Theoretical Physics Seminar

Ensembles of atoms are routinely employed in quantum sensors with applications ranging from atomic clocks to magnetometers and matter-wave interferometers. Today’s quantum devices can controllably entangle the atoms to prepare non-classical states that enable quantum-enhanced metrology, i.e., measurements with precisions beyond classical limits. In this talk, I will give an introduction to the field of quantum-enhanced metrology with atomic ensembles. I will discuss a typical metrology setting and the classical limits achievable with uncorrelated atoms, modeled as two-level systems or qubits. Subsequently, I will review ways to entangle the qubits and achieve precision beyond these limits using the intuitive idea of spin squeezing. Going further, I will introduce the concept of Fisher information and how it enables us to determine the metrological utility of highly non-classical states where simple intuition fails. Finally, I will present our recent results on the preparation and characterization of metrologically useful states in ensembles of three-level atoms or qutrits using experimentally feasible protocols.