The number and variety of device prototypes that have advanced from the lab into the real world in recent years offers irrefutable evidence that quantum sensing technologies are making major forward strides. As end users and systems integrators increasingly deploy these prototypes to perform useful, industrial applications, some have begun to emerge as bona fide disruptors to existing commercial systems. The innovative prototypes that have achieved this status have met two critical benchmarks. First, they effectively harness the advantages of quantum technology to improve upon the capabilities of baseline, nonquantum systems. Second, they target essential applications, often as these applications evolve or pose new challenges that push the limits of the current solutions. Quantum magnetometers, particularly those based on nitrogen-vacancy (NV) centers in diamonds, are among these innovations, offering a powerful alternative to conventional magnetic-based systems. For decades, magnetometers have been used in applications ranging from anti-submarine warfare to compassing technology. More recently, magnetic-based navigation has gained favor in global navigation satellite system-denied environments. In the present age of minerals, geophysical surveying is moving quickly toward autonomous platforms that use cost-effective and compact magnetometers to perform high-resolution surveys. And, with conflict zone complexities intensifying, so-called advanced concealment techniques — sensing technologies that “see” through smoke, underground, and underwater — are paramount. Because NV centers are atomic, their applicability is also extending into nano- and micrometer applications in the medical space. Critically, quantum magnetometry is also a room-temperature technique, which further broadens its application potential. Both as an improvement to conventional vector magnetometry, as well as in its widened range of supported use cases, NV centers are redefining how magnetometry can be used in the field by offering superior performance and situational awareness. The quantum edge At their core, quantum magnetometers harness the quantum mechanical properties of specific materials to detect magnetic fields with exceptional precision and sensitivity. These types of magnetometers — atomic vapor magnetometers, for example — have driven the adoption of large-scale regional magnetic surveys for geophysical modeling. Parameters such as size, drift, and environmental interference often constrain classical sensors. Quantum sensors by contrast can measure fields with precision down to one millionth of Earth’s magnetic signal, enabling the detection of magnetic signals over longer ranges and in environments where signals are weak or noisy. Additionally, the stability of quantum reference states enables drift-free measurements, circumventing the need for constant recalibration and ensuring that users can compare data sets with high reliability. And quantum sensors optimize size, weight, and power parameters. Miniaturized designs make them ideal for deployment on small autonomous platforms such as drones, or in restricted spaces such as inside medical equipment or in underground sensors. A green laser shines on a nitrogen-vacancy (NV)-center diamond. This excitation polarizes the spin system and results in the red light emission. The spin state determines the intensity of this photoluminescence. Courtesy of SBQuantum. A flawed photonic system NV centers are point defects in a diamond lattice in which a nitrogen atom replaces a carbon atom adjacent to a vacancy, which is an empty lattice site. This structure results in a two-electron spin system with unique quantum properties that can be optically initialized and read out. NV centers are particularly suited for magnetometry because of their quantum mechanical spin-1 property, which includes three energy levels: ms = 0, ±1. These energy levels are sensitive to the local magnetic field via the Zeeman effect, especially along the NV axis. Visible (green) laser excitation polarizes the spin system and results in red light emission, or photoluminescence, the intensity of which depends on the spin state. Upon the application of microwaves at resonant frequencies corresponding to the spin transitions, the fluorescence intensity dips. This action provides a means to detect magnetic fields via optically detected magnetic resonance. Due to the tetrahedral symmetry of the lattice, a diamond crystal typically contains NV centers in four orientations. With appropriate signal processing and a carefully applied bias magnetic field, each orientation can be resolved, enabling full vector magnetometry. This potential to reconstruct the vector components of magnetic fields in three dimensions is imperative for applications ranging from navigation to the advanced calibration of systems in complex environments. Field-ready advantages Traditional high-sensitivity vector magnetometers include superconducting quantum interference devices and vectorized atomic vapor magnetometers. These systems often require the use of cryogenics, or large, power-hungry electronics. NV magnetometers operate at room temperature with compact form factors and deliver similar or even superior performance in the field. Notably, since these magnetometers are based on a solid-state material — diamond — they avoid the need to vaporize a vacuum cell; this process requires heating elements that are apt to consume large quantities of energy. The performance benefits of NV magnetometers are particularly evident in challenging or dynamic environments. Because of their tolerance to high magnetic field gradients, due to the small sensing volume, NV centers maintain high resolution even in areas with steep field variations. The robustness of these quantum sensors to mechanical and thermal disturbances is another area in which the benefits are clear, especially for field deployment. The diamond host is both a mechanical and thermal insulator. Its inertness and stability enable sensing in conditions that would degrade or destroy conventional sensors. An artificial diamond with NV-center defects glows red upon laser excitation. Courtesy of SBQuantum. A third example relates to high dynamic range. NV magnetometers are operational in the presence of strong ambient fields and noise sources, such as metallic structures or electromagnetic interference from nearby equipment, without saturating or losing accuracy. This may not seem critically important. But, for field-deployed accurate sensors, the platform noise, such as from a drone or satellite, can alter readings to a point of frustration that forces many users to simply turn off their magnetometers. Streamlined quantum navigation One of the most compelling and high-growth applications of NV magnetometry is in navigation, especially in environments where global navigation satellite system signals are unavailable or degraded. Submarines, drones, spacecraft, certain indoor facilities, and even underground mining operations require alternative navigation systems that are accurate and autonomous. NV magnetometers offer a viable solution for magnetic navigation. By enabling precise readings of Earth’s magnetic field at high spatial resolution with vector readings, and operating reliably within a platform magnetic noise, these sensors represent a highly accurate alternative to traditional systems. For example, NV-based magnetometers used on small satellites allow for the creation and refinement of global magnetic field maps, such as the World Magnetic Model. This model underpins digital compasses used in smartphones and navigation systems, providing orientation cues in situations such as exiting a subway station — or orienting the blue arrow on your cellphone’s map. Additionally, NV magnetometers can be placed close to magnetic noise sources such as batteries or metallic components. This means that they can be used to accurately map and compensate for platform-induced fields, and that these sensors can be integrated into the very platforms that they help navigate, from autonomous drones to robotic explorers. This quality makes it possible to design potentially costly deployment platforms with compact and off-the-shelf components. Quantum geophysics and remote sensing In geophysics, precise magnetic field data helps locate mineral deposits, detect voids or anomalies underground, and map geological structures. Quantum sensors enable measurements with higher resolution and repeatability than traditional instruments, making them ideal for long-term monitoring or exploration in remote regions. In remote sensing scenarios such as detecting buried structures or monitoring magnetic signatures of underwater vehicles, the high sensitivity and dynamic range that NV magnetometers offer enable them to detect subtle changes in the environment, even when deployed at a distance or in noisy surroundings. Moreover, the potential for miniaturization and low-power operation means that arrays of NV sensors can be distributed over autonomous platforms to create an accurate digital magnetic twin. The result in this case is a compact solution that bypasses reliance on a magnetometer on a bulky boom. Overcoming technical barriers To realize the full potential of NV-based quantum magnetometers, designers and engineers must address several technical challenges. These range from optimizing the selection of the light source, to the further suppression of excess noise, to continued advancements in materials science. First, the efficient excitation of NV centers requires a powerful and compact light source, in the green band, typically at 532 nm. Although recent innovations to solid-state lasers and semiconductor diodes are making these devices more practical, these sources have historically been bulky, inefficient, or both. The collection of photoluminescence is another issue of efficiency. NV centers emit red light (~637 to 800 nm) upon relaxation. Collecting >50% of this light, particularly in compact devices, requires careful optical design due to the high refractive index and internal reflections of diamond. A portable quantum diamond magnetometer. The product achieves room-temperature operation and robust performance in a compact design form factor, optimizing its performance even in magnetically noisy environments. Courtesy of SBQuantum. NV magnetometers may also struggle with noise suppression and referencing. Instabilities in the green excitation laser directly translate into noise in the photoluminescence signal. This creates a need for advanced referencing systems and modulation techniques to suppress the effect. Additionally, more sensitive photodetectors, as well as low-noise electronics, are needed to read out potentially weak fluorescence signals from NV centers. Applications that take place in uncontrolled or high-noise environments highlight this need. Finally, there is an ongoing challenge to source and procure high-quality diamond materials. The attributes of a diamond crystal dictate the sensor’s performance. NV centers must exhibit long coherence times and minimal background noise, which depend on the concentration of defects. Achieving this balance between quantum coherence time and defects is a delicate trade-off; quantum diamond growth is itself an art mastered by few. From the lab to the field SBQuantum’s NV-based quantum magnetometer addresses two of the fundamental challenges to quantum magnetometer performance. The compact, portable product delivers sub-nT/√Hz vectorial sensitivity at room temperature. Such sensitivity is suitable for most real-world applications, especially where platform or environmental noise dominates. The solution additionally addresses potential bottlenecks caused by low-performing sources and material(s). Custom-designed optics ensure the sensor system’s efficient collection of fluorescence. Both compact visible green light sources and noise referencing circuits are incorporated. The noise referencing circuits suppress detection noise, even when the full system architecture uses lower-performing laser systems. Also, the solution benefits from high-quality diamonds, which are now on the market, to offer long coherence times and sensitivity. And these magnetometers are small and rugged enough to be integrated on drones, rovers, and/or satellites, making them suitable for mineral exploration in remote terrain, autonomous underwater navigation, and other demanding applications. Sensing tech: Making the quantum leap As quantum technologies continue to mature, the practical use of quantum sensors will reshape the landscape of sensing and navigation. Indeed, NV-based quantum magnetometers represent a key bridge between the quantum lab and the real world. Their room-temperature operation, compact design, and robust performance give them an edge compared to other systems, especially in more magnetically noisy environments. But the complete story extends beyond quantum sensing. Additional ancillary building blocks are required to fully harness quantum’s potential. These include platform noise reduction, high-accuracy map generation, and the fusion of data with other sources — for example, quantum gravimetry. Interpretation algorithms will also help to move magnetometry from a niche industry into the mass market. The industry is entering an era in which quantum sensing technologies will no longer be confined to research labs. With the commercialization of robust NV magnetometers, a fundamental change is underway in how we perceive, map, and navigate our environment, whether on Earth or beyond.