Recently, the quantum computer (QC) using the nano‐devices have significantly attracted attention, because a large‐scale extention of the qubits could be easily realized in the nano‐devices. However, some problems for the realization of the QC with nano‐devices arise from the short decoherence time and the interaction of qubits only between nearest‐neighbor qubits. Therefore, we try to design the optimal quantum circuit of the quantum Fourier transform in various network system by means of the genetic algorithm (GA). © 2004 American Institute of Physics