A novel quantum sensor that measures gravity changes by detecting variations in the travel time of falling atoms has been tested in a first of its kind experiment aboard an Australian naval ship.
The sensor—a dual gravimeter—has been developed by Australian company Q-CTRL and could reach the market in late 2026. During the tests onboard the Royal Australian Navy’s aviation training vessel MV Sycamore, the crew was able to navigate for 144 hours without GPS access using the autonomous prototype system.
According to Michael J. Biercuk, Q-CTRL CEO and founder, the test marked the first time such a sensor was used in a practical scenario aboard a moving vehicle.
The Trouble With GPS
Quantum gravimetry is among the plethora of technologies that are being developed to serve as a backup for global navigation satellite systems (GNSSs) such as the Global Positioning System (GPS). With the rise in conflict and geopolitical tensions all over the world, GNSS jamming and spoofing (confusing users with fake satellite signals) has become an everyday problem in many areas of the world.
In early May, a 300-meter-long container ship ran aground in the Red Sea reportedly because of GPS interference. Analysts’ data revealed the ship’s GPS position following the incident appeared hundreds of miles away from its actual spot, somewhere in the Sahara Desert. The incident underscored the growing vulnerability of GPS, a service of the U.S. government, which is indispensable not only for the transport sector but also for many other industries including banking, power-grid synchronization, or offshore drilling.
Maritime users all over the world have long been relying on inertial navigation systems as a backup for GPS, but these systems have their limitations. They depend on accelerometers and gyroscopes to track the speed and motion direction changes of a vehicle. Their reliability, however, decreases with the distance traveled as tiny errors accumulate causing an increasing gap between the reported and actual position.
Quantum gravity sensors, Biercuk said, don’t suffer from this problem. The system deduces the strength of Earth’s gravity in every given point of the journey from the motion of the atoms illuminated by laser beams inside a vacuum chamber and compares that data with gravity maps compiled from satellite measurements.
“This is not dissimilar from some of the new visual navigation systems that are emerging,” Biercuk said. “If you put a camera on a drone and you look at the ground, you can identify hills and valleys and buildings, and then do map matching. We’re doing the same thing, except the set of eyes that we’re using to see the Earth come from these quantum sensors.”
The Quantum Solution
Despite the planet’s relatively regular spheroid shape, the Earth’s gravitational pull is not uniform. It differs based on the distribution of mass inside the planet but also reflects features of the landscape such as hills and valleys and differences in density of the minerals underground.
In addition to the superb accuracy, quantum gravity sensing is also unjammable and unspoofable.
“You can’t spoof gravity without literally moving a mountain,” said Biercuk.
The passive nature of the sensor, which doesn’t require any active signal emissions (unlike lidar- or radar-based systems) helps defense users avoid detection by the adversary.
The prototype system tested off the Australian coast is about the size of a server rack, but Biercuk hopes Q-CTRL’s engineers will be able to further shrink it to about the size of a small fridge before taking it to the market next year. The development took about 14 months, he said, and challenged the team once they began experimenting with the sensor outside their labs.
“These sensors are extraordinarily sensitive and when you take them from a pristine laboratory environment to anything less than pristine, the whole world conspires against you,” said Biercuk. “Mechanical vibrations, radio interference, and the movements of a vessel in all directions creates noise, which completely obscures the signal.”
The Q-CTRL team solved the problem through a complex software solution that filters out the unwanted noise.
Despite the promising performance, Biercuk doesn’t think that quantum gravimeters could ever completely replace satellite navigation for any kind of users. But in addition to areas suffering from GPS interference, the system could help ships navigating around polar regions where GPS is notoriously unreliable due to the geometry of the satellites’ orbits.
“GPS is a very good technology when you can trust it,” said Biercuk. “But for the situations when you can’t or when it’s not available, you need a robust alternative.”
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