  The controlled-NOT gate and controlled square-root NOT gate play an important
role in quantum algorithm. This article reports the experimental results of
these two universal quantum logic gates (controlled square-root NOT gate and
controlled-NOT gate) on a 7-qubit NMR quantum computer. Further, we propose a
simple experimental method to measure and correct the error in the controlled
phase-shift gate, which is helpful to construct a more perfect phase-shift gate
experimentally and can also be used in more qubits discrete Fourier
transformation.
