Cold 87Rb ensembles: non-Gaussian state detection and spin tomography

Light interacting with atomic ensembles allows the possibility of strong, and thus deterministic, quantum interface processes. Recently demonstrated processes of interest for quantum networking include quantum memory for light and teleportation of a quantum state from light to matter. Many important results have been accomplished with room temperature ensembles, which has thus far limited the experiments to relatively long interaction times, ~ ms, large numbers of atoms ~10¹², and far-detuned interactions. In contrast, a cold, trapped atomic ensemble can have the same optical depth with far fewer atoms ~10⁶, simultaneous with faster ~mus interaction times. For a combination of technical and fundamental reasons, this allows for new types of experiments using light-ensemble interfaces. Here we describe methods to detect non-gaussian states and perform spin-state tomography.