Activity: Talk or presentation › Oral presentation
Performing quantum key distribution in fibre-optic networks over long distances is challenging due to inherent losses in fibre-optic cable and the inefficiency of quantum amplifier and repeater technology. To enable global quantum key distribution it is widely recognised that free-space channels between ground stations and airborne high-altitude platforms or satellite nodes is the fastest approach. Research initiatives around the globe are already performing proof-of-principle studies and field trials, for instance in China, Japan, Singapore, Europe, Canada, and other international partners. Wavefront distortions and intensity fluctuations due to atmospheric turbulence can lead to pointing-and-tracking errors during the quantum key sharing process in free-space quantum communication. These resultant errors can significantly increase the qubit error rate for time-bin quantum key distribution protocols due to a reduction in interferometric visibility with the changing angle-of-incidence. Here we present a time-bin optical receiver, designed to be robust to turbulent multimode free-space channels as well as pointing-and-tracking errors1. The receiver implemented a novel single-photon avalanche diode 2D array allowing us to measure the qubit time-bin information and incident position simultaneously. This allows us the possibility to reduce the complexities of conventional pointing and tracking for future demonstration. A wide aperture telescope was included in the design to enable a wide range of angles-of-incidence to be demonstrated. The presentation will include the concept design of the wide-angle receiver, and show operation performance for single and multimode free-space channels for a range of angles-of-incidence. 1. Jin, J. et al. Efficient time-bin qubit analyzer compatible with multimode optical channels. arXiv 4, 10 (2015).