  We propose to control the retinal photoisomerization yield through the
back-action dynamics imparted by a nonselective optical measurement of the
molecular electronic state. This incoherent effect is easier to implement than
comparable coherent pulse shaping techniques, and is also robust to
environmental noise. A numerical simulation of the quantum dynamics shows that
the isomerization yield of this important biomolecule can be substantially
increased above the natural limit.
