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Air-to-ground quantum communication


Quantum key distribution1,2 (QKD) is the first commercial application in the new field of quantum information, with first routine applications in government and financial sectors3 and with successful demonstrations of trusted node networks4,5. Today, the main goal is efficient long-range key distribution via either quantum repeaters6 or satellites7,8,9, with a view to enabling global secure communication. En route to achieving QKD via satellites, a free-space demonstration of secure key distribution was performed between two ground stations10, over a distance of 144 km. This scenario is comparable to links between satellites in low Earth orbit and ground stations with respect to both attenuation and fluctuations. However, key exchange with rapidly moving platforms remained to be demonstrated. Here, we prove, for the first time, the feasibility of BB84 QKD between an aeroplane and a ground station. By establishing a stable and low-noise quantum communication channel with the aeroplane moving at 290 km h−1 at a distance of 20 km—that is, 4 mrad s−1—our results are representative of typical communication links to satellites11 or to high-altitude platforms.

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Figure 1: Overview of the classical communication system of the German Aerospace Center's Institute of Communications and Navigation.
Figure 2: QKD and classical communication hardware.
Figure 3: Count rates registered during one aircraft passage (duration 10 min and 4 s).


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The authors acknowledge funding by the EU (Q-ESSENCE) and the German Bundesministerium für Bildung und Forschung (CHIST-ERA project QUASAR). S.N. acknowledges support by the Elite Network of Bavaria through the excellence programme QCCC.

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All authors contributed equally to the realization of the experiment, discussed the results and commented on the manuscript at all stages. S.N., M.R. and S.F. designed, built and operated the QKD hardware new to this project. F.M., C.F. and J.H. initially developed the optical communications (classical) system, took care of modifications and operations and organized the flight campaign, including airworthiness certification. S.N. evaluated the data and H.W. supervised the work.

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Correspondence to Sebastian Nauerth.

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The authors declare no competing financial interests.

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Nauerth, S., Moll, F., Rau, M. et al. Air-to-ground quantum communication. Nature Photon 7, 382–386 (2013).

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