Coherent effects in incoherent light harvesting

Photosynthetic organisms harvest light using large arrays of organic molecules, whose couplings are often large enough that energy transfer through the arrays is partially coherent. However, making precise claims about coherence in photosynthesis has been difficult because it requires expensive computational techniques. We accelerated simulations of energy transport in photosynthetic complexes by orders of magnitude by exploiting the incoherent nature of the incident light, showing that quantum coherence can enhance light harvesting even in incoherent sunlight [1,2]. The faster simulations allow us to screen many alternative scenarios—by changing couplings, energy offsets, geometries, etc.—to determine whether coherence is indeed important for biological function or is merely an evolutionary accident [3,4]. Indeed, we report the most statistically significant quantum enhancement identified in a photosynthetic complex so far [4].

[1] Ivan Kassal, Joel Yuen-Zhou, Saleh Rahimi-Keshari, J. Phys. Chem. Lett. 4, 362 (2013).
[2] Roberto de J. León-Montiel, Ivan Kassal, Juan P. Torres, J. Phys. Chem. B 118, 10588 (2014).
[3] Sima Baghbanzadeh, Ivan Kassal, Phys. Chem. Chem. Phys. 18, 7459 (2016).
[4] Sima Baghbanzadeh, Ivan Kassal, preprint: arXiv:1604.05482 (2016).