All-photonic quantum key distribution beyond the single-repeater bound

TL;DR

This paper introduces an all-photonic quantum key distribution protocol that surpasses traditional rate-loss limits by leveraging classical signaling speed and a novel architecture, enabling higher key rates without error correction or ideal quantum memories.

Contribution

The authors present a new all-photonic measurement-device-independent protocol exceeding the single-repeater bound and extend twin-field protocols to multiple nodes with a scalable architecture.

Findings

Key rate approaches η^{2/5} when signals travel at two-thirds the classical speed.

Protocol surpasses the single-repeater bound without error correction.

Proposed architecture extends twin-field protocols to multiple nodes.

Abstract

Quantum protocols require classical signaling, and when classical signals propagate faster than quantum ones, standard rate-loss limits can be surpassed. We introduce an all-photonic measurement-device-independent quantum key distribution protocol that exceeds the single-repeater bound without error correction. When quantum signals travel at two-thirds the classical speed, the key rate scaling approaches $\eta^{2/5}$. We propose a single-rail, temporally multiplexed architecture that extends twin-field-type protocols to multiple nodes and surpasses their key rate without ideal quantum memories.