Gaining mechanistic insight from closed loop learning control: The importance of basis in searching the phase space

Abstract

This paper discusses different routes to gaining insight from closed loop learning control experiments. We focus on the role of the basis in which pulse shapes are encoded and the algorithmic search is performed. We demonstrate that a physically motivated, nonlinear basis change can reduce the dimensionality of the phase space to one or two degrees of freedom. The dependence of the control goal on the most important degrees of freedom can then be mapped out in detail, leading toward a better understanding of the control mechanism. We discuss simulations and experiments in selective molecular fragmentation using shaped ultrafast laser pulses.

Strong‐Field Coherent Control

“…Coherent control of molecular excitations is a vast topic in the AMO community [49,50,64,65,83]. Molecules, just as atoms, can exhibit multiphoton transitions.…”

“…One solution to this problem is to use an algorithm capable of searching for extrema in a large space of variables. The genetic algorithm [48] (GA) is a very successful algorithm in such cases [8,46,47,49,50]. Details of our implementation of the GA can be found in [40,49].…”

Adaptive Femtosecond Quantum Control

“…A suitable parametrization of the spectral phases can also give a handle on time-domain parameterizations, e.g., by scanning only pulse sequences with a certain temporal spacing [164]. In several demonstrations of closed-loop quantum control, the additional information gained from closed-loop optimizations in restricted subspaces facilitated the interpretation of possible control mechanisms [45,53,54,[165][166][167][168][169][170][171][172]. The obtained results can also be used to change the basis of the search space, further simplifying the optimization procedure in subsequent experiments [165,166,170,173].…”

“…These landscapes, in which the fitness value is plotted as a function of the selected parameters [165,166,174,175], directly reflect the system's response to the different pulse shapes and give an indication about possible control mechanisms. Thus, testing different parameterizations that represent putative control scenarios allows to draw conclusions whether these play a decisive role or not.…”

Coherent control of biomolecules

“…This approach has been successfully applied in references [43,44] and is used in Chapter 7. The importance of the basis of the search space has also been discussed relating to gas-phase fragmentation studies in references [45][46][47].…”