Heralded-channel near-additivity conjecture

A flagged channel randomly selects one channel from a fixed ensemble and reports the selected channel along with the output state. A channel is strongly additive when its use together with any other channel does not exhibit superadditivity, and a flagged channel is nearly additive when its capacity is close to the corresponding single-use additive bound. Heralded-channel near-additivity conjecture. A flagged channel that with high probability applies a strongly additive channel is nearly additive. The conjecture formalizes the intuition that random application of an almost additive channel limits the entanglement available for superadditivity. The paper presents it as a conjecture motivated by entanglement monogamy, without establishing it.