In collaboration with the Chinese Academy of Sciences, in particular with the group of Jian-Wei Pan from the University of Science and Technology of China, we have been working on implementing quantum communication protocols between a Low-Earth-Orbit satellite and receiving stations on earth. The goal was to demonstrate secure quantum key distribution based on a decoy state protocol [1] intercontinentally between optical ground stations in Europe and China.

The satellite – named after the Chinese philosopher “Micius” – has been developed and constructed by our partners in China [2,3] and is in-orbit since 2016. Our group has developed the required technology for optical ground stations in Europe and executed the necessary adaptations. In 2017 we have performed downlink experiments to the laser ranging station in Graz Lustbühel (Austria).  We implemented the decoy state protocol and distributed secure quantum keys  between the optical ground station in Graz (Austria) and optical ground stations in Xinglong and Nanshan(China)[4] using “Micius” as trusted relay station. Finally, this key was used for the first intercontinental video call encrypted via quantum methods, demonstrated that a tap-proof quantum internet is no longer an utopian vision[5].

In the near future, downlinks to the optical ground station in Tenerife, IQOQI’s mobile ground station and the Hedy Lamarr telescope are forseen.

The satellite „Micius“ above the optical ground station in Graz(Lustbühel). The ground station sends a red beacon laser(671nm) towards the satellite whereupon the satellite answers with a green beacon laser (532nm) used for tracking and pointing. In addition the satellite sends also randomly polarized single photons for the actual quantum key exchange.
Time-lapse video of „Micius“ passing over the optical ground station in Graz. The whole pass takes in real time around 5 minutes.

[1] V. Scarani, H. Bechmann-Pasquinucci, N. J. Cerf, M. Dušek, N. Lütkenhaus, M. Peev, The security of practical quantum key distributions, Rev. Mod. Phys. 81, 1301-1350 (2009).

[2] Sheng-Kai Liao, Wen-Qi Cai, Wei-Yue Liu, Liang Zhang, Yang Li, Ji-Gang Ren, Juan Yin, Qi Shen, Yuan Cao, Zheng-Ping Li, Feng-Zhi Li, Xia-Wei Chen, Li-Hua Sun, Jian-Jun Jia, Jin-Cai Wu, Xiao-Jun Jiang, Jian-Feng Wang, Yong-Mei Huang, Qiang Wang, Yi-Lin Zhou, Lei Deng, Tao Xi, Lu Ma, Tai Hu, Qiang Zhang, Yu-Ao Chen, Nai-Le Liu, Xiang-Bin Wang, Zhen-Cai Zhu, Chao-Yang Lu, Rong Shu, Cheng-Zhi Peng, Jian-Yu Wang & Jian-Wei Pan, Satellite-to-ground quantum key distribution, Nature 549, 43 (2017)

[3] Juan Yin, Yuan Cao1, Yu-Huai Li, Sheng-Kai Liao, Liang Zhang, Ji-Gang Ren, Wen-Qi Cai, Wei-Yue Liu, Bo Li, Hui Dai1, Guang-Bing Li, Qi-Ming Lu1, Yun-Hong Gong, Yu Xu, Shuang-Lin Li, Feng-Zhi Li, Ya-Yun Yin, Zi-Qing Jiang, Ming Li, Jian-Jun Jia, Ge Ren, Dong He, Yi-Lin Zhou, Xiao-Xiang Zhang, Na Wang, Xiang Chang, Zhen-Cai Zhu, Nai-Le Liu, Yu-Ao Chen, Chao-Yang Lu, Rong Shu, Cheng-Zhi Peng, Jian-Yu Wang, Jian-Wei Pan, Satellite-based entanglement distribution over 1200 kilometers, Science 356, 1140 (2017)

[4] Sheng-Kai Liao, Wen-Qi Cai, Johannes Handsteiner, Bo Liu, Juan Yin, Liang Zhang, Dominik Rauch, Matthias Fink, Ji-Gang Ren, Wei-Yue Liu, Yang Li, Qi Shen, Yuan Cao, Feng-Zhi Li, Jian-Feng Wang, Yong-Mei Huang, Lei Deng, Tao Xi, Lu Ma, Tai Hu, Li Li, Nai-Le Liu, Franz Koidl, Peiyuan Wang, Yu-Ao Chen, Xiang-Bin Wang, Michael Steindorfer, Georg Kirchner, Chao-Yang Lu, Rong Shu, Rupert Ursin, Thomas Scheidl, Cheng-Zhi Peng, Jian-Yu Wang, Anton Zeilinger, and Jian-Wei Pan, Satellite-Relayed Intercontinental Quantum Network,
Physical Review Letters 120, 3(2018)

[5] Austrian and Chinese Academies of Sciences successfully conducted first inter-continental quantum video call(2017)

Zeilinger Group