Using light and diamonds can help us navigate Earth and create a new age of mineral exploration

The transition to renewable energy has begun. As the cost of wind and solar energy continue to drop, the energy industry needs to find additional sources of strategic minerals like iron, copper, and rare earth minerals to meet surging demand. That search is estimated to require up to 500 new mines becoming operational over the next 15 years—a massive amount of new capacity.

To achieve that capacity in the required timeframe, enhanced deep geophysical insights are needed to identify deposits of key minerals more quickly and determine whether or how they can be extracted.

To those ends, SBQuantum is using light, diamonds, and quantum effects to develop a highly accurate and sensitive quantum magnetometer mounted on a drone. As the first noninvasive sensing tool deployed on the field, it reveals key geological data within rock to steer mining exploration towards promising deposits quickly. The system is based on diamond nitrogen-vacancy (NV) vector magnetometer technology and resolves an important geological ambiguity—magnetic remanence—which has typically limited the confidence of ore-body modeling and the depth at which it can be done.

Another application of vector magnetic data is heading data, which is critical to autonomous vehicles in mining, agriculture, submarines, and your everyday blue pointer on your mapping app, which uses satellite generated maps to tell your digital compass where to point.

Over the past two decades, combining systems like GPS with high-density batteries has enabled the deployment of small, unmanned vehicles such as drones, small autonomous watercraft, and rovers. Controlling such vehicles remotely was considered science fiction not so long ago. However, in some scenarios, reliance on GPS may represent a critical vulnerability. The key point being that malicious actors can easily jam these systems and impede the deployment of drones with the flip of a switch, taking out the advantage they provide.

To combat this, a backup magnetic navigational map could be used. These global maps are highly dependent on high-resolution and accurate sensing technologies. An example would be magnetometers using NV centers in diamonds to sense the orientation of Earth’s magnetic field with extreme precision.

NV centers are atomic impurities in the clean and rigid diamond structure, which isolates the impurities from their noisy environment. Contrary to many other quantum technologies operating at cryogenic temperatures, the NV center method preserves quantum coherence properties even at room temperature, making it possible to deploy devices virtually anywhere.

Photonics play a key role in this process, providing reliable initialization and readout of NV centers at room temperatures. The key technique to make a magnetometer is the optically detected magnetic resonance (ODMR), which translates light into magnetic field readings. By illuminating a diamond with a green laser or with green LED excitation, a red light is re-emitted. This red light is visible even with the naked eye when using high-quality quantum diamonds with high concentrations of NV impurities. What sets NVs apart from other atomic quantum systems is that when resonant microwaves are applied at 3 GHz, a contrast will appear in the intensity of the red light, showing as an ODMR curve in the frequency domain. By tracking the ODMR resonance frequency, the orientation of Earth’s magnetic field can be inferred by probing different NV orientations within a single laser excitation spot.

Another key advantage of our technology is the access to a number of temperature and electronics calibration tools. By leveraging fundamental quantum properties, optimal magnetometer performance can be maintained even in the harshest environments. For instance, the diamond, laser, and photodiodes can be altered by radiation while leaving the magnetometer unaffected, as light phenomena involved are nonresonant.

SBQuanutm’s diamond quantum magnetometer.

This approach to magnetic sensing has led hundreds of research groups and a handful of companies to prototype the technology, moving it out of the labs and into the field. However, as this evolution of magnetic sensing continues, tradeoffs periodically surface. For every incremental gain of sensitivity, it seems that a new quantum physics phenomena is uncovered, spurring new waves of research and innovation. To leverage the collective sensitivity enhancement provided by millions of impurities within the diamond, density and laser-beam parameters must be carefully tuned.

Furthermore, because diamonds are an excellent optical waveguide, the NV red light tends naturally to exit in an isotropic fashion, meaning careful design of the diamond’s shape and its collection optics are required to detect every last photon for improved sensitivity.

Building a magnetometer has an additional complexity: magnetic noise. The omnidirectional nature of the magnetic signals means that the electronic and optical components must be packaged into nonmagnetic materials to avoid degrading the quality of the readings. Often used for medical applications, such as in magnetic resonance imaging equipment, such electronic components can readily be found. However, measuring Earth’s 50,000 nanotesla signal with 0.01 nanotesla precision requires an extreme level of component magnetic cleanliness. Hence, either developers must work closely with component manufacturers, or bespoke magnetic compensation algorithms must be integrated into the overall package.

But manufacturing an accurate and sensitive device is only the first step. Once deployed, we must then somehow compensate for the magnetic noise caused by a satellite or drone transporting the device. Metal parts, magnets, and even the currents running through the power systems onboard will need to be cancelled out. And all of that in some of the most demanding conditions anywhere on Earth. For example, in the mining industry, magnetometers are used as one of the primary sensing techniques for exploration, from the sweltering deserts of Australia to the frigid Canadian Arctic, and they often must be transported by a drone, on foot, or on an airplane. And when it comes to Earth observation from orbit, this technology is also subjected to massive vibrations at launch and exposed to radiation in space, which might degrade performance if left unchecked.

Even though it is early days for the technology, SBQuantum has already deployed its magnetometer in harsh arctic conditions, in cars, on airplanes and drones, and will soon do so in low-Earth- orbit. Space deployment of our accurate, direction-sensitive diamond magnetometer technology will provide dependable and resilient technology in a package smaller than a carton of milk, and that consumes less than a watt of power, making it ideal for spaceborne missions.

One might envision frequent deployment of small constellations of those spacecraft to develop and maintain high-resolution magnetic maps for positioning and navigation here on Earth. The devices could also track heat flows in areas where conventional sensing techniques fail (deep beneath the surface), exposing links between oceanic temperature flows and climate change, for example.

Miniaturized and high-accuracy diamond vector magnetometers will unlock better, faster mineral surveys at scale, with drone fleets flying close to ore bodies and exploiting diamond vector measurements to reveal deep and complex mineral structures currently blurred by the lack of rich and accurate magnetic data at a certain depth.

The future is bright for diamond sensing. In just a few short years, most smartphones may be using magnetic maps generated by quantum diamonds and lasers, the same ones being used by NASA and some of the world’s largest mining companies.

David Roy-Guay is Founder and CEO at SBQuantum.