Coherent control of atomic motion in an optical lattice for precise measurements of gravity

Coherent control of atomic motion inside an optical lattice allows precise measurement of forces by means amplitude-modulation (AM) driven resonant tunneling. We report about the recently-performed high precision measurements of gravitational acceleration using ultracold strontium atoms trapped in an AM driven vertical optical lattice.\footnote{A. Alberti \textit{et al.}, New J. Phys. 12, 065037 (2010).} We reached an uncertainty $\Delta g/g \approx 10^{-7}$ by measuring at the 5$^{th}$ harmonic of the Bloch oscillation frequency.\footnote{N. Poli \textit{et al.}, Phys. Rev. Lett. 106, 038501 (2011).} We analyzed the systematic effects induced by the trapping optical lattice, such as the intensity gradient and the lattice frequency-induced shift. We accurately measured the lattice frequency by means of an fiber link with a home-made frequency comb. The value of $g$ obtained with this microscopic quantum system is consistent with the one we measured with a classical absolute gravimeter. Short-distance measurements of gravity near dielectric surfaces are discussed. These results prospect a new way to new tests of gravity at micrometer scale.