Device-independent quantum key distribution over 100 km with single atoms
Bo-Wei Lu, Chao-Wei Yang, Run-Qi Wang, Boyang Gao, Yi-Zheng Zhen, Zhen-Gang Wang, Jia-Kai Shi, Zhong-Qi Ren, Thomas Hahn, Ernest Y.-Z. Tan, Xiu-Ping Xie, Ming-Yang Zheng, Xiao Jiang, Jun Zhang, Feihu Xu, Q. J. Zhang, Xiao‐Hui Bao, Jian-Wei Pan
Abstract
Device-independent quantum key distribution (DI-QKD) is a key application of the quantum internet. We report the realization of DI-QKD between two single-atom nodes linked by 100-kilometer (km) fibers. To improve the entangling rate, single-photon interference is leveraged for entanglement heralding, and quantum frequency conversion is used to reduce fiber loss. A tailored Rydberg-based emission scheme suppresses the photon recoil effect on the atom without introducing noise. We achieved high-fidelity atom-atom entanglement and positive asymptotic key rates for fiber lengths up to 100 km. At 11 km, 1.2 million heralded Bell pairs were prepared over 624 hours, yielding an estimated extractable finite-size secure key rate of 0.112 bits per event against general attacks. Our results close the gap between proof-of-principle quantum network experiments and real-world applications.