You've heard it in the season 1 finale (when Damon kisses Katherine, thinking she's Elena). So many people loved it that Stateless decided to make a new version free for download on their site.
click on the banner. You have to put your e-mail address. Once you've written it, just click on the link and download the song. Afterward, if you don't want the newletter from Stateless, just delete the message in your e-mail inbox.