Optimal detection of precessing spin ensembles

Precise knowledge of the spin orientation of atomic ensembles is demanded in a wide range of scenarios, from precision measurements and further progress in best-in-class atomic clocks and magnetometers to the preparation of non-classical states of matter and memories. Implementing quantum-limited detection schemes is challenging, however. Shot-noise in the detectors can mask the motion of the spins limiting the precision of estimations. Here I describe our recent work and results aimed at overcoming this challenge in alkali-based magnetometers. As a first step we have experimentally studied the quantum limits in the optimal estimation of system properties of atomic ensembles in thermal equilibrium via spin noise spectroscopy. We are currently extending these techniques to the time domain as required for real-time sensing and control applications, for example in magnetometry we will report our Progress.