A Generalized Measure of Quantum Fisher Information
Abstract
In this work, we present a lower bound on the quantum Fisher information (QFI) which is efficiently computable on nearterm quantum devices. This bound itself is of interest, as we show that it satisfies the canonical criteria of a QFI measure. Specifically, it is essentially a QFI measure for subnormalized states, and hence it generalizes the standard QFI in this sense. Our bound employs the generalized fidelity applied to a truncated state, which is constructed via the $m$ largest eigenvalues and their corresponding eigenvectors of the probe quantum state $\rho_{\theta}$. Focusing on unitary families of exact states, we analyze the properties of our proposed lower bound, and demonstrate its utility for efficiently estimating the QFI.
 Publication:

arXiv eprints
 Pub Date:
 October 2020
 arXiv:
 arXiv:2010.02904
 Bibcode:
 2020arXiv201002904S
 Keywords:

 Quantum Physics;
 Mathematical Physics;
 Physics  Data Analysis;
 Statistics and Probability
 EPrint:
 v3: fixed typos and equations, added references