By 31 March 2011 | Categories: news


Communication technologies have seen rapid advancements in recent years, from cables to wireless to cloud-based technology. But now researchers at the CSIR are pursuing methods of transmitting signals through the use of quantum mechanics.

At the CSIR's National Laser Centre (NLC), a team of researchers are pursuing Free Space Quantum Communication, that is, transmitting optical signals by using the quantum properties of laser light.

Project leader Dr. Stef Roux stated that the purpose of the research is to provide a safe and secure way of communicating via lasers instead of using fibre optic cables. “We want to communicate through the atmosphere from one tower to another – in the line of sight – using light,” said Roux. “We are trying to use quantum properties of light to communicate in a secure way.”

Roux said that traditional cable systems such as today's optical fibre cables can be easily tampered with, but that interference in quantum communication would be impossible without the system being able to detect it. According to Roux, the fledgling technology, “can be used in any form of communication intended for transmission in a secure fashion.”

Roux attempts to explain the physics behind the project saying, “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.”

The project is still in its infancy, being only a year old, but Roux says they have already made progress. A theoretical framework to predict how long quantum entanglement can be maintained has already been derived. It works like this – when entangled photons are sent through a turbulent atmosphere (like our own), they lose their entanglement in a process called de-coherence. The framework aims to predict how far entanglement can be maintained in a turbulent atmosphere.

“It [turbulence] seriously affects the entanglement of photons in that variations (changes) 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.

The refractive index mentioned above is simply a measure of the speed of light within a certain substance. For example, light travels at its maximum speed through a vacuum (space), but it travels slower when moving through any given material (such as our atmosphere).

On the experimental side, he notes, “We are still in the process of getting a proper laser and to get entanglement.”

Roux is also involved in a related project aimed at addressing the challenges of quantum computing. A quantum computer, unlike a regular computer which uses electrical signals, communicates via quantum mechanical phenomena such as the superposition of quantum particles and quantum entanglement to perform operations. The research is still at a very early stage, Roux said, “We are trying to figure out how to implement the elementary processes necessary to do quantum computations.”

“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.”

If you didn't understand much of this article, do not be alarmed, just know that these groundbreaking technologies have the potential of transforming the way we communicate and compute. Roux believes we should seize on this technology locally, saying, “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.”


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