Entanglement of dipolar coupling spins

Entanglement of dipole-dipole interacting spins 1/2 is usually investigated when the energy of interaction with an external magnetic field (the Zeeman energy) is greater than the energy of dipole interactions by three orders. Under this condition only a non-equilibrium state of the spin system, realized by pulse radiofrequence irradiations, results in entanglement. The present paper deals with the opposite case: the dipolar interaction energy is the order of magnitude or even larger than the Zeeman one. It was shown that entanglement appears under the thermodynamic equilibrium conditions and the concurrence reaches the maximum when the external field is directed perpendicular to the vector connecting the nuclei. For this direction of the field and a system of two spins with the Hamiltonian accounting the realistic dipole-dipole interactions in low external magnetic field, the exact analytical expression for concurrence was also obtained. The condition of the entanglement appearance and the dependence of concurrence on the external magnetic field, temperature, and dipolar coupling constant were studied.     

Entanglement under equilibrium establishing in spin systems subjected to radiofrequency field

We study the entanglement evolution in a dipolar-coupled spin system irradiated by a radiofrequency (RF) field in quasi-equilibrium state characterized by a two-temperature density matrix. Process of the establishment of equilibrium is in the equalization of these temperatures. The method of the nonequilibrium statistical operator in a rotating frame is used to describe the evolution of the spin system. It is shown that the equilibrium establishment has nonexponential character, and the time needed for this establishment depends strongly on the RF field strength. Particularly, the weak RF irradiation increases the lifetime of entanglement. Temporal and temperature dependencies of the concurrence of spin pairs are obtained and discussed. It is shown that application of RF field increases the time of the equilibrium establishment (up to order of 1,000 times) and lifetime of the existence of entangled states (up to order of 1,000 times). Thus, with the help of RF irradiation, we can govern the relaxation process and control entanglement in the system. The obtained results can be used for analysis of more complex spin systems because dipole–dipole interaction decreases proportionally to inverse third power of the distance between the spins, and influence of far way spins can be negligible.     

Entanglement and multiple quantum coherence dynamics in spin clusters

With the purpose to reveal consistency between multiple quantum (MQ) coherences and entanglement, we investigate numerically the dynamics of these phenomena in one-dimensional linear chains and ring of nuclear spins 1/2 coupled by dipole–dipole interactions. As opposed to the calculation of the MQ coherence intensity based on the density matrix describing the spin system as a whole, we consider the “differentiated” intensity related only to the chosen spin pair based on the reduced density matrix. It is shown that the entanglement and the MQ coherence have similar dynamics only for nearest neighbors while we did not obtained any consistency for remote spins.     

Entanglement manipulation via dynamics in multiple quantum spin systems

We study manipulation of entanglement between two identical networks of quantum mechanical particles. Firstly, we reduce the problem of entanglement transfer to the problem of quantum state transfer. Then, we consider entanglement concentration and purification based on free dynamics on the networks and local measurements on the vertices. By introducing an appropriate measure of efficiency, we characterize the performance of the protocol. We give evidence that such a measure does not depend on the network topology, and we estimate the contribution given by the number of entangled pairs initially shared by the two networks.     

Entanglement dynamics of two-qubit pure state

We show that the entanglement dynamics for the pure state of a closed two-qubit system is part of a 10-dimensional complex linear differential equation defined on a supersphere, and the coefficients therein are completely determined by the system Hamiltonian. We apply the result to two physical examples of Josephson junction qubits and exchange Hamiltonians, deriving analytic solutions for the time evolution of entanglement. The Hamiltonian coefficients determine whether the entanglement is periodic. These results allow of investigating how to generate and manipulate entanglements efficiently, which are required by both quantum computation and quantum communication.     

横风下高速列车系统动力学的平衡状态法

基于车辆-轨道耦合动力学和空气动力学提出了一种快速计算横风下高速列车系统动力学行为的平衡状态方法.首先,忽略轨道不平顺并利用流固耦合联合仿真方法计算横风下高速列车的平衡状态;然后,将平衡状态下的气动力加载到车辆-轨道耦合动力学模型并计算高速列车动力学响应.利用建立的平衡状态方法,研究了列车在速度为13.8 m/s的横风下以350 km/h速度运行时的流固耦合动力学行为.比较了平衡状态方法和联合仿真方法两种方法下列车姿态、安全性和舒适性指标的差异,计算结果差别在3.26%以内.研究结果表明:平衡状态方法计算横风下高速列车流固耦合的效率更高.     

Entanglement dynamics of a two-qutrit system under DM interaction and the relevance of the initial state

Using concurrence as a measure of entanglement, we present analytical and numerical study of entanglement dynamics in a two-qutrit system in the presence of the Dzyaloshinskii–Moriya interaction, as a function of the parameters involved. Three distinct initial states: a superposition of the ground and the first excited state, the Bell-type state and a superposition of qutrit coherent states will be considered in this investigation.     

The structure of enumerated spin glass state spaces

We enumerate the low energy part of the state space of an Ising spin glass using an efficient branch-and-bound algorithm. A coarse graining algorithm (NB-clustering) is employed to condense the inherent information to a system size which is treatable in computer simulations. The reduced state space still incorporates all ingredients necessary to simulate aging effects. We investigate its structure in detail and find that certain assumptions made in heuristical state space models which have been presented in the past to reproduce aging phenomena in spin glass experiments are indeed compatible with the data from the observed state spaces.     

模块化免疫神经网络平衡态检测模型*

基于神经网络原理、免疫系统和遗传算法的相关机理,构造了一个网络安全平衡器。该平衡器建立了抗原与抗体平衡态检测的数学模型、抗原与抗体的促进和抑制函数,提出了安全平衡态的概念,给出了抗原与抗体浓度的计算公式和模块化多层分类处理模型,利用促进、抑制函数和遗传算法适应度函数使已受攻击的网络再次达到一种新的安全平衡状态,这为网络安全提供了一个新的途径。理论证明网络安全方案是有效的。     

Entanglement and quantum state transfer between two atoms trapped in two indirectly coupled cavities

Quantum Information Processing - We propose a one-step scheme for implementing entanglement generation and the quantum state transfer between two atomic qubits trapped in two different cavities...     

Separable equilibrium state probabilities via time reversal in Markovian process algebra

The reversed compound agent theorem (RCAT) is a compositional result that uses Markovian process algebra (MPA) to derive the reversed process of certain interactions between two continuous time Markov chains at equilibrium. From this reversed process, together with the given, forward process, the joint state probabilities can be expressed as a product-form, although no general algorithm has previously been given. This paper first generalises RCAT to multiple (more than two) cooperating agents, which removes the need for multiple applications and inductive proofs in cooperations of an arbitrary number of processes. A new result shows a simple stochastic equivalence between cooperating, synchronised processes and corresponding parallel, asynchronous processes. This greatly simplifies the proof of the new, multi-agent theorem, which includes a statement of the desired product-form solution itself as a product of given state probabilities in the parallel components. The reversed process and product-form thus derived rely on a solution to certain rate equations and it is shown, for the first time, that a unique solution exists under mild conditions—certainly for queueing networks and G-networks.     

Distributed event-triggered generalized Nash equilibrium seeking in multi-coalition noncooperative games with coupling constraints

This paper is concerned with a multi-coalition noncooperative game with coupling equality constraints. Each coalition is a player consisted of multiple agents in noncooperative games and desire to minimize its own objective function based on local information. Each agent as actual decision maker in the same coalition is to optimize the objective function of the coalition cooperately. To seek a generalized Nash equilibrium (GNE) of the multi-coalition game, a distributed continuous-time algorithm is developed. Moreover, to further reduce the communication among agents and coalitions, an event-triggered mechanism (ETM) is introduced for the multi-coalition game. By using ETM, a novel distributed GNE seeking algorithm is proposed, where agents and coalitions are allowed to exchange estimation information with neighbors only when the triggering condition is satisfied. Remarkably, the proposed event-triggered scheme introduces internal variables to regulate its threshold dynamically, which excludes Zeno behavior. By Lyapunov analysis, it is proved that the coalitions' decision variables converge to a GNE in both algorithms. Finally, the effectiveness of the proposed methods is validated by numerical simulations.     

Entanglement generation and entanglement concentration of two-photon four-dimensional spatial modes partially entangled Dicke state

Two-photon four-dimensional spatial modes partially entangled Dicke state can be compactly generated from six concurrent spontaneous parametric down-conversion processes by cascading poling domain structures in 5% MgO-doped poled lithium niobate bulk crystal. Entanglement concentration of the two-photon four-dimensional spatial modes partially entangled Dicke state can be realized by using quantum nondestructive detection of nonlinear Kerr medium, optical beam splitter, and quantum gate operation.     

刚柔耦合系统动力学研究进展

首先简要回顾了柔性多体系统动力学前期研究的3个阶段．针对传统零次近似模型的缺陷提出了新的建模理论,并在新的一次近似耦合模型的基础上,就“动力刚化”问题和刚柔耦合动力学问题中的离散化方法与实验等方面进行研究;研制了供理论研究和动力学现象揭示的实验平台．文中对所取得的研究成果进行介绍．文末对今后的研究方向进行了展望．     

区域耦合状态转移概率化元胞自动机模型

针对多区域系统内部各个子区域属性的差异化,提出多区域耦合状态转移概率化元胞自动机模型。在该模型中,运用区域耦合原理和耦合区域信息交换规则来构造元胞自动机（CA）模型的演化规则,实现局部子区域之间的信息交换,运用不同类型的元胞自动机模型对子区域分别建立不同的CA模拟模型,并用概率化方法处理模拟模型中元胞状态的转化,实现各个子区域状态的演化。实验表明,子区域在保持自身演化形态相对独立的同时,通过边界区域耦合进行演化连接,各个子区域内的元胞能与其边界耦合区域内的元胞保持一种相对稳定的有序形态,且一个子区域的影响能在一定程度上传递到其他子区域内。该模型能很好地处理大规模复杂区域环境下的空间演化模拟。     

Entanglement and Yangian in a {V^{\otimes 3}} Yang-Baxter system

In this paper, a 8 × 8 unitary Yang-Baxter matrix \breveR₁₂₃(q₁,q₂,f){\breve{R}_{123}(\theta_{1},\theta_{2},\phi)} acting on the triple tensor product space, which is a solution of the Yang-Baxter Equation for three qubits, is presented. Then quantum entanglement and the Berry phase of the Yang-Baxter system are studied. The Yangian generators, which can be viewed as the shift operators, are investigated in detail. And it is worth mentioning that the Yangian operators we constructed are independent of choice of basis.     

相平衡和平衡级分离专用计算软件VB设计

本软件系统包括4个子系统：（1）平衡数据关联子系统－含Van Laar,Margules,NRTL,UNIQUAC和Wilson模型以及Antione常数回归方程；（2）精馏子系统－含间歇精馏，普通精馏和萃取精馏；（3）液液萃取子系统－包括无水和含水溶剂体系；（4）数据库子系统－建成bpd.mdb数据文件，具有查询和管理各种烷烃，芳烃和溶剂等基础物性的功能。软件系统采用VB设计，界面友好，操作简便，可用于汽液和液液平衡数据模型参数的关联以及多元多级汽液和液液平衡级的分离计算。     

Forced resonant oscillations of nonlinear autonomous system in equilibrium neighborhood

Consideration was given to existence and stability of oscillations in the case of resonance where in the neighborhood of equilibrium the autonomous nonlinear system is subjected to periodic perturbations. For each of the probable cases where the equilibrium is surrounded or not by a family of periodic oscillations, established were the sufficient conditions solving the problem. The amplitudes of the resonant oscillations were estimated in terms of the small parameter.