The path to faster and more powerful quantum computers could be paved with a gemstone called cuprite. Its unique properties have long made it useful for quantum research, but a new experiment could provide a stepping stone to transforming computing.
Cuprite is a gemstone formed from Cu2O. It is found in many places, but the only large cuprite crystals come from a single Namibian mine, which is thought to be exhausted. Although it has a pretty red shade, leading it to be known as ruby copper, it is not widely used in jewelry as it is too soft and the stones are usually tiny. Almost all the cuprites large enough to interest jewelers come from a mine in Onganja, Namibia.
Cuprite is significant to physicists because it produces uniquely large – and therefore easier to study – Rydberg excitons (quasiparticles made from bound combinations of electrons and electron holes). A team led by Dr Hamid Ohadi of the University of St Andrews announce they have coupled light to cuprite Rydberg excitons, making the largest matter-light hybrid particles ever created. The results are published in the journal Nature Materials.
Einstein proved energy (including light) and matter are equivalent, give or take division by the speed of light squared. Rydberg polaritons form a bridge between the two, switching back and forth between light and matter. In their matter state, they can interact with each other, opening the door to a type of quantum computer known as a quantum simulator.
Like all quantum computers, quantum simulators break the binary where information must be stored as zeros or ones, allowing it to be stored as anything in between. This enables processes that existing computers perform in sequence to be done simultaneously.
Although quantum simulators cannot perform as wide a range of functions as other quantum computers are theoretically capable of, they are well suited to solving certain important scientific problems. It is hoped they can allow us to understand the behavior of atoms at very cold temperatures and folding structure, for example, in ways that could lead to breakthroughs in superconducting and pharmaceutical design.
“Making a quantum simulator with light is the holy grail of science. We have taken a huge leap towards this by creating Rydberg polaritons, the key ingredient of it," said Ohadi in a statement.
The polaritons were created by polishing a cuprite crystal from Onganja until it was thinner than human hairs – just 0.03 millimeters (0.0012 inches) thick – and placing it between two ultra-reflective mirrors. Light was then trapped between the two mirrors, passing through the crystal to create Ryberg polaritons 0.5 μm wide, 100 times larger than any previously produced.
The next step is to control the polaritons to form quantum circuits.
The Onganja mine closed and flooded many years ago, so synthesizing large cuprite stones could become a priority, if no other natural source can be found. Luckily, this team managed to snag one on eBay.