Can you theoretically convert matter into energy and then convert the energy back into antimatter and matter?

According to Einstein's law that E=mc^2, it is possible to convert matter to energy and then convert the energy back in matter, as long as they come in equal pairs of matter and antimatter. Couldn't you then theoretically be able to store a large amount of matter on a spaceship and then convert it into energy, then into both antimatter and matter and then use it for propulsion? That way there will be no accidents of matter colliding with antimatter because the antimatter will only be created a few seconds before it is used.