In March 2024, a plane carrying the UK defense minister had its GPS signal jammed as it travelled close to the Russian exclave of Kaliningrad on a journey between the UK and Poland. The UK government later said the plane was never in danger but that jamming incidents were not unusual in the region. Indeed, various groups have noted that GPS jamming has become common since the start of the Russian-Ukraine war.

For decades, the standard backup for this kind of navigational failure has been inertial navigation, a method for tracking motion using accelerometers and gyroscopes. But these systems have an inherent weakness: tiny errors add up over time, causing position estimates to drift, potentially by many kilometers over long journeys. That makes them unacceptable in many critical applications.

What navigators desperately need is a new way to work out where they are that does not rely on satellite signals that can be jammed. Ideally, this system should be entirely passive so that it does not reveal its own location, unlike radar, for example.

Now Murat Muradoğlu and colleagues at Q-CTRL, a quantum technology company with offices in Sydney, Australia, have demonstrated just such a technology. Their approach is to sense anomalies in the Earth’s magnetic field and compare them with a known map of the field to work out their position. And because they use quantum sensors for this process, they can detect magnetic anomalies with much greater sensitivity than previously possible and significantly better than a high-end inertial navigation system.

The Q-CTRL system has the potential to be a passive, unjammable and universally available navigation aid that could revolutionize how vehicles find their way in environments where global navigation satellite systems are unavailable.

Landmark Advance

The concept behind MagNav isn’t new. The Earth’s magnetic field isn’t perfectly uniform; superimposed on the main field of up to 65,000 nanotesla generated by the planet’s core are small, localized variations known as magnetic anomalies. These anomalies typically range in size from 10 to 100 nanoteslas over a few kilometers. They arise from geological features in the Earth’s crust and are geographically distinct and stable over time.

Just as landmarks allow visual navigation, these magnetic features can serve as signposts. If a vehicle carries a sensitive magnetometer and has access to a map of these anomalies, it can determine its position by matching its real-time magnetic field measurements to the map. Global magnetic anomaly maps already exist, compiled from decades of geophysical surveys.

However, translating this elegant concept into a practical system has been challenging. First, the magnetic anomalies used for navigation are tiny compared to the Earth’s main field and can also be swamped by magnetic interference generated by the vehicle’s electronics and engines. Second, traditional magnetometers lack the required sensitivity, stability, or small size necessary for deployment on mobile vehicles.

The entire process also needs sophisticated algorithms to filter out noise and then match the sensor data, often noisy itself, to the map. In the past, this has required aircraft to perform complex “cloverleaf” maneuvers to calibrate the sensors.

Muradoğlu and co tackled these challenges with various hardware and software innovations. At the heart of their system is a proprietary quantum magnetometer, which measures the way an external field influences the spin of rubidium atoms, in a compact, lightweight package about the size of a Rubik’s cube.

This hardware is paired with a set of denoising and map-matching algorithms. Unlike traditional approaches that treat noise cancellation and map matching as separate steps, the Q-CTRL software integrates them. It uses a physics-driven model to learn the vehicle’s magnetic signature in real-time, as it changes with payloads, for example, and then to subtract it and the platform noise from the signal of interest.

To validate their system, the Q-CTRL team conducted extensive field trials. Airborne tests involved flying a Cessna 208B Grand Caravan over 6700 km near Griffith, Australia, at altitudes ranging from near ground level up to 19,000 feet. They tested various configurations, including internally mounted sensors (a high-noise environment) and externally mounted ones, comparing the MagNav performance against a strategic-grade inertial navigation system and against ground truth data from GPS.

They also evaluated the system in ground trials in a standard rental van driven over mixed terrain near Orange, NSW. This produced an even harsher noise and vibration environment. “To the best of our knowledge our successful ground-based trials themselves represent a world-first demonstration,” say the team.

The results were compelling. Across numerous airborne trials, the quantum-assured MagNav system consistently outperformed the inertial navigation system. ” Our MagNav solution achieves superior performance, delivering up to ∼46× better (lower) positioning error than the velocity-aided INS; the best final positioning accuracy we achieve on a flight trial is 22m or 0.006% of the flight distance,” say the researchers.

In the ground trials, the MagNav system achieved a final accuracy of 180 meters over an 18 km route, despite magnetic noise inside the van reaching levels 50 times greater than the anomaly signal.

That’s interesting work with significant implications. Given the increasing vulnerability of GPS systems, much work has gone into alternative forms of navigation but all have limitations. Camera-based terrain navigation and star trackers can fail when the weather is poor; radar and lidar are resilient options but reveal their position and beacon-based navigation systems based on mobile phone towers work poorly over oceans or in remote areas.

Q-CTRL’s quantum-assured MagNav has the potential to leapfrog these technologies. “The quantum-assured MagNav solution can outperform the inertial navigation systems across a wide range of conditions,” say Muradoğlu and co.

Magnetic Mapping

But it is not yet a slam dunk. One challenge will be to improve the resolution and coverage of public domain magnetic maps, which typically have a resolution of a few kilometers. That’s not good enough for many applications. These maps particularly need improving over oceans, where magnetic anomalies tend to be smaller than over land. An important question is how accurate the maps can be made.

Then there is the problem of geomagnetic storms caused by solar activity. These storms can generate fields that dwarf anomalies this system depends on for navigation. So it may become necessary to integrate predictive models of geomagnetic activity for path planning.

Another factor will be military capabilities developed in secret. “We acknowledge that clandestine demonstrations may exist of which we do not have knowledge,” say the team. The danger is that the military systems outperform Q-CTRL’s making it obsolete. Other “unjammable” quantum technologies could also compete, such as quantum inertial navigation, which is currently being tested by the UK technology company Infleqtion.

All this work suggests a new era of quantum-enabled navigation is dawning that should protect future UK defense ministers and others from jamming attacks. Of course, a new era of hacking, jamming and other nefarious activity cannot be far behind.

Ref: Quantum-assured magnetic navigation achieves positioning accuracy better than a strategic-grade INS in airborne and ground-based field trials : arxiv.org/abs/2504.08167