Perfect Teleportation of an Arbitrary Three-Qubit State by Using W-Class States

A new application of the W-class state is investigated for teleportation of an arbitrary three-qubit state. We demonstrate that three sets of W-class states can be used to realize the perfect teleportation of an arbitrary three-qubit state by performing only the three-qubit von Neumann measurements and local unitary operations.     

Quantum state sharing with a genuinely entangled five-qubit state and Bell-state measurements

We construct several distinct schemes for tripartite Quantum state sharing (QSTS) of arbitrary single- and two-qubit states. Our schemes use genuinely entangled five-qubit state that has recently been introduced by Brown et al. [J. Phys. A 38 1119 (2005)] as the quantum channel. The Bell-state measurements and the single-qubit measurement are needed in our schemes. In comparison with the QSTS scheme using the same quantum channel [Phys. Rev. A 77 (2008) 032321], not joint measurement, which makes this scheme simpler than the latter.     

Quantum Teleportation and State Sharing via a Generalized Seven-Qubit Brown State

In this paper, a novel scheme is investigated for quantum teleportation (QT) and quantum state sharing (QSTS). The generalized seven-qubit Brown state |B ₇〉 is used as information carrier. Firstly, for an arbitrary single-qubit state, we perfectly present a QT protocol and three QSTS ones, which is among three participants via |B ₇〉. Then we make an overall comparison among three QSTS protocols and present an almost even distribution principle of particles. Secondly, for two- and three-qubit cases, based on the almost even distribution principle we design several QT and QSTS protocols. Finally, we mainly consider our scheme’s security against dishonest participant attacks. Furthermore, for an arbitrary N-qubit state, there is a conjecture that QT and QSTS can be designed by using the generalized (2N+1)-qubit Brown state |B _2N+1〉 in Eq. (3) (N≥2) in theoretical aspects.     

Distillation of GHZ State from Multiple Copies of Arbitrary W-Class State

W. Dur et al. have shown that it is impossible to obtain a GHZ state from one copy of arbitrary W-class state via local operations and classical communication （LOCC） [W. Dur, G. Vidal, and J.I. Cirac, Phys. Rev. A 62 （2000） 062314]. In our paper, the more general case is carefully investigated. We first show that, with a supply of two copies of arbitrary W-class state, we can always construct an explicit procedure to distill a GHZ state with a nonzero probability. Then based on this result, a simple procedure for distilling GHZ state from n copies of arbitrary W-class state is presented. Finally, we briefly discuss the applications.     

Deterministic remote state preparation of arbitrary three-qubit state through noisy cluster-GHZ channel

We propose a novel scheme for remote state preparation of an arbitrary three-qubit state with unit success probability, utilizing a nine-qubit cluster-GHZ state without introducing auxiliary qubits. Furthermore, we proceed to investigate the effects of different quantum noises (e.g., amplitude-damping, phase-damping, bit-flip and phase-flip noises) on the systems. The fidelity results of three-qubit target state are presented, which are usually used to illustrate how close the output state is to the target state. To compare the different effects between the four common types of quantum noises, the fidelities under one specific identical target state are also calculated and discussed. It is found that the fidelity of the phase-flip noisy channel drops the fastest through the four types of noisy channels, while the fidelity is found to always maintain at 1 in bit-flip noisy channel.     

三量子位系统的消相干和退纠缠

基于多谐振子热库环境模型,采用求解非马尔可夫近似主方程方法,研究了三量子位系统由于相对位相变化引起的消相干和退纠缠.计算得到了初始态为GHZ-class态、W-class态和WGHZ-class态在演化过程中的消相干和退纠缠时间尺度.结果表明,对初始GHZ-class态,相干性全部丧失,退纠缠完全发生,纠缠度变为0;对初始W-class态,相干性和纠缠度被保持;对初始WGHZ-class态,消相干部分发生,纠缠首先随时间变化最后达到一个渐近值.     

Completely mixed state is a critical point for three-qubit entanglement

Pure three-qubit states have five algebraically independent and one algebraically dependent polynomial invariants under local unitary transformations and an arbitrary entanglement measure is a function of these six invariants. It is shown that if the reduced density operator of a some qubit is a multiple of the unit operator, than the geometric entanglement measure of the pure three-qubit state is absolutely independent of the polynomial invariants and is a constant for such tripartite states. Hence a one-particle completely mixed state is a critical point for the geometric measure of entanglement.     

用多粒子态进行量子信息分配

我们提出一个用五粒子态将量子信息分裂成几部分的方案.在这个过程中,如果有且只有接受者相互合作才能重建初始比特的态.我们所用的量子通道是Bell态和三比特GHZ态的组合态,这些态在实验上都是很容易制备的.这个方案对某些窃听攻击来说是安全的.而且,它还可以用来实现控制的量子隐形传态.     

Deterministic quantum dense coding networks

We consider the scenario of deterministic classical information transmission between multiple senders and a single receiver, when they a priori share a multipartite quantum state – an attempt towards building a deterministic dense coding network. Specifically, we prove that in the case of two or three senders and a single receiver, generalized Greenberger–Horne–Zeilinger (gGHZ) states are not beneficial for sending classical information deterministically beyond the classical limit, except when the shared state is the GHZ state itself. On the other hand, three- and four-qubit generalized W (gW) states with specific parameters as well as the four-qubit Dicke states can provide a quantum advantage of sending the information in deterministic dense coding. Interestingly however, numerical simulations in the three-qubit scenario reveal that the percentage of states from the GHZ-class that are deterministic dense codeable is higher than that of states from the W-class.     

Deterministic quantum teleportation and information splitting via a peculiar W-class state

In the paper ({\em Phys. Rev.} 2006 A {\bf 74} 062320) Agrawal {\em et al}. have introduced a kind of W-class state which can be used for the quantum teleportation of single-particle state via a three-particle von Neumann measurement, and they thought that the state could not be used to teleport an unknown state by making two-particle and one-particle measurements. Here we reconsider the features of the W-class state and the quantum teleportation process via the W-class state. We show that, by introducing a unitary operation, the quantum teleportation can be achieved deterministically by making two-particle and one-particle measurements. In addition, our protocol is extended to the process of teleporting two-particle state and splitting information.     

利用广义Bell态信道联合远程制备一个任意三量子比特态

研究了一个联合远程制备任意三量子比特态的方案。该方案利用广义的Bell态作为量子信道,两个发送者分别选择合适的测量基进行测量,然后利用经典信道把测量结果传送出去,接收者根据测量结果对自己手中的粒子采取适当的幺正操作,然后引入辅助粒子并进行选择性测量,就能概率性的得到想要制备的量子态。研究结果表明:利用不同形式的广义Bell态信道成功实现联合远程制备一个任意三量子比特态的概率是一样的,当量子信道处于最大纠缠态时,可以得到最大的成功概率。     

Quantum Information Splitting of an Arbitrary Three-Qubit State by Using Cluster States and Bell States

A new application of cluster states is investigated for quantum information splitting (QIS) of an arbitrary three-qubit state. In our scheme, a four-qubit cluster state and a Bell state are shared by a sender (Alice), a controller (Charlie), and areceiver (Bob). Both the sender and controller only need to perform Bell-state measurements (BSMs), the receiver can reconstruct the arbitrary three-qubit state by performing some appropriately unitary transformations on his qubits after he knows the measured results of both the sender and the controller. This QIS scheme is deterministic.     

Bisplitting an Arbitrary <Emphasis Type="Italic">N</Emphasis>-Qubit State with a Class of Asymmetric Three-Qubit W States

We propose a tripartite scheme for bisplitting an arbitrary single-qubit quantum information (QI) by using a class of asymmetric three-qubit W state as quantum channels. In the scheme, the sender Alice first performs a Bell-state measurement on her two qubits and then publishes her measurement result via a public classical channel. Based on Alice’s message, if the two receivers Bob and Charlie collaborate together, they can retrieve the QI, i.e., they can deterministically recover the QI in one receiver’s site by first performing a two-qubit unitary operation and then executing a single-qubit unitary operation. Afterwards, we sketch the extension of the single-qubit QI splitting to an arbitrary N-qubit QI splitting.     

Quantum Information Splitting of an Arbitrary Three-Atom State by Using W-class States in Cavity QED

We demonstrate that four sets of W-class states can be used to realize the deterministic quantum information splitting of an arbitrary three-atom state in cavity QED. The scheme does not involve Bell-state measurement and is insensitive to both the cavity decay and the thermal field.     

Quantum key distribution protocol using dense coding of three-qubit W state

The three-qubit W state, with an important feature that each pair of it’s qubits has the same and maximum amount of bipartite entanglement, can be reduced to an entangled 2-qubit system if one of its qubits is lost. Recently, Xue et al. proposed a three-party quantum secret sharing (QSS) protocol based on the three-qubit W state [Chinese Phys. 15, 7 (2006)]. Also, Joo et al. proposed a pair-wise quantum key distribution protocol among three users based on a special measurement on the three-qubit W state [eprint arXiv:quant-ph/0204003v2 (2002)]. This study aims to propose a novel quantum key distribution protocol (QKDP) for arbitrary two communications based on the dense coding and the special measurement of three-qubit W state with the X basis and the Z basis.     

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.     

Revisiting “Quantum State Sharing of an Arbitrary Two-Atom State by Using a Six-Atom Cluster State in Cavity QED”

In Nie et al. (Int. J. Theor. Phys. 50: 2526, 2011), authors put forward a cavity QED scheme for deterministic quantum state sharing (QSTS) of an arbitrary two-atom state. They claimed that, the quantum channel of the QSTS scheme is a six-atom cluster state. After simple calculation, one can see that the quantum channel they used is a direct product of two three-atom GHZ states. In this paper, we propose a cavity QED scheme for QSTS of an arbitrary two-atom state via a six-atom cluster state channel. In our scheme, two two-atom Bell state measurements are transformed into the discrimination of single-atom product states. Moreover, the two-atom unitary operation is changed to single-qubit unitary operations. Our scheme is insensitive to the cavity decay. The necessary time for the scheme is much shorter than the Rydberg-atom lifespan, therefore atom decays do not need to be considered.     

Deterministic joint remote state preparation of arbitrary two-and three-qubit states

We propose a novel deterministic protocol that two senders are capable of remotely preparing arbitrary two-and three-qubit states for a remote receiver using EPR pairs and GHZ state as the quantum channel.Compared with the existing deterministic protocols [An et al.2011 Phys.Lett.A 375 3570 and Chen et al.2012 J.Phys.A:Math.Theor.45 055303],the quantum resources and classical information in our scheme are decreased,and the whole operation process is simplified.     

Economic scheme for remote preparation of an arbitrary five-qubit Brown-type state

A scheme for remotely preparingan arbitrary five-qubit Brown state by using three three-qubit GHZ states as the quantum channel is proposed. It is shown that, after the sender performs two different three-qubit projective measurements, the receiver should introduce two auxiliary qubits and employ suitable C-NOT gates, Toffoli gate and unitary operations on his qubits, the original state can be recovered with unit probability. Compared with the previous scheme, the advantage of the present scheme is that the entanglement resource can be reduced.     

Effect of atmospheric turbulence on entangled orbital angular momentum three-qubit state

The entangled orbital angular momentum(OAM) three photons propagating in Kolmogorov weak turbulence are investigated. Here, the single phase screen model is used to study the entanglement evolution of OAM photons. The results indicate that the entangled OAM three-qubit state with higher OAM modes will be more robust against turbulence.Furthermore, it is found that the entangled OAM three-qubit state has a higher overall transmission for small OAM values.