Kanazawa University develops fundamental technology for qubit position control in diamond

A research group led by Assistant Professor Kan Hayashi and Professor Norio Tokuda at the Kanazawa University Advanced Research Center for Diamond Science and Technology announced on March 11 that they, in collaboration with Diamond and Carbon Applications (Germany), have developed a technology to generate NV centers, which can be used as qubits in diamond, at optional positions while keeping their orientation axes aligned. It is expected to contribute to the establishment of the technological foundation for diamond quantum computers. The results were published in Carbon.

NV centers in diamond, which can operate at room temperature with a long spin coherence time (duration in which qubit information is held), have attracted attention as a promising qubit material. For this purpose, it is necessary to control both the position of NV centers and the orientation axes. An ion implantation method has been used to control the position of NV centers, but this method had issues such as crystal damage and random orientation axes.

In this research, the group has developed a new diamond processing and growth process that combines plasma-generated radical etching technology using hydrogen and nitrogen gases with an Au/Ti metal mask fabricated by photolithography. After etching, CVD growth is also performed continuously without removing the sample from the CVD chamber, leading to successful buried growth of a diamond layer with highly oriented NV centers only in the etched area.

As a result, in the NV centers produced by this process, strong fluorescence from NV centers was observed only in the region of the NV centers generated by buried growth. Furthermore, it was confirmed that the NV centers formed by buried growth are oriented in a specific crystal orientation at a high percentage.

It was demonstrated that the developed process can simultaneously achieve high-orientation control and position control of NV centers.

Hayashi said, "This technology development utilizes a newly discovered property of 'nitrogen etching diamond.' Nitrogen is a familiar material in diamond device research and is widely used on a daily basis. This technology is unique in that it takes such a new aspect of nitrogen and turns it into a device process that is easy for many researchers to perform. I hope that our work will contribute to the development of the diamond research field and contribute, however modestly, to society."

Journal Information
Publication: Carbon
Title: Selective homoepitaxial growth of buried diamond films with NV centers
DOI: 10.1016/j.carbon.2026.121307