Security of decoy-state quantum key distribution with correlated bit-and-basis encoders

TL;DR

This paper develops a finite-key security proof for practical decoy-state BB84 quantum key distribution that accounts for correlations introduced by the encoder, bridging the gap between theory and real-world implementations.

Contribution

It introduces a security proof that rigorously incorporates encoder-induced correlations with only partial characterization, enhancing practical QKD security guarantees.

Findings

Provides a finite-key security proof for correlated decoy-state BB84.

Addresses correlations from practical encoders in security analysis.

Bridges the gap between theoretical security and real-world QKD implementations.

Abstract

Practical quantum key distribution (QKD) modulators inevitably introduce correlations, causing the state emitted in a given round to depend on the setting choices made in previous rounds. These correlations break the round-by-round independence structure on which many widely used security proof techniques rely, leaving a significant gap between available theoretical guarantees and the reality of practical implementations. In this work, we develop a finite-key security proof for decoy-state BB84 against general coherent attacks that rigorously incorporates correlations introduced by Alice's bit-and-basis encoder, while requiring only partial characterization of such correlations.