Bounding Quantum Capacities via Partial Orders and Complementarity

Quantum capacities are fundamental quantities that notoriously hard to compute and can exhibit surprising properties such as superadditivity. Thus, a vast amount of literature is devoted finding tight computable bounds on these capacities. We add new viewpoint by giving operationally motivated several capacities, including the quantum capacity private channel one-way distillable entanglement key state. These generally phrased in terms involving complementary or As tool obtain bounds, we discuss partial orders channels states, less noisy more capable order. Our help further understand interplay between different they give operational limitations superadditivity difference information-theoretic They also be used approach towards numerically bounding discussed with some examples.