  Topological insulators enable non-reciprocal light propagation that is
insensitive to disorder and imperfections. Yet, despite considerable attention
from the photonics community and beyond, the very feature that has inspired
numerous proposals for applications of topological transport also turns out to
be one of the main stumbling blocks for practical implementations: Accessing
topologically protected states is generally assumed to require their protection
to be lifted. We overcome this limitation by topology-entailed trivial (TET)
states that arise from the hybridization of counter-propagating interface
states. We demonstrate selective injection and extraction of light into
topological states as well as long-range coherent light exchange between
spatially separated topological channels. Our results highlight the potential
of TET states as protection-preserving paradigm to manipulate the flow of light
in topological platforms.
