  We study the simulation of a single qubit rotation and Controlled-Not gate in
a solid state one-dimensional chain of nuclear spins system interacting weakly
through an Ising type of interaction with a modular component of the magnetic
field in the z-direction, characterized by $B_z(z,t)=Bo(z)\cos\delta t$. These
qubits are subjected to electromagnetic pulses which determine the transition
in the one or two qubits system. We use the fidelity parameter to determine the
performance of the Not (N) gate and Controlled-Not (CNOT) gate as a function of
the frequency parameter $\delta$. We found that for $|\delta|\le 10^{-3} MHz$,
these gates still have good fidelity.
