Dissipative quantum Fisher information for a general Liouvillian parameterized process

TL;DR

This paper introduces a general framework for dissipative quantum Fisher information (DQFI) in open quantum systems, revealing how eigenvalues and eigenvectors of the Liouvillian influence parameter estimation precision over time.

Contribution

It derives a comprehensive form of DQFI in Liouville space, highlighting its dependence on Liouvillian spectrum properties and contrasting with traditional quantum Fisher information.

Findings

DQFI depends on eigenvalues and eigenvectors of the Liouvillian.

Eigenvalue dependence shows linear time scaling.

Eigenvector variation exhibits oscillatory and exponential behaviors.

Abstract

The dissipative quantum Fisher information (DQFI) for a dynamic map with a general parameter in an open quantum system is investigated, which can be regarded as an analog of the quantum Fisher information (QFI) in the Liouville space. We first derive a general dissipative generator in the Liouville space, and based on its decomposition form, find the DQFI stems from two parts. One is the dependence of eigenvalues of the Liouvillian supermatrix on the estimated parameter, which shows a linear dependence on time. The other is the variation of the eigenvectors with the estimated parameter. The relationship between this part and time presents rich characteristics, including harmonic oscillation, pure exponential gain and attenuation, as well as exponential gain and attenuation of oscillatory type, which depend specifically on the properties of the Liouville spectrum. This is in contrast to that of the conventional generator, where only oscillatory dependencies are seen. Further, we illustrate the theory through a toy model: a two-level system with spin-flip noise. Especially, by using the DQFI, we demonstrated that the exceptional estimation precision cannot be obtained at the Liouvillian exceptional point.