 The preferred methods in 2019 are measurements of electron anomalous magnetic moments and of photon recoil in atom interferometry.The theory of QED predicts a relationship between the dimensionless magnetic moment of the electron and the fine-structure constant (the magnetic moment of the electron is also referred to as "Landé -factor" and symbolized as ).The most precise value of obtained experimentally (as of 2012) is based on a measurement of using a one-electron so-called "quantum cyclotron" apparatus, together with a calculation via the theory of QED that involved tenth-order Feynman diagrams