This book reviews selected topics charterized by great progress and covers the field from theoretical areas to experimental ones. It contains fundamental areas, quantum query complexity, quantum statistical inference, quantum cloning, quantum entanglement, additivity. It treats three types of quantum security system, quantum public key cryptography, quantum key distribution, and quantum steganography. A photonic system is highlighted for the realization of quantum information processing.

Hiroshi Imai was born in 1958 at Kobe, Japan. He obtained B.Eng. in Mathematical Engineering, and M.Eng. and D.Eng. in Information Engineering, University of Tokyo in 1981, 1983 and 1986, respectively. In 1986-1990, he was an associate professor of Department of Computer Science and Communication Engineering, Kyushu University. He was also a visiting associate professor at School of Computer Science, McGill University in 1987 and a visiting scientist at IBM T. J. Watson Research Center in 1988. Since 1990, he joined Department of Information Science, University of Tokyo. He is now a professor in Department of Computer Science, Univeristy of Tokyo. He has been a project leader of ERATO Quantum Computation and Information Project, JST from 2000. His research interests include quantum information science, algorithmics, computational geometry, and optimization.

Masahito Hayashi was born in Japan in 1971.He received the B. S. degree from Faculty of Sciences in Kyoto University, Japan, in 1994 and the M. S. and Ph. D. degrees in Mathematics from Kyoto University, Japan, in 1996 and 1999, respectively. He worked in Kyoto University as a Research Fellow of the Japan Society of the Promotion of Science from 1998 to 2000, and worked in the Laboratory for Mathematical Neuroscience, Brain Science Institute, RIKEN from 2000 to 2003.In 2003, he joined Quantum Computation and Information Project, ERATO, JST as the Research Head. He also works in Superrobust Computation Project Information Science and Technology Strategic Core (21st Century COE by MEXT) Graduate School of Information Science and Technology. The University of Tokyo as Adjunct Associate Professor from 2004. He is an Editorial Board of International Journal of Quantum Information, and is the author of Quantum Information Theory, which will be published from Springer in this March. He also edited "Asymptotic Theory of Quantum Statistical Inference: Selected Papers" (World Scientific 2005) and Special Issue of EQIS'03 conference in International Journal of Quantum Information. His research interests include quantum information theory and quantum statistical inference.