South Africa, through the CSIR National Laser Centre (NLC), is one of the front-runners in pursuit of free space quantum communication - transmitting optical signals through the air using the quantum properties of laser light.
The aim of the channel, according to principal researcher and project leader Dr Stef Roux, is to provide secure and safe ways of communication using lasers as opposed to fibre-optic cables.
“We want to communicate through the atmosphere from one tower to another - in the line of sight - using light,” says Roux. “We are trying to use quantum properties of light to communicate in a secure way.”
He explains that optical fibres can be tapped or tampered with, but with quantum communication, no fiddling or tampering can be executed without the system being able to detect this.
Roux also notes that this technology “can be used in any form of communication intended for transmission in a secure fashion”.
Free space quantum communication, he says, is an international buzzword. “If we, in SA, jump on this bandwagon and make a significant contribution, it will have a huge impact for SA and position us as a key role player for this technology in the world.”
According to Roux, since the advent of the Internet, information security vulnerabilities emerged such as in the banking sector, for instance.
The eThekwini Metropolitan Municipality is already using a quantum cryptography system to communicate, albeit without quantum entanglement, he adds.
“Quantum entanglement has to do with quantum properties of light and there is no classic equivalent of it.”
Roux sheds light on the physics behind this project: “At the quantum level, light consists of photons. One can entangle these photons, which means that we set them up in such a way that by fiddling with one, the other is affected even when they are far apart.
Although the project is only about a year old, Roux has made headway. “We already have theoretical results,” he says.
When entangled, photons are sent through a turbulent atmosphere, they lose their entanglement through a process called de-coherence.
A theoretical framework has been derived with which they hope to predict how far the entanglement can be maintained amid the turbulence in the atmosphere.
“It [turbulence] seriously affects the entanglement of photons in that variations in the temperatures of the atmosphere cause variations in the refractive index of the air and affects the photons,” he says, adding that to mitigate the de-coherence, one can use shorter relay links in the free space quantum communication system with the aid of quantum teleportation.
On the experimental side, he notes: “We are still in the process of getting a proper laser and to get entanglement.”
Roux is collaborating with the University of KwaZulu-Natal for the project. Another possible collaboration with the University of Freiburg in Germany is also on the cards. Roux is also in discussions with the University of Ottawa in Canada around this project.
He will visit the Canadian university in the next two months. He says this university has top-class experts in free space communication and he wants to exchange ideas with them.
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