Another book on Quantum Optics? or Quantum Information? Well, not - actly. A more descriptive title might be: “A guided tour through basic qu- tum mechanics, quantum optics and quantum information”. Even better, a few words on its origin and our motivation for undertaking the task might be useful to the potential reader in deciding whether to turn the pages beyond this preface. For more than ten years now, a graduate course on quantum optics has been taught in the physics department of the University of Crete. Spanning two semesters, it originally consisted of a collection of topics representative of what can be found in the numerous by now excellent books on quantum optics. Over the last four years or so,however, the course acquired a gradually increasing segment of what is broadly referred to as quantum information, whichatthispointisapproximatelyhalfof thematerial.Inevitably,thetopics on standard quantum optics had to be reduced or compressed accordingly.