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.

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。

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.

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.

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 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.

Quantum Secret Sharing Using GHZ-Like State

这份报纸论述用象 GHZ 一样状态分享计划的一个简单、新奇的量秘密。象 GHZ 一样状态的特征被用来开发分享计划的量秘密。在有有一样的假设的另外的基于 GHZ 的 QSS 协议的对比，建议协议提供最好的量小点效率。

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 implement 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.

Decay of N-qubit GHZ states in Pauli channels

An N-qubit Greenberger–Horne–Zeilinger(GHZ) state has many applications in various quantum information tasks and can be realized in different experimental schemes. A GHZ diagonal state evolves to another GHZ diagonal state in independent parallel Pauli channels. We give the explicit expression of the resultant GHZ diagonal state in terms of the initial state and channel parameters. If the initial state is a pure N qubit GHZ state or a three-qubit GHZ diagonal state admits a condition, the full separability criterion of the Pauli noisy state is equivalent to positive partial transpose(PPT)criterion. Thus the fully separable condition follows.

Correspondence Between GHZ States and Oriented Links in Knot Theory

This article generalizes our previous results for a quantum system of two nodes to a quantum system ofm(m ≥ 2) nodes. It shows that there is a one to one correspondence between 2m GHZ states for a quantum system ofm(m ≥ 2) nodes and 2m oriented links of the linkage N1 in knot theory, where N = 4 C2m = 2m(m - 1) is the numberof crossings of the link with m components, the subscript 1 denotes the order of the unoriented m components link withN crossings, i.e. the first type, actually the simplest type.

Tetrapartite entanglement measures of generalized GHZ state in the noninertial frames

Using a single-mode approximation, we carry out the entanglement measures, e.g., the negativity and von Neumann entropy when a tetrapartite generalized GHZ state is treated in a noninertial frame, but only uniform acceleration is considered for simplicity. In terms of explicit negativity calculated, we notice that the difference between the algebraic average π_(4) and geometric average Π_(4) is very small with the increasing accelerated observers and they are totally equal when all four qubits are accelerated simultaneously. The entanglement properties are discussed from one accelerated observer to all four accelerated observers. It is shown that the entanglement still exists even if the acceleration parameter r goes to infinity. It is interesting to discover that all 1-1 tangles are equal to zero, but 1-3 and 2-2 tangles always decrease when the acceleration parameter γ increases. We also study the von Neumann entropy and find that it increases with the number of the accelerated observers. In addition, we find that the von Neumann entropy S_(ABCDI), S_(ABCIDI), S_(ABICIDI) and S_(AIBICIDI) always decrease with the controllable angle θ, while the entropies S_(3-3 non), S_(3-2 non), S_(3-1 non) and S_(3-0 non) first increase with the angle θ and then decrease with it.

Steganalysis and improvement of a quantum steganography protocol via a GHZ_4 state

Quantum steganography that utilizes the quantum mechanical effect to achieve the purpose of information hiding is a popular topic of quantum information.Recently,El Allati et al.proposed a new quantum steganography using the GHZ4 state.Since all of the 8 groups of unitary transformations used in the secret message encoding rule change the GHZ4 state into 6 instead of 8 different quantum states when the global phase is not considered,we point out that a 2-bit instead of a 3-bit secret message can be encoded by one group of the given unitary transformations.To encode a 3-bit secret message by performing a group of unitary transformations on the GHZ4 state,we give another 8 groups of unitary transformations that can change the GHZ4 state into 8 different quantum states.Due to the symmetry of the GHZ4 state,all the possible 16 groups of unitary transformations change the GHZ4 state into 8 different quantum states,so the improved protocol achieves a high efficiency.

Semi-quantum private comparison protocol of size relation with d-dimensional GHZ states

A novel efficient semi-quantum private comparison protocol based on the d-dimensional GHZ states is proposed.With the assistance of semi-honest third party,two classical participants can compare the size relation of their secrets without any information leakage.To reduce the consumption of quantum devices,the qubit efficiency of our protocol is improved by introducing the semi-quantum conception via the existing semi-quantum private comparisons.Furthermore,it is unnecessary to prepare the secure classical authentication channel among participants in advance.It is shown that our protocol is not only correct and efficient,but also free from external and internal attacks.

Measure-Resend Semi-Quantum Private Comparison Scheme Using GHZ Class States

Quantum private comparison is an important topic in quantum cryptography.Recently,the idea of semi-quantumness has been often used in designing private comparison protocol,which allows some of the participants to remain classical.In this paper,we propose a semi quantum private comparison scheme based on Greenberge-Horne-Zeilinger(GHZ)class states,which allows two classical participants to compare the equality of their private secret with the help of a quantum third party(server).In the proposed protocol,server is semi-honest who will follow the protocol honestly,but he may try to learn additional information from the protocol execution.The classical participants’activities are restricted to either measuring a quantum state or reflecting it in the classical basis{0,1}.In addition,security and efficiency of the proposed schemes have been discussed.

Quantum Risk Assessment Model Based on Two Three-Qubit GHZ States

With the acceleration of the construction of quantum communication networks,scholars have proposed different quantum communication protocols for different application scenarios.However,few scholars pay attention to the risk assessment process before communication.In this paper,we propose a novel quantum risk assessment model based on quantum teleportation technology with two three-qubit GHZ states.Only by using Bell states measurements(BSMs)and two-qubit projective measurements(PJMs),the communicators can recovery any arbitrary two-qubit state.This protocol can transmit two-dimension risk assessment factors with better security performance.On the one hand,more sufficient evaluation factors allow the two communicating parties to more objectively evaluate the risk level of communication with the other party,and on the other hand,it also improves the qubit efficiency of the protocol.Moreover,we introduce the third party in this scheme can be semi-trusted,which must be full-trusted in our previous work.This change can reduce the dependence of the communication parties on the third-party organization and improve the privacy of communication.The security analysis shows that this scheme can resist internal and external attacks,and the quantum circuit diagrams also prove that our protocol is physically easier to implement.