任意二粒子纠缠态的受控量子通信

为了解决任意二量子通信问题,首先给出了五粒子和七粒子纠缠态的构造方法,并提供了它们的量子线路图。其次,以该五粒子纠缠态为量子信道,提出一个任意二粒子未知量子态的受控隐形传态协议。该协议在监察者Charlie的控制下,Alice进行四粒子投影测量和经典通信,Bob采用简单酉变换就能以100%的概率成功重构一个任意二粒子纠缠态。最后,利用七粒子纠缠态为量子信道,提出了任意二粒子纠缠态的联合受控远程制备方案。在此方案中,发送者Alice用自己掌握被制备态的部分信息构造测量基,发送者Bob采用前馈测量策略,接收者Diana在监控者Charlie的帮助下,通过简单幺正变换就能确定性地恢复原始态。     

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.     

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 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.

     

Quantum state sharing against the controller’s cheating

Most existing QSTS schemes are equivalent to the controlled teleportation, in which a designated agent (i.e., the recoverer) can recover the teleported state with the help of the controllers. However, the controller may attempt to cheat the recoverer during the phase of recovering the secret state. How can we detect this cheating? In this paper, we considered the problem of detecting the controller’s cheating in Quantum State Sharing, and further proposed an effective Quantum State Sharing scheme against the controller’s cheating. We cleverly use Quantum Secret Sharing, Multiple Quantum States Sharing and decoy-particle techniques. In our scheme, via a previously shared entanglement state Alice can teleport multiple arbitrary multi-qubit states to Bob with the help of Charlie. Furthermore, by the classical information shared previously, Alice and Bob can check whether there is any cheating of Charlie. In addition, our scheme only needs to perform Bell-state and single-particle measurements, and to apply C-NOT gate and other single-particle unitary operations. With the present techniques, it is feasible to implement these necessary measurements and operations.     

利用纠缠态实现任意N粒子量子态的秘密共享

针对量子秘密共享的量子态局限于最大纠缠态的问题,提出一种实现任意N位量子态的秘密共享方案。该方案使用纠缠态作为量子信道,首先发送方对粒子进行Bell基测量,然后接收方Bob或Charlie使用单粒子测量,最后参与者根据Alice和单粒子测量得到的结果,选用合适的联合幺正变换对量子态进行相应的变换,这样可以实现任意N粒子量子态的秘密共享。该方案能够抵御外部窃听者和内部不诚实参与者的攻击,安全性分析表明此方案是安全的。     

通过五粒子信道的非对称双向量子信息传输

利用一个五粒子团簇态为信道,分别提出了三个关于二粒子态和单粒子态的双向受控量子信息传输协议。在第一个协议中,通过引入辅助粒子,实施受控非门运算和Bell态测量,Alice能把二粒子未知态传送给Bob,同时Bob也能把单粒子未知态传送给Alice。在第二个方案中,通过引入辅助粒子、巧妙构造正交基和执行单粒子投影测量,Alice能帮助Bob远程地制备二粒子已知态,同时Bob也能帮助Alice远程地制备单粒子已知态。由于他们充分利用了前馈策略去构造测量基,制备任务能够完美完成。在第三个方案中,结合前两个方案的特点,Alice能成功将二粒子未知态传送给Bob,Bob也完美地在Alice处制备单粒子已知态。上述三个方案离开监控者的允许是不能实现的。     

9-量子团簇态信道的非对称双向量子信息传输

利用一个9-量子团簇态为信道,分别提出了三个关于二量子态和三量子态的双向量子信息传输协议。在第一个协议中,Alice能把三量子a1、a2和a3的未知态传送给Bob,Bob能把二量子b1和b2的未知态传送给Alice。Alice采用特殊三粒子态测量基,使得方案简化了一半。在第二个协议中,Alice在远方的Bob处制备三粒子a1、a2和a3的已知态,同时Bob也能在Alice处制备二量子b1和b2的已知态。由于他们充分利用了前馈测量策略,制备任务能够完美完成。在第三个协议中,利用前两个协议的优点,Alice能成功将三量子a1、a2和a3的未知态传送给Bob,Bob也完美地在Alice处制备二量子b1和b2的已知态。     

Can quantum discord increase in a quantum communication task?

Quantum teleportation of an unknown quantum state is one of the few communication tasks which has no classical counterpart. Usually the aim of teleportation is to send an unknown quantum state to a receiver. But is it possible in some way that the receiver’s state has more quantum discord than the sender’s state? We look at a scenario where Alice and Bob share a pure quantum state and Alice has an unknown quantum state. She performs joint measurement on her qubits and channel to prepare Bob’s qubits in a mixed state which has higher quantum discord than hers. We also observe an interesting feature in this scenario, when the quantum discord of Alice’s qubits increases, then the quantum discord of Bob’s prepared qubits decreases. Furthermore, we show that the fidelity of one-qubit quantum teleportation using Bob’s prepared qubits as the channel is higher than using Alice’s qubits.     

Fault-tolerant high-capacity quantum key distribution over a collective-noise channel using extended unitary operations

We propose two fault-tolerant high-capacity quantum key distribution schemes, in which an entangled pair over a collective-noise channel consisting of one logical qubit and one physical qubit can carry four bits of key information. The basic idea is to use 2-extended unitary operations from collective noises together with quantum dense coding. The key messages are encoded on logical qubits of two physical qubits with sixteen 2-extended unitary operations based on collective noises. The key can be recovered using Bell-state analysis on the logical qubit and a single-photon measurement on the physical qubit rather than three-qubit GHZ joint measurements. The proposed protocols require a collation table to be shared between Alice and Bob in advance. Consequently, the key messages carried by an entangled state, in our protocol, have doubled at the price of sharing the collation table between Alice and Bob. However, the efficiency of qubits is enhanced because a quantum bit is more expensive to prepare than a classical bit.     

A highly efficient scheme for joint remote preparation of multi-qubit W state with minimum quantum resource

We present a highly efficient scheme for perfect joint remote preparation of an arbitrary \( 2^{n} \)-qubit W state with minimum quantum resource. Both the senders Alice and Bob intend to jointly prepare one \( 2^{n} \)-qubit W state for the remote receiver Charlie. In the beginning, they help the remote receiver Charlie to construct one n-qubit intermediate state which is closely related to the target \( 2^{n} \)-qubit W state. Afterward, Charlie introduces auxiliary qubits and applies appropriate operations to obtain the target \( 2^{n} \)-qubit W state. Compared with previous schemes, our scheme requires minimum quantum resource and least amount of classical communication. Moreover, our scheme has a significant potential for being adapted to remote state preparation of other special states.     

Bidirectional controlled quantum teleportation and secure direct communication using five-qubit entangled state

A scheme is presented to implement bidirectional controlled quantum teleportation (QT) by using a five-qubit entangled state as a quantum channel, where Alice may transmit an arbitrary single qubit state called qubit A to Bob and at the same time, Bob may also transmit an arbitrary single qubit state called qubit B to Alice via the control of the supervisor Charlie. Based on our channel, we explicitly show how the bidirectional controlled QT protocol works. By using this bidirectional controlled teleportation, espcially, a bidirectional controlled quantum secure direct communication (QSDC) protocol, i.e., the so-called controlled quantum dialogue, is further investigated. Under the situation of insuring the security of the quantum channel, Alice (Bob) encodes a secret message directly on a sequence of qubit states and transmits them to Bob (Alice) supervised by Charlie. Especially, the qubits carrying the secret message do not need to be transmitted in quantum channel. At last, we show this QSDC scheme may be determinate and secure.     

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.     

基于EPR对的任意四粒子Cluster类态全概率联合远程制备

采用4个EPR(Einstein-Podolsky-Rosen)对作为量子信道,提出一种新的全概率联合远程制备任意四粒子Cluster类态方案。在这个新的方案中,一个制备者执行四粒子投影测量,另一个制备者对手中的粒子执行二粒子投影测量。然后,接收者对手中二粒子进行某种幺正操作,并分别对两个辅助粒子进行受控非门操作,从而最终得到需要制备的Cluster类态。与其他制备任意四粒子Cluster类态的全概率制备方案相比,所提协议效率较高,而且在实验上更经济可行。     

Controlled teleportation against uncooperation of part of supervisors

We study the teleportation of an unknown quantum state from a sender (Alice) to a receiver (Bob) via the control of many supervisors (Charlie 1, Charlie 2, . . .) in a network. It has been shown that such a task can be achieved by distributing a GHZ-type entangled state among the participants in advance. In the protocols with GHZ-type entanglement channel, the achievement of teleportation between Alice and Bob is conditioned on the cooperation of all the supervisors. In other words, if anyone of the supervisors does not cooperate, the teleportation will fails. In this paper, we introduce another kind of controlled teleportaton protocol with other types of entangled states acting as the quantum channel, in which the teleportation between Alice and Bob can be realized with high degree of endurance against uncooperation of part of supervisors.      

Semi-quantum information splitting using GHZ-type states

By using a generalized Greenberger–Horne–Zeilinger (GHZ) state in which is locally unitarily connected with standard GHZ state as a communication channel, semi-quantum key distribution is extended to study semi-quantum information splitting protocols for secret sharing of quantum information. In our scheme, quantum Alice splits arbitrary two, three and N-qubit states with two classical parties, Bob and Charlie, in a way that both parties are sufficient to reconstruct Alice’s original states only under the condition of which she/he obtains the help from another one, but one of them cannot. The presented protocols are helpful for both secure against certain eavesdropping attacks and economical in processing of quantum information.     

Deterministic remote two-qubit state preparation in dissipative environments

We propose a new scheme for efficient remote preparation of an arbitrary two-qubit state, introducing two auxiliary qubits and using two Einstein–Podolsky–Rosen (EPR) states as the quantum channel in a non-recursive way. At variance with all existing schemes, our scheme accomplishes deterministic remote state preparation (RSP) with only one sender and the simplest entangled resource (say, EPR pairs). We construct the corresponding quantum logic circuit using a unitary matrix decomposition procedure and analytically obtain the average fidelity of the deterministic RSP process for dissipative environments. Our studies show that, while the average fidelity gradually decreases to a stable value without any revival in the Markovian regime, it decreases to the same stable value with a dampened revival amplitude in the non-Markovian regime. We also find that the average fidelity’s approximate maximal value can be preserved for a long time if the non-Markovian and the detuning conditions are satisfied simultaneously.     

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.     

Multi-party quantum secret sharing with the single-particle quantum state to encode the information

We present a three-party quantum secret sharing (QSS) scheme via the entangled Greenberger–Horne–Zeilinger state. In this scheme, the sender Alice encodes her arbitrary secret information by means of preparing a single-particle quantum state. The agent Bob obtains his shared information according to his hobby, while Charlie can easily calculate his shared information. The proposed scheme is secure. It is shown that even a dishonest agent, who may avoid the security checking, cannot obtain any useful information. Moreover, we further investigate the multi-party QSS scheme which allows most agents to predetermine their information.     

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.