Medium-range terrestrial free-space QKD performance modelling and analysis

Medium-range terrestrial free-space quantum key distribution systems enable widespread secure networked communications in dense urban environments, where it would be infeasible to install a large number of short optical fibre links. Such networks need to perform over a wide range of conditions and their design has to balance key rate maximisation versus robust key generation over the greatest range of circumstances. Practicalities, such as manufacturability and deployment, further constrain the design space. Here, we examine challenges in translating experiment into engineering reality and identify efficient BB84 weak coherent pulse-decoy state protocol parameter regimes suitable for medium-range QKD systems considering likely system performance and environmental conditions