Fundamental limits of pulsed quantum light spectroscopy

Quantum light spectroscopy is an emerging field wherein the quantum nature of light is exploited to reveal information about the properties of matter. Although there is evidence that spectroscopy with quantum light may have certain advantages compared to classical spectroscopic methods, this advantage has not been rigorously assessed. 

We use quantum estimation theory to identify the ultimate limit in the precision of estimating parameters of a matter system when probed by a (travelling) pulse of quantum light. Concretely, we consider the estimation of the dipole moment of a two-level atom interacting with different quantum states of quantum light, such as squeezed and entangled light, and compare their performance. We then study the attainability of the quantum limit. This should allow the identification of optimal quantum light spectroscopy setups.