Before revision: The phase qubit is a superconducting device based on the superconductor-insulator-superconductor (SIS) Josephson junction, designed to operate as a quantum bit, or qubit.
After revision: In quantum computing, and more specifically in superconducting quantum computing, the phase qubit is a superconducting device based on the superconductor-insulator-superconductor (SIS) Josephson junction, designed to operate as a quantum bit, or qubit.