Classical information and communication

Abstract

Information theory has, until relatively recently, almost exclusively focused on what is now considered classical information, namely, information as stored in or transferred by classical mechanical systems. Quantum information theory has also largely consisted of the extension of methods developed for classical information to analogous situations involving quantum systems. Furthermore, because measurements of quantum systems produce classical information, traditional information-theoretical methods play an essential role in quantum communication and quantum information processing because measurements play an essential role in them. Accordingly, a concise overview of the elements of classical information theory is provided in this chapter. Several specific classical information measures are discussed and related here, as are classical error-correction and data-compression techniques. The quantum analogues of these concepts and methods are discussed in subsequent chapters.