TY - JOUR

T1 - A device-independent quantum key distribution system for distant users

AU - Zhang, Wei

AU - van Leent, Tim

AU - Redeker, Kai

AU - Garthoff, Robert

AU - Schwonnek, René

AU - Fertig, Florian

AU - Eppelt, Sebastian

AU - Rosenfeld, Wenjamin

AU - Scarani, Valerio

AU - Lim, Charles C.W.

AU - Weinfurter, Harald

N1 - Funding information: We thank I. W. Primaatmaja, E. Y.-Z. Tan and K. T. Goh for useful inputs and discussions. W.Z., T.v.L., K.R., R.G., F.F., S.E., W.R. and H.W. acknowledge funding by the German Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung (BMBF)) within the project Q.Link.X (16KIS0880), QR.X (16KISQ002) the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy (EXC-2111–390814868) and the Alexander von Humboldt foundation. C.C.-W.L. and R.S. are funded by the National Research Foundation, Singapore, under its NRF Fellowship programme (NRFF11-2019-0001) and NRF Quantum Engineering Programme 1.0 (QEP-P2). V.S. and C.C.-W.L. acknowledge support from the National Research Foundation and the Ministry of Education, Singapore, under the Research Centres of Excellence programme.

PY - 2022/7/28

Y1 - 2022/7/28

N2 - Device-independent quantum key distribution (DIQKD) enables the generation of secret keys over an untrusted channel using uncharacterized and potentially untrusted devices1–9. The proper and secure functioning of the devices can be certified by a statistical test using a Bell inequality10–12. This test originates from the foundations of quantum physics and also ensures robustness against implementation loopholes13, thereby leaving only the integrity of the users’ locations to be guaranteed by other means. The realization of DIQKD, however, is extremely challenging—mainly because it is difficult to establish high-quality entangled states between two remote locations with high detection efficiency. Here we present an experimental system that enables for DIQKD between two distant users. The experiment is based on the generation and analysis of event-ready entanglement between two independently trapped single rubidium atoms located in buildings 400 metre apart14. By achieving an entanglement fidelity of ℱ≥0.892(23) and implementing a DIQKD protocol with random key basis15, we observe a significant violation of a Bell inequality of S = 2.578(75)—above the classical limit of 2—and a quantum bit error rate of only 0.078(9). For the protocol, this results in a secret key rate of 0.07 bits per entanglement generation event in the asymptotic limit, and thus demonstrates the system’s capability to generate secret keys. Our results of secure key exchange with potentially untrusted devices pave the way to the ultimate form of quantum secure communications in future quantum networks.

AB - Device-independent quantum key distribution (DIQKD) enables the generation of secret keys over an untrusted channel using uncharacterized and potentially untrusted devices1–9. The proper and secure functioning of the devices can be certified by a statistical test using a Bell inequality10–12. This test originates from the foundations of quantum physics and also ensures robustness against implementation loopholes13, thereby leaving only the integrity of the users’ locations to be guaranteed by other means. The realization of DIQKD, however, is extremely challenging—mainly because it is difficult to establish high-quality entangled states between two remote locations with high detection efficiency. Here we present an experimental system that enables for DIQKD between two distant users. The experiment is based on the generation and analysis of event-ready entanglement between two independently trapped single rubidium atoms located in buildings 400 metre apart14. By achieving an entanglement fidelity of ℱ≥0.892(23) and implementing a DIQKD protocol with random key basis15, we observe a significant violation of a Bell inequality of S = 2.578(75)—above the classical limit of 2—and a quantum bit error rate of only 0.078(9). For the protocol, this results in a secret key rate of 0.07 bits per entanglement generation event in the asymptotic limit, and thus demonstrates the system’s capability to generate secret keys. Our results of secure key exchange with potentially untrusted devices pave the way to the ultimate form of quantum secure communications in future quantum networks.

UR - http://www.scopus.com/inward/record.url?scp=85135031432&partnerID=8YFLogxK

U2 - 10.48550/arXiv.2110.00575

DO - 10.48550/arXiv.2110.00575

M3 - Article

C2 - 35896650

AN - SCOPUS:85135031432

VL - 607

SP - 687

EP - 691

JO - NATURE

JF - NATURE

SN - 0028-0836

IS - 7920

ER -