  We study the coupled-qubit oscillation driven by an oscillating field. When
the period of the non-resonant mode is commensurate with that of the resonant
mode of the Rabi oscillation, we show that the controlled-NOT (CNOT) gate
operation can be demonstrated. For a weak coupling the CNOT gate operation is
achievable by the commensurate oscillations, while for a sufficiently strong
coupling it can be done for arbitrary parameter values. By finely tuning the
amplitude of oscillating field it is shown that the high fidelity of the CNOT
gate can be obtained for any fixed coupling strength and qubit energy gap in
experiments.
