以最大slice 态为信道的受控量子远程控制

利用三量子最大slice态作为量子信道,提出了单量子酉算子的受控远程执行的两个协议。首先,利用双向量子隐形传态(BQST),给出了一个任意单量子酉算子的受控隐形传输方案。结果表明,通过非最大纠缠信道,发送者能够在遥远的接受者的量子系统上远程地执行一个任意单量子酉算子。如果发送者和控制者对各自量子执行恰当的投影测量,那么量子算子的受控远程执行的成功概率就能达到1。其次,提出了一种不使用BQST方法的部分未知算子的受控远程控制协议。此协议因部分未知算子取自于两个限制集,减少了量子纠缠和经典通信耗费。在这些方案中,当且仅当控制者愿意帮助接受者远程操作,量子算子的受控远程执行才能完成。     

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.     

Asymmetric bidirectional controlled remote preparation of an arbitrary four-qubit cluster-type state and a single-qubit state

In this paper, we propose a novel scheme for asymmetric bidirectional controlled remote state preparation (ABCRSP) via a ten-qubit entangled state as the quantum channel. In this scheme, two distant parties, Alice and Bob are not only senders but also receivers, and Alice wants to remotely prepare a single-qubit state at Bob’s site; at the same time, Bob wishes to help Alice remotely prepare an arbitrary four-qubit cluster-type entangled state. It is shown that only if the two senders and the controller collaborate with each other, the ABCRSP can be completed successfully. We demonstrate that the total success probability of the ABCRSP in this scheme can reach 1, that is, the scheme is deterministic.     

Deterministic controlled bidirectional remote state preparation via a six-qubit entangled state

In this paper, we presented a controlled bidirectional remote state preparation scheme which used the six-qubit entangled state as quantum channel. In our scheme, Alice and Bob can prepare simultaneously an arbitrary single-qubit state in each other’s place with the control of the supervisor Charlie. The success probability for our scheme reaches unit. Furthermore, we analyze the expression of quantum channel for controlled bidirectional remote state preparation. Finally, we discuss the security of our scheme, the detailed security analysis shows that the supervisor Charlie’s control can greatly improve the security of our scheme.

     

Fault-tolerant asymmetric quantum dialogue protocols against collective noise

In this paper, we propose two kinds of fault-tolerant asymmetric quantum dialogue (AQD) protocols and investigate the effect of collective noise on the proposed AQD protocols. In our work, logical qubits have been selected to build traveling blocks for constructing a decoherence-free subspace. Both communicants can encode each bit of secret message in the logical qubit with unitary logical operator. Compared with the previous quantum dialogue protocols, the proposed AQD protocols not only enable two users to transmit different amount of classical information to each other, but also can provide higher communication fidelity under the interference of collective noise. Furthermore, we will demonstrate the security of the AQD protocols against information leakage problem and Eve’s active eavesdropping attack.     

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。     

A comparative study of protocols for secure quantum communication under noisy environment: single-qubit-based protocols versus entangled-state-based protocols

The effect of noise on various protocols of secure quantum communication has been studied. Specifically, we have investigated the effect of amplitude damping, phase damping, squeezed generalized amplitude damping, Pauli type as well as various collective noise models on the protocols of quantum key distribution, quantum key agreement, quantum secure direct quantum communication and quantum dialogue. From each type of protocol of secure quantum communication, we have chosen two protocols for our comparative study: one based on single-qubit states and the other one on entangled states. The comparative study reported here has revealed that single-qubit-based schemes are generally found to perform better in the presence of amplitude damping, phase damping, squeezed generalized amplitude damping noises, while entanglement-based protocols turn out to be preferable in the presence of collective noises. It is also observed that the effect of noise depends upon the number of rounds of quantum communication involved in a scheme of quantum communication. Further, it is observed that squeezing, a completely quantum mechanical resource present in the squeezed generalized amplitude channel, can be used in a beneficial way as it may yield higher fidelity compared to the corresponding zero squeezing case.     

Cyclic quantum teleportation

We propose a scheme of cyclic quantum teleportation for three unknown qubits using six-qubit maximally entangled state as the quantum channel. Suppose there are three observers Alice, Bob and Charlie, each of them has been given a quantum system such as a photon or spin-\(\frac{1}{2}\) particle, prepared in state unknown to them. We show how to implement the cyclic quantum teleportation where Alice can transfer her single-qubit state of qubit a to Bob, Bob can transfer his single-qubit state of qubit b to Charlie and Charlie can also transfer his single-qubit state of qubit c to Alice. We can also implement the cyclic quantum teleportation with \(N\geqslant 3\) observers by constructing a 2N-qubit maximally entangled state as the quantum channel. By changing the quantum channel, we can change the direction of teleportation. Therefore, our scheme can realize teleportation in quantum information networks with N observers in different directions, and the security of our scheme is also investigated at the end of the paper.     

Asymmetric quantum dialogue in noisy environment

A notion of asymmetric quantum dialogue (AQD) is introduced. Conventional protocols of quantum dialogue are essentially symmetric as the users (Alice and Bob) can encode the same amount of classical information. In contrast, the proposed scheme for AQD provides different amount of communication powers to Alice and Bob. The proposed scheme offers an architecture, where the entangled state to be used and the encoding scheme to be shared between Alice and Bob depend on the amount of classical information they want to exchange with each other. The general structure for the AQD scheme has been obtained using a group theoretic structure of the operators introduced in Shukla et al. (Phys Lett A 377:518, 2013). The effect of different types of noises (e.g., amplitude damping and phase damping noise) on the proposed scheme is investigated, and it is shown that the proposed scheme for AQD is robust and it uses an optimized amount of quantum resources.     

多跳远程量子态制备

多跳远程量子态制备在量子无线网络、长距离量子信息传输中有重要价值。融合多跳隐形传态和远程态制备的思想，提出一个多跳远程任意单量子态制备协议。在每一跳中都以三粒子非最大纠缠GHz态为量子信道，利用远程态制备方法，原始单量子态通过中间节点逐跳被制备，每跳恢复的态被用着下一跳被制备的态。通过对单跳和两跳制备的分析，获得了[n]跳制备后方案成功的概率。在协议中，仅涉及到Pauli算子、单粒子测量和前馈策略，因此该方案易于物理实现。     

Hierarchically controlled remote preparation of an arbitrary single-qubit state by using a four-qubit $$|\chi \rangle $$ entangled state

In this paper, we present a scheme for Hierarchically controlled remote preparation of an arbitrary single-qubit state via a four-qubit \(|\chi \rangle \) state as the quantum channel. In this scheme, a sender wishes to help three agents to remotely prepare a quantum state, respectively. The three agents are divided into two grades, that is, an agent is in the upper grade and other two agents are in the lower grade. It is shown that the agent of the upper grade only needs the assistance of any one of the other two agents for recovering the sender’s original state, while an agent of the lower grade needs the collaboration of all the other two agents. In other words, the agents of two grades have different authorities to recover sender’s original state.     

Controlled remote state preparation protocols via AKLT states

In this paper, we proposed two controlled remote state preparation of an arbitrary single-qubit state schemes one for deterministic controlled remote state preparation the other for probabilistic controlled-joint remote state preparation with 2/3 probability. Both of them used the Affleck–Kennedy–Lieb–Tasaki (AKLT) state which consisted of bulk spin-1’s and two spin-1 \(/\) 2’s at the ends. Up to now, no RSP protocols using AKLT gapped ground states as a shared quantum resource had been presented thus far and Fan et al. showed the other AKLT property was that if we performed a Bell measurement on bulk, then a maximally entangled state would be shared by two ends. We utilized these properties to develop our controlled protocols.     

Joint remote control of an arbitrary single-qubit state by using a multiparticle entangled state as the quantum channel

We present a scheme for joint remote implementation of an arbitrary single-qubit operation following some ideas in one-way quantum computation. All the senders share the information of implemented quantum operation and perform corresponding single-qubit measurements according to their information of implemented operation. An arbitrary single-qubit operation can be implemented upon the remote receiver’s quantum system if the receiver cooperates with all the senders. Moreover, we study the protocol of multiparty joint remote implementation of an arbitrary single-qubit operation with many senders by using a multiparticle entangled state as the quantum channel.     

Four-party deterministic operation sharing with six-qubit cluster state

An efficient four-party scheme is proposed for remotely sharing an arbitrary single-qubit operation by using a six-qubit cluster state as quantum channel and local operation and classical communication. Some specific discussions are made, including the issues of the scheme determinacy, the sharer symmetry, the scheme security and the essential role of quantum channel as well as the current experimental feasibility.     

Efficient multiparty quantum key agreement protocol based on commutative encryption

A secure multiparty quantum key agreement protocol using single-qubit states is proposed. The agreement key is computed by performing exclusive-OR operation on all the participants’ secret keys. Based on the commutative property of the commutative encryption, the exclusive-OR operation can be performed on the plaintext in the encrypted state without decrypting it. Thus, it not only protects the final shared key, but also reduces the complexity of the computation. The efficiency of the proposed protocol, compared with previous multiparty QKA protocols, is also improved. In the presented protocol, entanglement states, joint measurement and even the unitary operations are not needed, and only rotation operations and single-state measurement are required, which are easier to be realized with current technology.     

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.     

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.     

Automatic translation of quantum circuits to optimized one-way quantum computation patterns

One-way quantum computation (1WQC) is a model of universal quantum computations in which a specific highly entangled state called a cluster state (or graph state) allows for quantum computation by only single-qubit measurements. The needed computations in this model are organized as measurement patterns. Previously, an automatic approach to extract a 1WQC pattern from a quantum circuit has been proposed. It takes a quantum circuit consisting of CZ and \(J(\alpha )\) gates and translates it into an optimized 1WQC pattern. However, the quantum synthesis algorithms usually decompose circuits using a library containing CNOT and any single-qubit gates. In this paper, we show how this approach can be modified in a way that it can take a circuit consisting of CNOT and any single-qubit gates to produce an optimized 1WQC pattern. The single-qubit gates are first automatically \(J\) -decomposed and then added to the measurement patterns. Moreover, a new optimization technique is proposed by presenting some algorithms to add Pauli gates to the measurement patterns directly, i.e., without their \(J\) -decomposition which leads to more compact patterns for these gates. Using these algorithms, an improved approach for adding single-qubit gates to measurement patterns is proposed. The optimized pattern of CNOT gates is directly added to the measurement patterns. Experimental results show that the proposed approach can efficiently produce optimized patterns for quantum circuits and that adding CNOT gates directly to the measurement patterns decreases the translation runtime.     

Cyclic joint remote state preparation in noisy environment

We propose a scheme of cyclic joint remote state preparation for three sides, which takes advantage of three GHZ states to compose product state as quantum channel. Suppose there are six legitimate participants, says Alice, Bob, Charlie, David, Emma and Fred in the scheme. It can be shown that Alice and David can remotely prepare a single-qubit state on Bob’s side; meanwhile, Bob and Emma can remotely prepare a desired quantum state on Charlie’s side, and Charlie and Fred can also remotely prepare a single-qubit state on Alice’s side at the same time. Further, it can be achieved in the opposite direction of the cycle by changing the quantum channel. Based on it, we generalize this protocol to \(N (N\ge 3)\) sides utilizing three multi-qubit GHZ-type states as quantum channel. Therefore, the scheme can achieve cyclic joint remote state preparation, which remotely prepares N states in quantum network with N-party, simultaneously. In addition, we consider that the effect of amplitude-damping noise of the initial states is prepared in four different laboratory. Clearly, we use fidelity to describe how much information has been lost in the cyclic process. Our investigation about the effect of noise shows that the preparing of the initial state in different laboratories will affect the loss of information.     

Deterministic single-qubit operation sharing with five-qubit cluster state

Perfect sharing of arbitrary single-qubit operation (PSASQO) with shared entanglements and LOCC is focused. A symmetric three-party PSASQO scheme is put forward by utilizing the five-qubit cluster state proposed by Briegel and Raussendorf (Phys Rev Lett 86:910, 2001). Some concrete discussions on the scheme are made, including its important features, the essential role of the quantum channel, its direct generalization to more-party cases, the problem of entanglement structure and its application perspective in some peculiar quantum scenario as well as its security analysis. Particularly, the experimental feasibilities of the scheme and its generalizations are demonstrated, i.e., showing the employed unitary operations are local and accessible single-qubit Pauli and two-qubit control NOT operations according to nowaday experimental techniques.