One thing that we have begun using, to simplify some quantum computational analysis are Graphical tensor networks as presented in this http://arxiv.org/abs/1111

One thing that we have begun using, to simplify some quantum computational analysis are Graphical tensor networks as presented in this http://arxiv.org/abs/1111.6950 http://arxiv.org/abs/1111.6950 paper. Hasn't caught much traction yet, but it and similar ideas could be the way forward.