A cell has about 42 million protein molecules working together in the most complex system mankind has ever known. It has been called the third infinity (Denton, 2020) because it is as far beyond any complexity we know, just as the universe is bigger than we know, and the quantum world is smaller than we know. No machine ever built even approaches a cell’s complexity, so the chance that trillions of atoms randomly formed millions of proteins in a primal stew to form a cell is effectively zero.
Evolution needed help, so the emerging field of quantum biology argues that it was a quantum effect (McFadden & Al-Khalili, 2018). Quantum effects like entanglement helped matter, stars and galaxies to evolve but until recently seemed to play no part in life. No-one doubted that quantum weirdness rules the atomic world but quantum entanglements were said to collapse too quickly to affect the macro-world of biology:
“On the face of it, quantum effects and living organisms seem to occupy utterly different realms. The former are usually observed only on the nanometer scale, surrounded by hard vacuum, ultra-low temperatures and a tightly controlled laboratory environment. The latter inhabit a macroscopic world that is warm, messy and anything but controlled. A quantum phenomenon such as ‘coherence’, in which the wave patterns of every part of a system stay in step, wouldn’t last a microsecond in the tumultuous realm of the cell. Or so everyone thought. But discoveries in recent years suggest that nature knows a few tricks that physicists don’t: coherent quantum processes may well be ubiquitous in the natural world.” (Ball, 2011) p272
Quantum effects can bypass classical laws, so one expects life to use that power if it can, and it had billions of years to do so. Biologists just had to look to find quantum effects in cells:
“…something quantum mechanical is going on inside living cells, whether it’s in photosynthesis, whether it’s in enzyme catalysis,[16] [17] [18] whether it’s in mutations of DNA,[19] [24] even more controversially the way we smell, the theories of olfaction,[25] or magnetoreception, the way certain animals can sense the Earth’s magnetic field, the chemical compass that allows them to detect the orientation of the field relies on quantum effects, quantum entanglement.[26] [27] [28]” (Al-Khalili & Lilliu, 2020)
The best-known example is photosynthesis, the process that sustains complex life on earth. It began over three billion years ago when bacteria harvested the sun’s light to create oxygen. Our electric motors are 25% efficient, losing the rest to heat, but low-light bacteria convert 100% of light energy into chemical energy (Magdaong et al., 2014). This energy efficiency is impossible for heat engines, by Carnot’s law, but bacteria have evolved a quantum heat engine (Al-Khalili & McFadden, 2014) p310 that can do what classical physics forbids:
“natural selection has come up with ways for living systems to naturally exploit quantum phenomena” (O’Callaghan, 2018).
Photosynthetic bacteria have light receptive molecules called chromophores that absorb light energy and send it to reaction centers that convert it into chemical energy. When a chromophore antennae registers a photon, its energy must pass through the forest of other antennae to reach the nearest reaction center, but:
“The problem, of course, is which route this energy transfer should take. If it heads in the wrong direction, randomly hopping from one molecule to the next in the chlorophyll forest, it will eventually lose its energy rather than delivering it to the reaction center.” (Al-Khalili & McFadden, 2014) p126
A photon pulse decays in nanoseconds so it should often go down a dead-end and die out but instead, nearly every photon arrives at a reaction center. This allows bacteria in the light-starved depths of the sea to survive, but how do they do it?
Studies show that bacteria chromophores vibrate in step to give quantum beats (Engel, 2007) that allow their electromagnetic fields to entangle (Maiuri, 2018). In physics, entanglement is a fragile quantum state that occurs in atoms or near absolute zero, so it should quickly collapse in a warm cell. However, identical matter entities whose quantum fields overlap will entangle (Lo Franco & Compagno, 2016), and densely packed chromophores vibrating in synchrony satisfy this demand, so many receptors entangle into one ensemble.
In physics, entangled photons going in opposite directions look like two photons but are actually one entity (Aspect et al., 1982), so if either interacts, both respond (3.8.5). If entangled photons can go in two ways at once, a photon registered by many entangled chromophore receptors can explore many the paths to a reactor at once. Once received, the energy spreads down all paths like a wave until it collapses at a reaction center. If that doesn’t happen in one molecular cycle, the synchrony repeats until it does. The bacterium uses quantum coherence to enhance photosynthesis in a way that supports the known transfer times:
“Coherent quantum beats have been observed in most light harvesting systems, where the coherences are stable over a time scale that is commensurate with the relevant energy transfer times.” (Scholes Group, 2018)
Chromophore molecules vibrating in synchrony let photon energy evolve down many paths simultaneously to find a reaction center before it decays. If light-harvesting bacteria achieved photosynthesis by coherence, all life on earth began with the quantum effect of entanglement
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