Unconstrained distillation capacities of a pure-loss bosonic broadcast channel

Understand

Bosonic channels are important in practice as they form a simple model for free-space or fiber-optic communication.

• Here we consider a single-sender two-receiver pure-loss bosonic broadcast channel and determine the unconstrained capacity region for the distillation of bipartite entanglement and secret key between the sender and each receiver, whenever they are allowed arbitrary public classical communication.
• We show how the state merging protocol leads to achievable rates in this setting, giving an inner bound on the capacity region.
• We also evaluate an outer bound on the region by using the relative entropy of entanglement and a `reduction by teleportation' technique.