Securing long-distance quantum communication could be just around the corner if this latest research has anything to do with it. While quantum communication over long distances may have been demonstrated in free space and fiber with 2D states, the link is so slow. In order to make it faster and more secure a higher-dimensional alphabet, such as patterns of light, would be needed.


One such pattern set is called the orbital angular momentum (OAM) of light. If OAM is used as the carrier of information, much higher bit rates can be achieved. The problem is that when transmitted over long distances, these photons states tend to decay. To overcome this, a quantum repeater, similar to that of an amplifier, is used to make a stronger signal.

A quantum repeater is a great device as it enables two photons to become entangled in a process called entanglement swapping. This is where two photons from different entangled pairs interfere and become entangled, reducing the effects of decay and loss as a result. An outcome of this process leads to another process called teleportation where information is simply “teleported” from one area to another. When two photons are entangled, changing the value of one will automatically alter that of the other even though physically these photons are unconnected and in completely different places.


This latest study concentrates on demonstrating the process of entanglement swapping and teleportation for OAM states of light. The team managed to successfully show that quantum correlations could be formed between photons that were previously independent and that this virtual link could be used to send information.

While present communications systems are good in terms of speed, they lack in security. To make them more secure, researchers exploit some of the unique properties of the quantum world, such as entanglement. Entanglement is essential in order for quantum networks to exist. But, even so, securing quantum communication networks over long distance is no easy task. Using patterns of light to establish quantum links are problematic as there’s no way to protect the link between noise. However, researchers got around this by having repeating stations at intermediate distances, allowing more information to be shared across a much further distance.

Research via; University of the Witwatersrand


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