基于电磁诱导透明机制的压缩光场量子存储

光场的量子存储不仅是构建量子计算机的重要基础,而且是实现量子中继和远距离量子通信的核心部分.由于存在不可避免的光学损耗,光学参量放大器产生的压缩真空态光场将变为压缩热态光场,不再是最小不确定态.因此,压缩热态光场的量子存储是实现量子互联网的关键.在原子系综中利用电磁诱导透明机制能够实现量子态在光场正交分量和原子自旋波之间的相互映射,即受控量子存储.本文根据量子存储的保真度边界,研究了实现压缩热态光场量子存储的条件.量子存储的保真度边界是通过经典手段能够达到的最大保真度,当保真度大于该边界时,就实现了量子存储.通过数值计算分析了不同情况下压缩热态光场的量子存储保真度边界,以及存储保真度随存储效率的变化关系,得到了实现量子存储的条件,为连续变量量子存储实验设计提供了直接参考.     

粒子数压缩态光场参与的和频过程

本文研究粒子压缩态光场参与的和频过程中各输出的光场的量子统计特性。我们导出各输出光场和总输出光场的归一化量子噪声（Ｆａｎｏ因子）随有效相互作用长度而变化的规律，发现非线性光学过程输入场的量子噪声变大，使和频光场的量子噪声变小，显示输入光场的统计性质的特点部分地转移和频光场。     

基于压缩光的量子精密测量

对任何物理量的测量都有一定的噪声, 经典测量所能达到的最小噪声一般称为散粒噪声, 对应着测量的标准量子极限. 利用压缩光可以突破标准量子极限, 从而提高测量精度. 本文介绍了压缩态光场用于突破标准量子极限的基本原理, 以及压缩态光场在相位测量、光学横向小位移及倾斜测量、磁场测量以及时钟同步等精密测量领域的应用和最新进展.     

基于量子增强型光纤马赫-曾德尔干涉仪的低频信号测量

利用低频光通信波段真空压缩态光场可实现基于光纤的量子精密测量.本文利用简并光学参量振荡器实验制备出1550 nm低频真空压缩态光场.在分析频段10—500 kHz范围内压缩态光场的压缩度均达3 dB.用实验制备的1550 nm真空压缩态光场填补光纤马赫-曾德尔干涉仪的真空通道,实现了量子增强型光纤马赫-曾德尔干涉仪,完成了突破标准量子极限的相位调制频率为500 kHz的低频信号测量.与光纤马赫-曾德尔干涉仪相比,测量信噪比提高了2 dB.     

利用PPKTP晶体产生真空压缩态及其Wigner准概率分布函数的量子重构

通过光学腔内置周期极化磷酸氧钛晶体的连续光学参量振荡器,以532nm光场为抽运场,产生1064nm的真空压缩态光场,利用平衡零拍探测技术得到3.41dB的实测压缩度,并采用量子层析技术重构出真空压缩态光场在相空间的Wigner准概率分布函数. 关键词： 真空压缩态光场 光学参量振荡器 量子层析 Wigner准概率分布函数     

优于12dB压缩态光场的产生与观察

压缩态、振幅压缩态和非经典相关态光场等均为非经典光场。压缩态体现着光场的一种新的量子特性,对它的研究有着重大的科学意义;而且因其电场正交相分量之一的量子噪声可低于散粒噪声极限(shot noise limit简称SNL)在光通信、光计算机、光学精密测量及光谱学、非线性光学中有着十分诱人的应用前景。 继非经典相关态光场产生与观察后,最近作者采用负反馈半导体激光器和平衡零拍探测器成功地产生并观察到了低于散粒噪声极限以下12dB的压缩态光场。本文所报道的产生压缩态光场的实验方案不同于业已报道的参量产生方案(如参量转换、四波混频等):首先实验利用半导体激光器作光源,经分束器将很少一部分光作为信号光束,而其主要部分光作为本振光束。没有用到光学腔,强泵浦光和非线性材料;其次,采用了信号光场量子涨落的     

量子信息光学

介绍了一门新的学科分支－量子信息光学。它是量子光学与信息科学相结合的产物。光场的量子效应在实现大容量的信息传输，超高精度的信息检测以及不可破译、不可窃听的量子密码术方面有着极其重要的应用前景，在光子学的发展中将发挥独特的作用。该文阐述了量子信息光学中若干物理问题和研究方向，包括超低噪声光源、量子信息复制、量子态工程、量子非破坏性测量和量子密码术。     

双模压缩真空态与原子相互作用中的量子纠缠和退相干

考虑双模压缩真空态光场与环境(原子)通过双光子过程发生相互作用,分别用量子约化熵和量子相对熵研究了在此作用过程中双模光场和原子间的纠缠以及双模光场的模间纠缠 关键词： 双模压缩真空态 量子纠缠 量子约化熵 量子相对熵     

基于平移压缩真空态的强反聚束光场

具有反聚束特性的非经典光场是量子信息与量子光学的重要资源。基于非线性光学的量子干涉效应，通过将压缩真空态与特定相位的相干态在光学分束器上合成的方法获得平移压缩真空态，对压缩度和相干分量进行独立控制以获得反聚束。本文结合实验系统参数，理论研究了压缩真空态的压缩度和相干态的幅度对实验产生反聚束光场的影响。在最优化平移条件下，我们分析了系统总效率、背景噪声，以及Hanbury Brown-Twiss(HBT)与Double HBT测量方法对反聚束光场g⁽(2))(0)测量的影响，并讨论了误差为零处相应量子态的g⁽(2))(0)值和平均光子速率。     

压缩态光场的四阶量子干涉

采用半经典理论讨论了同一抽运源抽运的两个独立光学参量振荡腔(OPO)所产生的压缩态光场的四阶量子干涉效应．结果表明：在OPO振荡阈值处,输出光场压缩度最高但四阶量子干涉最弱,条纹可见度为33.3%,远离阈值时干涉越来越强. 关键词：     

金刚石氮空位色心耦合机械振子和腔场系统中方差压缩研究

研究了金刚石氮空位中心(NV色心)同时耦合腔场和机械振子系统中声子场的方差压缩动力学特性,分析了金刚石NV色心初态和NV色心与机械振子耦合强度对声子场方差压缩影响.结果发现:可以制备压缩时间长、压缩幅度大的声子场压缩态,其物理原因是机械振子具有最大相干性,并且通过调控NV色心初态以及磁场梯度可以实现对机械振子方差压缩非经典特性的操控,从而在理论上提供了一种调控声子场方差压缩的方式.     

通信波长频率一致纠缠光源的频谱测量

本文利用光栅单色仪实现了对超短脉冲抽运周期极化磷酸氧钛钾晶体产生的通信波长频率一致纠缠光子源的频谱特性分析.测量到双光子的联合频谱呈正关联分布,为频率一致纠缠光源.信号光、闲置光中心波长分别为1574.4 nm和1574.9 nm,频谱宽度分别为35.3 nm和37.6 nm,双光子符合包络宽度约为3 nm.根据单光子频谱宽度与双光子符合包络宽度的比值可以得到双光子的频率纠缠参量R约为12,表征了信号光子与闲置光子之间具有较高的频率纠缠度.     

Communication via the statistics of photon-number squeezed light

A method of communication employing the second order statistics of photon-number squeezed light is demonstrated. The technique encodes the information content in both nonstationary noise processes and in the average optical power, thereby creating two orthogonal channels and increasing the transmission capacity. Communication via the fragile quantum state has potential applications for privatized communication.     

Simultaneous Preparation of Two Optical Cat States Based on a Nondegenerate Optical Parametric Amplifier

The cat state, known as the superposition of coherent states, has broad applications in quantum computation and quantum metrology. Increasing the number of optical cat states is crucial to implement complex quantum information tasks based on them. Here, two optical cat states are prepared simultaneously based on a nondegenerate optical parametric amplifier. By subtracting one photon from each of two squeezed vacuum states, two odd cat states with orthogonal superposition direction in phase space are prepared simultaneously, which have similar fidelity of 60% and amplitude of 1.2. Compared with the traditional method to generate two odd optical cat states based on two degenerate optical parametric amplifiers, only one nondegenerate optical parametric amplifier is applied in this experiment, which saves half of the quantum resources of nonlinear cavities. The presented results make a step toward preparing the four-component cat state, which has potential applications in fault-tolerant quantum computation.     

光晶格中玻色-爱因斯坦凝聚体的自旋和磁研究

近年应用光晶格（optical lattice)控制原子玻色－爱因斯坦凝聚体（BEC）的研究取得了突破性的进展。德国Munich研究小组首次在三维光晶格中观察到了超冷原子从BEC超流状态向Mott insulator状态的量子相变。这样的量子相变现象不仅具有重大的理论研究价值，而且为BEC的实际应用提供了新的途径。文章介绍了作者近来在光晶格中BEC的自旋和磁特性方面的一些研究进展，并探讨了它们在磁传感器及量子计算中的可能应用。     

Generation of optical frequency comb squeezed light field with TEM_(01) transverse mode

Nonclassical optical frequency combs find tremendous utility in quantum information and high-precision quantum measurement. The characteristics of a type-I synchronously pumped optical parametric oscillator with the TEM_(01) transverse mode below threshold are investigated and a squeezing of 0.7 dB for an optical frequency comb squeezed light field with the TEM_(01) transverse mode is obtained under the pump power of 130 m W. This work has a promising application in three-dimensional space-time measurement.     

High‐resolution spectral characterization of two photon states via classical measurements

Quantum optics plays a central role in the study of fundamental concepts in quantum mechanics, and in the development of new technological applications. Typical experiments employ sources of photon pairs generated by parametric processes such as spontaneous parametric down‐conversion and spontaneous four‐wave‐mixing. The standard characterization of these sources relies on detecting the pairs themselves and thus requires single photon detectors, which limit both measurement speed and accuracy. Here it is shown that the two‐photon quantum state that would be generated by parametric fluorescence can be characterised with unprecedented spectral resolution by performing a classical experiment. This streamlined technique gives access to hitherto unexplored features of two‐photon states and has the potential to speed up design and testing of massively parallel integrated nonlinear sources by providing a fast and reliable quality control procedure. Additionally, it allows for the engineering of quantum light states at a significantly higher level of spectral detail, powering future quantum optical applications based on time‐energy photon correlations.     

On a possibility to find experimental evidence for the many-worlds interpretation of quantum mechanics

The many-worlds interpretation of quantum mechanics predicts the formation of distinct parallel worlds as a result, of a quantum mechanical measurement. Communication among these parallel worlds would experimentally rule out alternatives to this interpretation. A possible procedure for “interworld” exchange of information and energy, using only state of the art quantum optical equipement, is described. A single ion is isolated from its environment in an ion trap. Then a quantum mechanical measurement with two discrete outcomes is performed on another system, resulting in the formation of two parallel worlds. Depending on the outcome of this measurement the ion is excited from only one of the parallel worlds before the ion decoheres through its interaction with the environment. A detection of this excitation in the other parallel world is direct evidence for the many-worlds interpretation. This method could have important practical applications in physics and beyond.