Path trace.m

Liouvillian path tracing. Treats the user-supplied Liouvillian as the adjacency matrix of a graph, computes the weakly connect- ed subgraphs of that graph and returns a cell array of project- ors into the corresponding independently evolving subspaces. Syntax:

             projectors=reduce(spin_system,L,rho)

where L is the Liouvillian and rho is the initial state (in the case of source state screening) or the detection state (if des- tination state screening is used). The output is a cell array of projectors into independently evolving reduced subspaces. Those projectors are to be used as follows:

          L_reduced=P'*L*P;     rho_reduced=P'*rho;

Further information is available here:

        http://link.aip.org/link/doi/10.1063/1.3398146
        http://dx.doi.org/10.1016/j.jmr.2011.03.010