  In Paris, we are using an atom interferometer to precisely measure the recoil
velocity of an atom that absorbs a photon. In order to reach a high
sensitivity, many recoils are transferred to atoms using the Bloch oscillations
technique. In this lecture, I will present in details this technique and its
application to high precision measurement. I will especially describe in
details how this method allows us to perform an atom recoil measurement at the
level of $1.3 \times 10^{-9}$. This measurement is used in the most precise
determination of the fine structure constant that is independent of quantum
electrodynamics.
