A group of researchers has created a quantum crystal of beryllium ions (formed from atoms that have gained or lost electrons) that is ten times more effective at detecting weak electromagnetic fields than other known quantum sensors. And because of this unique feature, the researchers are convinced that this new crystal could be used as a sensor to detect the presence of axion, a hypothetical elementary particle that is seen as a possible component of the also yet-to-be-confirmed dark matter (not visible and only interacting by gravitational force).

The work, published in the scientific journal Sciencequoted by EXAME Magazine, explains that to create the crystal were 'stuck' 150 beryllium ions, using a system of electrodes and magnetic fields, in order to prevent the natural separation that these particles would produce between them. As a result of this manipulation, a kind of sheet was created, with a crystal-like structure that is twice as thick as a human hair, explains the publication Space.com.

This structure has been shown to be extremely sensitive to external electromagnetic forces. "When you excite the atoms, they don't move individually. They move as a whole," stresses Ana Maria Rey of the Joint Institute of the US Astrophysical Laboratory (JILA), who participated in the study.

The group then exploits a quantum property known as quantum entanglement (a physical phenomenon that happens when the quantum states of two particles influence each other) to overcome difficulties that normally exist in very sensitive electromagnetic sensors, since the results are susceptible to 'noise' (in practice, interference other than those you want to measure). "To measure the displacement [of the crystal], we need a displacement greater than the noise," the researcher further explains.

The team believes that by trapping more beryllium ions in a crystal structure they will be able to create an even more sensitive element and then begin the search for axions. This hypothetical dark matter particle has, in theory, a mass one million times less than that of an electron, which has made it difficult to prove its existence. It is now speculated that if an axion were to come into contact with a beryllium quantum crystal, the crystal might be able to detect its presence.

But other applications are already planned for this type of quantum sensor, such as the detection of gravitational waves.