Observing Spontaneous Emission Phenomena Using Lattice-Trapped Atoms Coupled to Free Space

It has been predicted that quantum optical models for spontaneous emission in photonic band gap materials can be realized with ultracold atomic systems\footnote{I. de Vega et. al, Phys. Rev. Lett. \textbf{101}, 260404, 2008; M. Stewart et. al, Phys. Rev. A \textbf{95}, 013626, 2017}. We experimentally implement such a scenario using ultracold Rb-87 atoms initially trapped in a state selective optical lattice. Coupling to a freely propagating internal state releases matter-waves (wave-continuum), while a populated/unpopulated lattice site simulates the excited/ground states of an ``artificial atom''. We present recent experimental results on the time evolution of the system, for which we find both Markovian as well as strongly non-Markovian dynamics. We characterize the momentum distribution of the emitted matter waves, for which we find close agreement with theoretical predictions. A careful analysis allows for an identification of the equivalent of a Lamb shift, and provides indirect evidence for the analog of the atom-photon bound state in photonic band gap materials.