Classical–quantum arbitrarily varying wiretap channel: Ahlswede dichotomy, positivity, resources, super-activation

We establish the Ahlswede dichotomy for arbitrarily varying classical–quantum wiretap channels, i.e., either the deterministic secrecy capacity of the channel is zero, or it equals its randomness-assisted secrecy capacity. We analyze the secrecy capacity of these channels when the sender and the receiver use various resources. It turns out that randomness, common randomness, and correlation as resources are very helpful for achieving a positive secrecy capacity. We prove the phenomenon “super-activation” for arbitrarily varying classical–quantum wiretap channels, i.e., two channels, both with zero deterministic secrecy capacity, if used together allow perfect secure transmission.