Quantum diamond sensors capture the heartbeat’s magnetic whisper

Every beat of the human heart is accompanied not only by the electrical surge that clinicians have tracked for more than a century with electrocardiograms, but also by an exceedingly faint magnetic field that escapes into the space around the chest. Measuring that field has long promised a cleaner, contact-free window into cardiac function, yet the technology required has been bulky, cryogenically cooled, and prohibitively expensive. Now physicists at Johannes Gutenberg University Mainz report a decisive step toward changing that picture. In a study published in Science Advances, a team working within the DIAQNOS flagship project demonstrated that magnetometers built on nitrogen vacancy centers in diamond can record the human heart’s magnetic signal, opening a path toward compact, room-temperature quantum sensors for medical diagnostics.

The DIAQNOS project, short for DIAmond-based Quantum Sensing for NeurOSurgery, is funded by the German Federal Ministry of Research, Technology, and Space and coordinated in Mainz by Dr. Arne Wickenbrock. The research was carried out in the group of Prof. Dr. Dmitry Budker, a member of the PRISMA++ Cluster of Excellence and the Helmholtz Institute Mainz. The coordinating author of the new paper, doctoral student Muhib Omar, developed the quantum sensor during his doctoral research. According to Wickenbrock, the results are the product of more than ten years of development work, and the team works closely with neurosurgeons to ensure that the technologies do not remain confined to the laboratory but find clear practical applications. The primary goal, he explained, is to build highly sensitive sensors that function outside the laboratory and can fulfill important societal needs.

The heart of the technology lies in a remarkable defect of the diamond crystal lattice. A nitrogen vacancy center forms when a vacancy sits directly next to a nitrogen atom that has been incorporated into the diamond in place of a carbon atom. These atomic-scale defects possess energy levels that respond to their surroundings, and by interrogating them optically and with microwaves, researchers can measure magnetic fields, electric fields, temperature, and mechanical stress with extraordinary precision. Because the diamond host is chemically inert and biocompatible, and because the quantum states of NV centers can be read out at ambient conditions, the platform has long been viewed as a candidate for bringing quantum sensing out of shielded laboratory basements and into hospitals.

To prove that the concept could withstand the rigors of real biomagnetic measurement, the DIAQNOS consortium deployed three magnetometer systems developed independently by its partners: Johannes Gutenberg University Mainz, the Universities of Stuttgart and Freiburg, and the startup Q.ANT GmbH. Each system was used to measure the heart’s magnetic field, and the fact that three independently engineered instruments converged on the same physiological signals demonstrated that quantum technologies in Germany are ready to take the important step toward medical applications. The exercise also identified the improvements still needed before clinical deployment. The fiber-based NV-diamond magnetometer built by the Mainz group was designed as a portable endoscope and operates without a magnetic bias field, in contrast to the other two systems, which use such fields to filter out magnetic interference from the environment.

Understanding why this matters requires a look at how heart activity is measured today. The two common methods are electrocardiography and magnetocardiography. Electrocardiography, the ubiquitous ECG, uses electrode patches applied to the patient’s skin to detect the electrical activity within the heart. It is inexpensive and widely used, but it is susceptible to the differing conductivity of body tissues, and certain medical scenarios, such as burn wounds, can make it impossible to place electrodes on the skin at all. Magnetocardiography, by contrast, detects the magnetic fields produced by the heart’s electrical currents. It requires no contact with the skin and is only minimally influenced by tissue conductivity, but because the signals are vanishingly weak, the method has historically depended on costly and complex instruments such as superconducting quantum interference devices, known as SQUIDs, and optically pumped magnetometers, or OPMs.

The diamond-based system offers an alternative with several significant advantages over existing magnetocardiographic approaches. The most striking is size: the Mainz sensor is a truncated diamond pyramid with a volume of less than 0.5 cubic millimeters, small enough to be easily transported and positioned. Unlike SQUID-based systems, which require liquid-helium cooling, and unlike many OPMs, which rely on heated vapor cells, NV magnetometers operate at room temperature. That means they can be placed directly on the patient’s skin at any desired location, which opens the possibility of more precise mapping of biomagnetic signals. Potential applications include three-dimensional reconstruction of the heart’s electrical conduction system and the measurement of fetal heart activity, a task that is notoriously difficult with conventional electrodes because the fetal signal is buried within the maternal one. Wickenbrock summarized the appeal succinctly: NV magnetometers are characterized by fast initialization, excellent biocompatibility, and stable operation over a wide temperature range, making them particularly attractive for biomedical applications.

The study is candid about the remaining hurdles. NV diamond magnetometers still trail SQUIDs and OPMs in raw sensitivity and signal-to-noise ratio, a performance gap that must be closed before they can match the diagnostic quality of established instruments. Yet the researchers argue that the gap is bridgeable, and their strategy rests on a unique combination of wide dynamic range, noise suppression, and scalable geometry. Because the detectors are so compact, they can be combined with signal-enhancement mechanisms that could lift their performance to ECG-like quality. The most prominent of these are flux concentrators: engineered magnetic structures that gather and concentrate magnetic flux within the diamond, thereby amplifying the signals the NV centers detect. Thanks to the small sensor volume, amplifications of more than a factor of 100 can be achieved, and the development of flux concentrators that function at room temperature is one of Omar’s main research focuses. Adapting magnetic structures to optimally concentrate the field lines from a source within the diamond, he noted, is the path to bringing these quantum technologies into practical use.

The same compactness enables a second powerful trick: gradiometry. By pairing two spatially separated sensors and measuring the difference between their readings, a gradiometer rejects distant, spatially uniform interference while remaining sensitive to nearby sources such as the heart. This differential scheme supports intraoperative nerve monitoring in unshielded environments, a capability of direct interest to surgical teams. It also facilitates the noninvasive separation of maternal and fetal heart signals for prenatal monitoring, since the two sources occupy different positions and therefore produce different field gradients at the sensors. In surgical oncology as well, gradiometric readout offers a route to detecting subtle biomagnetic contrasts without the shielding infrastructure that conventional magnetometry demands.

Perhaps the most ambitious horizon lies in the brain. Magnetoencephalography, the magnetic analogue of measuring brain activity, currently requires either cryogenic SQUID arrays fixed in helmet-like dewars or, more recently, OPM arrays that still demand careful magnetic shielding. NV gradiometers could enable portable magnetoencephalography systems that operate at room temperature, which would open new possibilities for neurological diagnostics and for next-generation brain-computer interfaces. A wearable, unshielded brain imager would transform the study and treatment of conditions ranging from epilepsy, which the Mainz team explicitly cites as a target, to a broad spectrum of cognitive and movement disorders. The DIAQNOS project’s name reflects this ambition: the collaboration was conceived from the outset with neurosurgery in mind, and the cardiac measurements reported in Science Advances serve as a rigorous demonstration that the sensors can resolve genuine biomagnetic signals in practice, not merely in principle.

The study, titled Human Cardiac Measurements with Diamond Magnetometers and published on 16 September 2026, arrives at a moment when quantum sensing is moving rapidly from laboratory curiosity toward commercial and clinical reality. The convergence of three independently built instruments on the same cardiac signals suggests that the underlying physics is robust and the engineering reproducible. Challenges certainly remain: sensitivity must improve, flux concentrators must be perfected, and regulatory pathways for clinical use must be navigated. But the trajectory is clear. A sensor smaller than a grain of sand, needing no cooling, no shielding, and no skin contact, that can listen to the magnetic signature of a beating heart represents exactly the kind of quiet revolution that quantum technology has promised. If the Mainz group and its partners can close the remaining performance gap, the faint magnetic echo of every heartbeat may soon become as routine a diagnostic signal as the electrical spike that has dominated cardiology for a century.

Subject of Research: Nitrogen vacancy diamond quantum magnetometers for measuring human cardiac biomagnetic signals

Article Title: Diamond magnetometers can open a new window into heart activity

Article References: Diamond magnetometers can open a new window into heart activity. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: diamond magnetometers, nitrogen vacancy centers, quantum sensing, magnetocardiography, biomagnetic signals, heart activity, DIAQNOS, Science Advances, flux concentrators, gradiometry, medical diagnostics, brain-computer interfaces