 call here "macrosystems," such as a coin, a cat or a human being (see Chapter 15)! The expectations are high indeed if public audiences "buy in" the quantum state superposition concept as applicable to the macroscopic world. At a microscopic scale, however, the notions of QT and "nonlocality" implications, are absolutely correct. Suffice it to recall here that in the quantum world, any elementary object, such as an atom or a particle, is, to all intents and purposes, a quantum system, and there are no conceptual limitations involved therein, both in terms of locality and physical distance. As we shall see, however, there is no contradiction between QT and relativity laws, when it comes to measuring actual information. In this book, QT is, thus, our first quantum algorithm to "transport" quantum states, whose most elementary description is the qubit. The key to the QT algorithm is the use of an EPR-Bell state (or ebit), as a resource commonly shared between Alice and Bob, and making it possible for Alice to send any qubit to Bob. As we shall see, teleportation also requires the communication of two classical bits (cbits), using any classical communication channel, such as the telephone, or the Internet, for instance. This preliminary observation is completely sufficient to justify that indeed, teleportation does not violate relativity laws. The principle of the generic QT circuit is illustrated in Fig. 18.7. As the figure shows, this is a 3-qubit circuit, which includes a Bell-state measurement apparatus (as shaded), Qubit measurements, coding, and teleportation which outputs the two cbits m, m', and two gates (X, Z), which are used according to the powers of m, m'. The two top wires are connected to Alice's side, while Bob uses the bottom wire for final measurements. The qubit that Alice wants to transmit to Bob is |q) = a|0) + B|1), as shown at top left. Alice and Bob also share the resource of an EPR-Bell state, here, for instance, 1Boo>. The end result of the QT is that Bob is able to retrieve the qubit 1q) =