Quantum information—the basics
Vlatko Vedral · 2006
Abstract Quantum mechanics is a more accurate description of the microscopic world than classical mechanics, and quantum information, which is governed by the laws of quantum mechanics, is a more accurate description of information theory. The quantum laws of physics are fundamentally different from the classical laws and so, therefore, is the resulting information processing. In one limit, quantum information reduces to classical information; otherwise, quantum information is a much more general concept that allows information-processing protocols that have no classical analogue whatsoever. This chapter discusses the basics of quantum information, some differences between bits and qubits, quantum cryptography, trace and partial-trace operations, extension of Hilbert spaces, Schmidt decomposition, generalised measurements, CP-maps and positive operator-valued measurements, and the postulates of quantum mechanics.