Typical Purification Reproducing the Time Evolution of an Open Quantum System

TL;DR

This paper investigates the conditions under which a purification process can accurately reproduce the time evolution of an open quantum system interacting with an ancilla, especially when the ancilla is a macrosystem.

Contribution

It demonstrates that purification reproducing the system's time evolution is possible for specific initial states when the ancilla is a macrosystem.

Findings

Purification can reproduce the time evolution of the system.

Possible for specific initial states with a macrosystem ancilla.

Provides insights into quantum state purification dynamics.

Abstract

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 a quantity not dependent on the quantum state of the ancilla system. Otherwise, the possibility of purification cannot be elucidated. In this study, we focus on the cases where a quantum system S and the ancilla system interact with each other, and investigate whether purification, which correctly reproduces the time evolution of the system S, is possible. Accordingly, when the ancilla system is a macrosystem, it can be shown that this purification is possible for a specific initial state.