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Quantum key distribution over free space

: Beutel, F.; Rödiger, J.; Perlot, N.; Freund, R.; Benson, O.


Bartolo, B. di:
Quantum nano-photonics
Dordrecht: Springer, 2018 (NATO Science for Peace and Security. Series B, Physics and biophysics)
ISBN: 978-94-024-1543-8
Advanced Study Institute of Quantum Nano-Photonics <2017, Erice>
Fraunhofer HHI ()

Quantum key distribution (QKD) enables the creation of a common secret key between two remote parties that are connected by a quantum channel. In the time-frequency (TF)-QKD scheme, Alice encodes her bits either in the arrival time (Pulse Position Modulation) or in the center frequency (Frequency Shift Keying) of weak laser pulses. We have successfully implemented the TF-QKD scheme by using mostly off-the-shelf telecom components and avalanche photodiodes operating at 1550 nm. With our setup we achieve secret-key rates of more than 400 kbit/s back-to-back and 80 kbit/s over a 25 km fiber spool. Furthermore, we have tested our scheme over an outdoor free-space test range of 390 m in the Berlin city center and are currently in the process of extending it to longer outdoor test ranges.