Few people have heard of the French quantum computing startup C12 Quantum Electronics SAS, but that could change if its novel architecture for creating the qubits that power these next-generation computers lives up to its billing.

A lot of people seem to think it will, for C12 today announced it has raised €18 million ($19.4 million), its second big round after receiving $10 million from investors back in 2021. Today’s round was led by Varsity Capital, EIC Fund and Verve Ventures, and saw the participation of 360 Capital, Bpifrance and BNP Paribas Développement, who took part in the original funding round.

Founded in 2020 by the Desjardins brothers, Pierre and Matthieu, who serve as its chief executive and chief technology officer respectively, the startup is pioneering the development of a carbon nanotube-based quantum computer. The company was spun out of the physics laboratory of the École Normale Supérieure in Paris.

It aims to build a workable quantum computer that can scale far beyond the reach of today’s most sophisticated supercomputers. Carbon nanotubes are the main building blocks of its quantum processors, helping to improve the stability of those “qubits” and minimize errors.

Quantum computers have vast potential to solve complex problems that traditional systems are unlikely to ever be able to manage. As Pierre Desjardins explained in an interview with TechCrunch, problems such as creating an exhaustive simulation of chemical reactions, so researchers can see how new drugs might react with human cells, are simply beyond the reach of classical computers.

“There are a whole host of optimization problems to be solved, whether in transport, logistics or manufacturing,” he told TechCrunch. “They are impossible to run on a conventional computer because there will be too many variables, too many possible scenarios.”

Quantum computers could also have dramatic implications for artificial intelligence training and inference. Such tasks consume enormous amounts of energy and there are big concerns that we’ll never be able to keep pace with the development of new AI models using classical computing infrastructures. Quantum computers are a potential solution, as they use much less energy.

Quantum instability challenges

Qubit stability has long been the main roadblock on the road to creating a workable quantum computer. The problem is that these structures are so incredibly sensitive that even something like a vibration caused by a pin dropping on the floor, or a mouse scuttling past in the next room, could affect the stability of qubits. When qubits become unstable due to this “noise,” errors start occurring, which means quantum computers cannot be relied upon.

Big companies such as Google LLC and IBM Corp. have been trying to overcome this stability challenge using “superconducting materials” such as aluminum that’s placed on a silicon substrate. Although these techniques have had some success, C12 believes that they simply won’t be able to scale up enough to support the thousands of qubits needed to create a viable quantum machine.

That’s why it’s working on a different approach, using carbon nanotubes that are placed onto a silicon chip as the foundation of its qubits. It has devised a novel “nano-assembly” process to create those qubits. It’s an incredibly intricate process, as the diameter of a carbon nanotube is 10,000 times smaller than that of a human hair.

A new kind of qubit

To date, C12 has managed to demonstrate, both theoretically and in practice, that its nanotube-based architecture is the closest realization of a single-spin in a vacuum achieved thus far. Its method has been shown to reduce all sources of noise that can affect the stability of qubits. Now the company is looking to scale with the opening of a new Quantum Fab in Paris that will soon begin manufacturing its first qubits.

At the Quantum Fab, C12 manufactures its carbon nanotubes, controls them and integrates them with a silicon substrate, so all that has to be done then is to integrate them into a larger quantum computer.

Xavier Mesnier, a principal at Verve Ventures, said he has been convinced by the startup that carbon “has the potential to solve the major challenge of quantum computing at the core by changing the material of the qubit and leveraging its unique properties to develop a truly scalable hardware architecture.”

Today’s funding round is a validation of C12’s approach, and the concept has been boosted further by its selection for the Proqcima program, a French government initiative launched this year that aims to position France as the world’s leader in quantum computing. Backed by the French Ministry of the Armed Forces with the French Secretary General for Investment, Proqcima aims to have two prototypes of quantum computers up and running by 2032.

C12 said the money from today’s round will be used to accelerate its research and development efforts in order to achieve its next major goal – creating the first high-fidelity quantum operation on two distant spin qubits connected by a communication bus – which is an essential step toward integrating the thousands of qubits that will be required by tomorrow’s quantum computers.

“Our goal is to demonstrate long-distance entanglement between two qubits,” said Matthieu Desjardins. “This entanglement is at the heart of the quantum leap that will one day allow us to compute in a few seconds something that today takes several years to process.”

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