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Volume Bragg gratings for wavelength division multiplexing of entanglement-based quantum key distribution in free space

: Fazili, R.; Steinlechner, F.


Hemmer, P.R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Advanced Optical Techniques for Quantum Information, Sensing, and Metrology : 4-5 February 2020, San Francisco, California, United States
Bellingham, WA: SPIE, 2020 (Proceedings of SPIE 11295)
ISBN: 978-1-5106-3353-7
ISBN: 978-1-5106-3354-4
Paper 112950C, 6 pp.
Conference "Advanced Optical Techniques for Quantum Information, Sensing, and Metrology" <2020, San Francisco/Calif.>
Conference Paper
Fraunhofer IOF ()

Wavelength division multiplexing (WDM) improves key generation rates in quantum key distribution (QKD) and enables multi-user networks using shared quantum resources. The last years have seen a flurry of research on the implementation of WDM in fiber-based QKD where low-loss telecom components are widely available. However, WDM has not yet been demonstrated in free-space and satellite-based quantum communication in the wavelength range detectable by space suitable silicon single photon avalanche diodes. Here, we report a low-loss WDM at around 810 nm based on volume Bragg gratings. The total insertion loss for four wavelength channels matches state-of-the-art telecommunication WDM in the C-band. We characterize the performance in conjunction with a polarization-entangled photon source and report on preliminary assessments of background noise for a terrestrial free-space link in broad daylight.