Increased Secret Key Throughput in Twin Field Quantum Key Distribution using 4×4 Beam Splitter Detection Network

Twin Field Quantum key Distribution (TF-QKD) has attracted recent interest due to the higher secret key capacity better than the fundamental repeaterless limit and extending the achievable distance. The key generation in TF-QKD is based on the post selection of randomized phase slices. This paper describes a technique for enhancing the probability of choosing the phase slices by using four detectors at Charlie’s end placed after a 4x4 port beam-splitter network. Using theoretical modelling of secret key-rate and simulations using Strawberry-Fields, we observe an increase in secret key throughput when compared to conventional TF-QKD.