ig. 16.1. It is seen from the figure that the pure qubits |0) or |1) correspond to the cases 0 = 0 or 0 = IT, respectively, which occupy the north and south poles of the Bloch sphere. The key conclusion is that the qubit information corresponds to an infinite number of states, which are continuously distributed onto the surface of the Bloch sphere. The above description concerned single qubits, corresponding to single classical bits. It is possible to define higher-order qubits, which correspond to two classical bits or to even longer binary codewords. Since there exist four possible pairs of classical bits, which begins from a certain |alive) and evolves over time towards a certain |dead). After the 1-hour delay, the probabilities of the two states are equal, and the cat dwells in the state superposition hence, the name "cat state." At any time, one cannot be sure if the cat is dead or alive, and this infor- mation requires one to make a measurement by opening the box. Such a measurement results into the collapse of the cat's state into either of the pure states |dead) or |alive). The initial purpose of Schrödinger's though experiment was to illustrate that such a quantum view must be incomplete: the cat cannot be both dead and alive at the same time! And there is no need for someone to open the box to define in which state the cat actually exists. Yet such a view is consistent with the so-called "Copenhagen interpreta- tion," according to which systems can exist in such a superposition of states until reaching state collapse through physical observation. A fine argument, which reconciles this interpretation with Schrödinger's cat paradox, is the fact that a cat is a macroscopic or classical system, and, therefore, the microscopic quantum interpretation may not apply. See discussion, and more puzzling arguments in (for instance): http://en.wikipedia.org/wiki/Schr%C3%B6dinger's_cat 16.1 Quantum bits Figure 16.1 Representation of qubit |q) by a point on the surface of the Bloch sphere, as defined by the "colatitud