South Africa, through the CSIR National Laser Centre (NLC), is one of the frontrunners in pursuit of Free Space Quantum Communication – transmitting optical signals through the air, by using the quantum properties of laser light.
The aim – 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.”
According to him, optical fibres can be tapped or tampered with. With quantum communication, no fiddling or tampering can be executed without the system being able to detect this. Roux said 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 a buzzword internationally. “If we in South Africa jump on this bandwagon and make a significant contribution, it will have a huge impact for South Africa and position us as a key role player for this technology in the world.”
Since the advent of the Internet, information security vulnerabilities emerged such as in the banking sector for instance. Currently, the eThekwini Metropolitan Municipality is already using a quantum cryptography system to communicate, albeit without quantum entanglement. “Quantum entanglement” notes Roux,” has to do with quantum properties of light and there is no classic equivalent of it.”
Roux explains the physics behind this project and paints this picture: “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. Such entangled photons are used in our quantum communication scheme. Should an eavesdropper fiddle with one of them, the other would alert the sender and/or the receiver.”
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 amidst 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. Another possible collaboration with the University of Freiburg in Germany is on the cards. Roux is also in discussions with the University of Ottawa in Canada around this project. He will be visiting this university in the next two months. He says that this university has top class experts in free space communication and he wants to exchange ideas with them.
Bleeding edge of quantum computing
In another related project, Roux is working on quantum computing to address computing challenges. A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena such as, superposition and entanglement to perform operations on data. “At the moment we are at an early stage of this research – the technology development level,” reveals Roux. “We are trying to figure out how to implement the elementary processes necessary to do quantum computations.”
He continues: “We are working with light and we need two things: flying qubits – a unit of quantum information that moves with light – and stationary qubits such as ion traps. In our experiment we focus on the flying qubits.”
He has two doctoral degrees: one in electronic engineering from the University of Pretoria (UP) and another in theoretical particle physics from the University of Toronto in Canada.
Roux, 47, says he became interested in optics while at UP. He then joined the CSIR Aerotech (now known as the CSIR Defence, Peace, Safety and Security’s Aeronautics Systems Competency) in the late 1980s. He later left for the then Potchefstroom University (now North-West University) to work there as a researcher/lecturer.
“While there I developed an interest in particle physics.” Roux could not resist the hankering to study particle physics. He left the university and went to study at the University of Toronto. It is here that he pursued his second doctoral degree in theoretical particle physics. Having fulfilled his ambitions, he returned to optics and went to work for a company called JDS Uniphase Corporation in Ottawa, focusing on the design of optical fibre components.
“While at this company, there was a telecom bust and the timing was bad so I left again – this time for the University of Ottawa,” he says.
Roux eventually returned to South Africa in 2004 and went to work at UP before joining the CSIR NLC in 2009.
CSIR Strategic Communications and Stakeholder Relations
Mzimasi Gcukumana, email: MGcukumana@csir.co.za