We use Bloch oscillations to transfer coherently many photon momenta to atoms. Then we can measure accurately the recoil velocity $\hbar k/m$ and deduce the fine structure constant $\alpha$. The velocity variation due to Bloch oscillations is measured using atom interferometry. This method yields to a value of the fine structure constant $\alpha^{ -1}= 137.035 999 45 (62)$ with a relative uncertainty of about $4.5 \times 10^{ -9}$.
Categories: physics.atom-ph