Do coherences exist at all under natural incoherent sunlight?
In plain words
Laser pulses in the lab start all molecules oscillating together, but sunlight arrives as a steady random stream of photons. The question is whether any quantum coherence relevant to energy transfer exists inside a leaf in real light.
Precise statement
Under stationary, broadband thermal excitation (sunlight, roughly one photon absorbed per chlorophyll per 0.1 s, approximately) the steady-state excited density matrix of a light-harvesting complex is diagonal or nearly diagonal in the energy eigenbasis, so pulse-induced quantum beats are absent. Determine whether steady-state coherences (site-basis coherences, noise-induced Fano-type coherences) or transient coherences after individual photon absorptions change the transfer yield or rate by an amount above parameter uncertainty. An answer is a computed yield difference for a realistic complex under thermal illumination.
What would settle it
An open-quantum-system calculation of a realistic antenna driven by thermal light and coupled to its protein bath, compared with the same model with coherences removed, ideally checked by single-photon or incoherent-light spectroscopy.