I can tell you by the time I was interviewed, that very same day I was told I was shortlisted.

But also there are several ways to improve the time for response from the "potential employer". This is called follow up letter and if you google it there are plenty of examples about it.

Try contacting again your interviewer or the Head Hunter (if any) to keep in touch and then let them know you are interested in the position.

Hope this works for you...best of luck!!!