We combine the ideas of qubit encoding and dispersive dynamics to enable robust and easy quantum-information processing on paired superconducting charge boxes sharing a common bias lead. We establish a decoherence free subspace on these and introduce universal gates by dispersive interaction with a $\mathrm{LC}$ resonator and inductive couplings between the encoded qubits. These gates preserve the code space and only require the established local symmetry and the control of the voltage bias. The principle of dispersive manipulation of encoded qubits is general and beneficial to other physical systems.

• Received 9 March 2003

DOI:https://doi.org/10.1103/PhysRevA.69.030301