基于交叉相位调制制备四光子偏振纠缠态及其在隐形传态上的运用

利用克尔介质、偏振分束器、半波片和对强相干探测场的零拍探测,呈现了一个关于制备四光子偏振Diche态、GHZ态和W态的方案,当前量子光学实验技术条件均能有效满足该方案的要求.强的探测模相继和多个信号模光子相互作用,每次对于探测模而言,都会产生一个相位旋转.接下来,对探测模利用零拍探测,信号模可以投影得到想要的光子偏振纠缠态.此外,为了展现所制备的纠缠态作为重要的量子信息资源的价值,基于交叉相位调制进一步提出了一个隐形传送三光子偏振纠缠态的实验方案.     

基于偏振无关分束器的两光子部分纠缠态的简化浓缩方案

经由偏振无关的光学分束器实现对未知两光子部分纠缠态的纠缠浓缩,包括利用单光子探测器的线性光学浓缩方案,和利用弱交叉Kerr非线性媒质、零拍探测的浓缩方案。两对部分纠缠的光子对中各一个信号光子同时通过偏振无关分束器后,当探测到分束器输出模中各有一个光子时,剩余的两光子将处于最大纠缠态。与以前的浓缩方案相比较,我们的浓缩方案不需要额外的Hadmard门对信号光子施加作用,所需要的光学器件较少,这增加了方案在实验实现上的可行性。     

基于偏振无关分束器的两光子部分纠缠态的简化浓缩方案

经由偏振无关的光学分束器实现对未知两光子部分纠缠态的纠缠浓缩,包括利用单光子探测器的线性光学浓缩方案,和利用弱交叉Kerr非线性媒质、零拍探测的浓缩方案。两对部分纠缠的光子对中各一个信号光子同时通过偏振无关分束器后,当探测到分束器输出模中各有一个光子时,剩余的两光子将处于最大纠缠态。与以前的浓缩方案相比较,我们的浓缩方案不需要额外的Hadmard门对信号光子施加作用,所需要的光学器件较少,这增加了方案在实验实现上的可行性。     

利用交叉克尔效应制备六光子纠缠态

利用弱非线性的交叉克尔介质和对强相干探测场的动量积分零拍探测,呈现了一个关于制备六光子最大纠缠态的方案,如实现制备Dicke态和W态.在本方案中,只要相干探测光场的强度足够大时,对交叉克尔介质的非线性强度要求可以较弱,因而当前实验技术条件上均能满足本方案的要求.考虑到目前实验上实现单光子很是相对困难的,在信号模上仅用弱...     

利用交叉克尔效应制备六光子纠缠态

利用弱非线性的交叉克尔介质和对强相干探测场的动量积分零拍探测,呈现了一个关于制备六光子最大纠缠态的方案,如实现制备Dicke态和W态.在本方案中,只要相干探测光场的强度足够大时,对交叉克尔介质的非线性强度要求可以较弱,因而当前实验技术条件上均能满足本方案的要求.考虑到目前实验上实现单光子很是相对困难的,在信号模上仅用弱的相干光替代单光子源,从而进一步增强了本方案的实验可行性.     

基于两光子宇称门接近确定性的制备偏振Cluster态(英文)EI北大核心CSCD

基于弱的交叉克尔效应和线性光学元件,利用光子偏振宇称门呈现了一个关于制备Cluster态的方案.本方案引入了交叉克尔非线性介质,采用了对相干探测模的非破坏测量,有效实现了光子与光子间的相互作用,进而获得所期望的光子纠缠态,同时可以提高制备的成功概率和制备态的保真度.通过本方案可以制备接近完美保真度的四光子偏振Cluster态,并具有接近1的成功概率.在本方案的基础上通过利用线性光学元件还可以获得3N+1个光子的偏振Cluster态.     

基于自发参量下转换源二阶激发过程产生四光子超纠缠态

目前,多光子纠缠态的制备大多通过线性光学器件演化自发参量下转换一阶激发过程产生的纠缠光子对得到.本文考虑由自发参量下转换源二阶激发产生四个不可区分的纠缠光子制备四光子超纠缠态的情况.通过几组分束器、半波片和偏振分束器等线性光学器件设计量子线路演化四光子系统,结合四模符合探测,可得到同时具有偏振纠缠和空间纠缠的四光子超纠缠态.     

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.     

基于轨道角动量的多自由度W态纠缠系统

提出了一种制备三光子纠缠W态的方案, 该方案利用携带轨道角动量为lħ的光子(其中l可取(-∞, +∞)的任意整数)可构成无穷维向量空间的特性, 采用两种类型的参量下转换, 产生轨道角动量-自旋角动量纠缠的两对光子和一对偏振纠缠光子, 通过纠缠交换制备三光子多自由度的W态, 实现三光子体系纠缠的高维度、大容量量子信息处理. 方案采用q-plate相位光学器件和单模光纤等器件制备两个不同自由度(轨道角动量与偏振)混合的W态, 并利用计算机全息相位图改进方案制备三个不同自由度(轨道角动量、线动量和偏振)混合的W态. 本方案可稳定产生两种等概率互为对称的W态, 具有高维度、强纠缠特性与抗比特丢失能力, 信息量达log₂^m+2比特(m为l的可取值个数), 有望实现可扩容量子比特的安全通信.     

六光子超纠缠态制备方案

自发参量下转换对应于一种非线性光学过程, 实验上作为一种标准方法, 人们利用自发参量下转换源产生纠缠光子对. 本文考虑由自发参量下转换源产生三对纠缠光子的情况. 通过使用由几组偏振光 束分束器、分束器和半波片等线性光学器件组成的量子线路演化三对光子, 给出了一个高效制备 包含偏振纠缠和空间纠缠的六光子超纠缠态方案. 因为方案中包含了参量下转换源产生三对纠缠光子 的所有可能情况, 所以本方案有很高的效率. 基于弱非线性介质构建了一个量子非破坏性测量装置, 用于区分光子在两指定的空间模中的两种分布情况. 特别地, 方案中可以通过合理约束在量子非破坏性测量过程中引入的非线性强度来达到实际实验所限定的数量级, 因此, 该方案易于在实验上实现.     

Generating a Four-qubit Photon-Number Cluster State via Cross-Kerr Medium

A scheme is proposed for generating a photon-number entangled cluster state among four modes. The scheme only uses Kerr medium and homodyne measurement on probe coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a intense coherent state superposition. It is shown that under certain conditions, the four-photon cluster state can be generated effectively with high success probability and homodyne detection required only once, and the scheme is feasible by current experimental technology.     

Efficient preparation of a four-photon cluster state with homodyne measurement via cross-Kerr nonlinearity

A scheme is proposed for generating a multiphoton entangled cluster state among four modes. The scheme only uses Kerr medium, beam splitter and homodyne measurements on coherent light fields, which can be efficiently made in quantum optical laboratories. The photon in the signal mode is prepared in a superposition state of the vacuum state and one-photon state while the probe beam is initially set in a coherent state superposition. The strong probe mode interacts successively with multiple signal-mode photo...     

Hyperconcentration Based on Projection Measurements

We propose an efficient hyperconcentration protocol for distilling maximally hyperentangled state from partially entangled pure state, resorting to the projection measurement on an auxiliary photon. In our scheme, two photons simultaneously entangled in polarization states and spatial modes are considered. One party performs quantum nondemolition detections on his photon and an additional photon to produce three photon hyperentangled state, then he projects the assistant photon into an orthogonal basis composed of both the polarization and spatial degree of freedom. Then the state of the left two photons collapses into maximally hyperentangled state with a certain probability. In the rest cases, some less-entangled states are obtained, which can be used as resource for the next round concentration. By repeating the concentration process for several rounds, a higher success probability can be obtained, which makes our scheme useful in practical quantum information applications.     

Teleportation of a Photonic Qubit with Non-maximally Entangled State by Using Weak Cross-Kerr Nonlinearities

We present a scheme for teleporting an unknown single-photon polarization state by using the partially entangled state as the quantum channel. Based on weak cross-Kerr nonlinearity, in this scheme the sender utilizes the quantum parity-check detector (PCD) instead of the usual Bell state measurement. After getting the sender’s measurement result, the receiver of the scheme exploits another PCD to retrieve the original state with some additional photons being introduced. We work out the success probability of the scheme and show that the scheme is feasible with the current technology.     

Generation of hyperentangled four-photon cluster state via cross-Kerr nonlinearity

We propose a scheme for generating a hyperentangled four-photon cluster state that is simultaneously entangled in polarization modes and spatial modes. This scheme is based on linear optical elements, weak cross-Kerr nonlinearity, and homodyne detection. Therefore, it is feasible with current experimental technology.     

Robust scheme for the preparation of symmetric Dicke states with coherence state via cross-Kerr nonlinearity

A scheme is proposed for generating multiphoton maximally entangled states among four modes. These schemes only use Kerr medium and polarization beam splitters and P homodyne measurements on coherent light fields, which can be efficiently implemented in quantum optical laboratories. It's comparatively easy to realize symmetric Dicke state of light fields in the scheme. The scheme can be generalized to produce N-qubit maximally entangled states.     

Generation of Multiple-Atom Entangled States with Weak Cross-Kerr Nonlinearity

We propose a scheme to generate multiple-atom entangled states in separate cavities. In our scheme, only weak cross-Kerr mediums, homodyne measurement, and some linear elements are employed. With the help of homodyne measurement, four-atom GHZ state can be obtained with high probability and fidelity, and the proposal can be easily scaled to prepare multiple-atom GHZ state. Under ideal conditions, the success probability will not be affected by atomic numbers.     

Multiphoton path entanglement by nonlocal bunching

Multiphoton path entanglement is created without applying postselection, by manipulating the state of stimulated parametric down-conversion. A specific measurement on one of the two output spatial modes leads to the nonlocal bunching of the photons of the other mode, forming the desired multiphoton path entangled state. We present experimental results for the case of a heralded two-photon path entangled state and show how to extend this scheme to higher photon numbers.