Research done by University of the Witwatersrand (Wits) scientists shows that nature cannot always tell the difference between the quantum and the classical (or real) worlds.
The discovery has implications for fast and secure data transfer and will aid technological advances that seek to secure quantum communication links over long distances.
The researchers demonstrated how nature sometimes cannot tell the difference between particular types of laser beams and quantum-entangled photons.
This illustrates that a grey area exists between the quantum and the real worlds – called classical entanglement.
Present communication systems are very fast, but not fundamentally secure, said the researchers.
To make them secure, researchers use the laws of nature for encoding by exploiting the properties of the quantum world – as in the case of Quantum Key Distribution (QKD).
Quantum refers to “the small”, and in the photonics world this means one photon: a single particle of light.
The rules of the quantum world are different to those of the classical world and experiments are traditionally more difficult to conduct due to the difficulty in handling photons.
“In the classical world, our intuition holds true. There are no surprises and experiments can be done with many photons (billions), such as laser light,” said Professor Andrew Forbes, Wits Structured Light Laboratory.
“But not so in the quantum world, where things are never quite as they seem. Here waves sometimes look like particles, particles like waves, and measurements change the properties of the very thing you are trying to measure.”
The newly-discovered grey area opens the possibility of performing quantum experiments with a type of classical light called “classically entangled” light.