Squeezing bandwidth controllable twin beam light and phase sensitive nonlinear interferometer based on atomic ensembles

We review our recent experimental progress in quantum technology employing amplification effect of four-wave mixing in a rubidium vapor. We have produced an intensity difference squeezed light source at frequencies as low as 1.5 kHz which is so far the lowest frequency at which squeezing has been observed in an atomic system. Moreover, we find that the bandwidth of our squeezed light source can be controlled with light intensity pumping. Using our non-classical light source, we have further developed a nonlinear Mach-Zehnder (MZ) interferometer, for which the maximum fringe intensity depends quadratically on the intensity of the phase-sensing field at the high-gain regime, leading to much better sensitivity than a linear MZ interferometer in which the beam splitters have the same phase-sensing intensity. The quantum technologies developed by our group could have great potential in areas such as precision measurement and quantum information.     

First observation of mesospheric and thermospheric winds by a Fabry-Perot interferometer in China

A Fabry-Perot interferometer, funded by the Meridian Project in China, was deployed at the Xinglong station (40.2°N,117.4°E) of the National Astronomical Observatories in Hebei Province, China. The instrument has been operating since April 2010, measuring mesospheric and thermospheric winds. The first observational data of winds at three heights in the mesosphere and thermosphere were analyzed, demonstrating the capacity of this instrument to aid basic scientific research. The wavelengths of three airglow emissions were OH892.0, OI 557.7, and OI 630.0 nm, which corresponded to heights of 87, 98, and 250 km, respectively. Three 38-day data sets of horizontal winds, from April 5, 2010 to May 12, 2010, show clear day-to-day variations at the same height. The minimum and maximum meridional winds at heights of 87, 98, and 250 km were –16.5 to 8.7 m/s, –24.4 to 15.9 m/s, and –43.6 to 1.5 m/s. Measurements of zonal winds were –5.4 to 7.6 m/s, 2.3 to 23.0 m/s, and –22.6 to 49.3 m/s. The average data from the observations was consistent with the data from HWM93. The wind data at heights of 87 and 98 km suggest a semi-diurnal oscillation, clearly consistent with HWM93 results. Conversely there was a clear discrepancy between the observations and the model at 250 km. In general, this Fabry-Perot interferometer is a useful ground-based instrument for measuring mesospheric and thermospheric winds at middle latitudes.     

群组中实现的量子零知识证明

零知识证明是指证明者使验证者确信证明者拥有某一个秘密值,而证明者没有向验证者泄漏关于该秘密值的任何有用信息.其优点是在证明了自己身份的同时,还确保了有用信息不泄露,有效防止了他人冒充.经典的零知识证明均是基于计算复杂性的.用量子安全通信的传输方式,设计了一套在群组中实现的量子零知识证明方案.     

Wave mechanics in quantum phase space: hydrogen atom

The rigorous solutions of the stationary Schr?dinger equation for hydrogen atom are solved with the wave-mechanics method within the framework of the quantum phase-space representation established by Torres-Vega and Frederick. The “Fourier-like” projection transformations of wave function from the phase space to position and momentum spaces are extended to three-dimensional systems. The eigenfunctions in general position and momentum spaces could be obtained through the transformations from eigenfunction in the phase space.     

阻挫自旋梯子的纠缠与量子相变

对于具有阻挫作用的反铁磁自旋梯子,采用多体格林函数方法并结合Jordan-Wigner变换,计算系统中近邻双格点的纠缠,分析纠缠的奇异性与量子相变之间关系.发现随着外磁场的变化,纠缠出现奇异即发生量子相变,但在量子相变点纠缠不一定出现奇异,这说明纠缠奇异与量子相变并非一一对应,此外纠缠平台与磁化平台一一对应.     

GaAs—GaAlAs量子阱中光极化子

本文计及子带跃迁和双声子过程,计算了限制在量子阱中光极化子能级,给出了自陷能和重正化质量数值计算结果,它是阱宽的函数.发现自陷能和有效质量在二维结果和三维结果之间,子带跃迁和双声子过程对自陷能的贡献不是很重要的.     

磁场对量子阱中类氢杂质性质的影响

本文在弱场极限下应用微扰变分法,在强场极限下应用绝热微扰法,计算了位于,量子阱中心的一个类氢杂质在磁场中基态的束缚能和电子跃迁能量。结果表明:电子的基态束缚能随磁场的增加或量子阱宽的减小而增大;电子跃迁能量随量子阱宽的减小而变大;在强场极限和弱场极限下,电子跃迁能量随磁场变化的规律不同。在强场极限下,电子跃迁能随磁场的增加变大。在弱场极限下,当电子初态有横向激发,末态是基态时,跃迁能量随磁场的增加变大;当电子初态只有纵向激发,末态有横向激发时,跃迁能量随磁场的增加变小,当电子初态与末态横向激发的程度相同时,跃迁能量不随磁场变化。     

杯芳烃内相中3-环丁烯砜的分解反应研究

采用分子动态模拟及量子化学方法对杯芳烃内相中3环丁烯砜的取向及分解为二氧化硫和丁二烯的反应进行了研究。结果表明,3-环丁烯砜在杯芳烃分子反应器中发生分解反应的活化能比在自由状态下反应的活化能略高,这与3-环丁烯砜在杯芳烃中的表观分解温度提高的实验现象吻合。分析分子反应器与小分子的相互作用能以及分子反应器的变形能随反应进程的变化趋势,发现活化能的变化主要源自分子反应器与小分子的相互排斥作用。     

Numerical simulation of the asymmetric gas?phase flow field in a volute cyclone separator

The gas-phase flow field in a cyclone separator with a volute inlet is numerically simulated based upon the Reynolds stress model (RSM) on the platform of commercial computational fluid dynamics (CFD) software, FLUENT 6.1. The asymmetric characteristics of the flow field are analyzed in this paper. The results indicate that the gas?phase flow field is slightly asymmetric in the tube and cone spaces, but remarkably asymmetric in the annular space. Meanwhile, it can be seen that the axial center of the gas flow vortex deviates from the geometric center of the cyclone. This swirling eccentricity results from the asymmetrical inlet structure and the instability of the swirling flow. The deviated distance, and direction varies with the axial position and the maximal deviated distance is approximately 0.07R. The offset of two centers makes the radial velocity of the gas?phase flow field have a remarkable asymmetrical profile. The asymmetric characteristics of the radial velocity distribution are first explained in this study. The above results are in fair agreement with the experimental data from the literature.