Physicists trap and tame single particle of antimatter for months

Northwestern University physicists trapped a single positron, cooled it to near absolute zero, and kept it suspended in a near-perfect vacuum for months. They describe the result as a one-positron quantum cyclotron, where the particle behaves like an artificial atom with controllable quantum energy levels.

The work is meant to support an extremely precise comparison between positron and electron magnetic properties. If the measurements differ from what current theory predicts, the result would point to a limit of the Standard Model and could help explain why ordinary matter dominates the universe.

Reading notes

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• The team captured a positron from radioactive decay of sodium-22 and slowed it before loading it into the trap.
• The trap uses electric and magnetic fields to hold the positron in empty space, so it does not touch ordinary matter.
• The trap interior is cooled to about 300 millikelvins, placing the positron in its quantum ground state.
• The scientists used microwaves to add precise energy and detect transitions between the positron’s quantum states.
• The long-term goal is to measure the positron’s magnetic properties and compare them with electron measurements.
• The study builds on earlier work with a single electron and on methods for trapping and cooling antiprotons.