Magnetic Moments, Fine Structure Constant, and QED

这项工作的智力价值来自于在物理学中进行一些最精确和最基本的测量的可能性。其中一个目标是对基本粒子的性质进行最精确的测量——用玻尔磁子测量的电子磁矩。第二个目标是测试物理学中最成功、最基础的理论——量子电动力学（QED），其精确度达到前所未有的水平，可以说是所有理论和实验中最精确的比较。量子电动力学描述了物质和光的相互作用，它为现代粒子理论树立了标准。第三个目标是对轻子和反轻子、电子和正电子进行最精确的比较（以15倍或更多），作为CPT不变性的测试。第四个目标是最精确地确定基本精细结构常数。这个常数给出了低能量极限下电磁相互作用的强度，它表征了各种现象的大小，从原子的能量尺度，到交流约瑟夫森效应，再到量子霍尔效应。此外，精细结构常数是精确确定基本单位制的关键测量常数之一（与里德伯常数和普朗克常数一起），而基本单位制对植根于科学的技术社会至关重要。第五个目标是在比较反质子和质子的磁矩的过程中观察质子的自旋翻转，比以前可能的精确一百万倍。第六个目标是研究采用精密测量方法制造用于量子信息研究的第一个可扩展的单电子量子位的可能性。使这些异常精确的测量成为可能的设备和方法本身就很有趣。它们将包括冷却到100 mK的圆柱形Penning陷阱腔，单个电子单量子跃迁的量子非破坏观测，单粒子振荡器的自激，反馈冷却，自发发射的抑制，一个电子自旋和回旋水平的量子跳变光谱以及腔边带冷却。这些实验也提供了很好的教育机会。在这一领域学习技能的年轻参与者现在从事物理学各个分支领域的研究工作。

The intellectual merit of this work derives from the possibility to make some of the most precise and fundamental measurements in physics. One goal is to make the most precise measurement of the property of an elementary particle -- the electron magnetic moment measured in Bohr magnetons. A second goal is to test the most successful and fundamental theory of physics, quantum electrodynamics (QED), to an unprecedented level of precision, arguably the most precise comparison of any theory and experiment. Quantum electrodynamics describes the interaction of matter and light, and it sets the standard to modern particle theories aspire. A third goal is to make the most precise comparison of a lepton and an antilepton (by a factor of 15 or more), the electron and the positron, as a test of CPT invariance. A fourth goal is to make the most precise determination of the fundamental fine structure constant. This constant gives the strength of the electromagnetic interaction in the low energy limit and it characterizes the size of a wide variety of phenomena, ranging from the energy scales in atoms, to the ac Josephson effect, to the quantum Hall effect. In addition, the fine structure constant is one of the crucial measured constants (along with the Rydberg and Planck's constant) for accurately determining the system of basic units that are important to a technological society rooted in science. A fifth goal is to observe the spin flip of a proton on the way to comparing the magnetic moments of the antiproton and proton a million times more accurately than has previously been possible. A sixth goal is to investigate the possibility of adapting the precision measurement methods to make the first scalable, one-electron qubit for quantum information studies. The devices and methods that will make these unusually precise measurements possible are interesting in their own right. They will include a cylindrical Penning trap cavity cooled to 100 mK, quantum nondemolition observations of one-quantum transitions of a single electron, self-excitation of a one-particle oscillator, feedback cooling, inhibition of spontaneous emission, quantum jump spectroscopy of one electron's spin and cyclotron levels and cavity sideband cooling. The experiments also offer outstanding educational opportunities. Junior participants who learned their craft doing work in this area are now engaged in research careers in various subfields of physics.