UNITARY CONTROL IN QUANTUM ENSEMBLES - MAXIMIZING SIGNAL INTENSITY INCOHERENT SPECTROSCOPY

Experiments in coherent magnetic resonance, microwave, and optical spe ctroscopy control quantum-mechanical ensembles by guiding them from in itial states toward target states by unitary transformation. Often, th e coherences detected as signals are represented by a non-Hermitian op erator. Hence, spectroscopic experiments, such as those used in nuclea r magnetic resonance, correspond to unitary transformations between op erators that in general are not Hermitian, A gradient-based systematic procedure for optimizing these transformations is described that find s the largest projection of a transformed initial operator onto the ta rget operator and, thus, the maximum spectroscopic signal. This method can also be used in applied mathematics and control theory.