Optical control of atomic interactions in a quantum gas is a long-sought goal of cold atom research. Previous experiments have been hindered by short lifetimes and parasitic deformation of the trap potential. Here, we develop and implement a generic
scheme for optical control of Feshbach resonance in quantum gases, which yields long condensate lifetimes sufficient to study equilibrium and non-equilibrium physics with negligible parasitic dipole force. We show that fast and local control of interactions leads to intriguing quantum dynamics in new regimes, highlighted by the formation of van der Waals molecules and partial collapse of a Bose condensate.
