Quantum cryptography or quantum key distribution (QKD) can provide unconditional (i.e. information-theoretic) security based on the laws of quantum physics. It has been identified as the first technology in quantum information science to reach practical applications. During the past decade, commercial QKD products have appeared in the market; various field-test QKD networks have already been built in the USA, Europe, China, and Japan. However, owing to the imperfections in real-life implementations of QKD, a large gap between its theory and practice remains unfilled. In
particular, an eavesdropper may exploit these imperfections and launch quantum hacking not covered by the original security proofs of QKD. In this presentation, I will firstly review the recent developments of the field and discuss the quantum hacking activities by using some well-known quantum attacks for illustration. Then, I will present a novel countermeasure scheme, namely measure- device-independent QKD (MDI-QKD), which removes all attacks in the detection system, the most serious loophole of QKD implementations. Most importantly, I will show how to practically implement MDI-QKD, including a finite decoy-state method, a finite-key analysis and a polarization-encoding experimental demonstration.

Feihu Xu received his B.S. degree (Hons.) from the University of Science and Technology of China in 2009. After that, he went to the Department of Electrical and Computer Engineering, University of Toronto for graduate study, where he received M.A.Sc degree in 2011. Currently, he is a senior Ph.D. student in the same department, University of Toronto, under the supervision of Prof. Li Qian and Prof. Hoi-Kwong Lo. His research interest primarily lies in the field of quantum information processing, particularly in quantum cryptography, quantum communication, quantum random number generation and multi-photon quantum interference.