Experimental demonstration of high-rate measurement-device-independent quantum key distribution over asymmetric channels

TL;DR

This paper demonstrates a high-rate measurement-device-independent quantum key distribution over asymmetric channels, significantly improving key rate and distance in practical, asymmetric network conditions.

Contribution

First experimental demonstration of high-rate MDI-QKD over asymmetric channels using 7-intensity optimization, surpassing previous protocols in key rate and distance.

Findings

Achieved >10x higher key rate in asymmetric channels

Extended secure transmission distance by 20-50 km

Validated practicality of MDI-QKD in asymmetric network settings

Abstract

Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all detector side channels and it is practical with current technology. Previous implementations of MDI-QKD all use two symmetric channels with similar losses. However, the secret key rate is severely limited when different channels have different losses. Here we report the results of the first high-rate MDI-QKD experiment over $asymmetric$ channels. By using the recent 7-intensity optimization approach, we demonstrate $>$10x higher key rate than previous best-known protocols for MDI-QKD in the situation of large channel asymmetry, and extend the secure transmission distance by more than 20-50 km in standard telecom fiber. The results have moved MDI-QKD towards widespread applications in practical network settings, where the channel losses are asymmetric and user nodes could be dynamically added or deleted.