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arXiv · 2603.13754

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
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Abstract

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.

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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. 2026-03-14. A Highly Sensitive Diamond NV Magnetometer Using Ramsey Interferometry with a Short Sensor-to-Sample Distance. https://arxiv.org/abs/2603.13754

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