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 87Rb, 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 set-up. 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