After the first edition of this book was published, I received much positive feedback from the readers. It was very helpful to have all those comments sug­ gesting improvements and corrections. In many cases, it was suggested that more aspects on quantum information would be welcome. Unfortunately, I am afraid that an attempt to cover such a broad area as quantum informa­ tion theory would make this book too scattered to be helpful for educational purposes. On the other hand, ladmit that some aspects of quantum information should be discussed. The first edition already contained the so-called No­ Cloning Theorem. In this edition, I have added a stronger version of the aforementioned theorem due to R. Jozsa, a variant which also covers the no-deleting principle. Moreover, in this edition, I have added some famous protocols, such as quantum teleportation. The response to the first edition strongly supports the idea that the main function of this book should be educational, and I have not included furt her aspects of quantum information theory here. For further reading, I suggest [43] by Josef Gruska and [62] by Michael A. Nielsen and Isaac L. Chuang. Chapter 1, especially Section 1.4, includes the most basic knowledge for the presentation of quantum systems relevant to quantum computation. The basic properties of quantum information are introduced in Chapter 2. This chapter also includes interesting protocols: quantum teleportation and superdense coding.