We have built an atom interferometer and, by applying
an electric field on one of the two interfering beams, we
have measured the static electric polarizability of lithium
a=(24.33±0.16)×10–30 m3
with a 0.66% uncertainty. Our experiment is similar to an
experiment done on sodium in 1995 by Pritchard and
co-workers, with several improvements : the electric field
can be calculated analytically and the interference signals
have a large intensity and a high visibility, resulting in
accurate phase measurements. This experiment illustrates the extreme sensitivity of atom interferometry : when the atom enters the
electric field, its velocity increases and the fractional
change, equal to 4×10–9 for our largest
field, is measured with a 10–3 accuracy.
Voir en ligne : Phys. Rev. A 73, 011603(R) (2006)