N个热囚禁离子的GHZ态的制备

我们提出了一个简单的方法产生N个囚禁离子的GHZ态.在这个方法中,初始时处于相同态的N个两能级离子被囚禁在一个线性阱中,同时被两束均匀的经典激光照射.这个方法对振动模的加热不敏感,从退相干的观点来看这点很重要.     

一个囚禁离子运动压缩数态的制备

本文提出一个方案以制备一个被囚禁在谐势阱中的离子质心运动的压缩数态。在本方案中，这个离子受到两个分别调到第一高、低振动边带的激光场和一个与离子共振的激光场的轮流激发。系统最后被制备到运动压缩数态与电子基态的直积。     

应用相位调制驻波光场制备囚禁离子的暗压缩态

基于囚禁离子与驻波激光场相互作用,应用驻波光场的相位调制的方法,我们提出了一种制备离子振动压缩态的新方法.研究了压缩振幅与调制振幅的关系.我们发现:适当选择调制振幅,可把离子制备在最佳压缩振动态上,并且它们的产生伴随着自发辐射的相消.提出了一种实验构想,并进行了讨论.     

单离子囚禁和冷却的研究进展

激光冷却和离子囚禁技术的结合为表光谱和量子力学实验提供了非常有用的工具。文章主要介绍了单个囚禁冷却离子的研究动态和发展方向。     

应用频率调制激光制备二离子暗EPR态

提出了制备势阱中的两离子EPR态的一种方法. 这种方法是基于频率调制的行波光场与囚禁离子的相互作用.这种方法的一个突出优点是所制备的量子态为“暗态”,即自发辐射相消的量子态。另外,讨论了二模压缩运动态（两离子质心模式和呼吸模式）的制备.     

制备冷囚禁多离子W态的简单方案

提出实验上可行的制备冷囚禁多离子W态的方案.在此方案中制备的是对称W态,只需两个步骤,而在文献[H(a)aner H,H(a)ansel W,Roos C F,et al.Nature,2005,438:643-646.]中制备相同的W态,则需要更多的操作步骤,考虑到消相干机制,减少纠缠态制备过程中的步骤是非常有必要的,并且在方案中只需要一束激光.     

制备囚禁冷离子的振动压缩量子态

基于非Lamb-Dicke近似下激光-离子相互作用的动力学规律,讨论了如何利用一系列的激光脉冲来驱动囚禁冷离子.从囚禁冷离子的运动基态出发获得压缩相干态、压缩奇偶相干态、压缩真空态等一系列的振动数态的叠加态.结果表明,只要适当地调节各个所用激光脉冲的长度和相位,总能很好逼近所需要的压缩量子态. 关键词： 囚禁冷离子 激光脉冲 压缩量子态     

在离子阱体系中通过Bell态来产生簇态

我们对已存在的在离子阱体系中产生簇态的方案进行修改.本文中提出的方案是基于Bell态和控制相位门(cz门)的实现.通过Bell态和控制相位门,我们就可以产生4比特(qubit)以及6比特的簇态.     

Paul阱中囚禁离子质心运动量子态的压缩效应

文章研究Ｐａｕｌ阱中被囚禁离子才动量在奇偶相干的的压缩性质。研究结果表明，囚禁离子不仅有二阶压缩效应，而且有高阶压缩效应，本文具体给出了囚禁离子的位置和动量在奇偶相干态中的二阶和四阶压缩条件及压缩曲线。     

Cluster states prepared by using hot trapped ions

We propose a scheme for the preparation of one-dimensional and two-dimensional cluster states by using hot trapped ions. The scheme is based on the interaction between two ions and bichromatic radiation. The vibrational mode in our protocol is only virtually excited so that the system is insensitive to the thermal field. In addition, we only use two levels of ions as qubits and the successful probability may achieve 100%.     

Fast scheme for generating quantum-interference states and GHZ state of N trapped ions

We propose a fast scheme to generate the quantum-interference states of N trapped ions. In the scheme the ions are driven by a standing-wave laser beam whose carrier frequency is tuned such that the ion transition can take place. We also propose a simple and fast scheme to produce the GHZ state of N hot trapped ions and this scheme is insensitive to the heating of vibrational motion, which is important from the viewpoint of decoherence.     

Preparation of the four-qubit cluster states in cavity QED and the trapped-ion system

This paper proposes a simple scheme to generate a four-atom entangled cluster state in cavity quantum electrodynamics. With the assistantce of a strong classical field the cavity is only virtually excited and no quantum information will be transferred from the atoms to the cavity during the preparation for a four-atom entangled cluster state, and thus the scheme is insensitive to the cavity field states and cavity decay. Assuming that deviation of laser intensity is 0.01 and that of simultaneity for the interaction is 0.01, it shows that the fidelity of the resulting four-atom entangled cluster state is about 0.9886. The scheme can also be used to generate a four-ion entangled cluster state in a hot trapped-ion system. Assuming that deviation of laser intensity is 0.01, it shows that the fidelity of the resulting four-ion entangled cluster state is about 0.9990. Experimental feasibility for achieving this scheme is also discussed.     

Generation of motional Fock states of a trapped ion in the mediate-excitation regime

We propose a scheme to prepare Fock states for the vibrational motion of a trapped ion. Unlike previous schemes, the present scheme works in the mediate-excitation regime, in which the corresponding Rabi frequency is equal to the trap frequency. Thus, the required time is greatly shortened, which is important in view of decoherence.     

Generation of cluster states for cavity fields

This paper proposes an alternative scheme for generating cluster-type of entangled coherent states. This scheme is based on resonant interaction of a two-mode cavity with a two-level atom driven by strong classical fields. Thus the required interaction time is greatly shortened, which is very important in view of decoherence.     

Preparation of nonclassical states and measurement of the Wigner function for the collective motion of N trapped ions

We propose a scheme for generating nonclassical states for the centre-of-mass vibrational mode of N trapped ions,including superpositions of several coherent states on a circle and Fock states. In the scheme N trapped ions are driven by a laser beam tuned to the carrier. The scheme also provides a new prospect for laser cooling. The scheme can be used to measure the Wigner function of the collective vibrational mode.     

Generation of atomic Greenberger-Horne-Zeilinger states and cluster states through cavity-assisted interaction

This paper proposes a scalable scheme to generate n-atom GHZ states and cluster states by using the basic building block, i.e., a weak coherent optical pulse [α） being reflected successively from a single-atom cavity. In the schemes, coherent state of light is used instead of single photon source, homodyne measurement on coherent light is done kastead of single photon detection, and no need for individually addressing keeps the schemes easy to implement from the experimental point of view. The successful probabilities of our protocols approach unity in the ideal case.     

Quantum teleportation by entanglement swapping with trapped ions

An effective teleportation scheme for an unknown ionic internal state via trapped ions is proposed without joint Bell-state measurement (BSM). In the constructed quantum channel process, we make use of entanglement swapping to avoid decrease in entanglement during the distributing of particles. Thus our scheme provides new prospects for quantum teleportation in a longer distance. The distinct advantage of our scheme is insensitive to the heating of vibrational mode. Furthermore, our scheme has no any individual optical access, and the successful probability also can reach 1.     

A scheme for the implementation of unconventional geometric phase gates with trapped ions

We propose a scheme for the realization of unconventional geometric two-qubit phase gates with two identical two-level ions, In the present scheme, the two ions are simultaneously illuminated by a standing-wave laser pulse with its pulse frequency being tuned to the ionic transition. The gate operation time can be much shorter, making the system robust against decoherence. In addition, we choose the appropriate experimental parameters to construct the geometric phase gate in one step, and thus avoid implementing the pure geometric single qubit operation.[第一段]     

利用交叉克尔非线性产生四光子偏振态簇态

提出了一种基于交叉克尔非线性效应产生四光子偏振态簇态的方案,与其他产生四光子簇态的方案比较,该方案引入宇称门的思想和用到基于零差探测的非破坏测量方法,使得该方案在实验上更易于操作及实现.