Entanglement-based secure quantum cryptography over 1,120 kilometres

Juan Yin^{1

2

3}, Yu-Huai Li^{1

2

3}, Sheng-Kai Liao^{1

2

3}, Meng Yang^{1

2

3}, Yuan Cao^{1

2

3}, Liang Zhang^{2

3

4}, Ji-Gang Ren^{1

2

3}, Wen-Qi Cai^{1

2

3}, Wei-Yue Liu^{1

2

3}, Shuang-Lin Li^{1

2

3}, Rong Shu^{2

3

4}, Yong-Mei Huang⁵, Lei Deng⁶, Li Li^{1

2

3}, Qiang Zhang^{1

2

3}, Nai-Le Liu^{1

2

3}, Yu-Ao Chen^{1

2

3}, Chao-Yang Lu^{1

2

3}, Xiang-Bin Wang², Feihu Xu^{1

2

3}, Jian-Yu Wang^{2

3

4}, Cheng-Zhi Peng^{7

8

9}, Artur K Ekert^{10

11}, Jian-Wei Pan^{12

13

14}

Affiliations

¹ Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China.
² Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
³ Shanghai Research Center for Quantum Science, Shanghai, China.
⁴ Key Laboratory of Space Active Opto-Electronic Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China.
⁵ The Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, China.
⁶ Shanghai Engineering Center for Microsatellites, Shanghai, China.
⁷ Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China. pcz@ustc.edu.cn.
⁸ Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China. pcz@ustc.edu.cn.
⁹ Shanghai Research Center for Quantum Science, Shanghai, China. pcz@ustc.edu.cn.
¹⁰ Mathematical Institute, University of Oxford, Oxford, UK.
¹¹ Centre for Quantum Technologies, National University of Singapore, Singapore, Singapore.
¹² Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China. pan@ustc.edu.cn.
¹³ Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China. pan@ustc.edu.cn.
¹⁴ Shanghai Research Center for Quantum Science, Shanghai, China. pan@ustc.edu.cn.

PMID: 32541968
DOI: 10.1038/s41586-020-2401-y

Entanglement-based secure quantum cryptography over 1,120 kilometres

Juan Yin et al. Nature. 2020 Jun.

. 2020 Jun;582(7813):501-505.

doi: 10.1038/s41586-020-2401-y. Epub 2020 Jun 15.

Authors

Affiliations

¹ Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China.
² Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China.
³ Shanghai Research Center for Quantum Science, Shanghai, China.
⁴ Key Laboratory of Space Active Opto-Electronic Technology, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China.
⁵ The Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, China.
⁶ Shanghai Engineering Center for Microsatellites, Shanghai, China.
⁷ Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China. pcz@ustc.edu.cn.
⁸ Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China. pcz@ustc.edu.cn.
⁹ Shanghai Research Center for Quantum Science, Shanghai, China. pcz@ustc.edu.cn.
¹⁰ Mathematical Institute, University of Oxford, Oxford, UK.
¹¹ Centre for Quantum Technologies, National University of Singapore, Singapore, Singapore.
¹² Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, China. pan@ustc.edu.cn.
¹³ Shanghai Branch, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai, China. pan@ustc.edu.cn.
¹⁴ Shanghai Research Center for Quantum Science, Shanghai, China. pan@ustc.edu.cn.

PMID: 32541968
DOI: 10.1038/s41586-020-2401-y

Abstract

Quantum key distribution (QKD)^1-3 is a theoretically secure way of sharing secret keys between remote users. It has been demonstrated in a laboratory over a coiled optical fibre up to 404 kilometres long^4-7. In the field, point-to-point QKD has been achieved from a satellite to a ground station up to 1,200 kilometres away^8-10. However, real-world QKD-based cryptography targets physically separated users on the Earth, for which the maximum distance has been about 100 kilometres^11,12. The use of trusted relays can extend these distances from across a typical metropolitan area^13-16 to intercity¹⁷ and even intercontinental distances¹⁸. However, relays pose security risks, which can be avoided by using entanglement-based QKD, which has inherent source-independent security^19,20. Long-distance entanglement distribution can be realized using quantum repeaters²¹, but the related technology is still immature for practical implementations²². The obvious alternative for extending the range of quantum communication without compromising its security is satellite-based QKD, but so far satellite-based entanglement distribution has not been efficient²³ enough to support QKD. Here we demonstrate entanglement-based QKD between two ground stations separated by 1,120 kilometres at a finite secret-key rate of 0.12 bits per second, without the need for trusted relays. Entangled photon pairs were distributed via two bidirectional downlinks from the Micius satellite to two ground observatories in Delingha and Nanshan in China. The development of a high-efficiency telescope and follow-up optics crucially improved the link efficiency. The generated keys are secure for realistic devices, because our ground receivers were carefully designed to guarantee fair sampling and immunity to all known side channels^24,25. Our method not only increases the secure distance on the ground tenfold but also increases the practical security of QKD to an unprecedented level.

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Comment in

A step closer to secure global communication.
Diamanti E. Diamanti E. Nature. 2020 Jun;582(7813):494-495. doi: 10.1038/d41586-020-01779-7. Nature. 2020. PMID: 32572251 No abstract available.

References

1. Bennett, C. H. & Brassard, G. Quantum cryptography: public key distribution and coin tossing. In Proc. Int. Conf. on Computers, Systems and Signal Processing 175–179 (1984).
1. Ekert, A. K. Quantum cryptography based on Bell’s theorem. Phys. Rev. Lett. 67, 661 (1991). - PubMed
1. Bennett, C. H., Brassard, G. & Mermin, N. D. Quantum cryptography without Bell’s theorem. Phys. Rev. Lett. 68, 557 (1992). - PubMed
1. Peng, C.-Z. et al. Experimental long-distance decoy-state quantum key distribution based on polarization encoding. Phys. Rev. Lett. 98, 010505 (2007). - PubMed
1. Rosenberg, D. et al. Long-distance decoy-state quantum key distribution in optical fiber. Phys. Rev. Lett. 98, 010503 (2007). - PubMed

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Entanglement-based secure quantum cryptography over 1,120 kilometres

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Entanglement-based secure quantum cryptography over 1,120 kilometres

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