Coherent Control of Molecular Processes in the Condensed Phase: Theory and Applications
Cyrille Lavigne
Coherent control schemes are interference-based procedures for the control of quantum mechanical systems informed by a careful analysis of the physical conditions on interference. In this thesis, the coherent control approach is applied to experimental phase control in the condensed phase. Specifically, coherent control schemes are proposed as mechanisms for experimental manifestations of phase interference. First, a simulation of a ``black box'' feedback control experiment using realistic pulse shaping is shown to automatically find a specific, previously devised coherent control scheme. Qualitative features of experiments performed in this way are reproduced. Second, an analysis of interference in one-photon phase control yields an upper bound on the duration of phase effects. One-photon phase control was previously shown to be possible only over the transient (as opposed to steady-state) value of observables. The bound described here quantifies this statement and provide a rigorous definition of ``transient'' control. We propose that phase control beyond this bound, as reported in a number of weak-field experimental and computational studies, is the result of previously unaccounted for multiphoton effects. Third, we analyze a recent experiment showing phase control of the macroscopic current emanating from living brain cells photostimulated by two-photon absorption. We propose mechanisms for the phase dependence of the current that operate over fifteen orders of magnitude in time, from the femtosecond dynamics of light-matter interactions to the macroscopic dynamics of neuron current. Significantly, coherent control is extended to the case of systems repeatedly interacting with pulses of light; we show that macroscopic control is obtained, in this case, from the multi-pulse accumulation of small phase effects. Research into multiphoton control led to the development of a novel algorithm to compute higher order perturbation theory integrals, presented in the final chapter of this thesis. The Fourier-Laplace Inversion of the Perturbation Theory (FLIPT) method is a highly efficient, numerically exact, ``black box'' integration algorithm. The FLIPT method exploits the specific structure of the multidimensional perturbation theory integrals to obtain an exponential improvement in performance over standard quadrature.
•Nov 1, 2019•0 citations