量子安全直接通信研究进展

简要地介绍了量子安全直接通信的必要条件,初步介绍了两个量子安全直接通信模型,即Two-Step和Quantum-One-Time-Pad模型。 The requirements of quantum secure direct communication （QSDC） are briefly introduced. Two QSDC schemes i. e. , the Two-Step QSDC scheme and the Quantum-One-Time-Pad QSDC scheme, are discussed in brief.     

量子密钥分发与量子安全直接通信

量子通信具有高安全性等优点,是当前的国际研究前沿,量子安全直接通信和量子密钥分发是两种重要的量子信息方式.量子密钥分发通过量子信道产生随机的密钥,而量子安全直接通信直接在量子信道中传输秘密信息.本文力图利用浅显易懂的语言介绍量子安全直接通信和量子密钥分发的基本原理;重点描述几个典型的量子安全直接通信方案,介绍目前的发展状态并展望未来.     

基于量子隐形传态的量子保密通信方案

量子保密通信包括量子密钥分发、量子安全直接通信和量子秘密共享等主要形式.在量子密钥分发和秘密共享中,传输的是随机数而不是信息,要再经过一次经典通信才能完成信息的传输.在量子信道直接传输信息的量子通信形式是量子安全直接通信.基于量子隐形传态的量子通信(简称量子隐形传态通信)是否属于量子安全直接通信尚需解释.构造了一个量子隐形传态通信方案,给出了具体的操作步骤.与一般的量子隐形传态不同,量子隐形传态通信所传输的量子态是计算基矢态,大大简化了贝尔基测量和单粒子操作.分析结果表明,量子隐形传态通信等价于包含了全用型量子密钥分发和经典通信的复合过程,不是量子安全直接通信,其传输受到中间介质和距离的影响,所以不比量子密钥分发更有优势.将该方案与量子密钥分发、量子安全直接通信和经典一次性便笺密码方案进行对比,通过几个通信参数的比较给出各个方案的特点,还特别讨论了各方案在空间量子通信方面的特点.     

龙桂鲁教授和他的量子信息研究

主要研究成果 ＊量子安全直接通信：提出国际上第一个量子安全直接通信（QSDC）方案,建立和发展了量子通信的新方向。该方案不仅能现场发现窃听,而且能避免发现窃听前传输的信息泄露,与未来的全量子网络兼容。     

基于稳定子码的在噪声信道的量子安全直接通信方案研究

量子安全直接通信是继量子密钥分配后,量子通信领域又一重要的研究领域,它要求通信双方在预先不需要建立共享密钥的情况下就可以实现消息的保密传输。不同于属于非确定通信的量子密钥分配,量子直接通信受信道噪声的影响更大,需要更好的检错纠错能力。本文根据稳定子码纠错理论和GHZ三态纠缠粒子的特性提出了一套基于稳定子码理论的量子直接通信方案,使其在保持无条件安全性的基础上可以对单量子的相位和比特错误进行纠错检错,大大降低了信道的整个通信过程的量子比特错误率。     

两步量子安全直接通信协议的信息论分析

从信息论的角度分析了一个典型的两步量子直接通信方案的安全性,计算了该量子直接通信过程中攻击者Eve所能获得的信息量及在Eve进行攻击后合法通信者所能接收的信息量,为合法者对量子直接通信的安全性判定和对敌手的检测提供了一定的依据和标准.     

一种基于诱骗态的广域量子安全直接通信网络方案

提出了一种基于诱骗态的广域量子安全直接通信网络方案.在每一个局域网中设置一个服务器负责量子态的产生和测量,从而提高了通信距离;将诱骗态的思想引入量子安全直接通信,采用不同的强度发送光脉冲,能够克服光子数目分割攻击,从而提高通信的安全性;根据信道参量估计了不同通信距离的通过率,为信道编码提供了依据.对所提方案进行了安全性分析,结果表明此方案能够实现远距离量子安全直接通信.     

量子通信

量子通信是经典通信和量子力学相结合的一门新兴交叉学科。文章综述了量子通信领域的研究进展，既包括人们所熟知的量子隐形传态、密集编码和量子密码学，也包括刚刚兴起但却有巨大潜力的量子通信复杂度和远程量子通信等领域。文章介绍了量子通信的基本理论框架，同时也涉及了这个领域最新的实验研究的进展。     

多方控制的量子安全直接通信协议的分析及改进

对一种多方控制的量子安全直接通信协议(WCZT协议)进行了安全性分析,并利用隐形传态给出了一种新的攻击方法.利用该攻击方法,接收方可以在没有征得任何控制方同意的情况下获得发送方的消息,因此该协议是不安全的.对该协议进行了改进,分析表明改进后的协议能够抵抗这种攻击,可以满足多方控制的量子安全直接通信的目的. 关键词： 隐形传态 单光子 多方控制 量子安全直接通信     

基于Bell态粒子和单光子混合的量子安全直接通信方案的信息泄露问题

最近,一种基于Bell态粒子和单光子混合的量子安全直接通信方案[物理学报65 230301(2016)]被提出.文章宣称一个量子态可以编码3比特经典信息,从而使得协议具有很高的信息传输效率.不幸的是,该协议存在信息泄露问题:编码在单光子上的3比特经典信息有2比特被泄露,而编码在Bell态上的3比特经典信息有1比特被泄露,所以它不是一个安全的直接量子通信方案.在保留原协议思想且尽可能少地更改原协议的基础上,我们提出一种改进的消息编码规则,从而解决信息泄露问题,使之成为一个高效、安全的量子通信协议.衷心希望研究者能对量子安全通信协议中信息泄露问题引起足够重视,设计真正安全的量子通信协议.     

Quantum secure direct communication and deterministic secure quantum communication

In this review article, we review the recent development of quantum secure direct communication (QSDC) and deterministic secure quantum communication (DSQC) which both are used to transmit secret message, including the criteria for QSDC, some interesting QSDC protocols, the DSQC protocols and QSDC network, etc. The difference between these two branches of quantum communication is that DSQC requires the two parties exchange at least one bit of classical information for reading out the message in each qubit, and QSDC does not. They are attractive because they are deterministic, in particular, the QSDC protocol is fully quantum mechanical. With sophisticated quantum technology in the future, the QSDC may become more and more popular. For ensuring the safety of QSDC with single photons and quantum information sharing of single qubit in a noisy channel, a quantum privacy amplification protocol has been proposed. It involves very simple CHC operations and reduces the information leakage to a negligible small level. Moreover, with the one-party quantum error correction, a relation has been established between classical linear codes and quantum one-party codes, hence it is convenient to transfer many good classical error correction codes to the quantum world. The one-party quantum error correction codes are especially designed for quantum dense coding and related QSDC protocols based on dense coding.      

Fault tolerant quantum secure direct communication with quantum encryption against collective noise

We present two novel quantum secure direct communication(QSDC) protocols over different collective-noise channels.Different from the previous QSDC schemes over collective-noise channels,which are all source-encrypting protocols,our two protocols are based on channel-encryption.In both schemes,two authorized users first share a sequence of EPR pairs as their reusable quantum key.Then they use their quantum key to encrypt and decrypt the secret message carried by the decoherence-free states over the collective-noise channel.In theory,the intrinsic efficiencies of both protocols are high since there is no need to consume any entangled states including both the quantum key and the information carriers except the ones used for eavesdropping checks.For checking eavesdropping,the two parties only need to perform two-particle measurements on the decoy states during each round.Finally,we make a security analysis of our two protocols and demonstrate that they are secure.     

Quantum Secure Direct Communication by Using Three-Dimensional Hyperentanglement

We propose two schemes for realizing quantum secure direct communication (QSDC) by using a set of ordered two-photon three-dimensional hyperentangled states entangled in two degrees of freedom (DOFs) as quantum information channels. In the first scheme, the photons from Bob to Alice are transmitted only once. After insuring the security of the quantum channels, Bob encodes the secret message on his photons. Then Alice performs single-photon two-DOF Bell bases measurements on her photons. This scheme has better security than former QSDC protocols. In the second scheme, Bob transmits photons to Alice twice. After insuring the security of the quantum channels, Bob encodes the secret message on his photons. Then Alice performs two-photon Bell bases measurements on each DOF. The scheme has more information capacity than former QSDC protocols.     

Single-Photon Based Three-Party Quantum Secure Direct Communication with Identity Authentication

Multipartite quantum secure direct communication (MQSDC) enables multiple message senders to simultaneously and independently transmit secret messages to a message receiver through quantum channels without sharing keys. Existing MQSDC protocols all assume that all the communication parties are legal, which is difficult to guarantee in practical applications. In this study, a single-photon based three-party QSDC protocol with identity authentication is proposed. In the protocol, the message receiver first authenticates the identity of two practical message senders. Only when the identity authentication is passed, the legal message senders can encode their messages by the hyper-encoding technology. In theory, two bits of messages can be transmitted to the message receiver in a communication round. The protocol can resist the external attack and internal attack, and guarantee the security of the transmitted messages and the identity codes of each legal message sender. The secret message capacity of the protocol is simulated with two-decoy-state method. The maximal communication distance between any two communication parties can reach $\approx$31.75 km with weak signal and decoy state pulses. The three-party QSDC protocol can be extended to a general MQSDC protocol and has important application in the further practical MQSDC field.     

Quantum Secure Direct Communication with Authentication Expansion UsingSingle Photons

In this paper we propose two quantum secure direct communication (QSDC) protocols with authentication. The authentication key expansion method is introduced to improve the life of the keys with security. In the first scheme, the third party, called Trent is introduced to authenticate the users that participate in the communication. He sends the polarized photons in blocks toauthenticate communication parties Alice and Bob using the authentication keys. In the communication process, polarized single photons are used to serve as the carriers, which transmit the secret messages directly. The second QSDC process with authentication between two parties is also discussed.     

Quantum secure direct communication via partially entangled states

We present in this paper a quantum secure direct communication (QSDC) protocol by using partially entangled states. In the scheme a third party (Trent) is introduced to authenticate the participants. After authentication, Alice can directly, deterministically and successfully send a secret message to Bob. The security of the scheme is also discussed and confirmed.     

Two-step quantum secure direct communication scheme with frequency coding

Quantum secure direct communication(QSDC) is an important branch of quantum cryptography. It can transmit secret information directly without establishing a key first, unlike quantum key distribution which requires this precursory event. Here we propose a QSDC scheme by applying the frequency coding technique to the two-step QSDC protocol, which enables the two-step QSDC protocol to work in a noisy environment. We have numerically simulated the performance of the protocol in a noisy channel, and the results show that the scheme is indeed robust against channel noise and loss. We also give an estimate of the channel noise upper bound.     

Fault tolerant two-step quantum secure direct communication protocol against collective noises

This work proposes two fault tolerant quantum secure direct communication (QSDC) protocols which are robust against two kinds of collective noises: the collective-dephasing noises and the collective-rotation noises, respectively. The two QSDC protocols are constructed from four-qubit DF states which consist of two logical qubits. The receiver simply performs two Bell state measurements (rather than four-qubit joint measurements) to obtain the secret message. The protocols have qubit effciency twice that of ...     

Maximally efficient protocols for direct secure quantum communication

Two protocols for deterministic secure quantum communication (DSQC) using GHZ-like states have been proposed. It is shown that one of these protocols is maximally efficient and that can be modified to an equivalent protocol of quantum secure direct communication (QSDC). Security and efficiency of the proposed protocols are analyzed and compared. It is shown that dense coding is sufficient but not essential for DSQC and QSDC protocols. Maximally efficient QSDC protocols are shown to be more efficient than their DSQC counterparts. This additional efficiency arises at the cost of message transmission rate.