Remarkable recent developments in the field of quantum communications and quantum information processing include the achievement of quantum teleportation, quantum communication channels based on entangled states, and the discovery of quantum computing algorithms. The present book addresses the physical foundations of the subject, as well as the technological problems, discussing such aspects as photonics, quantum imaging, engineered entanglement in atomic and other physical systems, Bose-Einstein condensation, and decoherence. Indispensable reading for graduates and Ph.D. students in departments of physics, electrical and electronic engineering, mathematics, and computer science seeking both an orientation as well as advanced training in the field.