Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 77: Quantum Networks: Platforms and Components II

FM 77.4: Talk

Thursday, September 26, 2019, 15:00–15:15, 1098

Evaluation of Volume Bragg Gratings as a Wavelength Division Multiplexer in Entanglement-Based Free-Space Quantum Link — •Riza Fazili¹ and Fabian Steinlechner² — ¹Friedrich-Schiller University Jena, Abbe School of Photonics, Albert-Einstein-Str. 5, 07745 Jena, Germany — ²Fraunhofer Institute for Applied Optics and Precision Engineering IOF, Albert-Einstein-Str. 7, 07745 Jena, Germany

It has been shown that wavelength division multiplexing (WDM) is feasible in quantum key distribution (QKD) and has many advantages such as raising the key generation rate. Whereas all the previous attempts of multiplexing in quantum communication have been via optical fibers, a WDM in free-space quantum links can play a more crucial role due to technical challenges in particular the limited time window of the satellite-ground communication. Here, we report on designing and implementing the first low-loss WDM in entanglement-based free-space QKD using volume Bragg gratings (VBGs) at ~800 nm. The total insertion loss for two channels is 0.6 dB which matches the state of the art at telecommunication wavelengths (~1550 nm) and surpasses any known WDMs at ~800 nm. The low cross talk of 20 dB in 0.3 nm in our WDM, unleash the potential of having many channels in a given entangled photons spectrum. We demonstrate that our WDM could operate under turbulence effects and the insertion loss is ~0.6 dB for weak and ~2 dB for strong turbulences. This ability would simplify the coupling procedure at the receiving telescope and can be a game changing factor in the future of free-space QKD.