| （英） |
It is known that an arbitrary quantum state can always be expressed in a pure state by preparing an appropriate ancilla system, which is called purification. The purification can always be performed when considering only quantity not dependent on the quantum state of the ancilla system. However, if we consider quantity dependent on the quantum state of the ancilla system, it is not clear whether the purification is possible or not. In this study, we focus on the cases where the quantum system S and the ancilla system are interactive with each other, and investigate whether purification, which correctly reproduces the time evolution of the system S, is possible. As a result, when the ancilla system is a macro system, we show that this purification is possible for a specific initial state. |