Effects of the Coherence on the Parameter Estimation in a Quantum Metrology Scheme with Driving Fields

Abstract

The effects of the initial-state coherence on the quantum Fisher information(QFI) is studied in a parameter estimation scheme where the endowed unknown phase is measured after a driven two-level probing atom interacts with its environment. It is shown that the relatively large initial-state coherence couldn’t be necessary to achieve the large QFI, but it is necessary for the driving field to enhance the QFI. It is also found that the coherence plays its roles in the QFI through two paths. Generally, the QFI could lie at a low level in one path, but maintains a relatively high level in another path, even though the two paths correspond to the same initial-state coherence. This provides a way to achieve the large QFI with the less initial-state coherence.