Comment on "Coherent control of retinal isomerization in bacteriorhodopsin".

Prokhorenko et al. (Research Articles, 1 September 2006, p. 1257) reported that, in the weak-field regime, the efficiency of retinal isomerization in bacteriorhodopsin can be controlled by modulating the spectral phase of the photoexcitation pulse. However, in the linear excitation regime, the signal measured in an experiment involving a time-invariant, stationary process can be shown to be independent of the pulse spectral phase.