Electron magnetic moment measured with record precision

Physicists from Northwestern University in Illinois have determined the value of the electron's magnetic moment with

record accuracy.The measurement, with an uncertainty of 0.13 parts per trillion, reduces uncertainty by a factor of 2.2 compared to the previous record, achieved in 2008. High measurement accuracy will help expand the standard model of particle physics. 

The researchers developed a setup in whichone electron is held in a Penning trap in a constant magnetic field of 5 Tesla.  The elementary particle was cooled to a temperature at which the cyclotron motion of the electron inside the device is quantized. 

For measuring magnetic moment, frequencyrotation of the electron and the cyclotron frequency, physicists observed the "quantum jumps" of the electron between the lowest energy levels. At the same time, they used a small magnetic field gradient to conduct quantum non-destructive observations - not to change the uncertainty of a quantum system during the experiment.

Scheme of the experimental setup - cooling system (a) and Penning trap electrode (b), as well as the principle of measurement (c). Image: X. Fan et al., Physical Review Letters

Researchers succeeded in record accuracybe achieved due to the properties of the installation. The proposed system for cooling and capturing electrons increases the stability and uniformity of the magnetic field. In addition, scientists used an improved design of the trapping resonator, which can accurately control the axial movement of an electron and strongly suppress spontaneous emission transitions between the quantum levels of an elementary particle.

Physicists point out that the standard model of physicsrequires clarifications and additions. Accurate measurements of elementary particles and comparison of the obtained results with theoretical calculations will help to find the missing components of this model.

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On the cover: artistic illustration of the measurement of the magnetic moment of an electron. Image: Carin Cain, American Physical Society