1.1 全局概览

Quantum computation and quantum information is the study of the information processing tasks that can be accomplished using quantum mechanical systems. Sounds pretty simple and obvious, doesn’t it? Like many simple but profound ideas it was a long time before anybody thought of doing information processing using quantum mechanical systems. To see why this is the case, we must go back in time and look in turn at each of the fields which have contributed fundamental ideas to quantum computation and quantum information – quantum mechanics, computer science, information theory, and cryptography. As we take our short historical tour of these fields, think of yourself first as a physicist, then as a computer scientist, then as an information theorist, and finally as a cryptographer, in order to get some feel for the disparate perspectives which have come together in quantum computation and quantum information.

首先我们来看一下量子计算的概念：

量子计算和量子信息是研究如何利用量子力学系统来完成信息处理任务。

尽管这句话看起来简单，但人们利用量子力学进行信息处理还有很长的路要走。至于为什么，我们的思路必须要回到过去，看看为量子计算和量子信息贡献了基本思想的每个领域——量子力学、计算机科学、信息论和密码学。你可以把自己想象成一个物理学家，然后是计算机科学家，然后是信息理论家，最后密码学家，以便对量子计算和量子信息中汇集在一起的不同角度有一个总体感受。