A New Security Proof for Twin-Field Quantum Key Distribution (QKD)

Twin-field QKD (TF-QKD) protocols allow for increased key rates over long distances when compared to standard QKD protocols. They are even able to surpass the PLOB bound without the need for quantum repeaters. In this work, we revisit a previous TF-QKD protocol and derive a new, simple, proof of security for it. We also look at several variants of the protocol and investigate their performance, showing some interesting behaviors due to the asymmetric nature of the protocol.