Quantum Theory: An Information Processing Approach

The text offers a unique blend of insights both into the physical foundations and the practical application of quantum theory. It begins with a discussion of experimental evidence that forces us to abandon the classical description and to critically re-examine such basic notions as measurement, probability, and state. The thorough investigation of these concepts leads to the alternative framework of quantum theory, set in complex Hilbert space. The requisite mathematics is developed carefully and always linked to its operational meaning. This part of the text culminates in an exploration of some of the most vexing foundational issues of quantum theory, regarding locality, non-contextuality, and realism. The second half of the text explains how the peculiar features of quantum theory may be harnessed to tackle information processing tasks that are intractable or even impossible classically. It provides the essential tools for understanding and designing the pertinent protocols, and discusses a diverse range of examples representative of current quantum technology. These include standard examples like the secure distribution of cryptographic keys, as well as less known applications such as entanglement-assisted metrology. Throughout the text there is a wealth of classroom-tested and at times unconventional exercises.