Far-field signatures of a two-body bound state in collective emission from interacting two-level atoms on a lattice.

The collective emission from a one-dimensional chain of interacting two-level atoms is investigated. We calculate the light scattered by dissipative few-excitation eigenstates in the far field, and, in particular, focus on signatures of a lattice two-body bound state. We present analytical results for the angle-resolved, temporal decay of the scattered light intensity. Moreover, we find that the steady-state emission spectrum that emerges when the system is probed by a weak, incoherent driving field exhibits a distinct signature for the existence of a bound state, and allows us to determine the momentum distribution of the two-body relative wave function. Intriguingly, our study does not rely on single-atom addressability and/or manipulation techniques.