Twin-Field Quantum Key Distribution without Phase Postselection

In quantum cryptography, the twin-field (TF) quantum key distribution (QKD) protocol could extend theoretical key rates through a lossy channel, but most of its security proofs require phase postselection, which complicates practical systems and severely limits secure key rates. This study presents a truncated TF-QKD protocol without any postselection, gives a general security proof, and shows that this scheme may beat other protocols in terms of key rate, even when only finite decoy states are employed. By showing that a medium-range QKD system can reach much higher key rates, this protocol will make QKD systems more applicable in tomorrow's cybersecurity.