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 used 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 > 10 ×
higher key rate than the 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.
2019-04-28