  The past few decades have seen dramatic progress in our ability to manipulate
and coherently control matter-waves. Although the duality between particles and
waves has been well tested since de Broglie introduced the matter-wave analog
of the optical wavelength in 1924, manipulating atoms with a level of coherence
that enables one to use these properties for precision measurements has only
become possible with our ability to produce atomic samples exhibiting
temperatures of only a few millionths of a degree above absolute zero. Since
the initial experiments a few decades ago, the field of atom optics has
developed in many ways, with both fundamental and applied significance. The
exquisite control of matter waves offers the prospect of a new generation of
force sensors exhibiting unprecedented sensitivity and accuracy, for
applications from navigation and geophysics to tests of general relativity.
Thanks to the latest developments in this field, the first commercial products
using this quantum technology are now available. In the future, our ability to
create large coherent ensembles of atoms will allow us an even more precise
control of the matter-wave and the ability to create highly entangled states
for non-classical atom interferometry.
