Quantum broadcast scheme and multi-output quantum teleportation via four-qubit cluster state

In this paper, two theoretical schemes of the arbitrary single-qubit states via four-qubit cluster state are proposed. One is three-party quantum broadcast scheme, which realizes the broadcast among three participants. The other is multi-output quantum teleportation. Both allow two distant receivers to simultaneously and deterministically obtain the arbitrary single-qubit states, respectively. Compared with former schemes of an arbitrary single-qubit state, the proposed schemes realize quantum multi-cast communication efficiently, which enables Bob and Charlie to obtain the states simultaneously in the case of just knowing Alice’s measurement results. The proposed schemes play an important role in quantum information, specially in secret sharing and quantum teleportation.     

On the role of the four-qubit state in two-qubit gate teleportation

The full analysis of quantum protocols requires the knowledge of the role of quantum states, bases of measurement and quantum gates involved. In what concerns the famous two-qubit quantum gate teleportation protocol, the role of the basis of measurement was considered in a recent work by Mendes and Ramos. In this work, we analyze the role of the four-qubit state used as resource. We show that the quantum two-qubit gate teleportation divides the set of pure four-qubit states in two classes. For one class, deterministic and probabilistic teleportation can be achieved, while for the other class, probabilistic remote two-qubit gate preparation is achieved.     

Deterministic transmission of an arbitrary single-photon polarization state through bit-flip error channel

We present two error-tolerance transmission protocols of a single-photon polarization state when bit-flip error is taken into account. For achieving the transmission target of the single-photon state, the first protocol needs to encode it to a nonmaximally entangled Bell state. Exploiting the interaction of the polarization entanglement with spatial entanglement between two photons, its success probability is 100 %. Different from the first protocol, the second one utilizes the idea of teleportation with an auxiliary Bell state. By performing quantum nondemolition measurement to analyze the parity, conventional measurement, and unitary transformation operations, the success probability of the second protocol is approximately unity. Furthermore, the second protocol can be generalized to the error-tolerance transmission of an arbitrary mixed state or the distribution of an arbitrary multi-photon entangled state.     

Bell state entanglement swappings over collective noises and their applications on quantum cryptography

This work presents two robust entanglement swappings against two types of collective noises, respectively. The entanglement swapping can be achieved by performing two Bell state measurements on two logical qubits that come from two original logical Bell states, respectively. Two fault tolerant quantum secret sharing (QSS) protocols are further proposed to demonstrate the usefulness of the newly proposed entanglement swappings. The proposed QSS schemes are not only free from Trojan horse attacks but also quite efficient. Moreover, by adopting two Bell state measurements instead of four-qubit joint measurements, the proposed protocols are practical in combating collective noises. The proposed fault tolerant entanglement swapping can also be used to replace the traditional Bell-state entanglement swapping used in various quantum cryptographic protocols to provide robustness in combating collective noises.     

Quantum dialogue protocols immune to collective noise

This work proposes two quantum dialogue protocols, each of which is robust against one of the following two kinds of collective noise: collective-dephasing noise and collective-rotation noise. Both quantum dialogue protocols are constructed from four-qubit DF states that consist of two Bell states. The receiver simply performs two Bell state measurements to obtain the secret message. Moreover, the proposed protocols are free from information leakage because some shared private quantum states are established in the new protocols to allow the legitimate users to exchange their secret messages securely.     

Schemes for teleportation of quantum gates

Quantum teleportation is a computational primitive that allows non-local quantum communication and quantum computation. In this work, we present two schemes for quantum gate teleportation. The first scheme shows under what conditions an n-qudit gate can be teleported using a generalization of Gottesman-Chuang procedure [Nature 402, 390 (1999)]. The second scheme shows that quantum gate teleportation can be transformed in the teleportation of a single-qudit.     

Bidirectional teleportation of a pure EPR state by using GHZ states

In the present paper, a novel bidirectional quantum teleportation protocol is proposed. By using entanglement swapping technique, two GHZ states are shared as a quantum channel between Alice and Bob as legitimate users. In this scheme, based on controlled-not operation, single-qubit measurement, and appropriate unitary operations, two users can simultaneously transmit a pure EPR state to each other, While, in the previous protocols, the users can just teleport a single-qubit state to each other via more than four-qubit state. Therefore, the proposed scheme is economical compared with previous protocols.     

Faithful quantum broadcast beyond the no-go theorem

The main superiority of the quantum remote preparation over quantum teleportation lies the classical resource saving. This situation may be changed from the following constructions. Our purpose in this paper is to find some special differences between these two quantum tasks besides the classical resource costs. Some novel schemes show that the first one is useful to simultaneously broadcast arbitrary quantum states, while the second one cannot because of the quantum no-cloning theorem. Moreover, these broadcast schemes may be adapted to satisfying the different receivers’ requirements or distributing the classical information, which are important in various quantum applications such as the quantum secret distribution or the quantum network communication.     

N-qubit quantum teleportation, information splitting and superdense coding through the composite GHZ–Bell channel

We introduce a general odd qubit entangled system composed of GHZ and Bell pairs and explicate its usefulness for quantum teleportation, information splitting and superdense coding. After demonstrating the superdense coding protocol on the five qubit system, we prove that ‘2N + 1’ classical bits can be sent by sending ‘N + 1’ quantum bits using this channel. It is found that the five-qubit system is also ideal for arbitrary one qubit and two qubit teleportation and quantum information splitting (QIS). For the single qubit QIS, three different protocols are feasible, whereas for the two qubit QIS, only one protocol exists. Protocols for the arbitrary N-qubit state teleportation and quantum information splitting are then illustrated.     

Quantum operation sharing with symmetric and asymmetric W states

Two tripartite schemes for sharing a single-qubit operation on a remote target state are proposed with symmetric and asymmetric W states, respectively. They are treated and compared from the aspects of quantum resource consumption, operation complexity, classical resource consumption, success probability and efficiency. It is found that the first scheme is better than the second one. In particular, the sharing can be achieved probabilistically with the first scheme while deterministically with the second one.     

受控双向远程量子控制

融合远程量子控制与双向受控隐形传态的思想,率先提出了受控双向远程控制（CBRQC）的一个概念。利用五量子纠缠,提出执行任意单量子算子对的两个CBRQC方案。这两个方案是概率的,而在第一个方案中,增加局域Pauli算子将导致该方案成功概率和内在效率都翻倍。对于双向传送算子的限制集,两个确定的方案被提出,其中一个总体优于其他方案,并且这两个方案的成功概率和效率都可大大提高。从量子及经典资源消耗、必要的操作复杂性、成功概率和内在效率五个方面对这些方案进行了比较,阐明了选择量子通道的原因,指出提出的方案是安全的,并说明了在现有技术的分析下该方案的实验可行性。     

利用最大真纠缠六方态共享经典秘密信息

纠缠是一种重要的量子信息资源,Bell态、GHZ态等纠缠态被广泛用于量子秘密共享中。Borras等人发现的最大真六方纠缠态在任意的双方割之间具有最大的纠缠值,已经被证明可用于量子隐形传态,并表现良好的性质。通过分析Borras态的结构,利用广义Schmidt分解工具,构造了一个具体的量子秘密共享协议:事先在Alice和4个代理之间共享一个Borras纠缠态,Alice拥有其中2个qubit,代理们分别拥有它的1个qubit,则Alice可在代理间共享2bit经典信息。     

Controlled teleportation

In this article, we review the recent development of controlled teleportation which can be used for sharing quantum information and has important applications in remote quantum computation. We introduce the principles of a couple of controlled teleportation schemes with maximally entangled quantum channels and those with pure entangled quantum channels (non-maximally entangled states). The schemes based on maximally entangled states have the advantage of having maximal efficiency although there are differences in their implementations in experiment. In the controlled teleportation schemes using non-maximally entangled states as the quantum channels, the receiver can reconstruct the originally unknown state by adding an auxiliary particle and performing a unitary evolution. No matter what the unknown state is (a single qubit state or an m-qudit state), the auxiliary particle required is only a two-level quantum system.     

Localization of two-particle quantum walk on glued-tree and its application in generating Bell states

Studies on two-particle quantum walks show that the spatial interaction between walkers will dynamically generate complex entanglement. However, those entanglement states are usually on a large state space and their evolutions are complex. It makes the entanglement states generated by quantum walk difficult to be applied directly in many applications of quantum information, such as quantum teleportation and quantum cryptography. In this paper, we firstly analyse a localization phenomena of two-particle quantum walk and then introduce how to use it to generate a Bell state. We will show that one special superposition component of the walkers’ state is localized on the root vertex if a certain interaction exists between walkers. This localization is interesting because it is contrary to our knowledge that quantum walk spreads faster than its classical counterpart. More interestingly, the localized component is a Bell state in the coin space of two walkers. By this method, we can obtain a Bell state easily from the quantum walk with spatial interaction by a local measurement, which is required in many applications. Through simulations, we verify that this method is able to generate the Bell state \(\frac{1}{\sqrt{2}}(|A \rangle _1|A\rangle _2 \pm |B\rangle _1|B\rangle _2)\) in the coin space of two walkers with fidelity greater than \(99.99999\,\%\) in theory, and we have at least a \(50\,\%\) probability to obtain the expected Bell state after a proper local measurement.     

Controlled teleportation

In this article, we review the recent development of controlled teleportation which can be used for sharing quantum information and has important applications in remote quantum computation. We introduce the principles of a couple of controlled teleportation schemes with maximally entangled quantum channels and those with pure entangled quantum channels (non-maximally entangled states). The schemes based on maximally entangled states have the advantage of having maximal efficiency although there are differences in their implementations in experiment. In the controlled teleportation schemes using non-maximally entangled states as the quantum channels, the receiver can reconstruct the originally unknown state by adding an auxiliary particle and performing a unitary evolution. No matter what the unknown state is (a single qubit state or an m-qudit state), the auxiliary particle required is only a two-level quantum system.     

基于非最大纠缠GHZ态的一种量子信息集中方案

提出了一种以非最大纠缠的四粒子GHZ态作为量子信道的概率性量子信息集中方案. 方案首先将未知的克隆态与量子信道构造系统态; 其次空间分离的三方对手中的粒子进行Bell测量, 并将测量结果通过经典通信告诉信息恢复者; 最后信息重建者做适当的测量(投影测量或者POVM 测量),将信息集中回单量子态, 从而实现量子信息集中. 进而讨论了方案的安全性和效率, 并与文献[17,23]从多角度进行了比较.     

Faithful teleportation via multi-particle quantum states in a network with many agents

An efficient scheme is proposed for faithful teleportation of an arbitrary unknown multi-particle state via multi-particle quantum states, in which the teleportation is completely deterministic providing that one can successfully construct a group of EPR pairs. Our scheme can effectively avoid possible destruction of the unknown state to be teleported, which however may occur in existing probabilistic teleportation schemes. In addition, we develop a scheme for establishing a faithful quantum channel for both indirect and direct teleportation multi-particle system, which can be applied in a teleportation network where intermediate agents exist between a sender and a receiver. Compared to the indirect construction of the faithful channel, the required auxiliary particle resources, local operations and classical communications in the direct construction scheme are considerably reduced.     

Continuous-variable quantum network coding for coherent states

As far as the spectral characteristic of quantum information is concerned, the existing quantum network coding schemes can be looked on as the discrete-variable quantum network coding schemes. Considering the practical advantage of continuous variables, in this paper, we explore two feasible continuous-variable quantum network coding (CVQNC) schemes. Basic operations and CVQNC schemes are both provided. The first scheme is based on Gaussian cloning and ADD/SUB operators and can transmit two coherent states across with a fidelity of 1/2, while the second scheme utilizes continuous-variable quantum teleportation and can transmit two coherent states perfectly. By encoding classical information on quantum states, quantum network coding schemes can be utilized to transmit classical information. Scheme analysis shows that compared with the discrete-variable paradigms, the proposed CVQNC schemes provide better network throughput from the viewpoint of classical information transmission. By modulating the amplitude and phase quadratures of coherent states with classical characters, the first scheme and the second scheme can transmit \(4{\log _2}N\) and \(2{\log _2}N\) bits of information by a single network use, respectively.     

Generalized teleportation by quantum walks

We develop a generalized teleportation scheme based on quantum walks with two coins. For an unknown qubit state, we use two-step quantum walks on the line and quantum walks on the cycle with four vertices for teleportation. For any d-dimensional states, quantum walks on complete graphs and quantum walks on d-regular graphs can be used for implementing teleportation. Compared with existing d-dimensional states teleportation, prior entangled state is not required and the necessary maximal entanglement resource is generated by the first step of quantum walk. Moreover, two projective measurements with d elements are needed by quantum walks on the complete graph, rather than one joint measurement with \(d^2\) basis states. Quantum walks have many applications in quantum computation and quantum simulations. This is the first scheme of realizing communicating protocol with quantum walks, thus opening wider applications.     

两个基于四粒子纠缠态的量子秘密共享方案

本文分别基于四粒子Cluster态和一个非对称的四粒子纠缠态,提出两个量子秘密共享的方案,其中共享的秘密是未知的单粒子态。秘密的发送者需要对手中的粒子进行Bell基测量,协助者需要对手中的粒子进行测量或者实施幺正操作,最后接收者通过对手中的粒子进行相应的幺正变换或者受控非门操作,就可以重构原始秘密。通过分析表明,任何一个代理者在其他两方协助下是可以恢复秘密的,所以我所提出的方案是高效且安全可靠的。