Academic Training Lecture Regular Programme

Low Energy Experiments that Measure Fundamental Constants and Test Basic Symmetries (2/4)

by G. GABRIELSE (Professor of Physics and Chair of the Harvard Physics Department, Spokesperson for the

500/1-001 - Main Auditorium (CERN)

500/1-001 - Main Auditorium


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One-Electron Quantum Cyclotron The most accurate measurement of the electron magnetic moment (the electron g-2 value), the most accurate determination of the fine structure constant, and the most precise CPT test with leptons, have been realized with a single trapped electron and a single trapped positron. Recently the quantum limit of an electron cyclotron has been observed, in which the cyclotron motion of a single electron is cooled to its ground state, and quantum transitions stimulated by 1.6 Kelvin blackbody radiation are clearly observed. A quantum nondemolition (QND) measurement decouples the quantum system from the classical measurement circuit in the maximal way, and spontaneous emission is suppressed. Measurements underway with this artificial atom, an electron bound to a trap, have the goal of improving the mentioned measurements by an order of magnitude. The measured electron magnetic moment, an independently measured fine structure constant, and QED theory together provide the most stringent comparison of any theory and experiment. The accuracy of the electron g-2 measurements greatly exceeds that of the muon g-2 measurements, and provides the fine structure constant needed to allow the muon measurement to probe for new physics.
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