Quantum parameter estimation with general dynamics

TL;DR

This paper introduces a comprehensive framework linking quantum dynamics to the ultimate precision limits in quantum parameter estimation, providing methods to compute these limits and optimal states, and clarifying when ancillary systems are beneficial.

Contribution

It presents a general, systematic framework for quantum parameter estimation that directly relates dynamics to precision limits and optimal probe states, including conditions for ancillary system usefulness.

Findings

Derived a method to compute the ultimate precision limit.

Established a condition when ancillary systems do not improve precision.

Provided systematic tools for designing optimal quantum probes.

Abstract

One of the main quests in quantum metrology, and quantum parameter estimation in general, is to find out the highest achievable precision with given resources and design schemes that attain that precision. In this article we present a general framework for quantum parameter estimation which relates the ultimate precision limit directly to the underlying dynamics. With this framework we present systematical methods for computing the ultimate precision limit and optimal probe states. We further demonstrate the power of the framework by deriving a sufficient condition on when ancillary systems are not useful for improving the precision limit.