Human Cardiac Measurements with Diamond Magnetometers
Muhib Omar, Magnus Benke, Shaowen Zhang, Jixing Zhang, Michael Kuebler, Pouya Sharbati, Ara Rahimpour, Arno Gueck, Maryna Kapitonova, Devyani Kadam, Carlos Rene Izquierdo Geiser, Jens Haller, Arno Trautmann, Katharina Jag-Lauber, Robert Roelver, Thanh-Duc Nguyen, Leonardo Gizzi, Michelle Schweizer, Mena Abdelsayed, Ingo Wickenbrock, Andrew M. Edmonds, Matthew Markham, Peter A. Koss, Oliver Schnell, Ulrich G. Hofmann, Tonio Ball, Juergen Beck, Dmitry Budker, Joerg Wrachtrup, Arne Wickenbrock
physics.med-phquant-phSubmitted Jan 26, 2026• Announced Jan 27, 2026
We demonstrate direct, non-invasive and non-contact detection of human cardiac magnetic signals using quantum sensors based on nitrogen-vacancy (NV) centers in diamond. Three configurations were employed recording magnetocardiography (MCG) signals in various shielded and unshielded environments. The signals were averaged over a few hundreds up to several thousands of heart beats to detect the MCG traces. The compact room-temperature NV sensors exhibit sensitivities of 6-26 pT/Hz^(1/2) with active sensing volumes below 0.5 mm^3, defining the performance level of the demonstrated MCG measurements. While the present signals are obtained by averaging, this performance already indicates a clear path toward single-shot MCG sensing. To move beyond shielded environments toward practical clinical use, strong noise suppression is required. To this end, we implement NV-based gradiometry and achieve efficient common-mode noise rejection, enabled by the intrinsically small sensing volume of NV sensors. Together, these multi-platform results obtained across diverse magnetic environments provide a solid foundation for translating quantum sensors into human medical diagnostics such as MCG and magnetoencephalography (MEG).
We demonstrate direct, non-invasive and non-contact detection of human cardiac magnetic signals using quantum sensors based on nitrogen-vacancy (NV) centers in diamond. Three configurations were employed recording magnetocardiography (MCG) signals in various shielded and unshielded environments. The signals were averaged over a few hundreds up to several thousands of heart beats to detect the MCG traces. The compact room-temperature NV sensors exhibit sensitivities of 6-26 pT/Hz^(1/2) with active sensing volumes below 0.5 mm^3, defining the performance level of the demonstrated MCG measurements. While the present signals are obtained by averaging, this performance already indicates a clear path toward single-shot MCG sensing. To move beyond shielded environments toward practical clinical use, strong noise suppression is required. To this end, we implement NV-based gradiometry and achieve efficient common-mode noise rejection, enabled by the intrinsically small sensing volume of NV sensors. Together, these multi-platform results obtained across diverse magnetic environments provide a solid foundation for translating quantum sensors into human medical diagnostics such as MCG and magnetoencephalography (MEG).
Diamond quantum sensors utilizing nitrogen-vacancy (NV) centers in diamond can measure a tiny magnetic-field variation at room temperature with a high linearity and high spatial resolution. Because of these advantages, they have been actively studied for application to measure a biomagnetic field. In biomagnetic sensing applications, it is effective to measure at multiple points simultaneously with high sensitivity. In this study, we developed a highly sensitive diamond quantum sensor that can simultaneously measure the magnetic field at two points at the millimeter interval. We used two diamonds that were split from one HPHT-grown diamond and placed them at the 3-mm interval. A laser-induced fluorescence from the two diamonds were detected by a single photodiode. We applied different bias magnetic fields to each diamond, and thus the magnetic resonances at these diamonds had different resonance frequencies. By applying microwave fields whose frequencies were modulated at different modulation frequencies, the magnetic fields at the two diamonds can be obtained independently after demodulation. The noise spectral densities in the magnetic field measurement at the two diamonds’ locations. Since the measurement was performed outside a magnetic shield, a severe low-frequency environmental noise from railways and power line (50 Hz) noise peaks were observed. We evaluated the field sensitivities at the two diamonds to be 22 pT/√Hz in 25-300 Hz range with neglecting the power-line noise peaks and the environment noise peaks. The capability of simultaneously measuring a magnetic field at two points with the such high sensitivities will facilitate the biomagnetic sensing applications.
Abstract Solid state spins have demonstrated significant potential in quantum sensing with applications including fundamental science, medical diagnostics and navigation. The quantum sensing schemes showing best performance under ambient conditions all utilize microwave or radio-frequency driving, which poses a significant limitation for miniaturization, energy efficiency, and non-invasiveness of quantum sensors. We overcome this limitation by demonstrating a purely optical approach to coherent quantum sensing. Our scheme involves the 15N nuclear spin of the Nitrogen-Vacancy (NV) center in diamond as a sensing resource, and exploits NV spin dynamics in oblique magnetic fields near the NV’s excited state level anti-crossing to optically pump the nuclear spin into a quantum superposition state. We demonstrate all-optical free-induction decay measurements—the key protocol for low-frequency quantum sensing—both on single spins and spin ensembles. Our results pave the way for highly compact quantum sensors to be employed for magnetometry or gyroscopy applications in challenging environments.
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.
In modern-day quantum metrology, quantum sensors are widely employed to detect weak magnetic fields or nanoscale signals. Quantum devices, exploiting quantum coherence, are inevitably connected to physical constants and can achieve accuracy, repeatability, and precision approaching fundamental limits. As a result, these sensors have shown utility in a wide range of research domains spanning both science and technology. A rapidly emerging quantum sensing platform employs atomic-scale defects in crystals. In particular, magnetometry using nitrogen-vacancy (NV) color centers in diamond has garnered increasing interest. NV systems possess a combination of remarkable properties, optical addressability, long coherence times, and biocompatibility. Sensors based on NV centers excel in spatial resolution and magnetic sensitivity. These diamond-based sensors promise comparable combination of high spatial resolution and magnetic sensitivity without cryogenic operation. The above properties of NV magnetometers promise increasingly integrated quantum measurement technology, as a result, they have been extensively developed with various protocols and find use in numerous applications spanning materials characterization, nuclear magnetic resonance (NMR), condensed matter physics, paleomagnetism, neuroscience and living systems biology, and industrial vector magnetometry. In this chapter, NV centers are explored for magnetic sensing in a number of contexts. In general, we introduce novel regimes for magnetic-field probes with NV ensembles. Specifically, NV centers are developed for sensitive magnetometers for applications where microwaves (MWs) are prohibitively invasive and operations need to be carried out under zero ambient magnetic field. The primary goal of our discussion is to improve the utility of these NV center-based magnetometers.
Nitrogen-vacancy (NV) centers in diamond have emerged as a robust room-temperature solid-state platform for weak magnetic field detection. Several NV-based magnetometers have been proposed in the past decades, but they still suffer from either low sensitivity or high power consumption. This is a challenge for sensors deployed in remote locations on Earth or in space that are not connected to the power grid. Although sunlight-driven quantum magnetometry, which does not rely on conventional energy sources, has been proposed as a possible solution, its sensitivity remains a limitation. Here, we present an impressive improvement in the sensitivity of the sunlight-driven NV-diamond quantum magnetometer. A crucial aspect of our approach involves leveraging the ground-state level anti-crossing properties of the NV centers, coupled with magnetic flux concentrators. This integration enables us to achieve a magnetic-field sensitivity of 26 pT/Hz in a laboratory environment and 49 pT/Hz when the magnetometer operates outdoors under sunlight. We also illustrate the promising potential of further improving the sensitivity to the subpicotesla level by using cutting-edge technologies. Furthermore, we reveal the capability of this quantum magnetometer as a receiver of extremely low-frequency magnetic signals and pave the way for communication applications. These advancements represent a significant leap toward attaining high-sensitivity and energy-efficient magnetic field sensing and expanding the range of possible applications for these environmentally sustainable quantum technologies.
Gradiometry provides a versatile alternative to passive environmental shielding in quasi-static magnetometry, effectively suppressing background noise through differential signal extraction. Nevertheless, traditional implementations rely on multi-sensor architectures restricted to spatial gradients, where subtracting signals from independent detectors involves imperfect suppression of common-mode noise and artifacts, limiting their sensitivity. To overcome these limitations, we introduce a quantum control sequence that enables intrinsic temporal and spatial vectorial gradiometry of magnetic fields using a single quantum sensor. Our method provides direct access to first and higher-order derivatives of the magnetic field and extended applicability via auxiliary nuclear spin memory. We showcase this protocol on an ensemble of nitrogen-vacancy (NV) centers in diamond and combine it with mechanical control to realize high-precision differential sensing. Through detailed numerical simulations, we demonstrate the performance of our scheme in two critical DC magnetometry applications: (i) vector magnetic anomaly detection and (ii) non-invasive gradiometry of neuronal action potentials.