【作者】 万洪波；

【导师】 叶柳；

【作者基本信息】 安徽大学 ， 原子与分子物理， 2010， 硕士

【摘要】 量子信息学是一门新兴的交叉学科,它主要包括量子通信和量子计算两部分,而量子通信也是量子信息学当中非常重要的一个分支,目前量子通信主要研究的内容包括密集编码,隐形传态,量子克隆等。经过物理学家多年的研究,目前已经取得了显著的成果,而且该学科也已成为当前国际前沿热点课题之一目前,在量子信息的处理过程中,有许多不同的物理系统,例如,腔QED系统,核磁共振系统等,然而相对于前面几种系统,光子系统是一个被认为很有发展前景的系统,因为光子系统有很多优点,比如,消相干时间长,光子易于传输以及易于制备与操作等等,因此通过光学系统来处理量子信息是一个十分有前景的课题,本文就如何在线性光学系统中实现量子信息的处理作了一定的研究,取得了如下的结果：1、在线性光学系统中实现密集编码在线性光学系统中,提出一个使用三光子GHZ态实现密集编码的方案。该方案中,Alice首先对她所持有的两个光子通过线性光学元件进行编码,然后将这两个光子传送给Bob。接收到光子后Bob使用两个QND对等探测器以及PBS光学元件对他拥有的三个光子的八个量子态进行辨别,根据测量的结果辨别出Alice对她的两个光子所进行的操作。在密集编码过程中Alice仅传送两个光子,但Bob可以获得三比特的经典信息。探测使用的QND装置建立在Cross-Kerr nonlinearity基础上,目前已经可以通过电磁感应透明实现。2、通过使用线性光学元件实现最优普适克隆我们提出了一个在线性光学系统中实现1→3的实数态克隆。这个方案主要依靠一个偏振比特和两个路径比特,在当前的实验条件下是完全可以实现的。更多还原

【Abstract】 Quantum information science is new inter-discipline generally covering quantum communication and quantum computation, Quantum communication is an important branch of the Quantum information science, the research of Quantum communication including quantum dense coding, quantum teleportation and quantum cloning. After the research of many years by physicists, people have acquired a series of important achievement. And this subject becomes one of the hotspot in international leading edge.There are many physical systems for implementing quantum information processing at present, such as cavity, molecule nuclear magnetic and so on. Quantum electrodynamics photon systems are prominent candidates, since they provide many advantages, such as long decoherence time, photons being easily transported, prepared and manipulated. Therefore, it is a very promising subject to deal with quantum information processing using the optical system. This paper has done some research on how to deal with the processing of quantum information in linear optical systems. We have achieved the following results:1. Scheme for implementing quantum dense coding by using linear optical systemA novel scheme for realizing dense coding with Greenberger-Home-Zeilinger (GHZ) state in linear optical system is proposed. In this protocol, Alice codes on photon 1 and 2 by linear optical element and sends these photons to Bob. Then Bob will perform a joint measurement on photons 1,2, and 3 with the GHZ basis by employing two quantum nondemolition detectors (QND) and polarizing beam splitter (PBS). Eight GHZ states can be completely discriminated. According to the outcomes of his measurement Bob can determine which operation Alice applied. Alice only transmits two photons in this process of the quantum dense coding, but Bob can obtain three bits of classical information. The QND devices are generally based on cross-Kerr nonlinearities, and the cross-Kerr nonlinearities have become available with electromagnetically induced transparency (EIT). 2. Linear optical scheme for implementing the optimal real state cloningWe propose an experimental scheme for implementing the optimal 1→3 real state cloning via linear optical elements. This method relies on one polarized qubit and two location qubits and is feasible with current experimental technology.更多还原