Krenn Mario, Handsteiner Johannes, Fink Matthias, Fickler Robert, Ursin Rupert, Malik Mehul, Zeilinger Anton
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.
Proc Natl Acad Sci U S A. 2016 Nov 29;113(48):13648-13653. doi: 10.1073/pnas.1612023113. Epub 2016 Nov 15.
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.
光的空间模式有可能携带大量信息，这使其成为经典通信和量子通信的理想候选对象。然而，此类模式在长距离上的分布仍然困难重重。模式间耦合使得它们在普通光纤中的应用变得复杂，而自由空间传输则被认为会受到大气湍流的强烈影响。在此，我们展示了光的轨道角动量模式在两个加那利群岛之间143公里距离上的传输，这一距离比此前实现的最大距离大50倍。作为传输质量的一种展示，我们使用这些模式的叠加来编码一条短消息。在接收端，使用人工神经网络来区分不同的扭曲光叠加。该算法能够以超过80%的准确率识别直至三阶模式的不同模式叠加，并以8.33%的错误率解码传输的消息。利用我们的数据，我们估计在超过100公里的自由空间中分布轨道角动量纠缠是可行的。此外，通过使用最先进的自适应光学系统，我们自由空间链路的质量可以进一步提高。
