In recent years interest in what is called quantum computers has grown extraordinarily. The idea of using the possibilities of quantum mechanics in organizing computation looks all the more attractive now that experimenta work has begun in this area.
However, the prospects for physical realization of quantum computers are presently entirely unclear. Most likely this will be a matter of several decades. The fundamental achievements in this area bear at present a purely mathematical character.
This book is intended for a first acquaintance with the mathematical theory of quantum computation. For the convenience of the reader, we give at the outset a brief introduction to the classical theory of computational complexity. The second part includes the descriptions of basic effective quantum algorithms and an introduction to quantum codes.