Interaction-Induced Chiral Quantum States of the Ultracold Polar Molecules

The ultracold polar molecules with the tunable dipole-dipole interaction, not only would enable explorations of a large class of exotic many-body physics phenomena, but also could be used for quantum information processing. In the present paper we demonstrate that this dipole-dipole interaction can generate the degenerate chiral quantum states acting as a qubit robust against noise when the ultracold polar molecules are confined by a triangular lattice. Moreover, we also find two first-order quantum phase transitions by controlling an external driving field. One is the transition with the change of the different degenerate chiral quantum states. The other is the transition with the breaking of the degenerate quantum chiral states to the nondegenerate state. In experiment, these first-order quantum phase transitions can be detected by measuring the collective molecular population.     

Nonlinear Optical Susceptibilities of Polar Molecules

The third order nonlinear optical susceptibility is calculated taking into account the permanent dipole moments of the molecule and the population changes of the energy levels. It is shown that the expression of the susceptibility contains terms proportional to the difference or to the squared difference of permanent dipole moments, corresponding to different electronic states.     

外电场下极性量子阱中杂质态结合能

我们用变分方法研究了外电场下量子阱中的杂质态结合能,计算中既考虑了电子同体纵光学声子和界面光学声子的相互作用又考虑了杂质中心同体纵光学声子和界面光学声子的相互作用。我们以GaAs/Al_0.3Ga_0.7As量子阱为例,讨论了结合能随杂质位置、阱宽和电场强度的变化规律。得到了电子-声子相互作用对杂质态结合能和斯塔克效应的修正是相当明显的。     

Quantum States Transfer by Analogous Bell States

Transmitting quantum states by channels of analogous Bell states is studied in this paper. We analyze the transmitting process. constructed the probabilitic unitary operator, and gain the largest successful transfer quantum state probability.     

Voltage-Controlled Quantum Dynamics and Generation Entanglement between Two Separated Quantum-Dot Molecules Embedded in Photonic Crystal Cavities

Voltage-controlled quantum dynamics of two quantum-dot molecules （QDMs） embedded in two separated photonic crystal cavities are theoretically investigated. We show numerically that generation of entangled states and population transfer between the two QDMs can be realized with the same coupling parameters. The effects of parameters deviation and dissipations on generation entangled states be used for realization of new-type of solid state quantum and populations transfer are also discussed. The results may devices and integrated electro-optical devices,     

两二能级原子在共同环境下的量子关联动力学

通过精确求解带有偶极-偶极相互作用的两个二能级原子与一个共同热库相互作用模型, 得到了两原子间量子纠缠和量子失谐(quantum discord)的解析表达式. 综合考虑了环境的非马尔可夫效应、原子间的偶极-偶极相互作用以及原子的本征频率同腔模中心频率之间的失谐量对两原子间量子纠缠和quantum discord的影响. 研究显示: 在非马尔可夫机制下, 且原子的本征频率与腔模中心频率是共振时, 当两原子初态处于纠缠态时, 原子间偶极-偶极相互作用可以显著抑制包括量子纠缠和quantum discord等量子关联的衰减, 更特别的是, 如果原子的本征频率同腔模中心频率有一定的失谐时, 利用原子间偶极-偶极相互作用可大大地延长两原子退纠缠的时间; 当两原子初态处于可分离态时, 从短时间来看, 原子间偶极-偶极相互作用可以提高量子纠缠和quantum discord振荡的振幅,而在长时间极限下, 原子间偶极-偶极相互作用不会改变量子纠缠和quantum discord达到的稳定值. 最后, 讨论了原子间偶极-偶极相互作用对量子纠缠和quantum discord动力学不同的影响. 关键词： 量子纠缠 量子失谐 共同环境 偶极-偶极相互作用     

Teleportations of Mixed States and Multipartite Quantum States

In this paper, we propose a protocol to deterministically teleport an unknown mixed state of qubit by utilizing a maximally bipartite entangled state of qubits as quantum channel. Ira non-maximally entangled bipartite pure state is employed as quantum channel, the unknown mixed quantum state of qubit can be teleported with 1 -√ 1- C^2 probability, where C is the concurrence of the quantum channel. The protocol can also be generalized to teleport a mixed state of qudit or a multipartite mixed state. More important purpose is that, on the basis of the protocol, the teleportation of an arbitrary multipartite （pure or mixed） quantum state can be decomposed into the teleportation of each subsystem by employing separate entangled states as quantum channels. In the case of deterministic teleportation, Bob only needs to perform unitary transformations on his single particles in order to recover the initial teleported multipartite quantum state.     

Quantum Logic Network for Probabilistic Cloning Quantum States

We construct efficient quantum logic network for probabilistic cloning the quantum states used in implemented tasks for which cloning provides some enhancement in performance.     

基于量子模距离的量子态聚类识别

针对量子系统的状态识别，定义了一种量子模距离作为量子态之间的相似性度量，提出了一种基于量子模距离的聚类算法，它既适用于对量子叠加态的识别，也适合对量子纠缠态的识别。在算法中，根据待识别的样本量子态求取聚类中心，分别计算各量子态到聚类中心的量子模距离，根据量子模距离对量子态进行聚类识别。算例说明了这种聚类识别方法的合理性和有效性。     

Multiple Multi-Qubit Quantum States Sharing

A multiple multi-qubit quantum states sharing scheme is proposed,in which the dealer can share multiple multi-qubit quantum states among the participants through only one distribution and one recovery.The dealer encodes the secret quantum states into a special entangled state,and then distributes the particles of the entangled state to the participants.The participants perform the single-particle measurements on their particles,and can cooperate to recover the multiple multi-qubit quantum states.Compared to the existing schemes,our scheme is more efficient and more flexible in practice.     

连续变量量子态的光学操控

量子态的光学操控是指在光场的传输、存储和频率变换等过程中用光学方法对光场的量子态进行操作与控制.量子态操控是量子通讯及量子态制备和应用的基础.在简要介绍连续变量多组份纠缠态光场制备的基础上,概述基于多组份纠缠态光场的连续变量量子通讯网络及在执行压缩态和纠缠态光场操控方面的实验研究进展.     

芯片表面的冷极性分子静电阱与微阱阵列

提出一种利用三根载荷金属杆来实现在芯片表面陷俘冷极性分子的静电阱.给出空间静电场等高线分布.通过调节电极电压操控阱中心距离芯片表面的高度.用经典的蒙特卡罗方法模拟冷分子被装载和囚禁的动力学过程.方案对中心速度为11 m·s^-1的冷分子束,最大装载效率可以达到40%,阱中分子的温度大约为25 mK.方案可以进一步微型化、集成化,形成一维和二维静电微阱阵列,在量子计算、低维物理等方面有应用价值.     

一种针对弱场搜寻态冷极性分子的可控静电表面囚禁方案

提出一种使用带电金属环和六个球电极和一个外加偏置电场实现对冷极性分子静电囚禁的新方案.计算装载和囚禁时空间电场分布.囚禁中心距离芯片表面的高度可以通过外电场和环形电极所加电压来操控.蒙特卡罗模拟表明对于中心速度为15 m·s^-1的ND₃分子束,装载效率可以达到70%,得到冷分子的温度大约为45 mK.当继续增加偏置电场强度时,单阱分裂为对称的两个阱.如果同时改变球形电极上所加电压,得到不对称的两个阱,可以借此来调节两个阱中所囚禁的冷分子数目的比例.为了易于理解,用蒙特卡罗方法模拟了装载、囚禁、分裂冷分子波包的动力学过程.     

Anisotropy Effects on Polar Optical Vibrations in a Freestanding Wurtzite Cylindrical Quantum Dot

The properties of polar optical phonon vibrations in a quasi-zero- dimensional （QOD） anisotropic wurtzite cylindrical quantum dot （QD） are analyzed based on the dielectric continuum model and Loudon＇s uniaxial crystal model. The analytical electrostatic potentials of the phonon vibrations in the systems are deduced and solved exactly. The result shows that there exist four types of polar mixing optical phonon modes in the QOD wurtzite cylindrical QD systems. The dispersive equations and electron-phonon coupling function for the quasi-confined-half-space （QC-HS） mixing modes are derived and discussed. It is found that once the radius or the height of the QD approach infinity, the dispersive equations of the QC-HS mixing modes in the QOD cylindrical QD can naturally reduce to those of the QC and HS modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both of physicM and mathematical viewpoints.     

Deterministic Quantum Key Distribution Using Two Non-orthogonal Entangled States

A deterministic quantum key distribution scheme using two non-orthogonal entangled states is proposed.In the proposed scheme,communicators share key information by exchanging one travelling photon with two random and secret polarization angles.The security of the distributed key is guaranteed by three checking phases in three-way channel and the communicators' secret polarization angles.     

Quantum Correlations in a Family of Two-Qubit Separable States

Quantum correlations in a family of two-qubit separable classical-quantum correlated states are intensively studied with four diferent approaches,namely,quantum discord[Phys.Rev.Lett.88(2002)017901],measurementinduced disturbance(MID)[Phys.Rev.A 77(2008)022301],ameliorated MID[J.Phys.A:Math.Theor.44(2011)352002]and quantum dissonance[Phys.Rev.Lett.104(2010)080501].Quantum correlations captured with diferent approaches are compared and discussed so that their three distinct features are exposed.     

Discrimination Among Quantum States

It has recently been shown that quantum measurement is not always useful for discrimination among quantum states (K. Hunter (2003). Physical Review A 68, 012306). This paper provides another proof of the necessary and sufficient condition for quantum measurement not to be useful and examines the condition by considering quantum measurement which discriminates between two spin-1/2 states in thermal equilibrium.     

Anisotropy Effects on Polar Optical Vibrations in a Freestanding Wurtzite Cylindrical Quantum Dot

The properties of polar optical phonon vibrations in a quasi-zero- dimensional (Q0D) anisotropic wurtzite cylindrical quantum dot (QD) are analyzed based on the dielectric continuum model and Loudon's uniaxial crystal model.The analytical electrostatic potentials of the phonon vibrations in the systems are deduced and solved exactly. The result shows that there exist four types of polar mixing optical phonon modes in the Q0D wurtzite cylindrical QD systems. The dispersive equations and electron-phonon coupling function for the quasi-confined-half-space (QC-HS) mixing modes are derived and discussed. It is found that once the radius or the height of the QD approach infinity, the dispersive equations of the QC-HS mixing modes in the Q0D cylindrical QD can naturally reduce to those of the QC and HS modes in Q2D QWs or Q1D QWWs systems. This has been analyzed reasonably from both of physical and mathematical viewpoints.     

Remark on the One-Way Quantum Deficit for General Two-Qubit States

We reinvestigate the one-way quantum deficit,which is a measure of quantum correlation emerging from a thermodynamical approach.We give a tight upper bound of the one-way quantum deficit for general mixed states,and give a sufficient condition for this bound.Finally,we discuss a universal way to evaluate the one-way quantum deficit for general two-qubit states.