Hierarchy of measurement-induced Fisher information for composite states

TL;DR

This paper explores the hierarchical structure of measurement-induced Fisher information in quantum states, providing a framework to understand its distribution and transfer, with implications for quantum metrology and open quantum systems.

Contribution

It introduces a general framework for the distribution and transfer of measurement-induced Fisher information, revealing three extremal types and their roles in quantum information processes.

Findings

Identifies three extremal Fisher information distribution types

Establishes a hierarchical structure of measurement-induced Fisher information

Links Fisher information flow to physical phenomena like non-Markovianity and quantum cloning

Abstract

Quantum Fisher information, as an intrinsic quantity for quantum states, is a central concept in quantum detection and estimation. When quantum measurements are performed on quantum states, classical probability distributions arise, which in turn lead to classical Fisher information. In this article, we exploit the classical Fisher information induced by quantum measurements, and reveal a rich hierarchical structure of such measurement-induced Fisher information. We establish a general framework for the distribution and transfer of the Fisher information. In particular, we illustrate three extremal distribution types of the Fisher information: the locally owned type, the locally inaccessible type, and the fully shared type. Furthermore, we indicate the significant role played by the distribution and flow of the Fisher information in some physical problems, e.g., the non-Markovianity of open quantum processes, the environment-assisted metrology, the cloning and broadcasting, etc.