  It is shown that diffraction of Bose-Einstein condensates on a helical light
grating results in vortices in the condensate. Helical light gratings can be
produced by light interference of a Gaussian laser beam with a helical one.
Diffraction orders of the Bose-Einstein condensate contain vortices of
corresponding topological charge. The phenomena is illustrated by numerical
integration of the Gross-Pitaevskii equation in two dimensions.
