New Measurement of the Electron Magnetic Moment and the Fine Structure Constant .

Remarkably, the famous UW measurement of the electron magnetic moment has stood since 1987.~ With QED theory, this measurement has determined the accepted value of the fine structure constant.~~ This colloquium is about a~new Harvard measurement of these fundamental constants.~ The new measurement has an uncertainty that is about six times smaller, and it shifts the values by 1.7 standard deviations.~ One electron suspended in a Penning trap is used for the new measurement, like in the old measurement.~ What is different is that the lowest quantum~levels of the spin and cyclotron motion are resolved, and the cyclotron as well as spin frequencies are determined using quantum jump spectroscopy.~ In addition, a 0.1 K Penning trap that is also a cylindrical microwave cavity is used to control the radiation field, to suppress spontaneous emission by more than a factor of 100, to control cavity shifts, and to eliminate the blackbody photons that otherwise stimulate excitations from the cyclotron ground state.~ Finally, great signal-to-noise for one-quantum transitions is obtained using electronic feedback to realize the first one-particle self-excited oscillator.~ The new methods may also allow a million times improved measurement of the 500 times smaller antiproton magnetic moment. \textbf{New Measurement of the Electron Magnetic Moment} B. Odom, D. Hanneke, B. D'Urson and G. Gabrielse, Phys. Rev. Lett. \textbf{97}, 030801 (2006). \textbf{New Determination of the Fine Structure Constant} G. Gabrielse, D. Hanneke, T. Kinoshita, M. Nio, B. Odom, Phys. Rev. Lett. 97, 030802 (2006). \textbf{AIP Physics Story of the Year }(Phys. News Update, 5 Dec. 2006) \begin{itemize} \item Science \textbf{313}, 448-449 (2006) \item Nature \textbf{442}, 516-517 (2006) \item Physics Today, 15-17 (August, 2006) \item Cern Courier (October 2006) \item New Scientist \textbf{2568}, 40-43 (2006) \item Physics World (March 2007) \end{itemize}