Steklov Mathematical Institute, Gubkina 8, 119991 Moscow, Russia.
Rep Prog Phys. 2012 Apr;75(4):046001. doi: 10.1088/0034-4885/75/4/046001. Epub 2012 Mar 7.
One of the major achievements of the recently emerged quantum information theory is the introduction and thorough investigation of the notion of a quantum channel which is a basic building block of any data-transmitting or data-processing system. This development resulted in an elaborated structural theory and was accompanied by the discovery of a whole spectrum of entropic quantities, notably the channel capacities, characterizing information-processing performance of the channels. This paper gives a survey of the main properties of quantum channels and of their entropic characterization, with a variety of examples for finite-dimensional quantum systems. We also touch upon the 'continuous-variables' case, which provides an arena for quantum Gaussian systems. Most of the practical realizations of quantum information processing were implemented in such systems, in particular based on principles of quantum optics. Several important entropic quantities are introduced and used to describe the basic channel capacity formulae. The remarkable role of specific quantum correlations-entanglement-as a novel communication resource is stressed.
最近出现的量子信息理论的主要成就之一是引入并彻底研究了量子信道的概念，这是任何数据传输或数据处理系统的基本构建块。这一发展导致了一个精心设计的结构理论，并伴随着一系列熵量的发现，特别是信道容量，它们表征了信道的信息处理性能。本文综述了量子信道及其熵描述的主要性质，并给出了各种有限维量子系统的例子。我们还涉及了“连续变量”的情况，它为量子高斯系统提供了一个研究领域。量子信息处理的大多数实际实现都是基于这样的系统，特别是基于量子光学的原理。引入了几个重要的熵量，并用于描述基本的信道容量公式。特别强调了特定的量子相关性-纠缠-作为一种新型通信资源的重要作用。
