To constitute a desirable quantum-mechanical state.

A quantum-mechanical state comprising plural numbers of two level systems (X1, X2,..., X2n+1) is expressed by superposition of orthonormal bases where the respective level systems come to ground states or excited states. A desirable quantum-mechanical state entangled partially, in which all the coefficients of respective bases have real numbers, is constituted by conducting an operation by a network of quantum gates combined with a selective rotation operation and a deaveraging operation D.