Antimatter is not known for being easy to get ahold of. That’s part of why these particles remain so cryptic. But recently, a team of physicists at Northwestern University managed to trap a single antimatter particle for months. Cooling it to temperatures near absolute zero, they could control its quantum states with great precision without even touching it. The experiment, published in Physical Review Letters, represents a breakthrough in our understanding of one of the great mysteries of physics.

In theory, antimatter should be everywhere. Mathematics predicts that every particle of matter has an equivalent antiparticle, a fact that scientists have verified experimentally. The universe should therefore contain similar amounts of both, but almost everything we observe is made up of ordinary matter, and we still don’t know why.

It is possible to produce antimatter particles in laboratories, but studying them is still incredibly difficult. When an antiparticle comes into contact with ordinary matter, the two annihilate each other and release energy. To prevent research facilities from exploding, scientists use vacuum chambers and electromagnetic fields that suspend the antiparticles in isolation. But this only partially solves the problem. Studying these particles, especially experimenting with their behavior on a quantum scale, remains challenging.

For this experiment, researchers at Northwestern trapped a positron, the antimatter counterpart of electrons . The team, led by Gerald Gabrielse, developed a device known as a single-positron quantum cyclotron, which used electric and magnetic fields to hold the positron in a vacuum at a temperature close to absolute zero.

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