Quantum biology revisited

Abstract

Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.

Consciousness as an Emergent Phenomenon: A Tale of Different Levels of Description

“…This possibility was already pointed out by pioneer work of Franck and Teller [ 79 ] but it was not corroborated experimentally until recently. Indeed, nowadays, there seems to exist strong evidence of wavelike energy transfer through quantum coherence in photosynthetic systems [ 64 , 80 ], but also see [ 81 , 82 , 83 ] for an opposing view). This was possible originally with femtosecond transient absorption spectroscopy [ 84 , 85 , 86 , 87 , 88 , 89 ] and more recently with two dimensional electronic spectroscopy ([ 90 ]).…”

“…The subject is too new, and there is not enough experimental evidence in one sense or another. Even some basic results in quantum biology are under debate [ 83 ]. However, on the basis of what theories of quantum consciousness propose and the existing indirect experimental evidence shows, we have identified unifying principles that seem to underlie theories of consciousness independently of the scale.…”

Establishment of the Qy Absorption Spectrum of Chlorophyll a Extending to Near-Infrared

“…This is not quite the case. Naturally, the basic absorption–emission spectral data have been around for decades—see [ 1 ] for comprehensive reviews—yet, there are many details critical for understanding, e.g., coherent exciton transport in photosystems, a focus of many recent works [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”

Quantum simulation of clustered photosynthetic light harvesting in a superconducting quantum circuit

“…In the past few decades, many researches were focused on the study of the exciton energy transfer (EET) process in photosynthesis. [6][7][8][9][10][11] Based on the quantum dynamics of open systems, 2,12 much knowledge has been learned about the efficiency of the EET, [13][14][15][16][17] together with the spatial and energetic arrangement of the pigments. [18][19][20][21][22] The experimentally observed coherent phenomena in 2D spectroscopy may be attributed to nearly resonant coupling to an underdampped vibrational mode in the bath.…”

“…[18][19][20][21][22] The experimentally observed coherent phenomena in 2D spectroscopy may be attributed to nearly resonant coupling to an underdampped vibrational mode in the bath. 12,23 In natural photosynthesis, EET can be accomplished within 100 picoseconds with almost 100% efficiency. 24 Hu et al 25 observed that the bacteriochlorophylls involved in the overall excitation transfer are found in a coplanar arrangement.…”