Lie-group and Runge-Kutta-Munthe-Kaas solvers for the Lie equation. LG methods are implementations of Equation A.1, with minor typos fixed, from (http://dx.doi.org/10.1088/0305-4470/39/19/S07). The key difference from step.m function is that the Liouvillian can depend on the density matrix.
spin_system - Spinach data structure from create.m and basis.m constructors L - a handle to a function L(t,rho) that must take time and state vector, and return the evolution generator (in rad/s) of the Lie equation: d_rho/d_t = -i*L(t,rho)*rho rho_a - state vector at the start of the evolution period t - time at the start of the evolution, seconds dt - evolution time step, seconds method - 'PWCL', 'PWCM', 'RKMK4', or 'LG4', the latter one is recommended
rho_b - state vector at the end of the evolution time step