Convertisseur quantique
  • Research

A converter for quantum devices and future communications

Researchers at the Kastler Brossel Laboratory (LKB) have succeeded in building the first converter to make two types of quantum information coding communicate. This first could enable the interconnectivity of future networks.

Quantum information covers both the field of quantum communications, which allows a secure exchange of information as well as quantum computing. This makes it possible to solve problems that are currently unsolvable in reasonable amount of time.

In the race for quantum computing, many platforms are currently being developed, based on different quantum systems, such as photons, neutral atoms, ions, superconductors and semiconductors. For all these systems, several types of coding exist, and their choice depends on the specific applications and the available resources. Heterogeneity is therefore an urgent issue because there is currently no standardization of quantum telecommunications. However, these telecommunications are currently under development and could be available in the next five to ten years.

Physicist Julien Laurat and his colleagues at LKB have tackled this problem by creating a converter that allows future quantum devices to communicate with each other. This would enable the exchange of information in a future quantum internet that would rely on different machines, encodings and protocols. In the February edition of Nature Photonics, they reported the first successful demonstration of a conversion.

"We have taken on the scientific challenge of demonstrating that this conversion is possible and effective for the first time. We have designed a kind of black box that allows us to switch from one quantum information encoding to another thanks to the phenomenon of entanglement," explains the researcher. The subject of the 2022 Nobel Prize in Physics, at the heart of the current quantum revolution, quantum entanglement describes the fact that two particles (or groups of particles) form a linked system, and present quantum states that depend on each other regardless of the distance that separates them. "It describes correlations between beams of light that cannot be explained by classical physics," says the researcher. By using this phenomenon, scientists have been able to preserve the fragile quantum coded information signal while changing the basis on which it is written. "The second quantum revolution is driven by the ability to exploit and control entanglement at the quantum level. The ability to create, manipulate and distribute entanglement opens the door to many new applications and technologies that cannot be achieved with classical systems alone," says Tom Darras, first author of the study and CEO and co-founder of quantum startup Welinq.

“The success of this process is an important step for quantum technology infrastructures. Once we can interconnect quantum devices, more complex and efficient networks can be built," says Beate Asenbeck, a doctoral student at LKB who participated in the demonstration. “It's amazing to think that with the technology of just ten years ago, this task would have been nearly impossible. It's a very exciting moment to see our fundamental understanding of the quantum realm is pushing our technological limits."

Even though they have no direct industrial competition on this subject today, the researchers filed a patent carried by Satt Lutech to protect their innovation. This patent is now used by the start-up Welinq, which was founded by physicists Julien Laurat and Tom Darrras, who are the driving force behind this scientific breakthrough.

1 Sorbonne University, CNRS, ENS-Université PSL, Collège de France

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