Charge-Phase Qubit in Phase Regime

A superconducting qubit implementation is proposed that takes the advantage of both charge and phase degrees of freedom. Superpositions of flux states in a superconducting loop with three Josephson junctions form the states of the qubit. The charge degree of freedom is used to readout and couple the qubits. Cancellation of the first order coupling to the environment, at the working point of the qubit, protects it from the decoherence due to charge and flux fluctuations.