【作者】 刘红；

【导师】 刘金明；

【作者基本信息】 华东师范大学 ， 光学， 2008， 硕士

【摘要】 随着计算机的深度运用,人们发现目前所使用的数字计算机已遭遇到其发展的“瓶颈”。于是,科学家们提出了“量子计算机”的设想。这个设想的提出,无疑是推动了利用量子力学规律来表示和操作信息的一门新学科--“量子信息学”的飞速发展。其中,量子隐形传态是量子信息领域一个热门的研究课题,人们对它展开了大量的研究,并已取得了许多有价值的研究成果。本文首先简要回顾了量子信息学的发展过程和一些基本概念。接着,着重介绍了量子隐形传态的基本原理、量子纠缠态的制备以及量子隐形传态的研究进展。最后,本文提出了两种采用正定算符值测量(POVM)进行量子隐形传态的理论方案,并分别讨论了它们成功传输的相应几率。第一个方案中,假定发送者和接收者事先分享三个两体部分纠缠态作为量子通道,在发送者实施三个Bell基态测量以及接收者构造合适的POVM算符对辅助粒子进行广义测量后,任意三粒子纯态的概率量子隐形传送可得以实现。研究结果表明,该方案的成功传输几率仅与量子通道的参数有关,而且方案的平均保真度大于2/3,这要优于经典方案的保真度。在第二个方案中,利用两个部分纠缠态作为量子通道,提出了一种运用POVM测量辅助粒子,可控量子隐形传送一般的两体三维量子纠缠态方案。在该方案中,两个接收者中的一方需在另一方的协助下才能重构发送者所要传递的初始态。本文的工作不仅有助于进一步了解量子隐形传态过程中量子通道与成功传输几率的关系,同时对量子隐形传态的实际应用以及量子通信过程的深入研究都有一定的理论指导意义。更多还原

【Abstract】 With the widespread use of classical computers, it is inevitable to suffer from their developing bottle-neck. Under this background, the scientists put forward the idea of "quantum computer", which result in the rapid development of a new subject named quantum information sciences for applying quantum mechanics to denote and manipulate information. As an important branch in quantum information science, quantum teleportation (QT) has been extensively studied and many valuable results have been obtained both in theory and in experiment.In this thesis, we first briefly introduce the background and fundamental principles of quantum information. Then, we review the concept of QT, generation of entangled states, and research progress of QT. Finally, we propose two new schemes for quantum teleportation by the method of positive operator-valued measurement (POVM) and discuss the corresponding success probabilities. In the first scheme, if the sender and the receiver share three bipartite nonmaximally entangled states as quantum channel, we can achieve conclusive teleportion of an arbitrary tripartite state by performing three Bell-state measurements at the sender’s side and implementing a proper POVM on auxiliary particles at the receiver’s side. Our results show that the successful probability is only determined by the smaller coefficients of the threeinitial entangled pairs. Moreover, the average fidelity of the scheme is better than 2/3 ,which means that the teleportation scheme is superior to the classical communication protocols. In the second scheme, to realize probabilistic controlled teleportation of a two-particle three-dimensional entangled state via POVM, a sender and two receivers share two partially three-dimensional entangled states as quantum channel. It is found that one of the two receivers can recover the original state to be teleported only under the assistance of the other.Our results are useful to understand the relation between the quantum channel and the probability of successful teleportation, and are helpful for investigating the application of quantum teleportation and making a profound research on the process of quantum communication in a sense.更多还原