Billion times fainter than earth: Chinese-German researchers build floating compass that could hunt dark matter

Chinese researchers, along with a German team, have developed a table-top magnetic sensor that operates at room temperature capable of spotting magnetic signals a billion times fainter than the Earth’s own field. The Levitated Magnetometer (LeMaMa) act as a compass with a needle that floats in mid-air without any friction.

To spot the signals, the team can map magnetic fields down to the femtotesla level by tracking the needle’s tiny deflections. This is an advanced method that could increase the hunt for elusive dark matter particles or monitor brain signals. “The combination of room-temperature operation, tiny components and high sensitivity makes LeMaMa promising for fundamental physics experiments,” said Ji Wei, assistant professor at Peking University’s school of physics and corresponding author of the study.

Magnetic fields are 'omnipresent'

Magnetic fields exist all around us, spanning a huge range of strengths, from roughly 1.5 tesla in a hospital MRI machine to the incredibly faint femtotesla level (a quadrillionth of a tesla) produced by human brain activity. Detecting such minuscule magnetic fields has historically posed a major challenge.

Now, researchers from Peking University in China and Johannes Gutenberg University Mainz in Germany have developed the world's first room-temperature, ultraprecise magnetometer that relies on a levitated magnet. The findings of the work were published in the journal Science on August 6.

Previously, measuring magnetic fields at the femtotesla level has depended largely on two methods. The first is the superconducting quantum interference device (SQUID) magnetometer, known for its exceptional sensitivity but requiring extremely cold, near-absolute-zero temperatures—necessitating bulky, costly liquid-helium cooling systems.