As was discussed in Sect. 1.3, many (if not most) of the commercial efforts in quantum computing (and the other areas) lie with superconductivity and the use of Josephson junctions for qubits. This brings us to the use of quantum physics to actually create quantum bits, and also quantum circuits. The physics of superconductivity, and the Josephson junction (JJ), is rather deep. However, an overview of superconductivity and the JJ will be presented first in this chapter in order to acquaint the reader with the basis for this technology in the quantum world. Then, the discussion will move to the superconducting quantum interference device (SQUID) and qubits.