changed norm for operators to trace-norm from L2-norm.  Since these are matrices, it is best to use a matrix norm.
changed norm for operators to trace-norm from L2-norm.  Since these are matrices, it is best to use a matrix norm.

zasdfgbnm/qutip,anubhavvardhan/qutip,qutip/qutip,qutip/qutip,anubhavvardhan/qutip,zasdfgbnm/qutip,cgranade/qutip,cgranade/qutip