Three Attacks on the Mediated Semi-Quantum Key Distribution without Invoking Quantum Measurement

Semi-quantum key distribution is a very interesting new branch of quantum key distribution. It can be implemented when one or more participants are restricted to operate quantum states only on the quantum computational basis. Very recently, a mediated semi-quantum key distribution protocol without invoking two participants' quantum measurement has been proposed. The protocol allows two “classical” participants without sophisticated quantum capability to establish a shared secret key under an untrusted third party. It is claimed that the protocol is secure against several well-known attacks. However, in this paper, it is first pointed out that there exist three attacks “Measurement Attack, Modification Attack, and Collective Attack” on the mediated semi-quantum key distribution protocol without invoking quantum measurement. By proposed attacks, a malicious third party can obtain the secret key without being noticed by legitimated participants.     

Quantum Secure Direct Communication Using Entangled Photon Pairs and Local Measurement

We present a scheme for quantum secure direct communication, in which the message is encoded by local unitary operations, transmitted through entangled photons, and deduced from both the sender and receiver's local measurement results. In such a scheme, only one pair of entangled photons is consumed, and there is no need to transmit the sender's qubit carrying the secret message in a public channel, in order to transmit two-bit classical information.     

Parseval Theory of Complex Wavelet Transform for Wavelet Family Including Rotational Parameters

A rotational parameter R_θ has been introduced to complex wavelet transform (CWT). The rotational CWT (RCWT) corresponds to a matrix element 〈ψ|U₂ (θ;μ;k)|F〉in the context of quantum mechanics, where U₂(θ;μ;k) is a two-mode rotational displacing-squeezing operator in the 〈η| representation. Based on this, the Parseval theorem and the inversion formula of RCWT have been proved. The concise proof not only manifestly shows the merit of Dirac's representation theory but also leads to a new orthogonal property of complex mother wavelets in parameter space.     

Unsymmetrical Quantum Key Distribution Using Tripartite Entanglement

An unsymmetrical quantum key distribution protocol is proposed, in which Greenherger-Horne-Zeilinger （GHZ） triplet states are used to obtain the secret key. Except the lost qubits due to the unperfectness of the physical devices, the unsymmetrical characteristic makes all transmitted qubits useful. This leads to：an excellent efficiency, which reaches 100% in an ideal case. The ＇security is studied from the aspect of information theory. By using the correlation of the GHZ tripartite entanglement state, eavesdropping can be easily checked out, which indicates that the presented protocol is more secure.     

Efficient Three-Party Quantum Dialogue Protocol Based on the Continuous Variable GHZ States

Based on the continuous variable GHZ entangled states, an efficient three-party quantum dialogue protocol is devised, where each legitimate communication party could simultaneously deduce the secret information of the other two parties with perfect efficiency. The security is guaranteed by the correlation of the continuous variable GHZ entangled states and the randomly selected decoy states. Furthermore, the three-party quantum dialogue protocol is directly generalized to an N-party quantum dialogue protocol by using the n-tuple continuous variable GHZ entangled states.     

基于GHZ态的三方量子确定性密钥分配协议

基于连续变量GHZ态的纠缠特性,提出一种三方量子确定性密钥分配协议,其中密钥由GHZ态的振幅产生,而相位可以用来验证信道的安全性.现有的量子确定性密钥分配协议一次只能向一个接收方传送密钥,现实生活中经常要向多个接收方发送确定性密钥.信息论分析结果表明,当信道传输效率大于0.5时,该协议可以同时向两个接收方安全传送确定性密钥,制备多重纠缠态后,该协议还能够扩展成多方量子确定性密钥分配协议,这极大提高了密钥的整体传送效率,而且连续变量量子GHZ态信道容量较高,因此该协议具有重要的现实意义.     

New approach for obtaining the time-evolution law of chaotic light field in damping—gaining process

A new approach for studying the time-evolution law of chaotic light field in damping-gaining coexisting process is presented. The new differential equation for determining the parameter of the density operator ρ(t) is derived and the solution of f′ for damping and gaining processes are studied separately. Our approach is direct and the result is concise since it is not necessarily for us to know the Kraus operators in advance.     

Secure Quantum Dialogue Protocol Based on W States Without Information Leakage

A quantum dialogue protocol is proposed based on triple particle W states. Each particle is transferred only once in the entire communication, which reduces the risk of eavesdropping and improves the security of the protocol. The protocol can resist various attacks. The efficiency of this protocol can be up to 80 % without information leakage.     

Three-Party Stop-Wait Quantum Communication Protocol for Data Link Layer Based on GHZ State

Based on the delocalized entanglement correlation of GHZ state in quantum information theory, a three-party stop-wait quantum communication protocol for data link layer is presented. When three sites, Alice, Bob and Charlie, communicate in data link layer, data frame is sent to Bob and Charlie by Alice. When receiving the data frame within the set time, the receivers, Bob and Charlie, return to quantum acknowledgment frames or quantum negative acknowledgement frames via quantum channel. In the proposed protocol, the sender Alice can simultaneously receive and deal with quantum acknowledgment (QACK) frames or quantum negative acknowledgement (QNACK) frames from Bob and Charlie. And due to the transience of transferring quantum information, propagation delay and processing delay among three sites are reduced. As a result, the minimum time span between two successfully delivered data frames can be significantly reduced, the communication time is shortened. It is shown that the proposed protocol enhances the maximum throughout effectively and improves the communication efficiency for data link layer in a multicast communication network.