The researchers devised a one-positron quantum cyclotron to probe the particle's properties. Credit: Gerald Gabrielse/Northwestern University

Physicists have now suspended a single positron — the antimatter equivalent of an electron — in mid-air and cooled it to its lowest possible energy state.

The set-up will enable researchers to study magnetic properties of the positron with unprecedented precision. Physicists hope to spot subtle differences between matter and antimatter that could shed light on one of physics’ greatest mysteries.

No one knows why the world is made overwhelmingly of matter. Today’s best theory of particles and forces, the standard model, suggests that just as much antimatter should have been created during the Big Bang.

But when they come into contact, matter and antimatter — which have the same mass but are opposite in properties such as charge — disappear into a burst of energy.…