Rayon is a linear quantum optical simulator in Mathematica.
It can handle beam splitters and squeezers currently. But extending to other components is trivial.
A modern high-end computer can currently handle a 4 beam setup easily. I have not been very successful with running 8 beam setups, especially with lots of squeezers.
The program is in primitive shape currently. At some point in the future I hope to provide it as a Mathematica package.
You need at least Mathematica 9 to run it.