Quantum Computation and Information Seminar 

25/11/2011, 11:30 — 12:30 — Room P3.10, Mathematics Building
Marcos Curty, U Vigo

Taming detector side channels in quantum cryptography

Despite its often praised unconditional security, quantum key distribution (QKD) also relies on assumptions. Some of them are quite natural, such as the validity of quantum mechanics, the existence of true random number generators, or the assumption that the legitimate users are well shielded from the eavesdropper. Other assumptions, such as considering that the honest parties have an accurate and complete description of their physical devices, are more severe. Obviously, if the functioning of the real setup differs from that considered in the mathematical model, this may become completely vulnerable to new types of attacks not covered by the security proof. Indeed, quantum hacking against commercial QKD systems, particularly detector side channel attacks, have emerged as a hot topic. Here, we investigate a simple solution to this problem — measurement device independent QKD. It not only removes all detector side channels, but also doubles the secure distance with conventional lasers. In comparison to full device independent QKD (diQKD), our scheme does not require detectors of near unity detection efficiency in combination with a qubit amplifier or a quantum non-demolition measurement of the number of photons in a pulse, but can be implemented with standard optical components with low detection efficiency and highly lossy channels. Furthermore, its key generation rate is many orders of magnitude higher than that based on full diQKD.