Homepage: http://itensor.org/

A C++ library for creating efficient and flexible tensor product wavefunction calculations.

The foundation of the library is the Intelligent Tensor or ITensor. 
Contracting ITensors is no harder than multiplying scalars: matching indices 
automatically find each other and contract. This makes it easy to transcribe 
tensor network diagrams into correct, efficient code.

Installation instructions can be found in the INSTALL file.