Efficient multi-party quantum state sharing of an arbitrary two-qubit state

We present an efficient scheme for sharing an arbitrary two-qubit quantum state with n agents. In this scheme, the sender Alice first prepares an n + 2-particle GHZ state and introduces a Controlled-Not (CNOT) gate operation. Then, she utilizes the n + 2-particle entangled state as the quantum resource. After setting up the quantum channel, she performs one Bell-state measurement and another single-particle measurement, rather than two Bell-state measurements. In addition, except that the designated recover of the quantum secret just keeps two particles, almost all agents only hold one particle in their hands respectively, and thus they only need to perform a single-particle measurement on the respective particle with the basis X. Compared with other schemes based on entanglement swapping, our scheme needs less qubits as the quantum resources and exchanges less classical information, and thus obtains higher communication efficiency.     

Asymmetric five-party quantum state sharing of an arbitrary m-qubit state

We present an asymmetric scheme for five-party quantum state sharing of an arbitrary m-qubit state with the maximally entangled states of two-particle and three-particle. It involves two-particle Bell-basis or three-particle GHZ-basis measurements, rather than five-particle entanglements and five-particle joint measurements, which makes it more convenient in a practical application than some previous schemes. In addition, except that the designated recover of the quantum secret just keeps m particles, other agents only hold one particle in their hands respectively, and thus they only need perform a single-particle measurement on the respective particle with the basis X. Its intrinsic efficiency for qubits approaches 100%, and the total efficiency really approaches the maximal value.     

Efficient and economic five-party quantum state sharing of an arbitrary m-qubit state

We present an efficient and economic scheme for five-party quantum state sharing of an arbitrary m-qubit state with 2m three-particle Greenberger-Horne-Zeilinger (GHZ) states and three-particle GHZ-state measurements. It is more convenient than other schemes as it only resorts to three-particle GHZ states and three-particle joint measurement, not five-particle entanglements and five-particle joint measurements. Moreover, this symmetric scheme is in principle secure even though the number of the dishonest agents is more than one. Its total efficiency approaches the maximal value.     

Controlled quantum state sharing of arbitrary two-qubit states with five-qubit cluster states

In this paper, we propose a controlled quantum state sharing scheme to share an arbitrary two-qubit state using a five-qubit cluster state and the Bell state measurement. In this scheme, the five-qubit cluster state is shared by a sender (Alice), a controller (Charlie), and a receiver (Bob), and the sender only needs to perform the Bell-state measurements on her particles during the quantum state sharing process, the controller performs a single-qubit projective measurement on his particles, then the receiver can reconstruct the arbitrary two-qubit state by performing some appropriate unitary transformations on his particles after he has known the measured results of the sender and the controller.     

Generalized tripartite scheme for sharing arbitrary 2n-qudit state

Utilizing three non-maximally entangled qutrit pairs as quantum channels, we first propose a generalized tripartite scheme for sharing an arbitrary two-qutrit state with generalized Bell-state measurements. In the scheme if and only if the two recipients collaborate together, they can recover the split qutrit state with the probability determined uniquely by the smallest coefficients of the non-maximally entangled pairs. Afterwards, we further extend the scheme for sharing an arbitrary 2n-qudit state by taking 3n non-maximally entangled qudit pairs as quantum channels. Moreover, the scheme success probability relative to the inherent entanglement in quantum channels and its structure is simply discussed.     

Tripartite quantum state sharing

We demonstrate a multipartite protocol to securely distribute and reconstruct a quantum state. A secret quantum state is encoded into a tripartite entangled state and distributed to three players. By collaborating, any two of the three players can reconstruct the state, while individual players obtain nothing. We characterize this (2,3) threshold quantum state sharing scheme in terms of fidelity, signal transfer, and reconstruction noise. We demonstrate a fidelity averaged over all reconstruction permutations of 0.73+/-0.04, a level achievable only using quantum resources.     

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.     

基于非最大纠缠的五粒子Cluster态的高效量子态共享方案

本文提出了一个新的未知量子态共享方案,使用一个非最大纠缠的五粒子Cluster态作为量子通道来实现任意两粒子未知量子态的共享. 即就是发送方（Alice）,接收方（Bob）和控制方（Charlie）共享一个非最大纠缠的五粒子Cluster态. 与以前传统方案不同,在本方案中发送方引入一个辅助粒子,并对其手中的粒子进行正交完备基测量,而接收方不需要引入辅助粒子,只需要执行适当的幺正操作,即可以方便的完成信息的顺利接收. 控制方通过对自己手中的粒子做单粒子投影测量来控制和协助通信双方,使得任意两粒子的未知量子态共享方案得以成功实现. 关键词： 量子态共享 五粒子Cluster态 正交完备基测量 单粒子投影测量     

Quantum state sharing of an arbitrary qudit state by using nonmaximally generalized GHZ state

We present a scheme for quantum state sharing of an arbitrary qudit state by using nonmaximally entangled generalized Greenberger-Horne-Zeilinger （GHZ） states as the quantum channel and generalized Bell-basis states as the joint measurement basis. We show that the probability of successful sharing an unknown qudit state depends on the joint measurements chosen by Alice. We also give an expression for the maximally probability of this scheme.     

Quantum state sharing of an arbitrary multiqubit state using nonmaximally entangled GHZ states

We explicitly present a scheme for quantum state sharing of an arbitrary multiqubit state using nonmaximally entangled GHZ states as the quantum channel and generalized Bell states as the measurement basis. The scheme succeeds only probabilistically with its total success probability depending on the degree of entanglement matching between the quantum channel and the generalized Bell states. Security of the scheme is guaranteed by the fact that attacks of an outside eavesdropper or/and an inside dishonest party will inevitably introduce detectable errors.     

Hierarchical and probabilistic quantum information splitting of an arbitrary two-qubit state via two cluster states

Based on non-maximally entangled four-particle cluster states, we propose a new hierarchical information splitting protocol to probabilistically realize the quantum state sharing of an arbitrary unknown two-qubit state. In this scheme, the sender transmits the two-qubit secret state to three agents who are divided into two grades with two Bell-state measurements,and broadcasts the measurement results via a classical channel. One agent is in the upper grade and two agents are in the lower grade. The agent in the upper grade only needs to cooperate with one of the other two agents to recover the secret state but both of the agents in the lower grade need help from all of the agents. Every agent who wants to recover the secret state needs to introduce two ancillary qubits and performs a positive operator-valued measurement(POVM) instead of the usual projective measurement. Moreover, due to the symmetry of the cluster state, we extend this protocol to multiparty agents.     

Quantum state sharing of an arbitrary two-qubit state with two-photon entanglements and Bell-state measurements

Two schemes for sharing an arbitrary two-qubit state based on entanglement swapping are proposed with Bell-state measurements and local unitary operations. One is based on the quantum channel with four Einstein-Podolsky-Rosen (EPR) pairs shared in advance. The other is based on a circular topological structure, i.e., each user shares an EPR pair with his neighboring one. The advantage of the former is that the construction of the quantum channel between the agents is controlled by the sender Alice, which will improve the security of the scheme. The circular scheme reduces the quantum resource largely when the number of the agents is large. Both of those schemes have the property of high efficiency as almost all the instances can be used to split the quantum information. They are more convenient in application than the other schemes existing as they require only two-qubit entanglements and two-qubit joint measurements for sharing an arbitrary two-qubit state.     

通过四比特 态实现任意量子态的量子隐形传态方案

提出了一个将四比特|χ〉态作为量子通道实现任意单量子比特和两量子比特的量子态的隐形传送方案.该方案依赖于两个通信站点之间的纠缠.在这个方案里,我们给出了Alice的测量结果以及Bob进行的相应的幺正操作,计算结果表明,该隐形传送方案是完美的,也就是说它的成功概率可达到1.此外,该方案中用到的测量以及纠缠通道的制备在目前的技术下是完全可行的.因此,我们的方案有望在实验上实现.     

Quantum state sharing of an arbitrary three-qubit state by using four sets of W-class states

A new application of the W-class state is investigated for quantum state sharing (QSTS) of an arbitrary three-qubit state. We demonstrate that four sets of W-class states can be used to realize the deterministic QSTS of an arbitrary three-qubit state based on the three-qubit von Neumann measurements and the local unitary operations. Our scheme considered here is secure against certain eavesdropping attacks.     

A rational quantum state sharing protocol with semi-off-line dealer

A rational quantum state sharing protocol with the semi-off-line dealer is proposed. Firstly, the dealer Alice shares an arbitrary two-particle entangled state with the players by Einstein-Podolsky-Rosen (EPR) pairs and Greenberger-Horne-Zeilinger (GHZ) states. The EPR pairs are prepared by Charlie instead of the dealer, reducing the workload of the dealer. Secondly, all players have the same probability of reconstructing the quantum state, guaranteeing the fairness of the protocol. In addition, the dealer is semi-off-line, which considerably reduces the information exchanging between the dealer and the players. Finally, our protocol achieves security, fairness, correctness, and strict Nash equilibrium.     

Determinate joint remote preparation of an arbitrary W-class quantum state

A novel determinate joint remote preparation scheme of an arbitrary W-class quantum state is proposed to improve the probability of successful preparation. The presented scheme is realized through orthogonal projective measurement of the Hadamard transferred basis, which converts a global measurement to several local measurements. Thus orthogonal projective measurement of the Hadamard transferred basis enables quantum information to be transmitted from different sources simultaneously, which is a breakthrough for quantum network node processing. Finally, analysis shows the feasibility and validity of the proposed method, with a 100% probability of successful preparation.     

On the ground state of Ising models with arbitrary spin quantum number

The ground state of a class of Ising models with site dependent arbitrary spin quantum number is shown to be restricted to ±S_i^MAX state where S_i^MAX is the spin quantum number at the site i.     

用非最大纠缠信道对任意二粒子纠缠态的量子秘密分享

提出一个对任意二粒子纠缠态在N者之间的量子秘密分享方案,该方案利用非最大纠缠Einstein-Podolsky-Rosen(EPR)对作为量子信道,利用广义的贝尔基进行测量.接收者通过引入辅助粒子,并对其做选择性测量,就会概率性地得到最初的量子态. 关键词： 非最大纠缠的Einstein-Podolsky-Rosen(EPR)对 广义的贝尔测量     

Quantum state sharing of an arbitrary m-qudit state with two-qudit entanglements and generalized Bell-state measurements

A scheme for quantum state sharing of an arbitrary m-qudit state is proposed with two-qudit entanglements and generalized Bell-state (GBS) measurements. In this scheme, the sender Alice should perform m two-particle GBS measurements on her 2m qudits, and the controllers also take GBS measurements on their qudits and transfer their quantum information to the receiver with entanglement swapping if the agents cooperate. We discuss two topological structures for this quantum state sharing scheme, a dispersive one and a circular one. The former is better at the aspect of security than the latter as it requires the number of the agents who should cooperate for recovering the quantum secret larger than the other one.