Generation of Entangled Bloch States for Two Atomic Samples Trapped in Separated Cavities

A scheme is presented for the cavities. In the scheme, each a coherent state with a small generation of entangled states for two atomic ensembles trapped in two distant atomic sample is initially in a Bloch state and the cavity mode is initially in amplitude. The dispersive dependent phase shift on the atomic system. The detection atomic samples collapse to an entangled Bloch state. atom-cavity interaction leads to a photon-number of a photon leaking from the cavities makes the two     

Scheme for preparation of multi-partite entanglement of atomic ensembles

We show a scheme of preparing multipartite W type of maximally entangled states among many atomic ensembles with the generation time increasing with the party number only polynomially. The scheme is based on laser manipulation of atomic ensembles and single-photon detection, and fits well the status of the current experimental technology. We also show one of the applications of this kind of W state, demonstrating Bell theorem without inequalities.     

Quantum nonlocality of generic family of four-qubit entangled pure states

We directly introduce a Bell-type inequality for four-qubit systems. Using the inequality we investigate quantum nonlocality of a generic family of states |Gabcd[Phys. Rev. A 65 052112(2002)] and several canonical four-qubit entangled states. It has been demonstrated that the inequality is maximally violated by the so called "four-qubit the maximally entangled state |Gm" and it is also violated by four-qubit W state and a special family of states |Gab00. Moreover, a useful entanglement-nonlocality relationship for the family of states |Gab00is derived. Finally, we present a scheme of preparation of the state |Gmwith linear optics and cross-Kerr nonlinearities.     

Teleportation and dense coding with genuine multipartite entanglement

We present an explicit protocol E0 for faithfully teleporting an arbitrary two-qubit state via a genuine four-qubit entangled state. By construction, our four-partite state is not reducible to a pair of Bell states. Its properties are compared and contrasted with those of the four-party Greenberger-Horne-Zeilinger and W states. We also give a dense coding scheme D0 involving our state as a shared resource of entanglement. Both D0 and E0 indicate that our four-qubit state is a likely candidate for the genuine four-partite analogue to a Bell state.     

Scheme for implementing perfect quantum teleportation with four-qubit entangled states in cavity quantum electrodynamics

Recently, Peng et al. [2010 Eur. Phys. J. D 58 403] proposed to teleport an arbitrary two-qubit state with a family of four-qubit entangled states, which simultaneously include the tensor product of two Bell states, linear cluster state and Dicke-class state. This paper proposes to implement their scheme in cavity quantum electrodynamics and then presents a new family of four-qubit entangled state |Ω₄>₁₂₃₄. It simultaneously includes all the well-known four-qubit entangled states which can be used to teleport an arbitrary two-qubit state. The distinct advantage of the scheme is that it only needs a single setup to prepare the whole family of four-qubit entangled states, which will be very convenient for experimental realization. After discussing the experimental condition in detail, we show the scheme may be feasible based on present technology in cavity quantum electrodynamics.     

Unconditional two-mode squeezing of separated atomic ensembles

We propose schemes for the unconditional preparation of a two-mode squeezed state of effective bosonic modes realized in a pair of atomic ensembles interacting collectively with optical cavity and laser fields. The scheme uses Raman transitions between stable atomic ground states and under ideal conditions produces pure entangled states in the steady state. The scheme works both for ensembles confined within a single cavity and for ensembles confined in separate, cascaded cavities.     

量子隐形传态的类簇态信道方案(英文)

提出了利用一个四粒子类簇态来实现一个任意两粒子态的隐形传送方案.如果接受者能根据发送者提供的测量信息对量子态实施一个合适的幺正变换,那么隐形传送就能以一定的概率实现.由于该方案中充当量子信道的是部分纠缠态,因此该方案比以前基于最大纠缠态的方案更具有现实意义.同时研究导出一个重要的结论:可以从一个四粒子类簇态(部分纠缠态)中以一定的概率提取出一个四粒子簇态(最大纠缠态),这个概率等于成功隐形传态的概率.     

量子隐形传态的类簇态信道方案

提出了利用一个四粒子类簇态来实现一个任意两粒子态的隐形传送方案.如果接受者能根据发送者提供的测量信息对量子态实施一个合适的幺正变换,那么隐形传送就能以一定的概率实现.由于该方案中充当量子信道的是部分纠缠态,因此该方案比以前基于最大纠缠态的方案更具有现实意义.同时研究导出一个重要的结论：可以从一个四粒子类簇态（部分纠缠态）中以一定的概率提取出一个四粒子簇态（最大纠缠态）,这个概率等于成功隐形传态的概率.     

Optimal Remote Preparation of a Four-Qubit Entangled Cluster-Type State Via Two Non-Maximally Entangled GHZ-Type States

We devise an highly efficient protocol for remotely preparing a four-qubit entangled cluster-type state. In this protocol, two non-maximally entangled GHZ-type states are employed to link the sender Alice and the receiver Bob, and the to-be-prepared state can be reconstructed successfully with the probability of (b₁b₂)² in general case. Then to achieve our concerns of constructing efficient remote preparation with higher success probability, some special ensembles of four-qubit states are minutely investigated. As a result, it is shown that the total probability of the RSP protocol, in these particular cases, can be improved to twice or even fourfold as that in general case.     

Deterministic Remote Preparation of a Four-Qubit Cluster-Type Entangled State

We propose a scheme for remotely preparing a four-qubit cluster-type state with complex coefficients by using six EPR pairs as the quantum channel. To complete the remote state preparation scheme, a novel set of four-qubit mutually orthogonal basis vectors has been introduced. It is shown that, after the sender performs two different four-qubit projective measurements, the receiver can reconstruct the original state (to be prepared remotely) with unit successful probability. Moreover, the scheme is also generalized to the case that non-maximally two-qubit entangled states are taken as the quantum channel.     

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%。     

Comment on“Teleportation Protocol of Three-Qubit State Using Four-Qubit Quantum Channels”

Recently, Choudhury (Int. J. Theor. Phys. 10, 1007 2016), proposed a teleportation protocol of three-qubit state using four-qubit quantum channels.According to their scheme the three-qubit entangled states could be teleported by use of three simultaneous quantum channels of four-qubit cluster states. In this paper,we emphasize that the same three-qubit entangled states can be teleported perfectly by using only one quantum channel of four-qubit cluster states.     

Scheme for Entanglement Concentration of Unknown Multiparticle Greenberger-Horne-Zeilinger or W Class States

We present two schemes for concentrating unknown nonmaximally entangled Greenberger-Horme-Zeilinger (GHZ) or W class states. The first scheme for concentrating the nonmaximally entangled GHZ state is based on linear optical devices. The second scheme for concentrating the W class states can be applied to a wide variety of atomic state. Both of our schemes are not postselection ones and are within the current technologies.     

A Criterion to Identify Maximally Entangled Four-QubitState

Paolo Facchi, et al. [Phys. Rev. A77 (2008) 060304(R)] presented a maximally multipartite entangled state (MMES). Here, we give a criterion for the identification of maximally entangled four-qubit states. Using this criterion, we not only identify some existing maximally entangled four-qubit states in the literature, but also find several new maximally entangled four-qubit states as well.     

在腔QED中制备四原子的｜D42〉态

在腔QED系统中,通过原子与腔场的大失谐相互作用,我们设计了一个制备四原子的|D₄²〉态的方案。本文还把|D₄²〉态和其它的四原子纠缠态,如W,GHZ和团簇态进行了比较,发现|D₄²〉态有许多有趣的纠缠特征。     

Preparation of partially entangled W state and deterministic multi-controlled teleportation

We give a protocol to prepare special partially entangled multi-atom W states. Besides, a scheme for deterministic and multi-controlled teleportation of an arbitrary unknown two-level two-atom state via partially entangled W states is proposed.     

Entanglement witnesses of four-qubit tripartite separable quantum states

A quantum entangled state is easily disturbed by noise and degenerates into a separable state. Compared to the entanglement with bipartite quantum systems, less progress has been made for the entanglement with multipartite quantum systems. For tripartite separability of a four-qubit system, we propose two entanglement witnesses, each of which corresponds to a necessary condition of tripartite separability. For the four-qubit GHZ state mixed with a W state and white noise, we prove that the necessary conditions of tripartite separability are also sufficient at W states side.     

Entangled states in spin subsystems of polyatomic ensembles

The feasibility of formation entangled states in spin subsystems of two spatially separated atomic ensembles is discussed. It is shown that the process of cooperative Raman scattering of correlated photon pairs emitted by a parametric source in a below-threshold regime may serve as a physical mechanism for the entanglement. A scheme of teleportation of a coherent spin state in systems of spatially separated ensembles is proposed.     

Quantum Nondemolition Measurement of Entangled Atomic Ensembles in Coupled Cavity System

Quantum nondemolition measurement scheme for entangled atomic ensembles was presented when they are restricted in two distant coupled cavities. Under certain conditions, we showed that the entanglement evolution of both the atomic ensembles and cavity fields are of the same periods, which provides us with potential nondemolitionmeasurement of entangled atomic ensembles by experimentally detecting cavity fields. Including the dissipation of the cavity fields, the same steps of evolution still hold. Furthermore, it is shown that we can have the two-mode squeezing steady-states of both the cavity fields and the atomic ensembles, which really provides us with the quantum nondemolition measurement of the entangled atomic state.     

利用冷原子系综制备窄线宽三光子频率纠缠态

从理论上提出了一种制备窄线宽三光子频率纠缠态的实验方案,该三光子纠缠态利用在两个冷原子系综中的四波混频和电磁诱导透明来产生.利用二阶微扰理论完成了相关计算,并通过分析光子符合计数,研究了该三光子纠缠态的特性,证明其具有类似于离散变量三粒子W态的基本性质,并具有光子反群聚效应.