The field of quantum biology applies quantum mechanics to biological objects and problems. Usually it is taken[by whom?] to refer to applications of the "non-trivial" quantum features such as superposition, nonlocality, entanglement and tunneling, as opposed to the "trivial" but ubiquitous quantum mechanical nature of chemical bonding, ionization, and other phenomena that form the basis of the fundamental biophysics and biochemistry of organisms. As of 2015[update] quantum biology remains a tentative field, with research into it often being neglected[by whom?] in favor of other applications of quantum phenomena. It can be defined as the study of quantum phenomena within biological systems. Originally it had been thought  that the heat engines of biological systems were not enough to produce quantum phenomena, but as evidence mounts that view has ceased to be popular.
Recent studies have identified quantum coherence and entanglement between the excited states of different pigments in the light-harvesting stage of photosynthesis. Although this stage of photosynthesis is highly efficient, it remains unclear exactly how or if these quantum effects are relevant biologically.
^Iannis Kominis: "Radical-ion-pair reactions are the biochemical equivalent of the optical double-slit experiment", Physical Review E 83, 056118 (2011) (abstract)
^Erik M. Gauger, Elisabeth Rieper, John J. L. Morton, Simon C. Benjamin, Vlatko Vedral: Sustained quantum coherence and entanglement in the avian compass, Physics Review Letters, vol. 106, no. 4, 040503 (2011) (abstract, preprint)
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^Harald Krug; Harald Brune; Gunter Schmid; Ulrich Simon; Viola Vogel; Daniel Wyrwa; Holger Ernst; Armin Grunwald; Werner Grunwald; Heinrich Hofmann (2006). Nanotechnology: Assessment and Perspectives. Springer-Verlag Berlin and Heidelberg GmbH & Co. K. pp. 197–240. ISBN978-3-540-32819-3.