Fujitsu, and QuTech, in collaboration with Element Six, have achieved a major milestone toward fault-tolerant quantum computing by demonstrating a complete universal quantum gate set for diamond spin qubits with error probabilities below 0.1%. This marks the first time such a low error rate has been reported across all operations in a universal gate set for this qubit modality. The results, published in Physical Review Applied, exceed the threshold required for quantum error correction, laying important groundwork for practical and scalable quantum computation.
The experiment used nitrogen-vacancy (NV) centers in diamond to form a two-qubit system composed of an electron spin and its associated nitrogen nuclear spin. To reduce decoherence and enhance gate stability, the team used ultra-pure diamonds with a carbon-13 isotope concentration of just 0.01%, significantly lower than standard levels. They also applied decoupling gate sequences to suppress environmental interactions, and employed gate set tomography to fully characterize and optimize all gate operations. These efforts yielded >99.9% fidelity for both single- and two-qubit gates—surpassing even many superconducting and ion-trap systems currently in use.
Diamond spin qubits offer several key advantages: relatively long coherence times, operation at higher temperatures (~10 K) compared to superconducting qubits, and natural optical connectivity due to their coupling to photons. These features make them promising for both modular quantum computers and distributed quantum networks. The researchers demonstrated the precision of the gates by running artificial algorithms comprising up to 800 gate operations, with results matching theoretical predictions—showing both control and reproducibility.
Looking ahead, Fujitsu and QuTech plan to scale this architecture by expanding to larger nuclear-spin registers, developing optical interconnects between distant electron spin qubits, and integrating control circuits using cryo-CMOS technologies. The joint roadmap also includes chip-scale integration and architectural development for a full-stack quantum processor.
This achievement reinforces the growing momentum behind diamond-based quantum platforms and highlights the importance of cross-disciplinary collaboration between academia and industry. As noted by Prof. Tim Taminiau of TU Delft, achieving sub-0.1% error rates in a universal gate set is a key requirement for scalable quantum systems, and now opens the door to the next stage of system-level development.
Read the official announcements from Fujitsu here and QuTech here.
March 28, 2025
