连续变量六组份和八组份星型Cluster纠缠态光场产生系统

Cluster纠缠态是执行单向量子计算的基本资源。星型Cluster态可用于构建量子信息网络。以非简并光学参变放大器产生的双模压缩态光场为基础,设计了产生连续变量六组份和八组份星型Cluster纠缠态光场的实验方案,并推导了相应的量子不可分判据。计算结果指出,当量子不可分判据中的增益因子取为1时,需要一定的初始压缩度才能制备星型Cluster纠缠态;但当选取最佳增益因子时,极低的压缩也能产生星型纠缠。计算为实验系统设计提供了直接参考。     

Deterministic joint remote preparation of arbitrary multi-qudit states

In this Letter, we put forward a new nontrivial three-step strategy for joint remote preparation of arbitrary two-qudit states (JRSP) in a deterministic manner from a spatially separated multi-sender to one receiver. The scheme is then extended to the arbitrary multi-qudit case. In our schemes, various partially entangled GHZ-like states with arbitrary complex parameters are used as the quantum channels. It overcomes state preparation failure leading to the loss of valuable quantum channel resource and ensures the prepared data available for the remote terminals under extreme conditions such as limited number of quantum channels and limited quantum information processing technologies.     

通过cluster态实现两粒子纠缠态的量子几率隐形传态

提出通过一个四粒子cluster非最大纠缠态作为量子信道来实现一未知两粒子纠缠态的量子几率隐形传态方案。在此方案中,纠缠态可以实现一定的几率传输,此几率由cluster态中绝对值较小的两个系数决定。如果我们用cluster最大纠缠态作为量子信道,此时几率隐形传态就成了一般的隐形传态,即成功传输的几率为100%。     

通过幺正操作传送未知两个三能级粒子纠缠态

我们提出一个把未知的两个三能级粒子纠缠态传送给两个接收者的方案,该方案使用一个未知的五个三能级粒子纠缠态作为量子通道。必须指出该方案能够推广到传送未知的N个三能级粒子纠缠态给M个接收者的情况,使用的是未知(N.M 1)个三能级粒子纠缠态作为量子通道。在传送过程中,需要执行适当的幺正操作和(N.M 1)次独立测量,而且该方案不涉及Bell态测量。     

多个量子节点确定性纠缠的建立

量子纠缠是一种重要的量子资源,在多个空间分离的量子存储器间建立确定性的量子纠缠,然后在用户控制的时刻将所存储的量子纠缠转移到量子信道中进行信息的分发和传送,这对于实现量子信息网络是至关重要的.本文介绍了用光学参量放大器制备与铷原子D1吸收线对应的非经典光场,而且在三个空间分离的原子系综中确定性量子纠缠的产生、存储和转移.利用电磁感应透明光和原子相互作用的原理,将制备的多组分光场纠缠态模式映射到三个远距离的原子系综以建立原子自旋波之间的纠缠.然后,存储在原子系综中的纠缠态通过三个量子通道,纠缠态的量子噪声被转移到三束空间分离的正交纠缠光场.三束释放的光场间纠缠的存在验证了该系统具有保持多组分纠缠的能力.这个方案实现了三个量子节点间的纠缠,并且可以直接扩展到具有更多节点的量子网络,为未来实现大型量子网络通信奠定了基础.     

纠缠相干态的纠缠浓缩

利用线性光学元器件对光场量子态进行操纵,可以实现远程的量子纠缠调控和量子通讯.通过分析光学分束器对相干态光场的作用,发现当初始光场态是两个两部分纠缠态的直乘时,让其中的两模通过光学分束器作用后再对其进行光子计数,另外两模将会塌缩到新的纠缠态.基于这个特点,提出了一个实现部分纠缠相干态纠缠浓缩的方案.在这个方案中,两个部分纠缠相干态被用来作为量子信道,通过光学分束器作用后对光场进行光子数探测时,如果测量到光场的两模分别处于奇光子数态和零光子数态,则光场另外的两模将塌缩到最大纠缠态,从而完成纠缠浓缩的过程.计算结果表明,对于纠缠相干态,无论其初始的纠缠是多么微弱,利用这种方法总有一定的几率可以从中提纯出最大纠缠态.     

Affleck-Kennedy-Lieb-Tasaki state on a honeycomb lattice is a universal quantum computational resource

Universal quantum computation can be achieved by simply performing single-qubit measurements on a highly entangled resource state, such as cluster states. The family of Affleck-Kennedy-Lieb-Tasaki states has recently been intensively explored and shown to provide restricted computation. Here, we show that the two-dimensional Affleck-Kennedy-Lieb-Tasaki state on a honeycomb lattice is a universal resource for measurement-based quantum computation.     

纠缠相干态的纠缠浓缩

利用线性光学元器件对光场量子态进行操纵,可以实现远程的量子纠缠调控和量子通讯.通过分析光学分束器对相干态光场的作用,发现当初始光场态是两个两部分纠缠态的直乘时,让其中的两模通过光学分束器作用后再对其进行光子计数,另外两模将会塌缩到新的纠缠态.基于这个特点,提出了一个实现部分纠缠相干态纠缠浓缩的方案.在这个方案中,两个部...     

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.     

Scheme to Implement Optimal Symmetric 1→2 Universal Quantum Telecloning Through Cavity-Assisted Interaction

We propose a scheme to implement the optimal symmetric 1→2 universal quantum telecloning through cavity-assisted interaction. In our scheme, an arbitrary single atomic state can be telecloned to two single atomic states. And three atoms are trapped in three spatially separated cavities respectively. With a particular multiparticle entangled state acting as a quantum information channel and the trapped single atom acting as a quantum network node for its long-lived internal state, quantum information can be telecloned among nodes and can stored in the nodes.     

量子纠缠态的普适远程克隆

提出一种任意两粒子纠缠态1→2普适远程克隆方案. 此方案仅需一个特殊的四粒子纠缠态作为量子信道, 就可使处于空间不同位置的两个接收者分别以5/6的保真度得到任意输入态的近似拷贝, 该保真度远高于已有方案中的保真度. 将方案推广到任意两粒子纠缠态1→N(N>2)普适远程克隆的情况, 可使处于不同地点的N个接收者分别以(2N+1)/(3N)的保真度得到输入态的近似拷贝. 另外, 提出一种以上述单个特殊四粒子纠缠态作为量子信道, 在多目标量子比特受控非门和 关键词： 量子纠缠态 普适远程克隆 保真度     

On-chip multiphoton Greenberger–Horne–Zeilinger state based on integrated frequency combs

One of the most important multipartite entangled states, Greenberger–Horne–Zeilinger state (GHZ), serves as a fundamental resource for quantum foundation test, quantum communication and quantum computation. To increase the number of entangled particles, significant experimental efforts should been invested due to the complexity of optical setup and the difficulty in maintaining the coherence condition for high-fidelity GHZ state. Here, we propose an ultra-integrated scalable on-chip GHZ state generation scheme based on frequency combs. By designing several microrings pumped by different lasers, multiple partially overlapped quantum frequency combs are generated to supply as the basis for on-chip polarization-encoded GHZ state with each qubit occupying a certain spectral mode. Both even and odd numbers of GHZ states can be engineered with constant small number of integrated components and easily scaled up on the same chip by only adjusting one of the pump wavelengths. In addition, we give the on-chip design of projection measurement for characterizing GHZ states and show the reconfigurability of the state. Our proposal is rather simple and feasible within the existing fabrication technologies and we believe it will boost the development of multiphoton technologies.     

Theory for quantum state of photon pairs generated from spontaneous parametric down-conversion nonlinear process

A theory is presented for the quantum state of photon pairs generated from spontaneous parametric down-conversion nonlinear process. In this theory, the influence of the final sizes of nonlinear optical crystals on optical eigenmodes is explicitly taken into consideration. It was found that these photon pairs are not in entangled quantum states. Polarization correlations between the signal beam and the idler beam are explained. It is also shown that the two photons generated from SPDC are not spatially separated, therefore the polarization correlation between the signal and idler beams is not an evidence for quantum non-locality. The text was submitted by the authors in English.     

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,     

Preparation of multipartite entangled states used for quantum information networks

The preparation of multipartite entangled states is the prerequisite for exploring quantum information networks and quantum computation.In this paper,we review the experimental progress in the preparation of cluster states and multi-color entangled states with continuous variables.The preparation of lager scale multipartite entangled state provide valuable quantum resources to implement more complex quantum informational tasks.     

Quantum Computation and Entangled-State Generation Through Photon Emission and Absorption Processes in Separated Cavities

We propose a scheme to implement a two-bit conditional quantum phase gate and generate a multi-atom cluster state and a two-atom three-dimensional entangled state based on photon emission and absorption processes. In the scheme, a Λ-type atom and a V-type atom are individually trapped in two spatially separated cavities connected by an optical fiber. By choosing the interaction time and the ratio of coupling parameters appropriately, the gate operation and entanglement generation can be determinately achieved. We also discuss the influence of photon Leakage on the fidelities of the gate and entanglement and show that the scheme is scalable and feasible in the experimental realization and further utilization.     

Probabilistic Remote Preparation of a Four-Particle Entangled W State for the General Case and for All Kinds of the Special Cases

We present a protocol for probabilistic remote preparation of a four-particle entangled W state.The quantum channel is composed of two partial entangled four-particle cluster states.We calculate the total successful probability and total classical communication cost required for the general case and for all kinds of the special cases,respectively.It is shown that for two maximally entangled four-particle cluster states,such a scheme for the general case has the total successful probability of 25%and only consumes the total classical communication of 1 bit,while this scheme for the special cases under certain conditions can possess successful probability of 50%or 100%,the required classical communication will only be 2 bits or 4 bits.Meantime,we give in detail all unitary transformations for the general case and for all kinds of the special cases,respectively.     

基于绝热捷径快速实现远距离的四维纠缠态的制备

作为量子信息处理的载体,量子纠缠态一直以来都是量子信息领域的研究热点.相比于低维纠缠态,高维纠缠态使得量子通信具有更快的传输速度、更强的安全性、更高的噪声容忍阈值等特点.另外,绝热技术因其对实验参数起伏不敏感而被广泛应用于纠缠态的制备,然而绝热过程需要相当长的演化时间,因此绝热捷径应运而生.本文提出了一种采用无跃迁量子驱动构建绝热捷径实现快速制备两个原子的四维纠缠态的理论方案,该系统中的两个原子分别被囚禁在两个由光纤连接的双模腔中.为了获得一个技术上可操作的物理系统,本方案采用能级失谐设计出一个可精确驱动系统沿着某一个系统的瞬时本征态演化的哈密顿.该方案所采用的无跃迁量子驱动构建绝热捷径不仅大大缩短了演化时间,而且在实验上也比较容易实现.本文还数值模拟了消相干因素对四维纠缠态保真度的影响,结果表明,只要脉冲参数选取在一定范围内,光纤耗散、腔场耗散和原子自发辐射等不利因素都会被大大抑制.     

Multipartite entanglement detection in bosons

We propose a simple quantum network to detect multipartite entangled states of bosons and show how to implement this network for neutral atoms stored in an optical lattice. We investigate the special properties of cluster states, multipartite entangled states, and superpositions of distinct macroscopic quantum states that can be identified by the network.     

三粒子纠缠Ｗ态的隐形传态

提出利用三个二粒子纠缠态作为量子信道，实现三粒子纠缠Ｗ态的隐形传态的方案.首先考察量子信道是最大纠缠态的情形，然后进一步考察量子信道是非最大纠缠态的情形.发现在量子信道为非最大纠缠态时，通过引进一个辅助粒子，并构造一个幺正变换矩阵，即可以一定的概率完成三粒子纠缠Ｗ态的隐形传态. 关键词： 隐形传态 三粒子纠缠 纠缠Ｗ态 非最大纠缠量子信道