Quantum Computers World's First Functional Prototype of a Diamond-Spin Quantum Computer

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Fujitsu's new prototype diamond-spin quantum computer integrates tin vacancy centers (SnV centers) into photonic integrated circuits, marking an important step toward scalable quantum computers.

Fujitsu announced today that it has “developed the world’s first functional prototype of a diamond-spin quantum computer that integrates tin vacancy (Tin-Vacancy, SnV) in photonic integrated circuits (Notes 1, 2).”

The prototype operates at -271.6 °C (−456.9°F). This is a higher operating temperature than that of typical superconducting quantum computers (-273.13 °C). Fujitsu has also demonstrated in a test environment that users can operate it using the Fujitsu Hybrid Quantum Computing Platform without requiring any additional specialized knowledge. This development marks an important milestone on the path toward a modular architecture. Due to its high fidelity and efficient optical connectivity, this approach is considered one of the most promising ways to scale quantum computers.

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The prototype is based on the results of a joint research project launched in 2020 by Fujitsu, Delft University of Technology, and QuTech—a world-leading research institute for quantum technologies and part of TU Delft.

Three Key Technologies for the Diamond-Spin Quantum Computer

The prototype incorporates the following three technologies developed by Fujitsu:

• 1. Technology for Heterogeneous Bonding and Thinning of Materials for Scalable Quantum Computer Chips: Fujitsu developed a heterogeneous bonding technology for the fabrication of quantum computer chips based on SnV centers. It bonds high-quality, tin-ion-implanted diamond substrates to aluminum oxide/silicon dioxide substrates. In addition, Fujitsu developed a thinning technology that reduces the thickness of the diamond substrates from several hundred micrometers to several hundred nanometers. This makes the substrates suitable for use in scalable quantum computer chips.
• 2. Manufacturing Technology for Photonic Integrated Circuits with SnV Centers: Fujitsu has developed a fabrication technology for photonic integrated circuits (Note 3) that integrates nanometer-scale diamond crystals with SnV centers into aluminum oxide optical waveguides. These are transparent in the visible spectrum and enable the extraction of individual photons emitted by the SnV centers during the readout of the qubits. Fujitsu utilized findings from joint research with the University of Tokyo to process the diamonds.
• 3. Technology for converting quantum circuits for the diamond-spin approach: The diamond-spin approach controls qubits by combining light, microwaves, and radio waves. Fujitsu therefore developed a mechanism that converts quantum circuits—described by quantum gates—into control sequences for these physical operations. As a result, the Fujitsu Hybrid Quantum Computing Platform enables control of the system.

Roadmap for Multimodal and Hybrid Quantum Computing

Fujitsu plans to develop a functional prototype of a multimodular diamond-spin quantum computer by 2027. In addition, the company will begin developing technologies that integrate the diamond-spin approach with the superconducting approach. In doing so, Fujitsu is further advancing the development of large-scale quantum computers.

The initiative is part of Fujitsu's quantum computing roadmap. In it, the company sets out its goal of achieving practical quantum computing by 2030.

Background

The diamond-spin approach uses lattice defect structures in diamond crystals—known as color centers—as qubits. Diamond possesses intrinsic properties that keep quantum states stable (Note 4). As a result, the approach achieves high fidelity. Compared to superconducting and other approaches, it could also make it possible to reliably form logical qubits from a smaller number of physical qubits. Light can flexibly interconnect multiple quantum modules (Notes 5, 6). This allows systems with a modular architecture to be built and scaled efficiently.

Typically, the diamond spin approach uses nitrogen-vacancy (NV) centers. These are formed by nitrogen atom impurities in diamond crystals. For the development of this prototype, however, Fujitsu used tin vacancy centers (SnV centers). Their structure is symmetrical. In addition, they are less sensitive to external disturbances than NV centers. This makes them a promising option for stable, high-brightness color centers.

Notes

1 - According to Fujitsu, based on a survey conducted by Fujitsu in September 2026.

2 - Tin-vacancy (SnV) center: A lattice defect in diamond consisting of a tin atom (Sn) positioned between two adjacent vacancies. It is one of the structures referred to as color centers.

3 - Photonic integrated circuit: An integrated circuit that processes information by generating, controlling, and detecting light (photons). In contrast, electronic processes transmit information using the properties of electrons.

4 - Intrinsic properties that stabilize quantum states: Research groups, including Delft University of Technology and Fujitsu, have demonstrated the operation of a two-qubit gate with an error rate of less than 0.1 percent. To do so, they utilized electron spins and nuclear spins from NV centers in diamond (Phys. Rev. Applied 23, 034052 (2025)).

5 - Light enables the flexible interconnection of multiple quantum modules: An optical connection can couple electron-spin qubits even across separate chips or cryostats. To do this, photons create entanglement between spatially separated spins. For example, a joint research team from Delft University of Technology and Fujitsu has demonstrated entanglement and quantum gate operations between spatially separated NV centers located in separate cryostats (Nat Commun 17, 4694 (2026)).

6 - Quantum module: The basic building block of a diamond-spin quantum computer. It features two types of spin qubits: electron spin qubits and nuclear spin qubits of the carbon isotope ^13C. The system can be expanded by optically connecting multiple quantum modules. 

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