This is a header-only (template-based) C++11 quantum computing library, and it is work in progress.
If anyone else is interesting in contributing please let me known at vgheorgh@gmail.com for more details. There is still a lot of work left to be done, and I can provide you with more details about what I have in mind. If you are interested in contributing, you need to have a decent knowledge of C++ (preferably C++11), including templates and STL, a basic knowledge of quantum computing and linear algebra, and some experience with Eigen linear algebra library http://eigen.tuxfamily.org/ (although this is not mandatory, but it is highly desirable).
The ultimate goal of this project is to have a universal quantum simulator, applicable to a vast majority of problems in quantum information/computation, and nevertheless to be as fast as possible. Right now the parallelization is done using OpenMP, but probably one can create a new branch using GPU-type multi-processing like CUDA, although this may require a significant amount of code re-writing.
And finally, the simulator should be user-friendly, easy to use for anyone with a basic knowledge of C/C++. My intention is to have it publicly available, so do not expect to make money out of it :)