Overview
- Northwestern researchers report in Physical Review Letters that they trapped a single positron for months and drove individual quantum transitions and spin flips, confirming long-term control of one antiparticle.
- The team captured positrons from a sodium-22 source, slowed and loaded one into a cryogenic Penning trap cooled to about 0.3 kelvin, and used tuned microwaves to change and read its quantum state.
- Researchers detected each quantum jump and spin flip through tiny shifts in the particle’s oscillation frequency, and the size of those shifts showed only one positron was present in the trap.
- The immediate goal is to optimize the apparatus to measure the positron’s magnetic moment with precision comparable to the best electron measurements, a result that would enable a much stronger CPT symmetry test than exists today.
- If a statistically significant difference between electron and positron magnetic moments appears, it would point to physics beyond the Standard Model and could offer clues about the universe’s matter–antimatter imbalance, but that outcome depends on the future high-precision measurement.