但无法使双模相干光场完全退纠缠.强场条件下,可周期性获得光场与原子的EPR态和可分离态.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

虚光场对双模SU(1,1)相干态光场与原子玻色-爱因斯坦凝聚体相互作用系统中量子纠缠的影响

在双模SU(1,1)相干态光场和原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 在非旋波近似下, 分别利用量子约化熵和量子相对熵, 研究了双模SU(1,1)相干态光场与原子玻色-爱因斯坦凝聚体间的量子纠缠和双模光场的模间纠缠, 讨论了虚光场、原子-场的耦合常数和光场参数对场-凝聚体原子纠缠和光场模间纠缠的影响.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Bell态原子与双模纠缠相干光场相互作用的场熵演化特性

运用全量子理论研究了初始处于Bell态(对称迭加态或反对称态)的两原子与双模纠缠相干光场相互作用系统中场熵的演化特性. 分析了光场强度、光场纠缠度及原子间相互作用强度对场熵演化特性的影响. 结果表明：原子初态处于反对称态时,场熵始终为零;原子初态处在对称迭加态时,增大光场强度场熵的时间演化曲线逐渐变成较规则的振荡曲线,原子间的相互作用强度对双原子间纠缠度有显著的非线性调制作用.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.