  Entanglement assistance can improve communication rates significantly. Yet,
its generation is susceptible to failure. The unreliable assistance model
accounts for those challenges. Previous work provided an asymptotic formula
that outlines the tradeoff between the unassisted and excess rates from
entanglement assistance. We derive a full characterization for
entanglement-breaking channels, and show that combining entanglement-assisted
and unassisted coding is suboptimal. From a networking perspective, this
finding is nontrivial and highlights a quantum behavior arising from
superposition.
