  The quantum mechanical decay of two or more overlapped resonances in a common
continuum is largely influenced by Fano interference, leading to important
phenomena such as the existence of bound states in the continuum, fractional
decay and quiescent dynamics for single particle decay, and signature of
particle statistics in the many-body quantum decay. An overlooked yet essential
requirement to observe Fano interference is time reversal symmetry of the bath.
Here we consider multilevel quantum decay in a bath sustaining unidirectional
(chiral) propagating states, such as in quantum Hall or in Floquet topological
insulators, and show that the chiral nature of scattering states fully
suppresses Fano interference among overlapping resonances. As a result, there
are not bound states in the continuum, quantum decay is complete, and there is
not any signature of particle statistics in the decay process. Nonetheless,
some interesting features are disclosed in the multilevel decay dynamics in a
topological bath, such as the appearance of high-order exceptional points, long
quiescent dynamics followed by a fast decay, and the possibility to observe
damped non-Hermitian Bloch oscillations.
