【作者】 邓富国；

【导师】 龙桂鲁；

【作者基本信息】 清华大学 ， 物理学， 2004， 博士

【摘要】 量子通信是量子信息的核心内容之一。它为信息的安全传输提供了新的方法。自从BB84量子密钥分配方案以来,量子通信无论在理论上还是在实验上取得了大量的研究成果,吸引了许多科学家加入这一研究领域。本博士论文主要涉及了量子通信的四个方面,即量子密钥分配、量子安全直接通信、量子机密共享和量子信源编码。在量子密钥分配方面,我们提出了三种新的理论方案。第一种方案是一种新的技术,即控制顺序重排加密技术。它利用一组正交的Bell基态的传输来完成量子密钥分配,它具有传输率高和节省经典交换信息的优点。第二种方案是基于弱激光脉冲的双向量子密钥分配方案,这一方案可以允许每个弱脉冲中最多可以有两个单光子,缓解了对单光子源的压力,同时它还具有不需要双方公布测量基的优点。第三种方案是基于纠缠光子对序列的多用户网络结构下任意点对任意点的量子密钥分配方案。量子安全直接通信是将机密信息直接加载到量子态上直接传输,这与量子密钥分配不同,因而对它的安全性要求比量子密钥分配高。我们提出了判断量子通信是否是真正的量子安全直接通信的四个判据,并提出了三个安全的量子安全直接通信方案,即分步传输、量子一次一密、重复使用经典一次一密量子安全直接通信方案。分步传输方案引进了数据块传输的思想,它具有绝对安全和编码容量高的优点。量子一次一密方案使用极化单光子作为信号源,在量子信号的制备与测量上带来了方便,在实验上更容易实现。重复使用经典一次一密方案更进一步去掉了量子态的储存,使得经典一次一密密码能够重复使用,实现保密通讯,这不仅是密码学理论上的一个新观点,而且可以直接在实际应用中使用。我们提出将经典密码映射成量子态的思想,即将经典密码换成量子密钥,利用非克隆定理来保证量子密钥的安全性。在量子机密共享方面,我们提出了一个基于纠缠粒子对的量子机密共享方案、一个以极化单光子为信号源的量子机密共享方案和一个环形拓扑结构的量子机密共享方案。在信源编码方面,我们提出了两种提高测量基加密量子密钥分配编码容量的方法,即非对称量子信源编码和对称量子信源编码方法,从而提高了量子密钥分配信源编码的容量。更多还原

【Abstract】 Quantum communication provides a new way for transmitting message securely,and is one of the important parts of quantum information. Many researches on quantumcommunication have been done both in theory and experiment since the BB84 quantumkey distribution protocol in 1984. Many scientists are participating in the studies in this?eld. My study involves four areas in quantum communication, i.e., quantum key distri-bution (QKD), quantum secure direct communication (QSDC), quantum secret sharing(QSS) and quantum source coding. In the ?eld of quantum key distribution, we have developed three theoretical pro-tocols. First, we devised a novel technique, controlled-order-rearrangement-encryption(CORE) with which Bell states are used as quantum information carries. It has the ad-vantage of high intrinsic ef?ciency and saves much classical information. Secondly, weproposed a bi-directional quantum key distribution protocol with practical faint laserpulses. It is secure when each laser pulse contains no more than two photons. Thekey distribution task is completed in two transmissions. Bob ?rst sends the laser pulsesto Alice, and Alice encodes the key message through certain unitary operations andreturns the laser pulses to Bob. Security is achieved by placing eavesdropping checkprocedures in both transmissions. This protocol is secure and is closer to practicalcondition. In addition, it does not require the publication of measuring basis informa-tion. Thirdly, we designed a multi-user any-to-any QKD protocol on a passive opticalnetwork. Different from QKD whose objective is to establish a common random key, QSDCis to communicate the secret message directly without creating a key ?rst. Hence,QSDC requires more than QKD on the security. We established four criteria for secureQSDC. Furthermore, we have proposed three secure QSDC, i.e., the Two-Step QSDC,the Quantum-one-time- pad QSDC and Repeated-classical-one-time-pad QSDC proto-cols. In the Two-Step QSDC, an ordered set of EPR pairs is used as a data block forsending secret messages directly. It is divided into two particle sequences, a check-ing sequence and a message-coding sequence. After ascertaining the security of thetransmission of the checking sequence, Alice encodes the secret message directly on – II –<WP=6>Abstractthe message-coding sequence and sends them to Bob. The scheme is secure becausean eavesdropper cannot obtain both particle sequences simultaneously and read outthe messages Alice encodes. In the Quantum-one-time-pad QSDC, we exploited asequence of polarized single photons as the information carrier. Then the procedurefor preparing and measuring the quantum signal is very simple. Different from theQuantum-one-time-pad QSDC, the Repeated-classical-one-time-pad QSDC is a pro-tocol without storing the quantum states. Alice and Bob use a control key generatedwith BB84-QKD to make the secret message carried by quantum states be read outdirectly. Moreover, the quantum signal does not run the double distance between Aliceand Bob. The control key, mapped to a sequence of nonorthogonal states in quantumdirect communication can be used repeatedly after Alice and Bob ascertain that thequantum channel is secure. We have proposed three QSS protocols. One is a QSS protocol with EPR pairs,another is a QSS protocol based on polarized single photon and the third protocol is aCircle-QSS protocol. Moreover, an asymmetric and a symmetric coding for quantumsource in measuring-base-encrypted QKD are introduced. The capacity of this sourcecoding QKD is improved considerably.更多还原