A Highly Sensitive Diamond NV Magnetometer Using Ramsey Interferometry with a Short Sensor-to-Sample Distance

Quantum Physics [Submitted on 14 Mar 2026] A Highly Sensitive Diamond NV Magnetometer Using Ramsey Interferometry with a Short Sensor-to-Sample Distance Yuta Araki, Takeharu Sekiguchi, Yuji Hatano, Naota Sekiguchi, Chikara Shinei, Masashi Miyakawa, Takashi Taniguchi, Tokuyuki Teraji, Hiroshi Abe, Shinobu Onoda, Takeshi Ohshima, Takayuki Shibata, Mutsuko Hatano, Takayuki Iwasaki In this study, we developed a diamond quantum magnetometer based on Ramsey interferometry with a short sensor-to-sample distance. Conventional biomagnetic sensors with ensemble nitrogen-vacancy centers using continuous-wave optically detected magnetic resonance and Ramsey methods typically rely on watt-level lasers to achieve high sensitivity, resulting in thermal issues. In contrast, by employing the light-trapping diamond waveguide technique in a high-pressure and high-temperature diamond sample treated with electron beam irradiation, we obtained a high photon conversion efficiency of 9.5%, enabling us to simultaneously achieve a high sensitivity of 2.93(7) pT/Hz^1/2 in the 100-400 Hz frequency range and a minimal temperature increase of only approximately 13 K at a low laser power of 210 mW. Using a dry phantom designed to mimic magnetoencephalography signals, we measured a weak magnetic field of 77.7(2) pT without signal averaging at a sensor-to-sample distance of 2.5 mm. This short-distance measurement prevents severe spatial signal attenuation, yielding a high signal-to-noise ratio. The development here is crucial for practical biomagnetic applications based on Ramsey interferometry. Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2603.13754 [quant-ph]   (or arXiv:2603.13754v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2603.13754 Focus to learn more Submission history From: Takayuki Iwasaki [view email] [v1] Sat, 14 Mar 2026 05:03:07 UTC (824 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-03 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)