In the Jaynes-Cummings model of Chap. 2 , the actual qubit was a two-level system that was created in an atomic-like manner. But, there is nothing to forbid this two-level system to actually lie in the atomic structure of a single atom. In fact, discussion in Chap. 1 pointed out that more than one commercial approach is based upon the concept of trapped ions. The qubit is formed from atomic states of the trapped ion, either the ground and an excited state, or a pair of hyperfine separated states in the ground state itself. And, there is at least one commercial approach which uses neutral atoms as the qubits. In this latter approach, the neutral atoms are trapped on an optical lattice which creates a potential array, which can localize the neutral atom. Again, the qubit can be formed from a variety of the atom's energy levels.