Scientists Trap, Cool Single Positron to Quantum Ground
Northwestern University researchers held one antimatter particle for months, cooling it to its quantum ground state.
Updated on Nov. 4, 2026 in Physics
Northwestern University scientists trapped a single positron for months and cooled it to 300 millikelvins above absolute zero, reaching its quantum ground state. The trapping and cooling process took less than 12 hours, and the study was published in Physical Review Letters.
Why it matters
The matter-antimatter asymmetry suggests the Standard Model of physics is incomplete, making precise antimatter measurements a key test of current theory. Researchers plan to compare the positron's magnetic properties with a previous one-electron quantum cyclotron measurement.
The experiment held a single positron for months and cooled it to 300 millikelvins above absolute zero in under 12 hours, using microwaves to probe its quantum transitions. Precision measurements of its g factor have not yet been completed, leaving open whether it matches the electron's value.
The players
Northwestern University
A private research university in Evanston, Illinois, whose scientists conducted the positron trapping experiment.
Paolo Crivelli
A physicist at ETH Zurich who was not affiliated with the study and called the research an experimental breakthrough.
The details
Researchers guided a single positron into the near-perfect vacuum of a trap and used radioactive decay from sodium-22 as the source of positrons. They then delivered energy through finely tuned microwaves to study the particle's quantum transitions.
Timeline
Months: positron held in the trap
Less than 12 hours: trapping and cooling process completed
Study published in Physical Review Letters
The Big Picture
The experiment extends the single-particle quantum cyclotron approach used for the electron's magnetic moment to its antimatter counterpart. A close match between the two would reinforce current theory, while a mismatch would be the biggest discovery in physics in the last century.
Precise antimatter measurements could eventually sharpen understanding of fundamental particle behavior that underpins future technologies. The practical applications remain distant, as the current work is an early experimental step.
The takeaway
A single trapped particle can now be studied with precision that was previously out of reach. This capability opens a path toward testing whether the laws of physics treat matter and antimatter identically.
Further reading
Explore more Physics coverage for Evanston readers.
Source note: This article includes information reported by Popular Mechanics.
