Scientists Hold One Antimatter Particle for Months, Advancing Physics

WHO:

Nature - Gerald Gabrielse, a physicist at Northwestern University in Evanston, Illinois, led the research.

Nature - Barbara Maria Latacz, an antimatter physicist at CERN near Geneva, Switzerland, called the experiment a “remarkable achievement” and said it would provide “a powerful probe for physics beyond the standard model.”

Nature - Stefan Ulmer, a physicist at Heinrich Heine University Düsseldorf (HHU) in Germany, said, “I cannot wait to see their first precision measurements.”

Phys.org - Northwestern University physicists coaxed a single positron, the antimatter counterpart of an electron, into a controlled quantum state.

WHAT:

Nature - Researchers suspended and cooled a single positron to its lowest possible energy state using a one-positron quantum cyclotron.

Nature - The apparatus is intended to enable unprecedentedly precise measurements of the positron’s magnetic properties, including its magnetic moment, which determines how a particle wobbles on its axis in a magnetic field.

Nature - The team aims to compare electron and positron magnetic moments; the article says these can be measured with 10,000 times greater precision than the corresponding property in protons and antiprotons.

Nature - The experiment was detailed in Physical Review Letters.

Nature - Researchers have observed a slight preference for matter in the behavior of a handful of particles, but not enough to explain the universe’s matter composition; detailed proton–antiproton comparisons have not uncovered differences.

WHERE:

Nature - The research was led at Northwestern University in Evanston, Illinois; the article does not specify where the experiment itself was performed.

Nature - The positron trap’s location is not stated.

WHY:

Nature - The researchers seek subtle matter–antimatter differences that could help explain why the universe contains overwhelmingly more matter.

Nature - The Standard Model predicts that matter and antimatter should have been created in equal amounts during the Big Bang; because they annihilate on contact, equal quantities would have left no matter in the universe, Gabrielse said.

Nature - Gabrielse said finding a mismatch between matter and antimatter measurements “would be revolutionary in physics.” The article notes that the Standard Model cannot explain the apparent existence of dark matter.

HOW:

Nature - The team began with fast-moving positrons produced by radioactive decay, slowed them by scattering them off atoms in a tungsten crystal, selected the slowest surviving particles, and fed them into a trap.

Nature - Many positrons were annihilated during the slowing process.

Nature - Matter and antimatter have the same mass and opposite properties such as electric charge; when they meet, they annihilate in a burst of energy.

(UPDATED October 21, 2026 23:29 UTC)

Northwestern University physicists have placed a single positron, the antimatter counterpart of an electron, into a controlled quantum state. Led by physicist Gerald Gabrielse, the team suspended and cooled the particle to its lowest possible energy in a device called a one-positron quantum cyclotron. They started with fast-moving positrons from radioactive decay, slowed them in a tungsten crystal, and trapped the slowest survivors. The apparatus is designed to measure the positron’s magnetic properties with exceptional precision, then compare its magnetic moment with an electron’s. Such comparisons could reveal subtle differences between matter and antimatter, which may help explain why the universe contains far more matter. The Standard Model predicts equal amounts were created in the Big Bang, but equal quantities would have annihilated. Antimatter physicist Barbara Maria Latacz called the experiment remarkable, while Stefan Ulmer said he looked forward to its first precision measurements.