可用于实际测量的连续变量高斯混态保真度

从衡量纯态之间保真度的原始定义出发,给出了一个衡量高斯混态之间保真度公式.公式中所涉及的物理量只关系到输入(输出)量子态的起伏噪声,而量子态的起伏噪声是在实验中可以被直接测量到的物理量.用这个保真度公式可以很好地衡量连续变量量子克隆实验、量子离物传态实验等量子信息处理过程中量子态的相似程度.结果表明,在相同的量子信息处理过程中,输入纯态与其受到噪声影响后演化成的输入混态相比,输入纯态的保真度总是小于输入混态的保真度.相比混态,纯态的量子特性更易受到信息处理过程中噪声的影响.     

一种新的高效信息传输协议

针对量子通信协议中量子态传递信息效率低的问题,该文设计了一种新的高效量子信息传输协议,该协议利用三粒子GHZ态的纠缠特性,结合Pauli矩阵将身份认证信息加载在GHZ粒子上,在半可信第三方的协助下完成高效的信息传输。安全性分析表明,协议能够抵御截获重发攻击,纠缠攻击。效率分析表明该信息传输证协议比普通的量子身份认证协议更具有高效性。     

光纤中光孤子传输演化及相互作用研究

基于非线性薛定谔方程,采用分步傅立叶方法模拟了基阶、二阶和三阶皮秒光孤子以及光孤子对在光纤中的传输演化.结果表明,在长距离传输过程中基阶孤子的幅度和脉宽基本不变,是进行光孤子通信的理想载体.高阶孤子的幅度和脉宽变化较大,并呈现一种周期性的变化;孤子对的传输与两个脉冲的初始相位和输入强度相关.考虑三阶色散的飞秒量级孤子在光纤中的传输将不再出现对称性和周期性,脉冲的中心位置将发生偏移,同时脉冲的波形也会发生扭曲.     

面向图像传输的无线光通信发射机设计研究

针对传统视频图像无线传输在实际应用中所暴露出来的通信速率低、可靠性差等问题,对采用无线光通信技术传输图像视频信号展开分析研究。首先对无线光通信系统的工作原理进行分析论述,在此基础上给出了无线光通信发射机的功能设计,并对实现图像无线光通信传输的关键技术进行论证,从视频图像信号的调制方式和发射机无线光通信天线的设计两个角度给出系统的实现方案,对于进一步提高无线光通信的研究应用水平具有一定借鉴意义。     

2.5GHZ光孤子传输

报导了我国首次成功地实现了２．５ＧＨｚ光孤子传输。近变换极限的孤子脉冲源是带有Ｆ－Ｐ标准具的增益开关分布反馈激光二极管。孤子脉冲的功率通过分别由１４８０ｎｍ和９８０ｎｍ泵浦的两个掺饵光纤放大器放大，当入纤功率达到一阶孤子功率时，经过２１ｋｍ色散位移光纤传输后，孤子的输出脉宽保持不变。同时还观察到孤子脉冲压缩现象。     

自傅里叶光孤子与自傅里叶高斯光脉冲的混合传输

对一阶自傅里叶光孤子混合对信号在光纤中的演变和传输进行了数值模拟研究.所用方法为利用分步傅立叶变换方法数值求解非线性薛定谔方程,文中并证明了算法内部不存在理论误差.结果表明:一阶孤子与微扰的一阶孤子的相互作用以及一阶孤子对的初值稳定性依赖于起始输入的不同结构形式.一阶自傅里叶孤子混合对中的相互作用表现不同于一阶标准孤子混合对,它类似于二阶或准二阶孤子的相互作用特性;孤子相互作用特性不足以用孤子的阶去区分或分类.     

无机非线性光学材料（NLO）产业化前景

一、前言 二十世纪六十年代以来激光技术与光纤技术的相继兴起,逐步挣脱了电子信息载体在传输速度与载波密度上的局限性,使信息载体由电子向光子的转变成为现实。而光通信作为一门跨世纪发展的新兴产业,对电光和光学信息材料提出了日益迫切的要求。 光通信是一个通过光纤传输和激光光源将电信号转变为光信号的系统。除光纤外,光的发射、控制、接收、显示如放大、振荡、倍频、调制、电光与光电转换都要求相应的电光和光学晶体制成大量、种类繁多的电光和全光学信息处理器件,从而     

基于空间光孤子的温度传感器原理

提出一种基于非局域空间光孤子传输的温度传感器的理论方案。得出在环境温度0.32℃的改变就可以引起孤子π相移的结论。此温度改变对相移的调制有望为基于干涉仪原理的温度传感器提供一个可行且灵敏度较高的实现方案。     

超短孤子脉冲在色散缓变光纤中的时间抖动

通过微扰理论分析了超短孤子在色散缓变光纤(DDF)中传输的时间抖动。结果发现三阶色散和拉曼散射分别影响了孤子的位置和频率,是决定时间抖动大小的重要因素。在光纤的拉曼系数一定的情况下,选择不同的三阶色散参数,系统的时间抖动存在一个最小值。当DDF的三阶色散参数为接近零的一个负值的时候,系统时间抖动最小,这个负值与拉曼系数和传输距离有关,其绝对值随传输距离的增大而增大。在采用色散缓变光纤进行超短孤子传输的系统设计中应该重点考虑三阶色散的影响,当DDF的三阶色散参数较大的时候,必须对系统的三阶色散进行补偿,使时间抖动达到最小,能够极大地增加了孤子的传输距离。     

基于电磁场理论的光纤光栅孤子的理论分析

在电磁场理论基础上建立了光纤光栅孤子的矩阵传递函数进行理论分析.基于电磁场理论建立了光纤光栅中的孤子的光波传播电磁波模型,并用光波的复振幅矢量表达式描述,利用Cayley-Hamilton定理和第二类切比雪夫多项式进行化简计算.基于此数学模型的光栅反射率和透射率的数学分析,从理论上得到关于长短周期光栅和深浅度调制光栅的特性分析,并得到光栅初始位置的向前向后电场幅值差对终端孤子的电场分布的影响.此方法对进一步分析非线性光纤光栅的特性和多种形式的光纤光栅的制作有通用价值.     

A Novel Quantum Stegonagraphy Based on Brown States

In this paper, a novel quantum steganography protocol based on Brown entangled states is proposed. The new protocol adopts the CNOT operation to achieve the transmission of secret information by the best use of the characteristics of entangled states. Comparing with the previous quantum steganography algorithms, the new protocol focuses on its anti-noise capability for the phase-flip noise, which proved its good security resisting on quantum noise. Furthermore, the covert communication of secret information in the quantum secure direct communication channel would not affect the normal information transmission process due to the new protocol’s good imperceptibility. If the number of Brown states transmitted in carrier protocol is many enough, the imperceptibility of the secret channel can be further enhanced. In aspect of capacity, the new protocol can further expand its capacity by combining with other quantum steganography protocols. Due to that the proposed protocol does not require the participation of the classic channel when it implements the transmission of secret information, any additional information leakage will not be caused for the new algorithm with good security. The detailed theoretical analysis proves that the new protocol can own good performance on imperceptibility, capacity and security.     

Phase jitter control of ultrashort soliton in high-speed communication systems with nonlinear gain

An expression is derived for soliton phase jitter in soliton transmission with higher-order effects in the presence of nonlinear gain and filters. It is demonstrated that soliton phase jitter can be suppressed efficiently by nonlinear gain in addition to filters not only for long duration solitons but also for ultrashort solitons provided that the nonlinear gain coefficients satisfy specific conditions. This scheme offers an alternative means for the development of ultralong distance soliton transmission systems using differential phase-shift keying (DPSK), and exploits a robust technique to achieve a higher-speed soliton communication system using DPSK.     

Cross-Layer Design for EH Systems with Finite Buffer Constraints

Energy harvesting (EH) technology in wireless communication is a promising approach to extend the lifetime of future wireless networks. A cross-layer optimal adaptation policy for a point-to-point energy harvesting (EH) wireless communication system with finite buffer constraints over a Rayleigh fading channel based on a Semi-Markov Decision Process (SMDP) is investigated. Most adaptation strategies in the literature are based on channel-dependent adaptation. However, besides considering the channel, the state of the energy capacitor and the data buffer are also involved when proposing a dynamic modulation policy for EH wireless networks. Unlike the channel-dependent policy, which is a physical layer-based optimization, the proposed cross-layer dynamic modulation policy is a guarantee to meet the overflow requirements of the upper layer by maximizing the throughput while optimizing the transmission power and minimizing the dropping packets. Based on the states of the channel conditions, data buffer, and energy capacitor, the scheduler selects a particular action corresponding to the selected modulation constellation. Moreover, the packets are modulated into symbols according to the selected modulation type to be ready for transmission over the Rayleigh fading channel. Simulations are used to test the performance of the proposed cross-layer policy scheme, which shows that it significantly outperforms the physical layer channel-dependent policy scheme in terms of throughput only.     

Directional Modulation Based on a Quantum Genetic Algorithm for a Multiple-Reflection Model

Directional modulation is one of the hot topics in data security researches. To fulfill the requirements of communication security in wireless environment with multiple paths, this study takes into account the factors of reflections and antenna radiation pattern for directional modulation. Unlike other previous works, a novel multiple-reflection model, which is more realistic and complex than simplified two-ray reflection models, is proposed based on two reflectors. Another focus is a quantum genetic algorithm applied to optimize antenna excitation in a phased directional modulation antenna array. The quantum approach has strengths in convergence speed and the globe searching ability for the complicated model with the large-size antenna array and multiple paths. From this, a phased directional modulation transmission system can be optimized as regards communication safety and improve performance based on the constraint of the pattern of the antenna array. Our work can spur applications of the quantum evolutionary algorithm in directional modulation technology, which is also studied.     

Optical generation of millimeter-wave pulses using a fiber Bragg grating in a fiber-optics system

A scheme is proposed to transform an optical pulse into a millimeter-wave frequency modulation pulse by using a weak fiber Bragg grating (FBG) in a fiber-optics system. The Fourier transformation method is used to obtain the required spectrum response function of the FBG for the Gaussian pulse, soliton pulse, and Lorenz shape pulse. On the condition of the first-order Born approximation of the weak fiber grating, the relation of the refractive index distribution and the spectrum response function of the FBG satisfies the Fourier transformation, and the corresponding refractive index distribution forms are obtained for single-frequency modulation and linear-frequency modulation millimeter-wave pulse generation. The performances of the designed fiber gratings are also studied by a numerical simulation method for a supershort pulse transmission.     

Quantum Remote State Preparation Based on Quantum Network Coding

As an innovative theory and technology, quantum network coding has become the research hotspot in quantum network communications. In this paper, a quantum remote state preparation scheme based on quantum network coding is proposed. Comparing with the general quantum remote state preparation schemes, our proposed scheme brings an arbitrary unknown quantum state finally prepared remotely through the quantum network, by designing the appropriate encoding and decoding steps for quantum network coding. What is worth mentioning, from the network model, this scheme is built on the quantum k-pair network which is the expansion of the typical bottleneck network—butterfly network. Accordingly, it can be treated as an efficient quantum network preparation scheme due to the characteristics of network coding, and it also makes the proposed scheme more applicable to the large-scale quantum networks. In addition, the fact of an arbitrary unknown quantum state remotely prepared means that the senders do not need to know the desired quantum state. Thus, the security of the proposed scheme is higher. Moreover, this scheme can always achieve the success probability of 1 and 1-max flow of value k. Thus, the communication efficiency of the proposed scheme is higher. Therefore, the proposed scheme turns out to be practicable, secure and efficient, which helps to effectively enrich the theory of quantum remote state preparation.     

A Foundation of Quantum Channels with Super Additiveness for Shannon Information

This paper presents a review and some results on problems of super additiveness in quantum channel for Shannon information. Especially, how to investigate concrete systems showing super additiveness is discussed. It is verified that the concept of the conventional error correction scheme does not play an important role to demonstrate, at least, the super additiveness of quantum channel, and that rather one can apply them to only selection of code word states with desirable Hamming distance. Finally, some properties of quantum reliability function are given, which are useful to discuss the general property of coding with super additiveness. Received: September 29, 1998; revised version: July 9, 1999     

Continuous-Variable Quantum Network Coding Based on Quantum Discord

Establishing entanglement is an essential task of quantum communication technology. Beyond entanglement, quantum discord, as a measure of quantum correlation, is a necessary prerequisite to the success of entanglement distribution. To realize efficient quantum communication based on quantum discord, in this paper, we consider the practical advantages of continuous variables and propose a feasible continuous-variable quantum network coding scheme based on quantum discord. By means of entanglement distribution by separable states, it can achieve quantum entanglement distribution from sources to targets in a butterfly network. Compared with the representative discrete-variable quantum network coding schemes, the proposed continuous-variable quantum network coding scheme has a higher probability of entanglement distribution and defends against eavesdropping and forgery attacks. Particularly, the deduced relationship indicates that the increase in entanglement is less than or equal to quantum discord.     

State discrimination of two pure states with a fixed rate of inconclusive answer

We investigate the optimum strategy for state discrimination of two pure states when the probability of inconclusive answers is fixed. By varying a given rate of inconclusive probabilities, the strategy optimally interpolates between Unambiguous and Minimum-Error discrimination, the two standard approaches to quantum state discrimination. We derive the explicit expressions of all the probabilities using an ancillary system and introducing unitary transformations which act on the input states and produce the output measured on the ancilla. By exploring physically accessible transformation acting on the input states, we present an optical scheme to implement the state discrimination.     

Picosecond soliton transmission by use of concatenated gain-distributed nonlinear amplifying fiber loop mirrors

Stable picosecond soliton transmission is demonstrated numerically by use of concatenated gain-distributed nonlinear amplifying fiber loop mirrors (NALMs). We show that, as compared with previous soliton transmission schemes that use conventional NALMs or nonlinear optical loop mirror and amplifier combinations, the present scheme permits a significant increase of loop-mirror (amplifier) spacing. The broad switching window of the present device and the high-quality pulses switched from it provide a reasonable stability range for soliton transmission. We also show that a soliton self-frequency shift can be suppressed by the gain-dispersion effect in the amplifying fiber loop and that soliton-soliton interactions can be partially reduced by using lowly dispersive transmission fibers.