光孤子与光孤子通信

阐述了光纤中光孤子形成的物理机理及光孤子间相互作用对光孤子通信的影响，介绍了光孤子通信的关键技术－孤子脉冲激光器和光孤子放大器，展望了光孤子通信的应用前景。     

稳态光折变空间孤子传输的量子理论

稳态光折变空间孤子系统可用奇异Lagrange量描述，系统含Dirac约束.通常按对应原理写 出孤子系统的量子对易关系和量子运动方程时，未计及约束.对稳态光折变空间光孤子约束 系统进行Dirac括号量子化，给出了系统的对易关系和量子场方程.在线性近似下给出量子 非线性薛定谔方程的微扰解，并讨论了孤子的压缩性质. 关键词： 量子场论 量子光学 光折变空间孤子 压缩效应     

全光非线性光孤子通信系统技术

近年来光孤子通信技术发展很快,各种新方案不断提出,各种系统设计与试验系统技术取得了重大突破,使光孤子通信向衫化迈进一大步,文章综述了光孤子通信技术的最新进展,分析了光孤子通信技术的发展趋势。     

全光非线性光孤子通信系统技术

近年来光孤子通信技术研究发展很快，各种新方案不断提出，各种系统设计与试验系统技术均取得了重大突破，使光孤子通信向实用化迈进了一大步。本文对光孤子通信技术的最新发展进行了综述与概括，指出了光孤子通信技术的发展趋势。     

光纤中的光孤子

叙述了光纤中光孤子形成的物理机理。即光纤中光孤子的形成是光纤中散射效应和相应调制效应相互制约、平衡的结果。     

怎样才能有效地观察光孤子

到目前为止，国内仍没有成功地令人信服地观察和记录光孤子，要完成这一突破还需作艰苦的努力。该文论述了光孤子存在的物理条件，指出国内为成功观察光孤子而开展的基础研究和应用研究的方向。     

准光孤子特性及其通信技术研究

对准光孤子理论进行了研究，用一个合适的、持续的色散管理方法，从一个修正的非线性薛定谔方程得到一个精确解，用这个解构造一个非线性稳定的准光孤子脉冲。用数值模拟的方法得出了准光孤子和光孤子的波形。结果表明：准光孤子几乎具有光孤子的全部优点，其脉冲宽度比光孤子要小很多，并且准光孤子的脉冲宽度可以通过调节光纤的结构参数来进行调整，准孤子能够在光纤中稳定地实现长距离传输，而且能够很好地克服由孤子的固有特性造成的对通信容量的限制，所以准光孤子有望成为下一代通信系统的最佳信号载体。     

一种计算光孤子通信系统误码率的新方法

将最陡下降法（又称鞍点法）用于估算使用集总式放大器的超长距离光孤子通信系统的误码率，并将所得结果与高斯近似进行了比较． 关键词：     

全光非线性光的孤子通信系统技术

近年来光孤子通信技术研究发展很快，各种新方案不断提出，各种系统设计与试验系统技术均取得了重大突破，使光孤子通信实用化迈进了五大步。本文对光孤子通信技术的最新发展进行综述和概括，指出了光孤子通信技术的发展趋势。     

光折变空间孤子

概述了光折变空间孤子与类Ｋｅｒｒ孤子的区别，光折变空间孤子的产生条件，物理机制以及实验观察，并展望了它的应用前景。     

光纤中双孤子相互作用的等价粒子理论

本文给出了含有一般扰动的非线性薛定锷（Ｓｃｈｒｏｄｉｎｇｅｒ）方程的孤子等价粒子理论，它使人们对孤子的粒子性质有了更深的了解，同时给出了光纤中双孤子相互作用的等价粒子分析，得到了与基于逆散射及微扰变分法完全一致的结果，这一方法可用于多孤子相互作用的解析分析，并能给出这一过程的直观物理图象．     

Effective Field Theory of Random Quantum Circuits

Quantum circuits have been widely used as a platform to simulate generic quantum many-body systems. In particular, random quantum circuits provide a means to probe universal features of many-body quantum chaos and ergodicity. Some such features have already been experimentally demonstrated in noisy intermediate-scale quantum (NISQ) devices. On the theory side, properties of random quantum circuits have been studied on a case-by-case basis and for certain specific systems, and a hallmark of quantum chaos—universal Wigner–Dyson level statistics—has been derived. This work develops an effective field theory for a large class of random quantum circuits. The theory has the form of a replica sigma model and is similar to the low-energy approach to diffusion in disordered systems. The method is used to explicitly derive the universal random matrix behavior of a large family of random circuits. In particular, we rederive the Wigner–Dyson spectral statistics of the brickwork circuit model by Chan, De Luca, and Chalker [Phys. Rev. X 8, 041019 (2018)] and show within the same calculation that its various permutations and higher-dimensional generalizations preserve the universal level statistics. Finally, we use the replica sigma model framework to rederive the Weingarten calculus, which is a method of evaluating integrals of polynomials of matrix elements with respect to the Haar measure over compact groups and has many applications in the study of quantum circuits. The effective field theory derived here provides both a method to quantitatively characterize the quantum dynamics of random Floquet systems (e.g., calculating operator and entanglement spreading) and a path to understanding the general fundamental mechanism behind quantum chaos and thermalization in these systems.     

量子场论中的自旋算符

从量子场论的角度对相对论粒子的运动自旋概念作了进一步深入研究.构造了场量子自旋以及场系统运动自旋两个新算符.给出了场量子自旋动量空间的显式表达式以及用Poincar啨群生成元表示的场系统运动自旋的显式表达式.借助这两个算符,可以干净地解决有关场自旋的问题,表明它们才是场自旋的恰当的算符.     

Quantum Field Theory and Dense Measurement

We show, using quantum field theory (QFT), that performing a large number of identical repetitions of the same measurement does not only preserve the initial state of the wave function (the Zeno effect), but also produces additional physicaleffects. We first discuss the Zeno effect in the framework of QFT, that is, as a quantum field phenomenon. We then derive it from QFT for the general case in which the initial and final states are different. We use perturbation theory and Feynman diagrams and refer to the measurement act as an external constraint upon the system that corresponds to the perturbative diagram that denotes this constraint. The basic physical entities dealt with in this work are not the conventional once-perfomed physical processes, but their n times repetition where n tends to infinity. We show that the presence of these repetitions entails the presence of additional excited state energies, and the absence of them entails the absence of these excited energies.     

Toward a Finite-Dimensional Formulation of Quantum Field Theory

Rules of quantization and equations of motion for a finite-dimensional formulation of quantum field theory are proposed which fulfill the following properties: (a) Both the rules of quantization and the equations of motion are covariant; (b) the equations of evolution are second order in derivatives and first order in derivatives of the spacetime coordinates; and (c) these rules of quantization and equations of motion lead to the usual (canonical) rules of quantization and the (Schrödinger) equation of motion of quantum mechanics in the particular case of mechanical systems. We also comment briefly on further steps to fully develop a satisfactory quantum field theory and the difficuties which may be encountered when doing so.     

Interference in Quantum Field Theory: Detecting Ghosts with Phases

This study discusses the implications of the principle of locality for interference in quantum field theory. As an example, it considers the interaction of two charges via a mediating quantum field and the resulting interference pattern in the Lorenz gauge. Using the Heisenberg picture, it is proposed that detecting relative phases or entanglement between two charges in an interference experiment is equivalent to accessing empirically the gauge degrees of freedom associated with the so-called ghost (scalar) modes of the field in the Lorenz gauge. These results imply that ghost modes are measurable and hence physically relevant, contrary to what is usually thought. They also raise interesting questions about the relation between the principle of locality and the principle of gauge-invariance. This analysis also applies to linearized quantum gravity in the harmonic gauge, and hence has implications for the recently proposed entanglement-based witnesses of non-classicality in gravity.     

量子孤子在光纤中的传播特性

利用线性近似和分步傅里叶变换法，分析了量子孤子在无耗光纤中的传播规律.量子孤子在光纤中的行为由量子非线性薛定谔方程（QNSE）描述,用线性近似法求解此方程，将量子噪声与经典部分分离，着重讨论了孤子量子噪声的演化行为，分析了高阶色散对噪声压缩的影响.结果表明：在较短的传输距离内，孤子的压缩性依然存在，但无论初始时压缩参数如何，随着传输距离的增加，压缩比会达到一个极限;在负色散区，三阶色散对压缩效应无影响.     

在采用集总放大器的光孤子优越传输中啁啾的作用

讨论了光孤子传输中，由脉冲包络的相位变化产生的啁啾与孤子传输的关系。数值计算表明，当孤子脉冲收缩、展宽时，啁啾总是改变符号，利用啁啾也可以定出孤子传输的光纤临界长度（即孤子传输中集总放大器的间隔），其效果比用脉宽恢复定出的临界长度要好