Physicists make the most accurate measurement yet of an electron’s magnetic moment

A joint team of physicists from Harvard University and Northwestern University has found the most accurate value yet for an electron’s magnetic moment. In their paper published in the journal Physical review lettersthe group describes the methods they used to measure electron properties and the implications for the new resolution.

The magnetic moment of an electron, also known as the electron dipole moment, results from its electrical and spin properties. Of all the primary characteristics studied, these were the most accurately measured, and also the most thoroughly verified.

Measuring the electron’s magnetic moment to even greater levels of precision is important because physicists believe that, at some point, these measurements will help complete the Standard Model of Physics. In this new effort, the research group has measured the magnetic moment with twice as much accuracy as any other effort — the last best effort was 14 years ago.

Physicists use the magnetic moment of particles such as electrons to test the Standard Model by studying the interactions between them and virtual particles that appear inside a vacuum chamber. This study includes measuring the effect of collisions on both the magnetic moment and its factor g, and then comparing the results with what is described by the Standard Model.

The work involved suspending a single electron in a Penning trap with a magnetic field constant at 5 Ts. Then the chamber was cooled to almost absolute zero. Measurements were taken of what the team describes as “quantum jumps” of electrons between energy levels. Then, using a magnetic field gradient, they were able to perform quantum detection of non-refraction—a technique for measuring quantum jumps without changing the quantum state, which reduced the uncertainty in the magnetic moment measurements. The end result was a measurement of the magnetic moment to a degree of accuracy not achieved before – 0.13 parts in 1 trillion.

The new measurements are expected to influence the work involved in future tests of the Standard Model.