Non-Markovianity and Indivisible Quantum dynamics of a Apin-S System

Using a measure for the divisibility of a dynamical map,we study the non-Markovian character of a quantum evolution of a spin-S system,which is in an external field and weakly coupled to a bosonic bath with a certain temperature.The finite-temperature dynamics of the open system is obtained by the time-convolutionless master equation in the secular approximation.Besides the influence of the environmental spectral density function,the external field and low temperatures can afect the quantum non-Markovianity.It is found out that the non-Markovian feature of a dynamical map of a high-dimensional spin system is noticeable in contrast to that of a low-dimension spin system.     

双模Dicke模型的一级量子相变

多光场与多粒子相互作用的多模Dicke模型不但存在着更为丰富的量子相,而且在量子信息中有着重要的应用.本文运用Holstein-Primakoff变换和玻色扩展法研究双模Dicke模型的基态特性并从理论上发现了一个新的一级量子相变.该相变在实验上可以通过测量平均光子数或原子布居数进行观察.     

小世界网络中的量子纠缠渗流

本文研究了小世界复杂网络中的长程量子纠缠态的制备。提出了量子纠缠渗流优化网络量子通信的方案。通过在经典纠缠渗流协议(CEP)中引入局域化的"target-swap"量子操作,形成量子纠缠渗流协议(QEP)。研究表明QEP在长程纠缠制备的效能方面明显优于CEP,通过度分布变化的分析解释了QEP具有优势的原因。     

Multipartite Entanglement Transfer from Multi-Mode Coherent State to Spin Qubits

The multipartite entanglement transfer from continuous variable system to spin qubits is investigated. We select multi-mode coherent field as continuous variable field. It is found that the qubits can not gain tripartite entanglement for states of close to GHZ state from the multi-mode coherent field. Moreover, the ability of the qubits gain the tripartite entanglement for states close to W state and bipartite entanglement from the continuous variable system is depended on the phase of multi-mode coherent field.     

通过纠缠交换实现N粒子任意态的概率传态

量子隐形传态的杰出安全特性使其在未来的通讯领域充满潜力.量子力学的不确定性原理和不可克隆定理禁止对量子态进行直接复制,因此,量子隐形传态将量子态划分为经典和量子两部分,信息分别经由经典和量子通道从发送者Alice传递给远方的接收者Bob,根据这两种信息,Bob实行相应操作就可以以一定的几率重建初始传送态.利用一般意义的隐形传态方案,提出一种简便的新方法实现了一个N粒子任意态的概率传态.方法采用N个非最大纠缠的三粒子GHZ态作为量子通道,避免了引入额外的辅助粒子.为了实现传态,Alice将所有粒子分成N份,对第i份的粒子对(i,x_i)实行Bell测量并将结果通过经典通道通知Bob,Bob对粒子(y_i,z_i)进行相应的操作就可以完成第i个粒子信息的传送.当完成N次相似的重复操作后,Bob就可以准确地重建初始传送态.文中以Bell态测量为基本手段,重复的操作同时也降低了实验难度,作为一个特例,文中给出了一个两粒子任意态的传态方案.     

各向异性非均匀海森堡XY链中的量子关联

研究了各向异性非均匀海森堡周期性XY链中的量子失协(QD)和形成纠缠(EOF)。量子失协一般大于形成纠缠。两者之间的差距随着温度的升高或外磁场的增大而减小。调节各向异性系数的大小,可以发现,有些情况下形成纠缠已经消失,而量子失协仍然存在。在大部分参数区域内,量子失协总是大于形成纠缠。     

Stochastic properties coupling between of tumor growth with non-Gaussian and Gaussian noise terms

Dynamical behavior of a tumor-growth model with coupling between non-Gaussian and Gaussian noise terms is investigated. The departure from the Gaussian noise can not only reduce the probability of tumor cells in the active state, induce the minimum of the average tumor-cell population to move toward a smaller non-Gaussian noise, but also decrease the mean first-passage time. The increase of white-noise intensity can increase the tumor-cell population and shorten the mean first-passage time, while the coupling strength between noise terms has opposite effects, and the noise correlation time has a very small effect.     

Rabi模型的光场压缩

电路量子电动力学的实验实现了光与人造原子的超强耦合相互作用, 相互作用强度与光场频率在同一个数量级.在超强耦合区域, 著名的旋波近似失效, 因此系统的动力学必须用含有反旋波项的Rabi模型描述.本文研究Rabi模型中的光场压缩.数值模拟结果发现, 光场压缩不是随耦合强度线性增加, 而是在合适的超强区域获得最大值.同时, 我们还发现, 较小的反旋波项有助于提高光场压缩.所得结果有利于实验上在超强区域中制备所需的压缩态. 关键词： Rabi模型 超强耦合 光场压缩