2015-10-23

The Research group of Prof. GUO Guangcan from the Key Laboratory of Quantum Information, CAS made great progress in the quantum key distribution. Researcher YIN Zhenqiang,WANG Shuang, HAN Zhengfu and CHEN Wei et al. realized the first reference-frame-independent (RFI) measurement-device-independent (MDI) quantum key distribution (QKD) experiment around the world. The rejection of the phase-frame-calibrating part will intrinsically reduce the consumption of resources as well as the potential security flaws of practical MDI systems, and exhibit its potential advantage in mature MDI QKD scenarios. This work was published on Physical Review Letters [Phys. Rev. Lett. 115, 160502 (2015)] as editors’ suggestion with the title of “Phase-Reference-Free Experiment of Measurement-Device-Independent Quantum Key Distribution”.

QKD provides an optimal way for two distant parties to share secret keys because of its unconditional security. But due to the imperfection of practical devices, QKD systems rarely conform the idealized models, which result in various security loopholes. The MDI QKD, proposed by H. K. Lo in 2012, does not rely on any assumption of measurement devices; thus, it is intrinsically immune to all detector side-channel attacks, and provides a practical solution to detector loopholes in real-world QKD systems. However, the reference frames from all parties of MDI QKD system are supposed to be strictly synchronized, which may be a critical technical challenge owing to the complex real-life conditions and will result in expensive overheads.

To solve this problem, Prof. Zheng-Fu Han’s group proposed the RFI MDI QKD protocol, which is immune to detector-side-channel attacks without the two parties having aligned reference frames. Then, based on the self-developed timing, polarization and wave chopping alignment system, as well as Faraday-Michelson interferometers with self-owned independent intellectual property rights, the group successfully accomplished the first phase-coding RFI MDI QKD experiment that requires no phase alignment between two remote parties. The result shows this novel scheme can fundamentally reduce the requirements of phase reference frame calibrating, and avoid the extra consumption of resources and potential security flaws of MDI QKD protocol. This can be practical and promising in complex conditions.

Prof. Zheng-Fu Han’s group is engaged in quantum key distribution research since 1999, they have overcome some key issues of QKD research, such as the stability of end-to-end QKD system, expansibility of optical full-time all-pass quantum network and so on. And recent work will further advance the practicability of secure QKD systems.

This work was supported by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences, the National Basic Research Program of China and the National Natural Science Foundation of China.

(School of Physical Sicences)