This book is a comprehensive yet concise overview of quantum information science, which is a rapidly developing area of interdisciplinary investigation that now plays a significant role in physics, information technology and engineering. The most well-known applications of quantum information science are quantum key distribution and quantum computation. This book is a handy reference for practitioners and students covering foundational issues as well as these and other applications. It contains more than 25 illustrations that encapsulate essential ideas and fundamental constructs. Foreword by Prof. Tommaso Toffoli.