用激光-二能级原子系统实现一位通用量子逻辑门

使用代数动力学方法，对激光-二能级原子系统的含时薛定谔方程进行求解.该系统哈密顿量具有SU(2)代数结构，得到了严格解.基于严格解，适当调节单模激光场的频率和振幅以及短脉冲激光与二能级原子的二阶虚光子作用强度，可实现一位通用量子逻辑门. 关键词： 代数动力学 激光-二能级原子系统 一位量子逻辑门     

自旋团簇量子主方程的复合动力学对称性和热力学性质

基于三同核线型自旋团簇(每个粒子的自旋为S=1/2)的非自治量子主方程,研究了处于热辐射场中的自旋团簇的热力学性质.利用新颖的代数动力学方法,即引入动力学群的左右表象,不仅发现了自旋团簇的一个子空间态具有的SU(2)U(1)U(1)结构,而且对该子空间态在演化中所产生的耗散和退相干性质进行了计算.     

两粒子自旋系统量子纠缠的时间演化

研究了两个具有海森伯耦合的自旋为1/2的粒子在随时间变化的磁场中的运动情况.系统的哈密顿量具有SU（2）代数结构,运用代数动力学方法对此系统进行求解,得到了时间演化算子的严格解.基于严格解,求得两粒子体系随时间变化的波函数,从而计算得到两粒子体系的纠缠.对不同初始波函数,研究了系统纠缠随时间的变化情况.讨论了外场影响纠缠的条件. 关键词： 二粒子系统纠缠 代数动力学解法     

SU(3)线性非自治量子系统的代数动力学求解

利用代数动力学方法，得到了量子物理中十分重要的SU（3）线性非自治量子系统的严格解及其不变Cartan算子，并建立起量子解与经典解之间的对应关系．同时计算了周期系统的非绝热Berry相因子 关键词：     

量子辐射场与经典流的相互作用 hω(4)线性非自治量子系统的代数动力学求解

利用代数动力学方法,分别在两种不同的规范条件下,得到了描述量子辐射场与经典流相互作用的hw(4)线性非自治量子系统在谐振子表象和相干态表象中的精确解及其Cartan不变算子,建立和澄清了量子解与经典解之间存在的直接对应的规则.结果表明代数动力学方法对于具有非半单李代数结构的线性动力系统仍然适用.     

代数动力学与SU(2)线性非自治量子系统

利用代数动力学方法得到了SU(2)线性非自治量子系统的精确及其Cartan不变算子,并应用得到的解计算了时间有关的磁场中中微子的反转概率以及束流动力学中的粒子自旋极化问题,另外还讨论了周期系统的非绝热Berry相因子. 关键词：     

具有半单李代数结构的线性非自治量子系统的精确解

给出了对于具有半单李代数结构的线性量子系统求其精确解的代数动力学方法. 这个方法通过一系列规范变换,把哈密顿量逐步简化为Cartan算子的函数. 规范变换的系数由一组常微分方程确定,Schrodinger方程的完全解通过这组规范变换的逆变换得到.与此同时,还可以得到一组与时间有关的动力学不变量. 作为例子,又具体求解了一个SU(3)模型.     

时间有关的广义谐振子与外场的相互作用 SU(1,1)(?)h(3)线性非自治量子系统的严格解

利用代数动力学方法得到了SU(1,1)(?)h(3)线性非自治量子系统的精确解及其Cartan不变算子,并发现了量子解与经典解之间的新的间接对应关系.结果还表明代数动力学方法对于这种具有非半单李代数结构的线性动力系统仍然适用. 关键词：     

对线性光学量子融合门的简化

作为一种特殊的多体纠缠态,簇态可以用来进行通用的量子计算.量子融合门可以有效地扩展簇态,将一维的簇态进行任意加长,或者把一维的簇态融合为多维的簇态从而获得具有我们所需要的构型的簇态.文章对两类线性光学量子融合门进行了讨论,并且在Ⅱ类融合门的基础上提出一种更加简洁的融合簇态的方法,精简了融合门中的线性光学元件,同时简化了计算过程.     

量子辐射场与经典流的相互作用：hw（4）线性非自治量子系统的代数动力…

利用代数动力学方法，分别在两种不同的规范条件下，得到了描述量子辐射场与经典流相互作用的ｈｗ（４）线性非自治量子系统在谐振子表象和相干态表象中的精确解及其Ｃａｒｔａｎ不变算子，建立和澄清了量子解与经典解之间存在的直接对应的规则。结果表明代数动力学方法对于具有非半单李代数结构的线性动力系统仍然适用。     

Single Qubit and Its Universal Logic Gate Made of a Heisenberg Spin Cluster with Five Particles

We investigate an anisotropic Heisenberg spin cluster with five particles controlled by a time-dependent magnetic field. With the algebraic dynamical method, we obtain the exact analytical solution to the time dependent Schr6dinger equation. Based on the analytical solution, it is shown that the system can be used as a universal single qubit logic gate controlled by the strength and frequency of the magnetic field, and the six special single qubit logic gates can be realized physically. We also discuss the anti-decoherence property of the qubit and its logic gates resulted from particle coupling effect and collectivity of the cluster.     

Computing with spins: from classical to quantum computing

This article reviews the use of single electron spins to compute. In classical computing schemes, a binary bit is represented by the bistable spin polarization of a single electron confined in a quantum dot and subjected to a weak magnetic field. The spin orientation can be either parallel or anti-parallel to the field, so that it becomes a binary variable which can encode logic 0 and logic 1. Coherent superposition of these two polarizations can represent a qubit for quantum computing. By engineering the exchange interaction between closely spaced spins in neighboring quantum dots, it is possible to implement either classical or quantum logic gates.     

Anisotropic Spin Cluster as a Qubit

We study an anisotropic spin cluster of 3 spin S=1/2 particles with antiferromagnetic exchange interaction with non-uniform coupling constants. A time-dependent magnetic field is applied to control the time evolution of the cluster. It is well known that for an odd number og sites a spin cluster qubit can be defined in terms of the ground state doublet. The universal one-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the six basic one-qubit gates can be realized by adjusting the applied time-dependent magnetic field.     

Anisotropic Spin Cluster as a Qubit

We study an anisotropic spin cluster of 3 spin S=1/2 particles with antiferromagnetic exchange interaction with non-uniform coupling constants. A time-dependent magnetic field is applied to control the time evolution of the cluster. It is well known that for an odd number of sites a spin cluster qubit can be defined in terms of the ground state doublet. The universal one-qubit logic gate can be constructed from the time evolution operator of the non-autonomous many-body system, and the six basic one-qubit gates can be realized by adjusting the applied time-dependent magnetic field.     

Entanglement control in a superconducting qubit system by an electromagnetic field

By making use of the dynamical algebraic method we investigate a quantum system consisting of superconducting qubits interacting with data buses, where the qubits are driven by time-dependent electromagnetic field and obtain an explicit expression of time evolution operator. Furthermore, we explore the entanglement dynamics and the influence of the time-dependent electromagnetic field and the initial state on the entanglement sudden death and birth for the system. It is shown that the entanglement between the qubit and bus as well as the entanglement sudden death and birth can be controlled by the time-dependent electromagnetic field.     

蓝移阱中单个铯原子基态磁不敏感态的相干操控

单个中性原子的超精细微波跃迁能级的相干性是基于中性原子量子计算、量子信息处理和量子模拟的基础.我们在实验上利用微波双光子拉曼过程实现了蓝移阱中铯原子基态超精细态|6S1/2,F=3,mF=-1〉和|6S1/2,F=4,mF=1〉间的相干操控,并研究了其相对能级频移随磁场的变化,获得了"魔术"磁场的大小为1.4(2)Gauss(1 Gauss=10-4 T).结果表明,利用魔术磁场可大幅改善超精细态|6S1/2,F=3,mF=-1?和|6S1/2,F=4,mF=1〉之间的相干性,测量到的相干时间可达1.0(1)s.     

Entanglement Evolution of Two-Coupled Spins in a Time-Dependent Rotating Magnetic Field

We study the dynamics evolution of a two-qubit Heisenberg XXX spin chain under a time-dependent rotating magnetic field. Based on the algebraic structure of the non-autonomous system, the exact solution of the Schrödinger equation is obtained by using the method of algebraic dynamics. Based on the time-dependent analytical solution, we further study the entanglement evolution between the two coupled spins for different initial states, and find that the entanglement is determined by the coefficients of the initial state and the coupling constant $J$ of the system.     

含时旋转磁场中的两耦合粒子的纠缠演化(英文)

我们研究了含时旋转磁场中海森堡XXX模型下的双量子比特的动力学演化情况.基于此非自治系统的代数结构,我们用代数动力学方法求得了系统的精确解析解.在此基础上,进一步研究了在不同初态下系统的纠缠测度随时间的演化,发现纠缠测度由系统的初态的系数和耦合强度决定.