The quantum computer is a potential computing machine which employs interacting quantum two level systems as quantum bits. We studied a problem simulating a C^nNOT gate by a combination of CNOT gates and 1-bit phase rotation gates. The results are that, of 8(n-3) C^2NOT gates, 8(n-5) gates can be simulated by two CNOT and two 1-bit gates, 8 gates by 3 CNOT and 4 1-bit gates, and residual 8 gates by 48 CNOT and 52 1-bit gates
