Physicists Trap a Single Positron for Months to Probe Antimatter's Secrets
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A Northwestern University team held a single positron — antimatter's twin of the electron — in a quantum cyclotron for months, aiming to measure its magnetic properties at the same precision already achieved for the electron.
Physicists led by Dr. Gerald Gabrielse at Northwestern University have trapped a single positron — the antimatter counterpart of an electron — inside a cryogenic magnetic trap for several months. By cooling the particle to near absolute zero, the team created what they describe as a one-positron quantum cyclotron, an artificial atom whose quantum energy levels can be precisely controlled and observed. The positron was sourced from the nuclear decay of a radioactive sodium atom, which releases positrons at high energy and speed; coaxing one into the cold trap was a central challenge of the work. With the positron held in place, the researchers used radio and microwave signals to drive transitions between individual quantum energy levels and detect those jumps. This technique allowed them to measure the positron's magnetic moment. Gabrielse's group had previously achieved the same kind of quantum measurement for the electron at a precision of one part in ten to the thirteenth power, and the team now aims to reach that same level of precision for the positron. The ultimate scientific goal is to determine whether the positron is a truly exact opposite of the electron in every measurable property, or whether tiny physical differences exist between them. Any such difference would point toward physics beyond our current understanding of the universe. Dr. Gabrielse discussed the research on Science Friday with host Flora Lichtman.
