Unfortunately, technology has not yet been developed which is powerful enough to teleport full human beings. It is unlikely that it will be practical any time in the future as well, due to the inordinate amount of energy it would require.
*coughs*
Uh, you don't go back to the start after just one boss. You have to wait until after you've beaten Mecha Birdo, and the section after that. After that, there'll be a thing that says "go here to warp back to start" or something.
