In Chaps. 18 and 19, we analyzed the Hamiltonian and its eigenstates and eigenvectors of a Cooper pair box using two-basis-state approximation and numerical calculation. Regardless of its operating regime (small \(\frac {E_J}{E_c}\) as a charge qubit or large \(\frac {E_J}{E_c}\) as a transmon qubit), it has well-defined levels and high enough anharmonicity. Therefore, it fulfills one of DiVincenzo’s criteria to have a “well-characterized qubit” (Sect. 1.3). In this chapter, we will study how to map the qubit states to the Bloch sphere and apply voltage pulses to manipulate the qubit to obtain a general one-qubit gate. We will work on the charge qubit because it is simple and instructive, despite the fact that transmon qubit, which is much less sensitive to charge noise, is the dominant qubit being used as a superconducting qubit. Transmon qubit will be discussed in the following chapters.