An interdisciplinary team of theoretical and experimental researchers from WPI-QUP/KEK and Kyoto University has theoretically demonstrated that the performance of ultralight dark matter searches can be significantly enhanced by exploiting the three-level quantum structure, or qutrit, of nitrogen vacancy (NV) centers in diamond. The research team comprised Xiaolin Ma, Volodymyr Takhistov, Norikazu Mizuochi and Ernst David Herbschleb, bringing together expertise in high energy physics and quantum sensing. The study established a broadly applicable principle, realized concretely with diamond NV centers but applicable more generally to multilevel platforms such as superconducting, neutral atom and trapped-ion systems, by which higher dimensional quantum systems can enhance sensitivity in searches for fundamental physics.

Although dark matter is believed to account for most of the matter in the Universe, its true nature remains one of the greatest mysteries in modern physics. Diamond quantum sensors with NV centers have emerged as a promising platform for detecting the extremely weak signals expected from ultralight dark matter candidates such as axions. However, previous studies have treated NV centers as conventional two-level quantum bits (qubits), utilizing only two of their three quantum states and leaving the full potential of multilevel quantum systems largely unexplored.

In this work, the researchers demonstrate that operating the NV center as a three-level quantum system (qutrit), together with a sensing protocol that enhances dark matter-induced signals while suppressing common environmental noise such as temperature fluctuations and electric-field variations, enables substantially higher measurement precision. The results were published as a Letter in Physical Review A in June 2026.

Volodymyr Takhistov, a principal investigator and associate professor at QUP, who led the project, says "Our work highlights the largely untapped potential of multilevel quantum systems for basic science. Quantum properties can offer new ways to detect extraordinarily weak signals, and I expect these ideas to open broader directions beyond dark matter. We have only begun to explore what quantum sensors can reveal about nature’s underlying laws."

Published details
Journal: Physical Review A (Letter)
Title: Beyond Qubits: Multilevel Quantum Sensing for Dark Matter
Authors: Xiaolin Ma, Volodymyr Takhistov, Norikazu Mizuochi, Ernst David Herbschleb
DOI: 10.1103/zvzb-yv67

Related links
Press release from KEK
(Web page) https://www.kek.jp/en/press/202607091400
(Press release document) https://www.kek.jp/wp-content/uploads/2026/07/202607091400e.pdf

Research Topics | ICR, Kyoto University (in Japanese)
https://www.kuicr.kyoto-u.ac.jp/sites/topics/260709/