Physics (Internal)

Cavity mediated optical feedback to collective atomic motion and spin

This event is part of the Biophysics/Condensed Matter Seminar Series.

Ultracold atoms coupled to optical cavities are an ideal system for studying quantum measurement and control. Through sensitivity to the atomic state, the cavity field can apply coherent backaction, modifying the dynamics of the atomic ensemble. In addition, photons leaking out of the cavity provide real-time information about these dynamics. In this seminar, I will introduce our platform for measurement and autonomous feedback to the collective spin and motion of an atomic ensemble within a high-finesse optical cavity. We have demonstrated feedback stabilization of the atomic spin in its inverted, high-energy state, where its dynamics can be described as an effective negative-mass oscillator. I will present our further realization of a negative-mass instability, generated by cavity-mediated collective spin-orbit coupling in the atomic ensemble. The instability arises from a resonant pair-creation interaction between the effective negative-mass spin and the atomic center-of-mass motion, and drives amplification and correlation of both modes. Finally, I will describe ongoing work toward stabilization of non-equilibrium spin states and preparation of sub-Poisson atomic ensembles through cavity feedback.