Finite-key analysis for practical implementations of quantum key distribution

TL;DR

This paper develops finite-key security bounds for practical quantum key distribution implementations, enabling more realistic security assurances for real-world quantum communication systems.

Contribution

It provides the first finite-key unconditional security bounds for both prepare-and-measure and entanglement-based QKD, including decoy state protocols, tailored for experimental application.

Findings

Finite-key bounds for prepare-and-measure QKD without decoy states.

Finite-key bounds for entanglement-based QKD.

Simplified bounds for prepare-and-measure with decoy states.

Abstract

The lists of bits processed in quantum key distribution are necessarily of finite length. The need for finite-key unconditional security bounds has been recognized long ago, but the theoretical tools have become available only very recently. We provide finite-key unconditional security bounds for two practical implementations of the Bennett-Brassard 1984 coding: prepare-and-measure implementations without decoy states, and entanglement-based implementations. A finite-key bound for prepare-and-measure implementations with decoy states is also derived under a simplified treatment of the statistical fluctuations. The presentation is tailored to allow direct application of the bounds in experiments. Finally, the bounds are also evaluated on a priori reasonable expected values of the observed parameters.