Quantum parameter estimation with general dynamics

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.