To provide methods, which can realize q-bit and basic arithmetic without requiring a large-scale device in a quantum computer.

A q-bit expressing the variable of the quantum computer is made general, and the general q-bit is considered as the source of a Hilbert space CN and realized as the state of an N terminal. The arithmetic of the quantum computer is decomposed and provided as combination of basic arithmetic to the states of two terminals for realizing the general q-bit converted from M input variables by a converting circuit by using the circuit for realizing each of basic arithmetics.