While researchers are still busy constructing stable quantum computers, they are also working on the infrastructure necessary to have these future computers communicating. Fiber optics and wireless have already been tested, and now we can add the first test to quantum satellite communication.
In a study published in Quantum Science and Technology, researchers from the University of Waterloo have shown that it’s possible to transmit quantum information from a ground station to a moving aircraft. The test could allow quantum communication that cannot be decrypted.
"Quantum key distribution (QKD) establishes cryptographic keys between two distant parties in a way that is cryptanalytically unbreakable,” lead author Christopher Pugh said in a statement. “Ground-based QKD systems use optical fiber links, and are limited to distances of a few hundred kilometers due to absorption losses, which get exponentially worse as the distance increases."
Wireless systems don’t do much better, as they are affected both by losses and atmospheric turbulence. The team thought, then, that instead of sending a signal across the surface of our planet, they could send it up into space and back down again.
"Satellite-based system expands quantum communication to a global scale," he continued.
The system was tested using an aircraft that mimicked how high or low a satellite might appear in the sky. The aircraft, with the name Twin Otter, carried out 14 passes over the facility at varying distances. Only half of the passes were successful in establishing a quantum link, and in six out of those seven passes, the team was successful in extracting the quantum key.
"This is an extremely important step which took almost eight years of preparation. It finally demonstrates our technology is viable,” team leader Professor Thomas Jennewein added. "We achieved optical links at similar angular rates to those of low-Earth-orbit satellites, and for some passes of the aircraft over the ground station, links were established within 10 seconds of position data transmission. We saw link times of a few minutes and received quantum bit error rates typically between three and five percent, generating secure keys up to 868 kb in length.”
"We have proved the concept, and our results provide a blueprint for future satellite missions to build upon, just in time for the announcement of a quantum satellite mission by the Canadian Government," said Jennewein.
Private quantum computers are likely still decades away, but we are making huge progress towards them.