Ancient Namibian gems hold the key to future quantum computers

Copper oxide

Copper oxide – the extracted crystal from Namibia used to make Rydberg polaritones. Credit: University of St. Andrews

A special kind of light made using an ancient Namibian gemstone may be the key to new light-based quantum computers that can solve long-lasting scientific mysteries, according to new research led by the University of St. Andrews.

The research was conducted in collaboration with researchers at Harvard University in the USA, Macquarie University in Australia and Aarhus university in Denmark and published in Natural materials, used a naturally extracted copper oxide (Cu2O) Namibian gemstones for the production of Rydberg polaritons, the largest hybrid particles of light and matter ever created.

The Rydberg polaritons are constantly changing from light to substance and back again. In Rydberg polaritons, light and matter are like two sides of a coin, and the substance side is what causes polaritons to interact with each other.

This interaction is crucial because it is what allows the creation of quantum simulators, a special type of quantum computer where information is stored in quantum bits. These quantum bits, unlike the binary bits in classical computers, which can only be 0 or 1, can have any value between 0 and 1. They can therefore store much more information and perform multiple processes simultaneously.

This ability could allow quantum simulators to solve important mysteries in physics, chemistry, and biology, such as how to make high-temperature superconductors for high-speed trains, how to make cheaper fertilizers that potentially solve global hunger, or how proteins fold, making it easier to produce more effective drugs.

Project manager Dr. Hamid Ohadi, from the School of Physics and Astronomy at the University of St. Andrews, said: “Making a quantum simulator with light is the holy grail of science. We have taken a big leap towards this by creating Rydberg polaritons, the most important ingredient in it.”

To create Rydberg polaritons, the researchers captured light between two highly reflective mirrors. A copper oxide crystal from a stone extracted in Namibia was then diluted and polished to a 30 micrometer thick plate (thinner than a hair) and squeezed between the two mirrors to make the Rydberg polaritons 100 times larger than ever before demonstrated.

One of the leading authors Dr. Sai Kiran Rajendran, from the School of Physics and Astronomy at the University of St. Andrews, said: “It was easy to buy the stone on eBay. The challenge was to make Rydberg polaritons, which are found in an extremely narrow range of colors.”

The team is currently refining these methods further to explore the possibility of making quantum circuits, which is the next ingredient in quantum simulators.

Reference: “Rydberg exciton-polaritons in a Cu2O microcavity ”by Konstantinos Orfanakis, Sai Kiran Rajendran, Valentin Walther, Thomas Volz, Thomas Pohl and Hamid Ohadi, 14 April 2022, Natural materials.
DOI: 10.1038 / s41563-022-01230-4

The research was funded by the UK Engineering and Physical Sciences Research Council (EPSRC).