title: Unitary control in quantum ensembles: maximizing signal intensity in coherent spectroscopy
abstract: Experiments in coherent magnetic resonance, microwave, and optical spectroscopy control quantum-mechanical ensembles by guiding them from initial states toward target states by unitary transformation. Often, the coherences detected as signals are represented by a non-Hermitian operator. Hence, spectroscopic experiments, such as those used in nuclear magnetic resonance, correspond to unitary transformations between operators that in general are not Hermitian. A gradient-based systematic procedure for optimizing these transformations is described that finds the largest projection of a transformed initial operator onto the target operator and, thus, the maximum spectroscopic signal. This method can also be used in applied mathematics and control theory.
authors.affiliation: S. J. Glaser, O. Schedletzky, C. Griesinger, Institut fur Organische Chemie, J. W. Goethe-Universitat, Marie-Curie-Strasse 11, D-60439 Frankfurt, Germany. T. Schulte-Herbruggen, Laboratorium fur Physikalische Chemie, ETH Zentrum, CH-809.
authors.initials: SJ
authors.lastname: Glaser
authors.initials: T
authors.lastname: Schulte-Herbruggen
authors.initials: M
authors.lastname: Sieveking
authors.initials: O
authors.lastname: Schedletzky
authors.initials: NC
authors.lastname: Nielsen
authors.initials: OW
authors.lastname: Sorensen
authors.initials: C
authors.lastname: Griesinger