  Low-frequency noise can induce serious decoherence in superconducting qubits.
Due to its diverse physical origin, such noise can couple with the qubits
either as transverse or as longitudinal noise. Here, we present a universal
quantum degeneracy point approach that can protect an encoded qubit from
arbitrary low-frequency noise. We further show that universal quantum logic
gates can be performed on the encoded qubits with high fidelity. The proposed
scheme can be readily implemented with superconducting flux qubits or with a
qubit coupling with a superconducting resonator. Meanwhile, the scheme is also
robust against small parameter spreads due to fabrication errors in the
superconducting systems.
