1. A superconducting qubit comprising: a qubit loop formed by a first superconducting current path; a first compound Josephson junction structure formed by a first pair of parallel superconducting current paths, wherein the first compound Josephson junction structure interrupts the qubit loop, and wherein each superconducting current path in the first pair of parallel superconducting current paths is interrupted by at least one Josephson junction; and a series LC-circuit coupled in parallel with the first compound Josephson junction structure through a superconducting current path, wherein the series LC-circuit realizes a tunable capacitance.