Physics Division Colloquium - 8 Dec 2006

For the first time since 1987, the magnetic moment of the electron and the fine structure constant have been measured with a greatly improved accuracy. A quantum cyclotron is used for the first time -- an isolated electron cooled to a low enough temperature that the lowest quantum levels of its cyclotron and spin motions are cleanly resolved. The electron is thus weakly bound in an artificial atom in which the "nucleus" is an apparatus that we build. QND Quantum jump spectroscopy of these levels yields a magnetic moment for the electron with an uncertainty that is six times lower than that for the famous 1987 measurement, but the measured moment is also shifted by 1.7 standard deviations. Cavity-inhibited spontaneous emission, a cylindrical Penning trap, and the first one-particle self-excited oscillator are examples of new techniques which make possible the new measurement. The new electron magnetic moment, together with QED theory, determines the fine structure constant about ten times more accurately than any rival method. The significance of the new measurements for searching for new physics, testing QED, and for our system of fundamental constants will be mentioned.

ANL Physics Division Colloquium Schedule