Photoselective adaptive femtosecond quantum control in the liquid phase

Abstract

Coherent light sources can be used to manipulate the outcome of light-matter interactions by exploiting interference phenomena in the time and frequency domain. A powerful tool in this emerging field of 'quantum control' is the adaptive shaping of femtosecond laser pulses, resulting, for instance, in selective molecular excitation. The basis of this method is that the quantum system under investigation itself guides an automated search, via iteration loops, for coherent light fields best suited for achieving a control task designed by the experimenter. The method is therefore ideal for the control of complex experiments. To date, all demonstrations of this technique on molecular systems have focused on controlling the outcome of photo-induced reactions in identical molecules, and little attention has been paid to selectively controlling mixtures of different molecules. Here we report simultaneous but selective multi-photon excitation of two distinct electronically and structurally complex dye molecules in solution. Despite the failure of single parameter variations (wavelength, intensity, or linear chirp control), adaptive femtosecond pulse shaping can reveal complex laser fields to achieve chemically selective molecular excitation. Furthermore, our results prove that phase coherences of the solute molecule persist for more than 100 fs in the solvent environment.

Non-dispersive wave packets in periodically driven quantum systems

“…As an alternative example, we have briefly touched upon the atomic realization of the gravitational bouncer, though many other realizations in simple quantum optical or atomic and molecular systems can be thought of. Let us only mention unharmonic traps for ions, atoms, or BEC condensates, periodically kicked atoms [229], as well as molecular dynamics [230,231] on adiabatic potential surfaces (the driven frozen planet briefly discussed in section 6.2 may be conceived as opening a perspective in this direction). Nontheless, atomic Rydberg states remain arguably the best objects to study the fundamental properties of non-dispersive wave-packets as the realization of Schrödinger's dream [2].…”

Searching for quantum optimal controls under severe constraints

“…Successful optimal control experiments (OCEs) have included selective control of molecular vibrational [10][11][12][13][14][15][16][17] and electronic states [18][19][20][21][22][23][24][25][26][27], preservation of quantum coherence [28,29], control of photoisomerization reactions [30][31][32][33][34][35], selective manipulation of chemical bonds [36][37][38][39][40][41][42][43][44], high-harmonic generation and coherent manipulation of the resulting soft X-rays [45][46][47][48][49][50][51], and control of energy flow in biomolecular complexes [52][53][54][55]. Optimal control theory (OCT) [7,9,…”

Adaptive Femtosecond Quantum Control

“…Adaptive femtosecond quantum control has proven to be a very powerful tool to control a variety of chemical reactions and physical processes [15,45,49,52,53,56,59,127,159]. However, in many cases it is quite difficult to extract the control mechanism(s) utilized by the optimal pulse shape obtained in the optimal control experiment, a problem already encountered in chapter 4.…”

“…This approach has proven to be an excellent method for reaching specific control objectives [15,45,49,52,53,56,59,127,159]. However, it is usually difficult to gain insight into the reaction mechanisms at play or to extract information on the interaction of the investigated system with electromagnetic fields from the optimized field shapes.…”