Experimental quantum key distribution with source flaws

TL;DR

This paper demonstrates secure quantum key distribution over long distances using imperfect sources, providing rigorous security bounds and addressing real-world device flaws, advancing practical quantum cryptography.

Contribution

It presents the first experimental demonstration of secure decoy-state QKD with source flaws and finite-key security bounds against coherent attacks.

Findings

Achieved secure QKD over long distances with source imperfections

Quantified source flaws experimentally and incorporated into security analysis

Demonstrated robustness against channel loss despite device imperfections

Abstract

Decoy-state quantum key distribution (QKD) is a standard technique in current quantum cryptographic implementations. Unfortunately, existing experiments have two important drawbacks: the state preparation is assumed to be perfect without errors and the employed security proofs do not fully consider the finite-key effects for general attacks. These two drawbacks mean that existing experiments are not guaranteed to be secure in practice. Here, we perform an experiment that for the first time shows secure QKD with imperfect state preparations over long distances and achieves rigorous finite-key security bounds for decoy-state QKD against coherent attacks in the universally composable framework. We quantify the source flaws experimentally and demonstrate a QKD implementation that is tolerant to channel loss despite the source flaws. Our implementation considers more real-world problems than most previous experiments and our theory can be applied to general QKD systems. These features constitute a step towards secure QKD with imperfect devices.