Researchers at Northwestern University held one positron, the antiparticle of an electron, in an electromagnetic trap for several months. The particle was isolated in a vacuum and cooled to almost absolute zero. Under these conditions, the team manipulated its quantum states and repeated the measurements without destroying the sample. The work was published in Physical Review Letters. A positron cannot simply be placed in an ordinary container: when it encounters matter, it annihilates. Therefore, it is the long-term retention and control of one particle that makes the method useful for future experiments.
Physicists are interested in how closely the properties of matter match the properties of antimatter. The mass of an electron and a positron is the same, but the electric charges are opposite. Now we can more accurately compare their magnetic properties. According to an estimate cited by WIRED, the new setup could improve the accuracy of positron measurements by about 30 times. This is the perspective of the method, and not a message about a deviation already found. So far, the experiment has not shown an unexpected difference between the particles. Its result is different: the researchers have a more sensitive instrument, capable of looking for small differences and testing physical theories that explain the predominance of ordinary matter in the Universe.