elow, the action of the exponential
 of the Magnus operator is also calculated through the algorithm specified
 by this variable.

<br/><i>Options</i>:
<ul>
<li><b>lanczos</b>:  Allows for larger time-steps.
 However, the larger the time-step, the longer the computational time per time-step.
 In certain cases, if the time-step is too large, the code will emit a warning
 whenever it considers that the evolution may not be properly proceeding --
 the Lanczos process did not converge. The method consists in a 