(Phys.org) Researchers from Nanjing University of Posts and Telecommunications have demonstrated secure measurement-device-independent quantum key distribution (MDI-QKD) transmission over a record-breaking 170 kilometers.
Qin Wang from Nanjing University of Posts explains, “We investigate the three-state MDI-QKD protocol with uncharacterized sources and conduct an experimental demonstration, where it allows imperfect state-preparation and the only assumption is the prepared states are in a two-dimensional Hilbert space,” said Wang. “This work significantly improves both the security and practicability of QKD under current technology.”
Although QKD has been demonstrated over relatively long distances, it has been difficult to accomplish this with high transmission rates while maintaining security. To overcome this challenge, Wang developed a new MDI-QKD transmission protocol that uses photons with three characterized quantum states to encode data.
Using a state-of-the-art experimental setup for encoding and detection, the researchers showed that the new QKD approach could transmit keys over longer distances and at higher rates (10-7 /pulse key rate) than other similar measurement-device-independent QKD protocols. Theoretical calculations showed that secure transmission could be possible over distances up to 200 kilometers.