Finite-key analysis for measurement-device-independent quantum key distribution

TL;DR

This paper provides a rigorous finite-key security proof for measurement-device-independent quantum key distribution, demonstrating its practical feasibility for long-distance secure communication.

Contribution

It extends security proofs to finite-key scenarios using large deviation theory, enabling practical long-distance MDI-QKD implementations.

Findings

Security proof valid for finite keys and general attacks

Demonstrates feasibility of long-distance MDI-QKD

Uses Chernoff bound for parameter estimation

Abstract

Quantum key distribution promises unconditionally secure communications. However, as practical devices tend to deviate from their specifications, the security of some practical systems is no longer valid. In particular, an adversary can exploit imperfect detectors to learn a large part of the secret key, even though the security proof claims otherwise. Recently, a practical approach---measurement-device-independent quantum key distribution---has been proposed to solve this problem. However, so far its security has only been fully proven under the assumption that the legitimate users of the system have unlimited resources. Here we fill this gap and provide a rigorous security proof against general attacks in the finite-key regime. This is obtained by applying large deviation theory, specifically the Chernoff bound, to perform parameter estimation. For the first time we demonstrate the feasibility of long-distance implementations of measurement-device-independent quantum key distribution within a reasonable time-frame of signal transmission.