Adjusting the properties of the photon generated via an optical parametric oscillator by using a pulse pumped laser

The cavity-enhanced spontaneous parametric down-conversion far below threshold can be used to generate a narrow-band photon pair efficiently. Previous experiments on the cavity-enhanced spontaneous parametric down-conversion almost always utilize continuous wave pump light, but the pulse pumped case is rarely reported. One disadvantage of the continuous wave case is that the photon pair is produced randomly within the coherence time of the pump, which limits its application in the quantum information realm. However, a pulse pump can help to solve this problem. In this paper, we theoretically analyze pulse pumped cavity-enhanced spontaneous parametric down-conversion in detail and show how the pump pulse affects the multi-photon interference visibility, two-photon waveform, joint spectrum and spectral brightness.     

Properties of a dielectric plate using entangled two-photon states

We theoretically study the properties of a dielectric plate with a modified Hong-Ou-Mandel interferometer. The fourth-order correlation functions are calculated in two regimes, which are divided depending on the relative size between the thickness of the dielectric plate and the one-photon coherence length. When the thickness of the dielectric plate is less than the one-photon coherence length, a novel modulation behavior of the coincidence rate is observed, which has not been discussed before. If the thickness of the dielectric plate is larger than the one-photon coherence length, coalescence and anti-coalescence are observed. The obtained results highlight the effects of a linear optical element on fourth-order interference.     

Slow light via four-wave mixing in a hot rubidium vapour

In this work,we report on an off-resonant four-wave mixing experiment via a ladder-type configuration in a hot rubidium atomic vapour.We find for the first time,to the best of our knowledge,that the generated light is delayed compared with the reference.At the same time,the seeded signal beam is also delayed,though the delay time is not as so large as the one that the generated light has.Both delayed times can be adjusted experimentally by controlling the two-photon detuning.The experimental results are in good agreement with our theoretical predictions.Our results may be important for storing telecom-band photons.     

基于PPKTP波导产生多通道光子对

提出了一种基于PPKTP波导利用自发参量产生多通道纠缠光子对的方案.计算在使用脉冲,连续激光,Ⅰ型、Ⅱ型相位匹配这些不同条件下,同时产生位于通信波段的多通道纠缠光子对的特性.结果显示该方案能够为量子密钥分配网络提供更为高效易行的方案.     

Review of quantum simulation based on Rydberg many-body system

Quantum simulation has been developed extensively over the past decades,widely applied to different models to explore dynamics in the quantum regime.Rydberg atoms have strong dipole-dipole interactions and interact with each other over a long distance,which makes it straightforward to build many-body interacting quantum systems to simulate specific models.Additionally,neutral atoms are easily manipulated due to their weak interactions.These advantages make Rydberg many-body system an ideal platform to implement quantum simulations.This paper reviews several quantum simulations for different models based on Rydberg many-body systems,including quantum Ising models in one dimension and two dimensions mainly for quantum magnetism,XY model for excitation transport,SSH model for symmetry-protected topological phases,and critical self-organized behaviors in many-body systems.Besides,some challenges and promising directions of quantum simulations based on Rydberg many-body system are discussed in this paper.     

冷~(85)Rb原子中的非共线非简并四波混频的实验研究

文章介绍了在磁光阱制备的Rb85冷原子团中通过特定时序的光场进行四波混频的实验研究,我们观察到了混频光强度的空间分布,简要讨论了三束作用光场的频率和光强对混频光产生的影响.时序调制下的四波混频实验为利用冷原子系综制备非经典关联光子对提供了基础.     

Non-classical correlation between a single photon and the collective spin excited state of a cold atomic ensemble

We experimentally establish a non-classical correlation between a single Stokes photon and the collective spin excited state of a cold atomic ensemble by using a spontaneous Raman scattering process. The correlation between them can be proved by transferring the spin excited state of the atomic ensemble into an anti-Stokes photon and checking the Cauchy-Schwarz inequality between the Stokes and the anti-Stokes photons. The non-classical correlation can be kept for at least 300 ns.     

在AgGaSe2晶体中TEA CO2激光的倍频产生

用炉温下降法生长出尺寸为φ２０×６０ｍｍ的ＡｇＧａＳｅ２单晶体。在１２ｍｍ长，切角为５５°的ＡｇＧａＳｅ２中，获得了ＴＥＡＣＯ２激光的倍频输出，其功率转换效率为１．１２％。泵浦阈值和破坏阈值分别为３ＭＷ／ｃｍ２和１１ＭＷ／ｃｍ２。还讨论了泵浦束的发散角对二次谐波转换效率的影响。     

Up-conversion detection of mid-infrared light carrying orbital angular momentum

Frequency up-conversion is an effective method of mid-infrared (MIR) detection by converting long-wavelength photons to the visible domain, where efficient detectors are readily available. Here, we generate MIR light carrying orbital angular momentum (OAM) from a difference frequency generation process and perform up-conversion on it via sum frequency conversion in a bulk quasi-phase-matching crystal. The maximum quantum conversion efficiencies from MIR to visible are 34.0%, 10.4%, and 3.5% for light with topological charges of 0, 1, and 2, respectively, achieved by utilizing an optimized strong pump light. We also verify the OAM conservation with a specially designed interferometer, and the results agree well with the numerical simulations. Our study opens up the possibilities for generating, manipulating, and detecting MIR light that carries OAM, and will have great potential for optical communications and remote sensing in the MIR regime.     

基于PPKTP波导产生多通道光子对

提出了一种基于PPKTP波导利用自发参量产生多通道纠缠光子对的方案.计算在使用脉冲,连续激光,Ⅰ型、Ⅱ型相位匹配这些不同条件下,同时产生位于通信波段的多通道纠缠光子对的特性.结果显示该方案能够为量子密钥分配网络提供更为高效易行的方案.