Laser-cooling of atoms and atom-trapping are finding increasing application in many areas of science. One important use of laser-cooled atoms is in atom interferometers. In these devices, an atom is placed into a superposition of two or more spatially separated atomic states; these states are each described by a quantum-mechanical phase term, which will interfere with one another if they are brought back together at a later time. Atom interferometers have been shown to be very precise inertial sensors for acceleration, rotation and for the measurement of the fine structure constant. Here we use an atom interferometer based on a fountain of laser-cooled atoms to measure g, the acceleration of gravity. Through detailed investigation and elimination of systematic effects that may affect the accuracy of the measurement, we achieve an absolute uncertainty of Δg/g ≈ 3 x 10~(-9), representing a million-fold increase in absolute accuracy compared with previous atom-interferometer experiments. We also compare our measurement with the value of g obtained at the same laboratory site using a Michelson interferometer gravimeter (a modern equivalent of Galileo's 'leaning tower' experiment in Pisa). We show that the macroscopic glass object used in this instrument falls with the same acceleration, to within 7 parts in 10, as a quantum-mechanical caesium atom.
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机译：原子的激光冷却和原子俘获在许多科学领域中的应用越来越广泛。激光冷却原子的一个重要用途是原子干涉仪。在这些装置中，一个原子被放置在两个或多个在空间上分离的原子态的叠加中。这些状态分别由一个量子力学相位项来描述，如果稍后将它们重新组合在一起，则会相互干扰。原子干涉仪已被证明是非常精确的惯性传感器，用于加速度，旋转和精细结构常数的测量。在这里，我们使用基于激光冷却原子源的原子干涉仪来测量重力加速度g。通过详细研究和消除可能影响测量精度的系统影响，我们实现了Δg/ g≈3 x 10〜（-9）的绝对不确定度，与以前的原子相比，绝对精度提高了100万倍。干涉仪实验。我们还将测量结果与使用迈克尔逊干涉仪重力仪（与伽利略在比萨的“倾斜塔”实验的现代等效物）在同一实验室位置获得的g值进行比较。我们证明了该仪器中使用的宏观玻璃物体与量子力学铯原子的加速度相同，下降到十分之七。
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