Dear Isobel, the usual bottleneck for Tkwants numerical accuracy and speed is the calculation of the manybody integral. In your script however, you are only evolving a onebody state, so this could not be the reason. There are two other things which could go wrong when evolving a onebody state:
1. turn of the extrapolation of the perturbation as described here: https://tkwant.kwant-project.org/doc/dev/tutorial/onebody_advanced.html#time-dependent-perturbation 2. change the time-stepping accuracy (less likely however) You can find both points in a new documentation section about common pitfalls: https://tkwant.kwant-project.org/doc/dev/tutorial/pitfalls.html Still, it is strange that your calculation takes hours and not seconds or respectively minutes, as what I would expect for a typical onebody simulation. Running the script with MPI on a cluster does not help either, as a onebody simulation is not parallelized over several cores. So I wonder if there are no other problems involved. One other possibility is that you don't have leads attached, so your will get reflections from the boundaries over time which will mess up your smooth initial behavior. Second, I don't know what means "short" for the simulated time. Short and long time is always with respect to the relevant energy scales of your system, which you should know in advance. Best, Thomas