There are two pieces of Downloadable Content available for Quantum Conundrum.
The Desmond Debacle was released on Steam July 31, 2012 and on Xbox Live and the PlayStation Network in mid-August.
IKE-aramba! was made available August 28, 2012 on Steam and mid-September on consoles.
Though strictly speaking not an add-on for the game, also released on Steam on August 28, 2012 was the game's soundtrack.