Second-order coding rates for pure-loss bosonic channels

Understand

A pure-loss bosonic channel is a simple model for communication over free-space or fiber-optic links.

• More generally, phase-insensitive bosonic channels model other kinds of noise, such as thermalizing or amplifying processes.
• Recent work has established the classical capacity of all of these channels, and furthermore, it is now known that a strong converse theorem holds for the classical capacity of these channels under a particular photon number constraint.
• The goal of the present paper is to initiate the study of second-order coding rates for these channels, by beginning with the simplest one, the pure-loss bosonic channel.