  We apply the nested algebraic Bethe ansatz method to solve the eigenvalue
problem for the SU(4) extension of the Hubbard model. The Hamiltonian is
equivalent to the SU(4) graded permutation operator. The graded Yang-Baxter
equation and the graded Quantum Inverse Scattering Method are used to obtain
the eigenvalue of the SU(4) extension of the Hubbard model.
