Werner state structure and entanglement classification
  We present applications of the representation theory of Lie groups to the analysis of structure and local unitary classification of Werner states, sometimes called the {\em decoherence-free} states, which are states of $n$ quantum bits left unchanged by local transformations that are the same on each particle. We introduce a multiqubit generalization of the singlet state, and a construction that assembles these into Werner states. 
David W. Lyons and Abigail M. Skelton and Scott N. Walck
quant-ph math-ph math.MP