Bloch oscillations of ultracold atoms: A tool for a metrological determination of h/mRb

We use Bloch oscillations in a horizontal moving standing wave to transfer a large number of photon recoils to atoms with a high efficiency (99.5% per cycle). By measuring the photon recoil of Rb87, using velocity-selective Raman transitions to select a subrecoil velocity class and to measure the final accelerated velocity class, we have determined h/mRb with a relative precision of 0.4 ppm. To exploit the high momentum transfer efficiency of our method, we are developing a vertical standing wave setup. This will allow us to measure h/mRb better than 10-8 and hence the fine structure constant α with an uncertainty close to the most accurate value coming from the (g-2) determination