When a final state of a quantum interaction can be reached through several paths, the transition rate can be modified by changing the phases of the interfering transition amplitudes. Those phases could be controlled through the optical phase of the exciting light. This is the underlying principle of quantum coherent control.
Our group demonstrated some of the basic principles of quantum control with shaped femtosecond pulses using simple atomic and molecular systems, and later demonstrated its application to spectroscopy and microscopy.
For a review, see Silberberg, Y (2009). Quantum Coherent Control for Nonlinear Spectroscopy and Microscopy. Annual Review Of Physical Chemistry. 60:277-292.