Bottom-up approach to room-temperature quantum systems

We demonstrate a key ingredient in a bottom-up approach to building complex quantum matter using thermal atomic vapors. We isolate and track very slowly moving individual atoms without the aid of laser cooling. Passive filtering enables us to carefully select atoms whose three-dimensional velocity vector has a magnitude below $\overline{v}/20$, where $\overline{v}$ is the mean velocity of the ensemble. Using a photon correlation technique, we can extract the velocity distributions. We can also follow the trajectory of slowly moving single atoms for more than $1\phantom{\rule{4pt}{0ex}}\textmu{}\mathrm{s}$ within a $25\text{\ensuremath{-}}\textmu{}\mathrm{m}$ field of view, with no obvious limit to the tracking ability while simultaneously observing Rabi oscillations of these single emitters. In addition, we measure the third-order correlation function of single thermal atoms. Our results demonstrate the power and scalability of thermal ensembles for utilization in quantum memories, imaging, and other quantum information applications through bottom-up approaches.