Autonomous feedback stabilization of a cavity-coupled spin oscillator

TL;DR

This paper demonstrates autonomous feedback control to stabilize the collective spin of an atomic ensemble using a driven optical cavity, enabling precise state stabilization and characterization of the feedback system.

Contribution

It introduces a novel method for out-of-equilibrium stabilization of atomic spins via cavity-mediated autonomous feedback, with detailed experimental and theoretical analysis.

Findings

Successful stabilization of atomic spin states using cavity feedback

Close agreement between experimental results and analytic models

Characterization of feedback gain spectrum and set point tracking

Abstract

We report out-of-equilibrium stabilization of the collective spin of an atomic ensemble through autonomous feedback by a driven optical cavity. For a magnetic field applied at an angle to the cavity axis, dispersive coupling to the cavity provides sensitivity to a combination of the longitudinal and transverse spin. Coherent backaction by cavity light onto the atoms, conditioned by the optical cavity susceptibility, stabilizes the collective spin state at an arbitrary energy. The set point tracking and closed-loop gain spectrum of the feedback system are characterized and found to agree closely with analytic predictions.