how to swap between tab groups

if I have a two different files open in two different tab groups, does anyone know the command to swap between them? atm the best I can come up with is Ctrl-N or Ctrl-Shift-N and use the class/file name to swap. This is a bit tedous and I'm hoping for something better....

any suggestions would be welcomed with open arms (o: I'd imagine that Ctrl-TAB might be a good shortcut to assign - but I dont know what to assign it to...

cheers
dim