Measurement-device-independent quantum key distribution over 200 km

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Quantum Communication Networks

Background:

• Measurement-device-independent quantum key distribution (MDIQKD) offers information-theoretical security against detector attacks, even with imperfect detectors.
• Previous MDIQKD demonstrations were limited by short distances and low key rates (<0.1 bit/s).

Purpose of the Study:

• To significantly extend the secure transmission distance of MDIQKD.
• To dramatically increase the secure key rate for MDIQKD.
• To advance the development of practical quantum networks with enhanced security.

Main Methods:

• Development of a fully automatic, highly stable 75 MHz clock rate system.
• Utilization of superconducting nanowire single-photon detectors with over 40% detection efficiency.
• Implementation of MDIQKD over extended fiber optic links.

Main Results:

• Extended secure MDIQKD transmission distance to 200 km.
• Achieved a secure key rate three orders of magnitude higher than previous demonstrations.
• Demonstrated a robust and stable MDIQKD system.

Conclusions:

• The developed system and detectors enable long-distance MDIQKD with unprecedented key rates.
• These advancements are crucial for building secure quantum networks.
• MDIQKD is a viable technology for future secure communication infrastructure.