A quantum device that can determine its position in three dimensions is more accurate than non-quantum versions. Vehicles could use it to navigate even if GPS stopped working.
One way to keep track of something鈥檚 position is with an accelerometer, which is a small device that is found in everything from phones to drones. Accelerometers work by detecting changes in movement and therefore position.
It has been known for decades that quantum effects could be used make more accurate accelerometers, but most quantum accelerometers built so far can only measure in one dimension, along a straight line.
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聽at the French National Centre for Scientific Research and his colleagues have now built a quantum accelerometer that can measure in three dimensions.
Its outer casing is a 40-centimetre-long metal box. Inside, there are three lasers and a smaller glass box filled with rubidium atoms kept at just a small fraction above absolute zero. This cold temperature introduces quantum effects, making the atoms behave like waves of matter.
To measure changes in movement, the three lasers 鈥� which point along the box鈥檚 length, width and height 鈥� illuminate the atoms. This forces them to collide, causing ripples, the nature of which depends on the device鈥檚 movements. By analysing the ripple patterns, the device can calculate the acceleration in the laser鈥檚 three directions.
The atoms can be controlled extremely precisely, which makes the whole device very accurate, says Bouyer.
To test this, the researchers mounted their accelerometer on a table that shakes and rotates. They found that if acceleration measurements were used to calculate the device鈥檚 position in space, after a few hours, it would be inaccurate by around 20 metres. In the same time, a standard non-quantum version would be off by 1 kilometre.
鈥淢easuring in three dimensions is a big deal, a necessary and excellent engineering step towards any practical use of quantum accelerometers,鈥� says at the Australian National University in Canberra.
Large vehicles that absorb lots of vibrations, such as ships, could be a good match for this new technology, he says. Equipped with a quantum accelerometer, a ship could keep a very accurate course if the GPS signal malfunctioned or was jammed by hackers, without its crew needing to resort to paper maps.
All objects close to the surface of Earth experience acceleration from the planet鈥檚 gravity and the new device could very accurately measure that too, says at the Technical University of Denmark. This could be useful for more precisely mapping Earth鈥檚 interior for mining because the device would detect a slightly different gravitational acceleration when placed above, for instance, an underground oil well, he says.
Reference:听arXiv,
