Fujitsu Develops Diamond-Spin Quantum Computer Prototype
Fujitsu has developed what it describes as the world’s first working prototype of a diamond-spin quantum computer integrating tin-vacancy (SnV) centers with photonic integrated circuits. The system operates at around -271.6°C and has been demonstrated through Fujitsu’s Hybrid Quantum Computing Platform, giving researchers access to the prototype without needing specialist knowledge of its underlying physical controls.
The development comes from a research collaboration between Fujitsu, Delft University of Technology and QuTech that began in 2020. Rather than relying on superconducting circuits alone, the approach uses quantum states associated with defects inside diamond and photons to support connections between quantum modules.
Diamond Defects Form the Basis of the Qubits
Diamond-spin quantum computers use microscopic defects known as color centers as qubits. Fujitsu chose tin-vacancy centers for the new prototype instead of the more commonly studied nitrogen-vacancy centers. According to the company, SnV centers have a more symmetrical structure and are less susceptible to certain types of external noise, making them promising for stable optical connections.
To build the device, Fujitsu developed techniques for bonding diamond substrates containing tin with alumina and silicon-dioxide substrates. It also thinned the diamond material from several hundred micrometers to several hundred nanometers so that it could be incorporated into chip-scale photonic structures.
Photonics Could Help Quantum Systems Scale
A key part of the prototype is its photonic integrated circuit. Fujitsu integrated diamond nanocrystals containing SnV centers with alumina optical waveguides, which can transmit light used to read quantum states. The company sees optical connections as an important part of linking separate quantum modules into a larger system.
This modular design is one of the main reasons Fujitsu is pursuing diamond-spin technology. Instead of attempting to build one increasingly large quantum processor, multiple smaller modules could potentially be connected optically. Diamond-based qubits also offer high-fidelity operation and stable quantum states, although demonstrating reliable communication across many modules remains a significant engineering challenge.
The System Still Operates at Cryogenic Temperatures
Fujitsu reports an operating temperature of -271.6°C, or roughly 1.6 kelvin. That is warmer than the approximately -273.13°C temperature typically associated with superconducting quantum computers, but the prototype is still a cryogenic system rather than a room-temperature quantum computer.
The difference could nevertheless become relevant to system design if diamond-spin architectures can maintain their performance while requiring less extreme cooling than superconducting approaches. Fujitsu is also developing software that translates conventional quantum circuits into the combination of optical, microwave and radio-frequency controls required by the diamond-spin system.
Fujitsu Plans Multi-Module Prototype by 2027
The current machine is an early prototype rather than a demonstration of a large-scale, fault-tolerant quantum computer. Fujitsu has not disclosed a qubit count or presented evidence of a practical quantum advantage from the prototype. The immediate objective is to demonstrate that the underlying hardware, photonics and control technologies can work together reliably.
Fujitsu plans to develop a multi-module diamond-spin quantum computer prototype by 2027. The company is also investigating ways to combine its diamond-spin technology with superconducting quantum computing, potentially allowing different architectures to contribute different capabilities within a larger system.
Fujitsu's broader roadmap targets 250 logical qubits by fiscal 2030 and 1,000 logical qubits by fiscal 2035. Those targets remain longer-term goals, and the next major test will be whether the company can move from a single working prototype to reliable optical connections between multiple modules.
