Physicists trap single positron for record month at CERN

Physicists at the University of Washington, working with collaborators at the Max Planck Institute for Nuclear Physics, announced on Tuesday that they have confined a single positron – the antimatter counterpart of the electron – for more than a month inside a cryogenic Penning trap. The achievement, made possible by ultra‑high vacuum and magnetic‑field stabilization, marks the longest continuous hold of an isolated antimatter particle and opens the door to quantum‑level measurements that were previously impossible.

Trapping antimatter long enough to study its quantum properties has been a major hurdle for decades. Earlier experiments could keep positrons or antiprotons for only seconds or, at best, minutes, limiting the precision of tests of fundamental symmetries such as charge‑parity‑time (CPT) invariance. The new record builds on advances in trap design, laser‑cooling techniques and noise‑reduction electronics that were refined during the hunt for antihydrogen at CERN. By reducing the surrounding temperature to 4 kelvin and achieving a pressure below 10⁻¹⁵ torr, the team eliminated collisions that would normally eject the particle, allowing it to remain isolated for 30 days – roughly 2.6 million seconds.

During the confinement the researchers performed repeated spin‑flip measurements, demonstrating coherent control of the positron’s quantum state for hours at a time. The data show a spin‑coherence time an order of magnitude longer than any prior antimatter experiment, a key metric for precision spectroscopy. “Holding a single antiparticle for this duration is a game‑changer,” said Dr Lena Hoffmann, a senior scientist on the project. “It lets us probe the magnetic moment of the positron with unprecedented accuracy and compare it directly to that of the electron.” The team plans to use the trap to measure the positron’s g‑factor to a fractional precision of 10⁻¹², a test that could reveal tiny differences between matter and antimatter and inform theories about why the universe is dominated by matter.

If the measurements confirm the Standard Model’s predictions, they will tighten constraints on new physics. Conversely, any discrepancy could point to unknown forces or particles that helped shape the early cosmos. The breakthrough also paves the way for exploring antimatter in quantum information experiments, where the unique properties of antiparticles might enable novel computing schemes. Researchers expect to publish detailed results later this year and are already designing next‑generation traps that could hold multiple antiparticles simultaneously, further expanding the frontier of antimatter research.