Adjustable spatial filter for optimal free-space quantum communication round the clock

作     者：Kržič, Andrej Döll, Nico Chandrashekara, Uday Spiess, Christopher Steinlechner, Fabian 

作者机构：Fraunhofer Institute for Applied Optics and Precision Engineering Albert-Einstein-Str. 7 Jena07745 Germany Abbe Center of Photonics Friedrich Schiller University Jena Albert-Einstein-Str. 6 Jena07745 Germany 

出 版 物：《Optics Express》 (Opt. Express)

年 卷 期：2023年第31卷第20期

页      面：32362-32372页

核心收录：

学科分类：0810[工学-信息与通信工程] 070207[理学-光学] 0809[工学-电子科学与技术（可授工学、理学学位）] 07[理学] 08[工学] 0803[工学-光学工程] 0702[理学-物理学] 

基　　金：Bundesministerium für Bildung und Forschung (16KIS1263K) European Space Agency (4000125842/18/NL/MH/mg).Acknowledgments. We thank Herbert Gross for fruitful discussions and help with the spatial filter design Mirko Liedtke and Carl Zeiss Microscopy GmbH for providing the adjustable field stop Sakshi Sharma for help with the entangled pair source Matthias Goy and Daniel Heinig for experimental support Stadtwerke Jena for giving us access to their rooftop for experiments. This research was conducted within the scope of the project QuNET, funded by the German Federal Ministry of Education and Research (BMBF) in the context of the federal government’s research framework in IT-security "Digital. Secure. Sovereign." AK and CS are part of the Max Planck School of Photonics supported by the BMBF, the Max Planck Society, and the Fraunhofer Society. AK is supported by ESA through the Networking/Partnering Initiative 

主　　题：Quantum communication 

摘      要：Free-space quantum communication in daylight relies crucially on spatial filtering. The optimal filter configuration, however, depends on ever-changing link conditions. To this end, we developed an adjustable spatial filter that can be used to change the system field of view on the fly. We demonstrate its use in quantum key distribution over a 1.7-km free-space link. Furthermore, we compare it to filtering with multi-mode fiber coupling. Finally, we extrapolate our results to a broader range of realistic link conditions and show that active field-of-view optimization has the potential to substantially improve the overall secure key output of the system. © 2023 Optica Publishing Group.