Quantum Evolution, Johnjoe McFadden. Chapter 10

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Quantum Evolution - Chapter 10 - The beginning

‘…If you remember, the inverse quantum Zeno effect represents one of the peculiarities of quantum measurement whereby a dense series of measurements along a particular path can draw that system along the path. Insertion of extra Polaroid lenses, between vertically and horizontally polarised lenses (a perpendicular or orthogonal pair) rotates the angle of polarisation of light. Without the extra lenses, the distance between the two states (vertical and horizontally polarised light) is too great. No light gets through. But insertion of the extra lenses – each performing a quantum measurement – lays down a series of stepping stones that rotates the light from one state (vertically polarised) to another (horizontally polarised) in a series of short hops. A sufficiently dense series of measurements will lay down a paved path that will allow the photons to evolve smoothly from one state into another. Similarly, a dense series of quantum measurements of a particle along a positional path can move the particle along that path. The path may be only one path out of a trillion equally probable paths but quantum measurement can force the system to evolve in that measured direction.

But isn’t this more or less what we want to do when we evolve the single amino acid arginine (R), along a single path through peptide multidimensional space to synthesise the self-replicator, RMKQLEEKVYELLSKVACLEYEVARLKKLVGE? In classical terms, the probability of the peptide taking the right route is close to zero (in fact 1/20³²). But if quantum measurements were performed along the route, then the inverse quantum Zeno effect could make that path much more likely. Can the inverse quantum Zeno effect make the reaction more probable? To see how, you must recall how the inverse quantum Zeno effect actually works. It depends on the ability of oblique quantum measurements to decompose a quantum state into sets of orthogonal (perpendicular) states. Measurement then forces one of those states to become real and a dense series of measurement forces the system along the measured path. The polarisation state of photons can be rotated by the inverse Zeno effect, as can the position of particles. If positional measurements can be performed to move electrons around in empty space, they can also be performed to move electrons (or protons) around in the space of atoms and molecules.

Looked at this way, the chemical reaction leading to the first self-replicator (or indeed any chemical reaction) becomes a sequence of electron and proton movements within and between molecules. The walk in multidimensional peptide addition space that led to the self-replicating peptide becomes a walk in position space for electrons and protons. The route to a single self-replicator will still be extremely improbable but quantum measurement and the inverse Zeno effect could capture the motion of particles along that route and thereby make it more likely.

But how can the motion of particles within and between molecule, be measured? As we discussed above, enzymes can perform that feat. The precise position and energy of particles within enzymes is crucial for their enzymatic activity. Enzymes regularly perform quantum measurements of the states of their own particles. I have already described how proto-enzymes would have inevitably emerged in the quantum peptide. The enzymatic actions performed by these proto-enzymes would have performed quantum measurement of the particles that make up those peptides. The proto-enzymes would have emerged unscathed from the measurement process and - after measurement - their quantum state would have drifted back into quantum realm. However, any chain of electron and proton motion that led to a self-replicator, would have been irreversibly amplified into the classical world. Although proto-enzymes may remain at the quantum level, a self-replicator inevitably amplifies its quantum state to the classical level. The self-replicator nailed the growing peptide to the classical world.

We are then left with a chain of quantum measurement terminating with a self-replicator that amplified the quantum system to the classical level. This is an exactly analogous situation to the way we first illustrated the inverse quantum Zeno effect (Figure 8.3). Whereas in the light and sunglasses experiment, we rotated the angle of polarisation of light by quantum measurements performed by a series of Polaroid lenses; in the quantum proto-cell, it was a series of proto-enzymes that performed the quantum measurements. In the light experiment, it was our observation of light passing through the horizontal lens that performed the final irreversible act of measurement that amplified the quantum system to the classical realm; but in the proto-cell it was the emergence of the self-replicator that nailed the system to the classical world. Emergence of the self-replicator was the end of the line for the inverse quantum Zeno effect. Quantum measurements by proto-enzymes along the route to the self-replicator laid down a series of stepping stones that led to the emergence of life.

Only a few measurement steps would have been necessary to significantly enhance the probability of generating the first self-replicator. Remember that a single Polaroid lens performing quantum measurement can increase the probability for photon transmission through a crossed lens system (combination of horizontal and vertical lenses) from zero to 6% - an infinite increase! Even if only two or three steps along the path to self-replication were subject to quantum measurement, it may have been sufficient to raise the probability of our self-replicating peptide from 1/20³², to a value achievable in a quantum proto-cell within a small warm primordial pond. In this guise the inverse quantum Zeno effect performed a role that was later taken over by Darwinian natural selection. Just as the evolution of the highly improbable structure of the eye was guided through the multiverse of design by the ability of natural selection to capture beneficial mutations; so the evolution of the highly improbable self-replicator was guided through a prebiotic chemical multiverse by the ability of quantum measurement to capture the quantum states that led to the self-replicator.’