Researchers invent first ever 3D quantum accelerometer for use in ships and submarines

A team at the French National Centre for Scientific Research has invented a first-of-its-kind 3D quantum accelerometer that uses lasers and ultra-cold rubidium atoms to measure movement in all three dimensions, according to a New Scientist article published last week.

The discovery could lead to accurate navigation without GPS and reliable detection of valuable mineral deposits.

Today mechanical accelerometers are very useful but not very reliable. Given enough time, they'll accumulate errors on the scale of kilometers.

This isn't a problem for phones briefly out of touch with GPS, but it becomes an issue when devices travel out of range for extended periods. However, precise positional accelerometer tracking would be extremely useful on submarines—which don't have easy access to GPS underwater without the interference of new technology.

They could also serve as reliable backup navigation on ships should they lose GPS.

Replacing GPS systems

Researchers have long been working on quantum accelerometers that measure the wave-like properties of matter to replace GPS systems. The devices function by using lasers to slow and cool clouds of atoms, allowing them to behave like waves of light, creating interference patterns as they move.

The lasers then measure how these patterns change to track the device's location through space. These devices are called atom interferometers, and they used to be quite bulky.

But now scientists have managed to produce small practical ones that are even 3D. This is what the team in France has achieved in a metal box about the length of a laptop computer.

The new accelerometer consists of lasers located along all three spatial axes that can manipulate a cloud of rubidium atoms trapped in a small glass box and chilled nearly to absolute zero. These lasers generate ripples in the cloud of atoms and measure the resulting interference patterns to estimate motion.

This new layout allows the team to control the atoms with extreme precision. This leads to measurements that can be relied on to be accurate. Tests undertaken by the team found the system was 50 times more reliable than classical sensors.

Useful applications

We won't be seeing this tool in phones any time soon, though, as it's still too big for these kinds of applications. But with a few tweaks, the team says it could be installed on ships or submarines for precise navigation or be used by geologists looking for mineral deposits by measuring subtle changes in gravity.

The team in France is not the only one looking to make more practical accelerometers. In September 2019, researchers used the highly conductive nanomaterial graphene to create the world's smallest accelerometer.

The new technological achievement, created by researchers at KTH, was touted as a potential breakthrough for body sensor and navigation technologies that could be used in mobile and gaming.

Xuge Fan, a researcher in the Department for Micro and Nanosystems at KTH, explained that graphene and its unique properties helped him and his team to create these ultra-small accelerometers. "Based on the surveys and comparisons we have made, we can say that this is the smallest reported electromechanical accelerometer in the world," he said in 2019.

The new study was published as a pre-print paper posted on arXiv in September.

Study abstract:

Robust and accurate acceleration tracking remains a challenge in many fields. For geophysics and economic geology, precise gravity mapping requires onboard sensors combined with accurate positioning and navigation systems. Cold-atom-based quantum inertial sensors can potentially provide such highprecision instruments. However, current scalar instruments require precise alignment with vector quantities. Here, we present the first hybrid three-axis accelerometer exploiting the quantum advantage to measure the full acceleration vector by combining three orthogonal atom interferometer measurements with a classical navigation-grade accelerometer triad. Its ultra-low bias permits tracking the acceleration vector over long timescales—yielding a 50-fold improvement in stability (6 × 10−8g) over our classical accelerometers. We record the acceleration vector at a high data rate (1 kHz), with absolute magnitude accuracy below 10 µg, and pointing accuracy of 4 µrad. This paves the way toward future strapdown applications with quantum sensors and highlights their potential as future inertial navigation units.