Shaped pulse af.m

Shaped pulse in amplitude-frequency coordinates using Fokker-Planck formalism. Syntax:

  rho=shaped_pulse_af(spin_system,L0,Lx,Ly,rho,rf_frq_list,...
                  rf_amp_list,rf_dur_list,rf_phi,max_rank,method)

Parameters:

       L0          - drift Liouvillian that continues
                     running in the background

       Lx          - X projection of the RF operator

       Ly          - Y projection of the RF operator

       rho         - initial condition

       rf_frq_list - a vector of RF frequencies at each
                     time slice, Hz

       rf_amp_list - a vector of RF amplitudes at each
                     time slice, Hz

       rf_dur_list - a vector of time slice durations,
                     in seconds

       rf_phi      - RF phase at time zero

       max_rank    - maximum rank of the Fokker-Planck
                     theory

       method      - propagation method, 'expv' for Krylov
                     propagation, 'expm' for exponential
                     propagation, 'evolution' for Spinach
                     evolution function