Quantum secure direct communication with Greenberger-Horne-Zeilinger-type state (GHZ state) over noisy channels

We propose a quantum error-rejection scheme for direct communication with three-qubit quantum codes based on the direct communication of secret messages without any secret key shared in advance. Given the symmetric and independent errors of the transmitted qubits, our scheme can tolerate a bit of error rate up to 33.1%, thus the protocol is deterministically secure against any eavesdropping attack even in a noisy channel.

A （2, 3） quantum threshold scheme based on Greenberger-Horne-Zeilinger state

In this paper, by using properties of quantum controlled-not manipulation and entanglement states, we have designed a novel （2, 3） quantum threshold scheme based on the Greenberger- Horne -Zeilinger （GHZ） state. The proposed scheme involves two phases, i.e. a secret sharing phase and a secret phase. Detailed proofs show that the proposed scheme is of unconditional security. Since the secret is shared among three participants, the proposed scheme may be applied to quantum key distribution and secret sharing.

Economical multiparty simultaneous quantum identity authentication based on Greenberger-Horne-Zeilinger states

A multiparty simultaneous quantum identity authentication protocol based on Creenberger-Horne-Zeilinger （GHZ） states is proposed. The multi-user can be authenticated by a trusted third party （TTP） simultaneously. Compared with the scheme proposed recently （Wang et al 2006 Chin. Phys. Lett. 23（9） 2360）, the proposed scheme has the advantages of consuming fewer quantum and classical resources and lessening the difficulty and intensity of necessary operations.

一种基于GHZ态的半量子双方身份认证协议

半量子身份认证在保障通讯安全方面发挥着至关重要的作用。通过引入一个量子第三方对密钥进行集中管理,提出一种新的基于Greenberger-Home-Zeilinger (GHZ)态的半量子双方身份认证协议。首先,对参与者的量子能力进行限制,两个认证者都只具有半量子的能力,协议使用更少的量子资源。其次,协议中两个半量子参与者只需要执行简单的测量操作和异或操作。安全性分析发现,利用该协议进行量子通信时,假冒攻击、截获重发攻击和纠缠附加攻击等攻击都无法引起合法身份信息的泄露,表明该协议可以有效防止非法的不诚实参与者获得合法身份,具有较好的安全性和实用性。

Remote preparation of a Greenberger-Horne-Zeilinger state via a two-particle entangled state

We present two schemes for realizing the remote preparation of a Greenberger-Horne-Zeilinger （GHZ） state. The first scheme is to remotely prepare a general N-particle GHZ state with two steps. One is to prepare a qubit state by using finite classical bits from sender to receiver via a two-particle entangled state, and the other is that the receiver introduces N - 1 additional particles and performs N - 1 controlled-not （C-Not） operations. The second scheme is to remotely prepare an N-atom GHZ state via a two-atom entangled state in cavity quantum electrodynamics （QED）. The two schemes require only a two-particle entangled state used as a quantum channel, so we reduce the requirement for entanglement.

Novel traveling quantum anonymous voting scheme via GHZ states

Based on traveling ballot mode,we propose a secure quantum anonymous voting via Greenberger–Horne–Zeilinger(GHZ)states.In this scheme,each legal voter performs unitary operation on corresponding position of particle sequence to encode his/her voting content.The voters have multiple ballot items to choose rather than just binary options“yes”or“no”.After counting votes phase,any participant who is interested in voting results can obtain the voting results.To improve the efficiency of the traveling quantum anonymous voting scheme,an optimization method based on grouping strategy is also presented.Compared with the most existing traveling quantum voting schemes,the proposed scheme is more practical because of its privacy,verifiability and non-repeatability.Furthermore,the security analysis shows that the proposed traveling quantum anonymous voting scheme can prevent various attacks and ensure high security.

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.

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 linearoptical 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.

Deterministic generation of Greenberger-Horne-Zeilinger and W states for three distant atoms via adiabatic passage

We propose two schemes for generating Greenberger-Horne-Zeilinger and W states of three distant atoms. In the present schemes, the atoms are individually trapped in three spatially separated optical cavities coupled by two optical fibres. Performing an adiabatic passage along dark states, the population of cavities and fibres excited is negligible under certain conditions. In addition, the spontaneous decay of atoms is also efficiently suppressed based on our proposals. Furthermore, the discussion about the entanglement fidelity is given and we point out that our schemes work robustly with small fluctuations of experimental parameters.

Generation of Atomic Greenberger-Horne-Zeilinger States Based on Faraday Rotation

Based on the input-output relation of the cavity and the Faraday Rotation mechanism, we propose ascheme for generating the n-atom Creenberger-Horne-Zeilinger state. In the scheme, the n-atom trapped respectively inn spatially separate cavities would be entangled with the photons going through the atom-cavity system. The successfulprobabilities of our protocol approach unity in the ideal case. What is more, no requirement for separately addressingfurther lowers experimental difficulties.

用Greenberger-Horne-Zeilinger态作量子信道实现多点控制的远程单比特幺正变换(英文)

提出了一个用三粒子纠缠的GHZ态作为量子信道实现多点控制的远程单比特幺正变换的操纵方案.在该方案中,发送者Alice能"传送"一个幺正变换给远距离的接收者Bob,此幺正变换的结构分别由Alice和Bob决定.而Alice与Bob间的量子信道宽度,亦远程单比特幺正变换的成功操纵几率则由第三者Cindy控制.Cindy与Alice(Bob)间的经典通讯也由Cindy控制.

基于Greenberger-Horne-Zeilinger态的控制量子安全直接通讯(英文)

我们利用Greenberger-Horne-Zeilinger(GHZ)态,提出了一个控制量子安全直接通讯方案。在方案中,我们不仅分析了这个方案的安全性,而且指出了这个方案可以有效地抵御截取再发送袭击和干扰袭击。

广义Greenberger-Horne-Zeilinger态纠缠度和Bell型不等式实验

利用制备的三光子偏振广义Greenberger-Horne-Zeilinger纠缠态,测量了三体纠缠度、Svetlichny不等式和广义Greenberger-Horne-Zeilinger态的密度矩阵.根据密度矩阵计算了三体纠缠度,测量得到了广义Greenberger-Horne-Zeilinger纠缠态的纠缠和非定域性之间的关系.结果表明:在实验误差范围内,三体纠缠度的实验测量值和理论值一致;Svetlichny算符的期望值和理论计算结果具有较好的一致性;体系非定域特性和体系的纠缠程度密切相关,当纠缠度减小时,非定域性减弱.

A nearly deterministic scheme for generation of multiphoton GHZ states with weak cross-Kerr nonlinearity

We propose a scheme to generate polarization-entangled multiphoton Greenberger-Horne^Zeilinger （GHZ） states based on weak cross-Kerr nonlinearity and subsequent homodyne measurement. It can also be generalized to produce maximally N-qubit entangled states. The success probabilities of our schemes are almost equal to 1.

A simple scheme for generating multi-atom GHZ state via cavity QED

This paper proposes a simple scheme for generating a three-atom GHZ state via cavity quantum electrodynamics （QED）. The task can be achieved through the interaction between two EPR states, which can be prepared easily with current technology. In this scheme, the cavity field is only virtually excited during the interaction process, and no quantum information transfer between the atoms and the cavity is required. Thus it greatly prolongs the efficient decoherent time. Moreover, this scheme is also applicable for generating an N-atom GHZ state.

Efficient scheme for realizing quantum dense coding with GHZ state in separated low-Q cavities

We propose an efficient scheme for realizing quantum dense coding with three-particle GHZ state in separated low-Q cavities. In this paper, the GHZ state is first prepared with three atoms trapped, respectively, in three spatial separated cavities. Meanwhile, with the assistance of a coherent optical pulse and X-quadrature homodyne measurement, we can im- plement quantum dense coding with three-particle GHZ state with a higher probability. Our scheme can also be generalized to realize N-particle quantum dense coding.

Controlled Teleportation of an Unknown N-qubit Entangled GHZ State

<正> A scheme for controlled teleportation of an unknown N-qubit entangled GHZ state from the sender Aliceto the distant receiver Bob is proposed.And m-qubit GHZ state is sufficient for the task of control by m spatially-separated supervisors.Conditioned on the local operations executed by all participants,Bob can faithfully restore theoriginal state by performing relevant unitary transformations with the aid of some classical message about measurementresults.Anyone's absence will absolutely lead to the failure of teleportation.

Improved Quantum ＂ Ping-Pong＂ Protocol Based on Extended Three-Particle GHZ State

In order to transmit secure messages, a quantum secure direct communication protocol based on extended three-particle GHZ state was presented, in which the extended three-particle GHZ state was used to detect eave sdroppers. In the security analysis, the method of the entropy theory is introduced, and three detection strategies are compared quantitatively by using the constraint between the information eavesdroppers can obtain and the interference introduced. If the eavesdroppers intend to obtain all information, the detection rate of the original "Ping-pong" protocol is 50%; the second protocol used two particles of EPR pair as detection particles is also 50%; while the presented protocol is 58%. At last, the security of the proposed protocol is discussed. The analysis results indicate that the protocol in this paper is more secure than the other two.

Probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel and its application in quantum state sharing

This paper presents a scheme for probabilistic teleportation of an arbitrary GHZ-class state with a pure entangled two-particle quantum channel. The sender Alice first teleports the coefficients of the unknown state to the receiver Bob, and then Bob reconstructs the state with an auxiliary particle and some unitary operations if the teleportation succeeds. This scheme has the advantage of transmitting much less particles for teleporting an arbitrary GHZ-class state than others. Moreover, it discusses the application of this scheme in quantum state sharing.