Plants perform quantum computation for photosynthesis

If they really do is not proven.

Chroloplast is a chemical device that obeys quantum chemistry and thus is hampered by quantum decoherence. But if how molecules there organize to overcome this is truly and not only seemingly isomorphic to performing quantum computation is unproven yet. In particular Alan Aspuru-Guzik disproved Engel's result from linked article, at the same time discovering possibility of quantum computation of another kind, claim unverified as of yet.

In other news, optimization of solar panel cell geometry was proposed long, long ago as a case of practical utility of quantum information theory.

Detailed discussion of most recent results here: http://scottaaronson.com/blog/?p=401