Twisted Light Transmission over 143 kilometers

TL;DR

This study demonstrates the successful transmission of twisted light modes over 143 kilometers between two Canary Islands, utilizing neural networks for mode identification and message decoding, indicating potential for long-distance quantum communication.

Contribution

First to transmit orbital angular momentum modes over such a long distance of 143 km, showing feasibility for quantum communication and encoding messages with high accuracy.

Findings

Achieved 80% accuracy in mode superposition identification

Decoded messages with an 8.33% error rate

Estimated feasibility of distributing orbital angular momentum entanglement over 100 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, while 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 kilometers between two Canary Islands, which is 50 times 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 kilometers 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.