High-Rate Free-Running Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution with Classified Distillation

TL;DR

This paper introduces a novel free-running RFI-MDI-QKD protocol with classification-distillation that sustains high key rates despite rapid reference-frame changes, outperforming previous methods significantly and enabling practical mobile quantum communication.

Contribution

It presents a new protocol that maintains high key rates under fast reference-frame variations using classification-distillation, without requiring hardware modifications.

Findings

Key rate more than nine times higher than previous schemes

Tolerates channel losses exceeding 24 dB

Enables practical quantum key distribution on mobile platforms

Abstract

Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) eliminates detector side-channel attacks and avoids reference-frame calibration. While its feasibility has been widely demonstrated, existing implementations typically assume fixed or slowly drifting reference-frame misalignment, conditions rarely satisfied outside the laboratory. In realistic environments, rapid and free-running reference-frame variations can severely degrade both the key rate and transmission distance of conventional RFI-MDI-QKD. Here we propose a free-running RFI-MDI-QKD protocol that maintains high-rate key generation under rapid reference-frame variations. By introducing a classification-distillation method that reclassifies total detection events, secure keys can be extracted without modifying the experimental setup. Our protocol achieves a key rate more than nine times higher than the best previous RFI-MDI-QKD scheme and tolerates channel losses exceeding 24 dB, where earlier approaches fail. These results enable practical quantum key distribution on mobile platforms, including satellite-to-ground links and airborne nodes.