  The manipulation of matterwave represents a milestone in the history of
quantum mechanics. It was at the basis of its experimental validation through
the observation of diffraction of matter on crystals, as well as grating and
Young's double-slit interference with electrons, neutron, atoms and molecules.
More recently matterwave manipulation has become a building block in the
implementation of quantum devices such as quantum sensors and it plays an
essential role in many proposals for implementing quantum computers. In this
letter we coherently control the spatial extent of the wavefunction by
reversibly stretching and shrinking the wavefunction over a millimeter
distance. The remarkable experimental simplicity of the scheme would ease
applications in the field of quantum transport and quantum computing.
