  Coherent control is extended to macroscopic processes under continuous pulsed
laser irradiation. Here, this approach is used to analyze the experimentally
measured two-photon phase control of currents emanating from a living brain
cells expressing channelrhodopsin-2, a light-gated ion channel. In particular,
a mechanism is proposed that encompasses more than 15 orders magnitude in time,
from the ultrafast dynamics of retinal in channelrhodopsin-2 to the slow
dynamics of the neuron current. Implications for other photochemical processes
are discussed.
