A sensor made from extremely cold atoms can detect forces as small as a millionth septillionth of the gravitational force on an apple falling from a tree. It could help reveal the existence of completely new forces in the future.
All known forces stem from four fundamental ones 鈥� gravity, electromagnetism and the strong and weak nuclear forces. But attempts to explain mysteries of the universe, such as what dark matter is, often suggest that there may be an as-yet-unknown fifth force.
Such a force is thought to be weak and only detectable very close to objects, so researchers need extremely sensitive devices to look for it. at the French National Laboratory of Metrology and Testing and his colleagues used rubidium atoms to build the most sensitive force detector yet.
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The researchers first placed 120,000 rubidium atoms in an airless metal-and-glass cylinder. They used lasers to cool the atoms to only a small fraction of a degree above absolute zero. The resulting ultracold atoms are very sensitive to electric fields and light, which can be used to precisely control their quantum states.
The team used this control to turn the components into an interferometer 鈥� a device filled with waves of matter that clash into each other and produce patterns that change predictably when there is a nearby force.
To test the sensitivity of the sensor, the researchers measured the force between the atoms in the device and a mirror. This force is caused by quantum processes that happen in seemingly empty space and is very weak. The team measured it unprecedentedly precisely: down to 4 quectonewtons or a tenth of the force you would need to pick up a single electron.
鈥淲e don鈥檛 know any other method that could achieve this sensitivity,鈥� says Balland.
at Simon Fraser University in Canada says this force is extremely hard to measure and the new sensor could do so from a few micrometres away.
鈥淭here are theories of physics beyond the Standard Model that predict new effects, like modifications to standard Newtonian gravity at distances in the nanometre to millimetre range. Extremely sensitive devices like this one are promising for testing these predictions,鈥� he says.
at the French National Laboratory of Metrology and Testing who also worked on the project says that it has taken the team more than a decade to build the new sensor. 鈥淎nd the way to go now may be to actually take a step back, understand the limitations that we have and modify to progress in sensitivity even more,鈥� he says.
Reference:
arXiv
