Quantum Key Distribution with High Loss: Toward Global Secure Communication

TLDR

The authors propose a decoy‑pulse technique to mitigate photon‑number‑splitting attacks in BB84 quantum key distribution under high‑loss conditions. The method replaces signal pulses with randomly chosen multiphoton decoy pulses, compares their losses, aborts if decoy loss is anomalously low, and otherwise estimates signal multiphoton loss from the decoy loss assuming comparable values. The authors provide justification for the assumption that decoy and signal losses are similar.

Abstract

We propose a decoy-pulse method to overcome the photon-number-splitting attack for Bennett-Brassard 1984 quantum key distribution protocol in the presence of high loss: A legitimate user intentionally and randomly replaces signal pulses by multiphoton pulses (decoy pulses). Then they check the loss of the decoy pulses. If the loss of the decoy pulses is abnormally less than that of signal pulses, the whole protocol is aborted. Otherwise, to continue the protocol, they estimate the loss of signal multiphoton pulses based on that of decoy pulses. This estimation can be done with an assumption that the two losses have similar values. We justify that assumption.