title: Twisted light transmission over 143 km.
abstract: Spatial modes of light can potentially carry a vast amount of information, making them promising candidates for both classical and quantum communication. However, the distribution of such modes over large distances remains difficult. Intermodal coupling complicates their use with common fibers, whereas free-space transmission is thought to be strongly influenced by atmospheric turbulence. Here, we show the transmission of orbital angular momentum modes of light over a distance of 143 km between two Canary Islands, which is 50× greater than the maximum distance achieved previously. As a demonstration of the transmission quality, we use superpositions of these modes to encode a short message. At the receiver, an artificial neural network is used for distinguishing between the different twisted light superpositions. The algorithm is able to identify different mode superpositions with an accuracy of more than 80% up to the third mode order and decode the transmitted message with an error rate of 8.33%. Using our data, we estimate that the distribution of orbital angular momentum entanglement over more than 100 km of free space is feasible. Moreover, the quality of our free-space link can be further improved by the use of state-of-the-art adaptive optics systems.
authors.affiliation: Faculty of Physics, Vienna Center for Quantum Science and Technology, University of Vienna, A-1090 Vienna, Austria; mario.krenn@univie.ac.at anton.zeilinger@univie.ac.at.|Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Mario
authors.initials: M
authors.lastname: Krenn
authors.affiliation: Faculty of Physics, Vienna Center for Quantum Science and Technology, University of Vienna, A-1090 Vienna, Austria.|Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Handsteiner
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Fink
authors.affiliation: Faculty of Physics, Vienna Center for Quantum Science and Technology, University of Vienna, A-1090 Vienna, Austria.|Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.|Department of Physics, University of Ottawa, Ottawa, ON, Canada K1N 6N5.|Max Planck Centre for Extreme and Quantum Photonics, University of Ottawa, Ottawa, ON, Canada K1N 6N5.
authors.forename: Robert
authors.initials: R
authors.lastname: Fickler
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Rupert
authors.initials: R
authors.lastname: Ursin
authors.affiliation: Faculty of Physics, Vienna Center for Quantum Science and Technology, University of Vienna, A-1090 Vienna, Austria.|Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Mehul
authors.identifier: 0000-0001-8395-160X
authors.initials: M
authors.lastname: Malik
authors.affiliation: Faculty of Physics, Vienna Center for Quantum Science and Technology, University of Vienna, A-1090 Vienna, Austria; mario.krenn@univie.ac.at anton.zeilinger@univie.ac.at.|Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-1090 Vienna, Austria.
authors.forename: Anton
authors.initials: A
authors.lastname: Zeilinger
keywords: atmospheric turbulence; high-dimensional states; long-distance communication; orbital angular momentum