Plate Nº 51 · recorded November 13, 2026
PhysicsReported finding
Physicists Hold a Single Antimatter Particle for Months in a Quantum Trap
Northwestern physicists held one positron in a quantum ground state for months, at 0.3°C above absolute zero, to test why matter outlived antimatter after the Big Bang.
By Nathan Brooks3 min read679 words
In brief
- Northwestern physicists trapped a single positron in a quantum ground state for months, a first for antimatter.
- The trap runs at about 300 millikelvins, just 0.3°C above absolute zero, in a near-perfect vacuum.
- Earlier electron work measured the magnetic moment to one part in 10 trillion — the positron measurement is next.
- The study by Myers, Soucy, Sukra, Sinha and Gabrielse appeared in Physical Review Letters on August 20, 2026.
- The U.S. National Science Foundation funded the research.
Northwestern University physicists have trapped a single positron — the electron's antimatter counterpart — and held it in a precisely controlled quantum state for months at a time. The achievement, described in Physical Review Letters on August 20, 2026, marks the first time researchers have brought an individual antimatter particle under this level of quantum control.
The result matters because of a number physicists can't explain: zero. The Big Bang should have produced equal amounts of matter and antimatter, and that mixture should have annihilated itself completely. Yet stars, planets and people exist, which means something in the current theory is missing.
What did the team actually build?
Study leader Gerald Gabrielse calls the device a "one-positron quantum cyclotron." Think of it as an artificial atom: the trapped positron occupies distinct quantum energy levels that the researchers can both manipulate and observe.
Getting there took several steps. The team captured an energetic positron emitted by the radioactive decay of sodium-22, a rare isotope of sodium. They then slowed the particle dramatically and guided it into a specialized trap, where electric and magnetic fields suspend it away from the walls and a near-perfect vacuum minimizes contact with ordinary matter.
That isolation is essential. When matter and antimatter meet, they annihilate — both particles vanish — so an ordinary container would destroy the sample instantly. Gabrielse is quick to defuse the drama, though: "To be clear, it's not dangerous. We don't have enough antimatter to make an explosion."
How cold is the trap?
The positron sits at about 300 millikelvins — just 0.3 degrees Celsius (0.54 degrees Fahrenheit) above absolute zero. At that temperature, the particle's cyclotron motion, its circling movement in the magnetic field, settles into its lowest quantum energy state.
"We cool it down so much that it's in its quantum ground state," Gabrielse said. "We actually coaxed this very fast positron to sit there and behave for months at a time."
The researchers then used carefully tuned microwaves to nudge the positron between individual quantum states, and they detected each transition. Triggering and observing those jumps is what gives them the control needed for an exceptionally precise magnetic measurement.
Why compare matter and antimatter?
The experiment builds on Gabrielse's earlier work. His group previously used a one-electron quantum cyclotron to measure the electron's magnetic moment — how strongly a particle interacts with a magnetic field — to about one part in 10 trillion. That ranks among the most precise measurements ever made of an elementary particle.
The next goal is a comparable measurement of the positron. Electrons and positrons carry opposite electric charges, and theory predicts their magnetic moments are equal in magnitude but opposite in direction. Any unexpected mismatch would challenge the Standard Model, the framework describing fundamental particles and three of nature's four forces.
The stakes are high because the Standard Model, despite surviving decades of tests with extraordinary precision, cannot explain why the universe contains overwhelmingly more matter than antimatter. "We know the Standard Model has to be wrong somewhere — or at least incomplete," Gabrielse said. "For example, it cannot predict why the universe exists, so that's a pretty big loophole."
"Antimatter gets its popular charm from science fiction," he added. "If you take an electron and an anti-electron (or positron) and collide them together, they both disappear... The big mystery of the universe is the Big Bang should have created equal amounts of matter and antimatter."
What comes next?
The team expects the two measurements to match. "Current theories suggest that there will be no difference in the two measurements," Gabrielse said. "If it turns out they are not equal, that would be the biggest discovery in physics in the last century."
The study, authored by T. G. Myers, L. Soucy, B. A. D. Sukra, B. Sinha and G. Gabrielse, was funded by the U.S. National Science Foundation. For now, the result is a proof of control rather than a discovery — but it opens the door to one of physics' most consequential comparisons.
via google.com (Original)
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