A team of scientists from the University of the Witwatersrand, South Africa, and Huzhou University, China, has discovered a hidden ‘topological universe’ in entangled light. Using everyday laboratory equipment, the researchers identified more than 17,000 unique patterns in 48 dimensions.
Entangled photons, which are produced by spontaneous parametric down conversion (SPDC), have spatial correlations that result in the formation of topologically robust structures.
“We report a major advance in this work. We only need one property of light, the orbital angular momentum (OAM), to create topological patterns,” says Professor Andrew Forbes from the Wits School of Physics. In the past, scientists thought that two properties were needed, often OAM and polarization.
In this study, the process results in mapping these ‘doughnut-like’ structures in 48 dimensions, yielding more than 17,000 topological signatures, the richest set ever recorded in any physical system. “You get the topology for free, from the entanglement in space.
It was always there; it just had to be found,” says Pedro Ornelas, a key team member. Theoretical guidance from Professor Robert de Mello Koch of Huzhou University helped pinpoint the precise spots where these patterns exist in terms of concepts of quantum field theory.
Topological entanglement helps protect quantum information from noise, a significant problem in quantum computing and communications. The OAM-based systems, once thought to be fragile, can now enable more robust quantum communications systems.
The researchers explained that these 17,000 patterns represent a quantum alphabet that could enable secure communication systems that are hack-resistant.
