C12 Quantum Electronics, founded in 2020 as a spin-off from the physics laboratory of the École normale supérieure in Paris, builds spin qubits from single carbon nanotubes placed on chips. The company, led by Pierre and Matthieu Desjardins, says its approach combines semiconductor speed with isolation from noise. In July 2025 C12 and French research partners reported coherence times of 1.3 microseconds in Nature Communications, about ten times better than comparable silicon devices.
The European Innovation Council granted €2,499,000 towards HiFiQC, a €3.6 million project from January 2023 to December 2024 aimed at high-fidelity quantum computing with carbon nanotubes. The final report says the team shifted from a 5-qubit target to a 2-qubit demonstrator whose production "has started", documented single-qubit gate fidelity, and expected two-qubit fidelity "soon". It pushed a quality-factor target to 2026. In June 2024 C12 raised €18 million, and in April 2026 it published a roadmap to a first logical qubit in 2027.
Company file
- Legal entity
- C12 Quantum Electronics SAS, 880 700 596 RCS Paris
- Founded
- 2020, ENS Paris spin-off
- CEO
- Pierre Desjardins
- CTO and co-founder
- Matthieu Desjardins
- Technology
- Carbon nanotube spin qubits; Callisto emulator
- EIC project
- HiFiQC, 1 Jan 2023 to 31 Dec 2024, closed
- EIC funding
- Grant first
Where C12 Stands Now
In June 2026 C12 announced a patented "Pick & Place" process that assembled 50 nanotube devices in four weeks, as many as it made in the whole of 2025, and a chip with 17 devices. Its roadmap runs from 16 physical qubits forming one logical qubit in 2027 to more than 100,000 physical qubits in 2033. It has partnerships with Classiq and QC Design, and its Callisto emulator is used for industrial algorithm studies.
"Our objective is not simply to build more qubits. The real challenge is building quantum computers that can scale reliably."
Pierre Desjardins, CEO, C12, April 2026The Technology: A Qubit in a Nanotube
Each qubit is formed in a carbon nanotube suspended over a chip, which C12 says isolates it from noise while keeping semiconductor-speed operations. The 2025 record was measured at 300 millikelvin without external magnetic fields. The EIC report adds that new equipment cut the R&D cycle "from months to just 6-8 weeks", and that the Callisto simulator was connected to cloud APIs and tested by outside users.
What the EIC Project Promised, and What CORDIS Shows
HiFiQC promised a high-fidelity processor. By the end of 2024 the company had lowered the target to two qubits, started producing that demonstrator and measured single-qubit fidelity; two-qubit fidelity was still to come, and a quality-factor goal was moved to 2026 after C12 concluded it was not needed for a useful demonstrator.
- 5-qubit processorCut to 2Per final report.
- Single-qubit fidelityDocumentedPer final report.
- Two-qubit fidelityPending"Soon" in 2024.
- Emulator for usersDeliveredCallisto, cloud access.
The Money
C12 reported net losses of €1.21 million in 2022 and €1.57 million in 2023, with 28 staff in 2023, according to Pappers. Later accounts are not shown. Its June 2024 round brought in €18 million in equity.
What Cannot Be Checked
Questions for the EIC
Whether the two-qubit demonstrator reached useful fidelity, whether the EIC agreed the target change in advance, and how C12's losses developed after 2023 are not public.
Why Europe Should Care
The EIC funded C12's carbon nanotube platform at an early stage; the project showed how hard the physics is, and the company's claims now rest on a roadmap stretching to 2033.
What the project promised
High-fidelity quantum computing with a multi-qubit carbon nanotube processor.
What the record shows
A two-qubit demonstrator in production, a published coherence record, €18 million raised and a roadmap to 2033.
The Verdict
Scientific progress, targets trimmed
C12 scaled back what the EIC paid for and made real scientific advances. Whether its approach produces a useful quantum computer will not be known for years.
C12 and the EIC have not been asked for comment for this article. It is based entirely on public records and published statements, linked throughout.
