Increased Secret Key Throughput in Twin Field Quantum Key Distribution using 4x4 Beam Splitter Detection Network

Twin Field Quantum key Distribution (TFQKD) 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 TFQKD 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 end placed after a 4x4 port beam-splitter network. Using theoretical modelling of secret keyrate and simulations using StrawberryFields, we observe an increase in secret key throughput when compared to conventional TFQKD.