基于交叉相位调制制备四光子偏振纠缠态及其在隐形传态上的运用

利用克尔介质、偏振分束器、半波片和对强相干探测场的零拍探测,呈现了一个关于制备四光子偏振Diche态、GHZ态和W态的方案,当前量子光学实验技术条件均能有效满足该方案的要求.强的探测模相继和多个信号模光子相互作用,每次对于探测模而言,都会产生一个相位旋转.接下来,对探测模利用零拍探测,信号模可以投影得到想要的光子偏振纠缠态.此外,为了展现所制备的纠缠态作为重要的量子信息资源的价值,基于交叉相位调制进一步提出了一个隐形传送三光子偏振纠缠态的实验方案.     

基于交叉相位调制制备四光子偏振纠缠态及其在隐形传态上的运用

利用克尔介质、偏振分束器、半波片和对强相干探测场的零拍探测,呈现了一个关于制备四光子偏振Diche态、GHZ态和W态的方案,当前量子光学实验技术条件均能有效满足该方案的要求.强的探测模相继和多个信号模光子相互作用,每次对于探测模而言,都会产生一个相位旋转.接下来,对探测模利用零拍探测,信号模可以投影得到想要的光子偏振纠缠态.此外,为了展现所制备的纠缠态作为重要的量子信息资源的价值,基于交叉相位调制进一步提出了一个隐形传送三光子偏振纠缠态的实验方案.     

一种新的非线性叠加相干态的相位特性

根据Pegg-Barnett 相位定义,计算了一种新的非线性叠加相干态的相位概率分布函数和光子数-相位压缩效应,并进行了数值模拟.     

相干态的海森堡不确定关系验证实验

由于量子理论和实验的微观特性,导致海森堡不确定性原理的实验验证十分困难.针对这一问题,本文从光量子化入手,介绍了量子正交算符的海森堡不确定关系,通过平衡零拍技术探测了量子正交算符的方差,验证海森堡不确定性原理.实验结果表明:光场正交算符在相干态中具有最小不确定关系.通过该实验,学生在掌握海森堡不确定性原理的同时,了解量...     

q变形对相干态的相位概率分布特性

通过推广Pegg和Barnett的相位算符和相位态到q变形的双模情况, 应用数值计算 研究了q变形对相干态的相位概率分布特性. 结果表明, q变形对相干态的相位概率分布受到相位参数、q参数和参数│ξ│的调节, 从而反映出不同的量子相干特性.     

一种新的偶奇非线性相干态中测量相位算符的压缩效应

利用Bamett和pegg提出的测量相位算符讨论了一种新的偶奇非线性相干态的压缩效应。结果表明，在这种偶奇非线性相干态中测量相位算符不存在CN和SN类压缩，只存在CS类压缩。利用数值计算方法研究了CS类压缩效应，结果表明与通常的偶奇相干态的不同的是，偶非线性相干态在大区域内出现压缩效应而奇非线性相干态在小区域内才出现压缩效应。     

叠加对相干态的相位概率分布特性

讨论了叠加对相干态的完备性关系,并根据Pegg和Barnett的相位算符和相位态的定义,计算了叠加对相干态的相位概率分布函数,并应用数值计算讨论了其特性.结果表明,叠加对相干态的相位概率分布受到相位参数和叠加参数的调制.     

增光子奇偶相干态的相位特性

借助于Pegg-Barnett相位算符理论和数值计算方法,研究了增光子奇偶相干态的相位概率分布,在此基础之上,讨论了有关数算符和相位算符的压缩特性。结果表明,增光子奇偶相干态的相位概率分布与通常的奇偶相干态、非线性相干态不同,在这种新的奇偶相干态中,其Pegg-Barnett相位概率分布能明显地反映出不同的量子相位信息和干涉特性。同时发现,在参量α的某些不同的取值范围内,增光子奇偶相干态在数算符和相位算符分量上均存在压缩效应。     

纠缠相干态的量子隐形传态

提出利用双模纠缠相干态作为量子信道，实现纠缠相干态量子隐形传态的方案. 分别在非正交的相干态表象和另一个由相干态构成的正交态表象对双模纠缠相干态的隐形传态进行具体分析. 发现在相干态表象，虽然只要线性光学元件就可以完成隐形传态，但成功的概率小于1/2，而在正交态表象，只要能分辨4个由相干态构成的Bell态，成功的概率就是1. 关键词： 隐形传态 纠缠相干态 纠缠相干态量子信道     

新的奇偶非线性相干态及其非经典性质

构造出了一种新的奇偶非线性相干态, 并借助于数值计算方法研究了它们的压缩、振幅平方压缩、反聚束和相位概率分布等非经典性质. 结果表明, 与通常的奇偶相干态和非线性奇偶相干态不同, 在参数|λ|的不同取值范围内, 新的奇偶非线性相干态在Y₁和Y₂两个方向均可呈现振幅平方压缩效应, 而压缩效应仅在偶非线性相干态的X₂方向上呈现, 反聚束效应仅在奇非线性相干态中呈现. 另外, 通过研究新的奇偶非线性相干态相位概率分布, 发现新的奇偶非线性相干态具有完全不同的量子干涉特性. 关键词： 新的奇偶非线性相干态 压缩效应 反聚束 相位概率分布     

Long-distance quantum state transfer through cavity-assisted interaction

We propose a scheme for long-distance quantum state transfer between different atoms based on cavity-assisted interactions. In our scheme, a coherent optical pulse sequentially interacts with two distant atoms trapped in separated cavities. Through the measurement of the state of the first atom and the homodyne detection of the final output coherent light, the quantum state can be transferred into the second atom with a success probability of unity and a fidelity of unity. In addition, our scheme neither requires the high-Q cavity working in the strong coupling regime nor employs the single-photon quantum channel, which greatly relaxes the experimental requirements.     

相位式激光测距全数字锁相环控制系统

针对减小相位式激光测距中的误差,介绍了一种基于现场可编程门阵列（FPGA）实现的全数字锁相环（ADPLL）控制系统的技术原理。此系统可以提高相位频率检测器的精度,同时不受温度和电压的影响,大幅降低相位式激光测距在测相过程中的频率误差。系统主要由数字鉴相器、数字滤波器和数字控制振荡器等逻辑设备组成,系统中的信号全部为数字信号。实验结果表明,当FPGA内部的参考信号为40 Hz时,采样周期为0.025 s,滤波器在300 ms达到约5 V的电压饱和状态。ADPLL系统避免了模拟电路中常常遇到的不全传输、寄生能力、温度浮动及老化等问题,并且可以在使用重置器件的情况下运行,因此很容易测试和复原。     

相位式激光测距全数字锁相环控制系统

针对减小相位式激光测距中的误差,介绍了一种基于现场可编程门阵列（FPGA）实现的全数字锁相环（ADPLL）控制系统的技术原理。此系统可以提高相位频率检测器的精度,同时不受温度和电压的影响,大幅降低相位式激光测距在测相过程中的频率误差。系统主要由数字鉴相器、数字滤波器和数字控制振荡器等逻辑设备组成,系统中的信号全部为数字信号。实验结果表明,当FPGA内部的参考信号为40 Hz时,采样周期为0.025 s,滤波器在300 ms达到约5 V的电压饱和状态。ADPLL系统避免了模拟电路中常常遇到的不全传输、寄生能力、温度浮动及老化等问题,并且可以在使用重置器件的情况下运行,因此很容易测试和复原。     

Quantum interference between heralded single photon state and coherent state

Balanced homodyne detection has been introduced as a reliable technique of reconstructing the quantum state of a single photon Fock state, which is based on coupling the single photon state and a strong coherent local oscillator in a beam splitter and detecting the field quadrature at the output ports separately. The main challenge associated with a tomographic characterization of the single photon state is mode matching between the single photon state and the local oscillator. Utilizing the heralded single photon generated by the spontaneous parametric process, the multi-mode theoretical model of quantum interference between the single photon state and the coherent state in the fiber beam splitter is established.Moreover, the analytical expressions of the temporal-mode matching coefficient and interference visibility and relationship between the two parameters are shown. In the experimental scheme, the interference visibility under various temporalmode matching coefficients is demonstrated, which is almost accordant with the theoretical value. Our work explores the principle of temporal-mode matching between the single photon state and the coherent photon state, originated from a local oscillator, and could provide guidance for designing the high-performance balanced homodyne detection system.     

基于广义M估计的鲁棒容积卡尔曼滤波目标跟踪算法

为减小测量异常误差对非线性目标跟踪系统的影响, 提出了一种基于广义M估计的鲁棒容积卡尔曼滤波算法. 首先将非线性测量方程等价变换, 利用约束总体最小二乘准则构建广义M估计极值函数, 在不进行线性化近似的前提下将其引入到容积卡尔曼滤波求解框架中. 然后根据Mahalanobis距离构建异常误差判别量, 利用卡方分布的置信水平确定判决门限, 并建立改进的三段Huber权函数, 使其能够降低小异常误差权值, 剔除大异常误差. 理论分析表明, 该方法具有无需求导、跟踪精度高、实时性好等优点, 且无需已知异常误差的统计特性; 实验结果表明, 所提算法能够有效减小异常误差的影响, 在实际非线性物理系统中具有广阔的应用空间.     

基于偏振鉴相的相干合成技术

推导了偏振相干合成后任意方向检偏的光强受束间相位差调制的解析表达式,并通过实验验证了表达式的正确性。开展了基于偏振鉴相的相干合成实验研究,用梯度下降算法锁定了两束激光的相位,获得了稳定的输出功率,验证了基于偏振鉴相的相干合成技术可行性;分析了基于偏振鉴相的相干合成技术的优点和对激光器的要求;提出了一种基于偏振鉴相的可定标放大全口径相干合成方法,采用多探测器和多级并行相位调制的方法,解决了随机并行梯度下降（SPGD）算法闭环带宽随合成光束数增加而快速退化的问题。     

Kalman filter based initial guess estimation for digital image correlation

In applications digital image correlation based algorithms often present a basis for analysis of movement/deformation of bodies. The sequence of the obtained images is analyzed for this purpose. Especially, in cases when the body׳s movement/deformation between two successive images is significant, the initial guess can have a major influence on the execution speed of the algorithm. In the worst case it can even cause the divergence of the algorithm. This was the inspiration to develop a new and unique approach for an accurate and reliable determination of an initial guess for each image pixel. Kalman filter has been used for this purpose. It uses past measurements of observed variable(s) for calculations. Beside that it also incorporates state space model of the actual system. This is one of the most important advantages provided by Kalman filter. The determined initial guess by the proposed method is actually close to the true one and it enables fast convergence. Even more important property of this approach is the fact that it is not path-dependant because each image pixel, which is defined in ROI, is tracked through the sequence of images based on its own past measurements and general state space model. Consequently, the proposed method can be used to analyze tasks where discontinuities between image pixels are present. The applied method can be used to predict an initial guess where reference and deformed subsets are related by translational and rotational motion. The advantages mentioned above are verified with numerical and real experiments. The experimental validations are performed by NR (Newton–Raphson) approach which is the most widely used. Beside NR method the presented algorithm is applicable for other registration methods as well. It is used as an addition for calculation of initial guesses in a sequence of deformed images.     

Analysis of BPSK homodyne receivers based on modified balanced optical phase-locked loop in the presence of non-negligible loop propagation delay

Optical homodyne receivers based on modified balanced optical phase-locked loop is analyzed taking into account loop propagation delay. This modified loop contains all the components of a standard BOPLL in conjunction of an additional phase modulator. This modified loop offers a much improved tracking performance and also shows good improvements in the reduction performance over previously reported methods, like, relaxed line-width requirement and improved lock-in range. This study for the first time shows the imperfect-phase-recovery-induced power penalty as a function of laser line-width with the optimum phase deviations in the presence of non-negligible loop propagation delay. It is found that in order to maintain a 10⁻¹⁰ BER system performance with ξ = 1, R = 1 A/W, P_R = −53 dBm, Δυ = 1 MHz, phase modulator sensitivity K_PM = 10 rad/V and 10° phase deviation between the two transmitted bits, the loop delay must be kept below 3 ns. Further, the required line-width with the non-negligible loop delay time is evaluated and found to be (2.1 × 10⁻³)/τ, where τ (s) is the loop delay. This number corresponds to BER = 10⁻¹⁰, imperfect phase recovery power penalty of 1 dB and phase modulator sensitivity K_PM = 20 rad/V.     

双数态输入型M-Z干涉仪中量子相位的最大似然估计和贝叶斯分析

本文采用最大似然估计和贝叶斯分析两种方法,对双数态输入型马赫-曾德尔干涉仪中的量子相位估计进行研究.通过对干涉仪输出端粒子数差和宇称进行理论计算和数值模拟,发现采用贝叶斯分析和粒子数差测量的组合,可以在全相位空间实现最优测量,即待估相位精度达到由量子克拉美罗下界所给定的测量极限,同时,利用贝叶斯分析进行相位估计所需样本数较最大似然估计更少.在通过宇称测量进行相位估计的研究中,发现无法利用贝叶斯分析实现相位估计,但可采用最大似然估计进行研究.借助蒙特卡洛数值模拟分析,我们验证了理论计算结果,即相位估计精度会随待估相位θ₀的变化而改变,将其与粒子数差测量结果对比,进一步确认了粒子数差测量方案的优越性.     

Analysis of BPSK homodyne receivers based on modified dither optical phase-locked loop

Optical homodyne receivers based on modified Dither Optical Phase-Locked Loop is analyzed taking into account the laser phase noise, photo detectors shot noise and the dither signal. This modified loop contains all the components of a standard Dither OPLL in conjunction of an additional phase modulator. This modified loop considerably improves the performance of the homodyne reception technique over the earlier technique with the help of commercially available external cavity lasers with line-width of about few hundred kHz. This modified dither OPLL seems a realistic approach for receiving modulated signal for inter-satellite communication systems. This modified technique provides the advantage of low weight, small size and above low cost because the proposed technique significantly reduces the requirement of very narrow line-width lasers. This modified dither loop shows good improvements in the reduction performance over previously reported methods, like, less system power penalty, relaxed line-width requirement.