Observing Spin-Squeezed States under Spin-Exchange Collisions for a Second
Meng-Zi Huang, Jose Alberto de la Paz, Tommaso Mazzoni, Konstantin Ott, P. Rosenbusch, Alice Sinatra, Carlos L. Garrido Alzar, Jakob Reichel
Abstract
Using the platform of a trapped-atom clock on a chip, we observe the time evolution of spin-squeezed hyperfine clock states in ultracold rubidium atoms on previously inaccessible time scales up to 1 s. The spin degree of freedom remains squeezed after 0.6 s, which is consistent with the limit imposed by particle loss and is compatible with typical Ramsey times in state-of-the-art microwave clocks. The results also reveal a surprising spin-exchange interaction effect that amplifies the cavity-based spin measurement via a correlation between spin and external degrees of freedom. These results open up perspectives for squeezing-enhanced atomic clocks in a metrologically relevant regime and highlight the importance of spin interactions in real-life applications of spin squeezing.