Coherence in spontaneous matter-wave emission

An excited two-level emitter (e.g. an atom) decays spontaneously and irreversibly due to its coupling to a radiative environment. The presence of multiple emitters changes this picture, and the decay dynamics can be coherently enhanced, suppressed, and modified. In this talk, we investigate how the coherence effects emerge with matter-wave emitters, which spontaneously decay by emitting an atom, instead of a photon. By preparing coherent initial states in an array of matter-wave emitters, we demonstrate super- and subradiant dynamics, and observe retardation effects due to the slow propagation of matter waves coupling the emitters. Furthermore, we directly probe the properties of a fully-excited emitter array, revealing the fundamental role of spontaneous decay in the emergence of coherence.