Measurement-Device-Independent Quantum Key Distribution

TLDR

Removing detector side‑channel attacks has been a notoriously hard problem in quantum cryptography. The authors propose measurement‑device‑independent QKD as a simple solution to eliminate these attacks. The scheme uses standard optical components with low detection efficiency and tolerates highly lossy channels. It removes all detector side channels, doubles the secure distance with conventional lasers, achieves key rates many orders of magnitude higher than full device‑independent QKD, and enables secure 200‑km quantum cryptography even with flawed detectors.

Abstract

How to remove detector side channel attacks has been a notoriously hard problem in quantum cryptography. Here, we propose a simple solution to this problem--measurement-device-independent quantum key distribution (QKD). It not only removes all detector side channels, but also doubles the secure distance with conventional lasers. Our proposal can be implemented with standard optical components with low detection efficiency and highly lossy channels. In contrast to the previous solution of full device independent QKD, the realization of our idea does not require detectors of near unity detection efficiency in combination with a qubit amplifier (based on teleportation) or a quantum nondemolition measurement of the number of photons in a pulse. Furthermore, its key generation rate is many orders of magnitude higher than that based on full device independent QKD. The results show that long-distance quantum cryptography over say 200 km will remain secure even with seriously flawed detectors.