Gems from Namibia may hold a key to quantum computers in the future

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An international team of researchers has succeeded in producing Rydberg polaritons from ore containing copper oxide crystals from ancient deposits in Namibia. The resulting particles are the largest hybrid particles of light and matter ever created and could hold the key to new light-based quantum computers.

Atoms can interact with each other but move very slowly while photons move quickly but do not interact with each other. However, producing optical photons and making them interact in a controlled manner are necessary prerequisites for the development of long-range quantum communications and, more generally, for the quantum processing of information encoded on photons.

To achieve this goal, one way is to create hybrid particles, whether matter or light, called Rydberg polaritons; These particles are transmitted almost constantly from light to matter and vice versa. A team has now reported the formation of such particles using a crystal of copper oxide (Cu2s). Their work constitutes a real breakthrough: interactions between polaritons are essential to creating quantum simulators, which can solve science’s greatest mysteries.

Exciting interactions between photons

Making a quantum simulator with light is the holy grail of science Hamid Ohadi, a physicist at the University of St Andrews in the UK and co-author of the study that presented this work, said in a press release. A quantum simulator is a special type of quantum computer that controls the interactions between quantum bits (qubits) so that it can simulate some quantum problems that are particularly difficult to model. In other words, the simulator is more specific than a quantum computer – which should be able to solve any kind of problem.

The researchers at Polariton Rydberg, explain that light and matter are two sides of the same coin. It is the aspect of matter that makes the polaritons interact with each other. They are formed through the coupling of excitons and photons. To produce it, the researchers used a precious stone (called cuprite) containing copper oxide, because when cooled to a critical temperature, this material is a super-strong conductor. Previous research has also shown that copper oxide contains “giant” Rydberg oxytones on the order of the micrometer – a dimension that favors interactions.

Excitons are electrically neutral quasi-particles – which can be thought of as an electron-hole pair, bound by Coulomb forces – which under the right conditions can couple with particles of light. Thus, copper oxide excitons can be coupled to photons, in a device called a Fabry-Perot interferometer, consisting of two plane, parallel, semi-reflecting mirrors, with high reflection coefficients. In this interferometer, the incoming light makes multiple trips back and forth within the optical cavity and appears partially at each reflection, and the outgoing rays interfere with each other.

The researchers used such a device to create a Rydberg polariton. A copper oxide crystal, taken from a stone extracted from ancient sulfur deposits in Namibia, was softened and polished to obtain a plate 30 micrometers thick (thinner than a strand of human hair!); This plate was then inserted between two highly reflective mirrors.

Fundamentals of future quantum circuits

Thanks to the new device, the team obtained a Rydberg polariton with a diameter of 0.5 micrometers, which is 100 times larger than those obtained so far! ” Buying a stone on eBay was easy. The challenge was to make Rydberg polaritons that are in a very narrow color gamut Physicist Sai Kiran Rajendran, of the University of St Andrews and co-author of the study, confirms. The goal was achieved and this work lays the foundations for future quantum circuits with high computing power.

Combining the interaction potential of matter with the speed of light particles could allow quantum simulators to solve important puzzles in physics, chemistry and biology that current computers cannot solve. The researchers note in particular the development of high-temperature superconductors for high-speed trains. This technology could also help to better understand how proteins fold, facilitating the production of more effective drugs.

The team is currently continuing their research to explore the possibility of controlling these polaritons to fabricate quantum circuits, which are the next component of quantum simulators. ” These results open the way for the realization of the strong exciton-polariton interaction and the exploration of the phases of the hyperbonded material using light-on-a-chip. Summarizing the researchers nature materials.

Source: K. Orfanakis et al., Nature Materials

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