Life on the Edge: The Coming of Age of Quantum Biology

by Johnjoe McFadden

discovered in the early years of the twentieth century that subatomic particles can behave like waves; and light waves can behave like particles.

Wave-particle duality

“quantum tunneling.”

Just as waves can flow around objects, like the pebbles on the seashore, they can also flow through objects, like the sound waves that pass through your walls when you hear your neighbor’s TV. Of course, the air that carries sound waves doesn’t actually pass through the walls itself: it’s the

vibrations in the air—sound—that cause your common wall to vibrate and push on the air in your room to transmit the same sound waves to your ear. But if you could behave like an atomic nucleus then you would sometimes be able to pass, ghost-like, straight through a solid wall.*2 A hydrogen nucleus in the interior of the sun manages to do precisely this: it can spread itself out and “leak” through the...

superposition

The key point is that the deuteron owes its existence to its ability to exist in two states simultaneously, by virtue of quantum superposition.

It was discovered back in the late 1930s that within the deuteron these two particles are not dancing together in either one or the other of these two states, but in both states at the same time—they are in a blur of waltz and jive simultaneously—and it is this that enables them to bind together.*4

The answer is no, for it has been confirmed in many laboratories over and over again that if the proton and neutron were performing the equivalent of either a quantum waltz or a quantum jive, then the nuclear “glue” between them would not be quite strong enough to bind them together; it is only when these two states are superimposed on top of each other—the two realities existing at the same time—that the binding force is strong enough.

MRI uses big powerful magnets to align the axes of spinning nuclei of hydrogen atoms within the patient’s body. These atoms are then zapped with a pulse of radio waves, which forces the aligned nuclei to exist in that strange quantum state of spinning in both directions at once.

This is important when considering that weird quantum property of spin, since paired electrons tend to spin in opposite directions, so their total spin cancels to zero. But, without a spin-canceling twin, the lone electrons in free radicals have a net spin that gives them a magnetic property: their spin can be aligned with a magnetic field.

Schulten then went on to propose that the enigmatic avian compass might be using this kind of quantum entanglement mechanism.

We haven’t mentioned quantum entanglement yet because it is probably the strangest feature of quantum mechanics. It allows particles that were once together to remain in instant, almost magical, communication with each other, despite being separated by huge distances.

we now know empirically that quantum particles really can have instantaneous long-range links.

Aspect generated pairs of photons with polarization directions that were not only different—let’s say that one was pointing up and the other down—but entangled; and, like our previous dancing partners, neither of the entangled pair was actually pointing one way or another: they were both pointing in both directions simultaneously, until they were measured.

What is so special about measurement that allows it to convert quantum behavior to classical behavior?

For now, we will just consider the simplest interpretation of the phenomenon and say that when a quantum property, such as polarization state, is measured by a scientific instrument then it is instantly forced to forget its quantum abilities, such as pointing in many directions simultaneously, and must take on a conventional classical property, such as pointing in a single direction only.

So, when Aspect measured the polarization state of one of any pair of entangled photons, by observing whether it could pass through a polarized lens, it instantly lost its spooky connection with its partner and adopted just a single polarization direction.

And so did its partner, instantly, no matter how far away it was; at least, that’s what the equations of quantum mechanics predicted, which was of ...

Aspect and his team carried out their famous experiment for pairs of photons that had been separated by several meters in his laboratory, far enough away that not even an influence traveling at the speed of light—and relativity tells us that nothing can travel faster than the speed of light—could have passed between them to coordinate their angles of polarization. Yet the measurements on paired particles were correlated: when one photon’s polarization was pointing up, the other’s was found to point down. Since 1982, the experiment has been repe...

Despite the European robin being a nocturnal migrant, activation of its magnetic compass required a small amount of light (around the blue end of the visible spectrum), hinting that the bird’s eyes played a significant role in how it worked.

But in 1998 Schulten read that an enigmatic light receptor, called cryptochrome, had been found in animal eyes. This immediately set his scientific alarm bell ringing, because cryptochrome was known to be a protein that could potentially generate radical pairs.

Why is there a fault line, an edge, between the world that we see and the world that physicists know really exists beneath its surface? This is one of the deepest problems in the whole of physics, and one that relates to the phenomenon of quantum measurement we introduced a little earlier. When a quantum system interacts with a classical measuring device, such as the polarizing lens in Alain Aspect’s experiment, it loses its quantum weirdness and behaves like a classical object. But the measurements carried out by physicists cannot be responsible for the way the world we see around us appears. So what is it that carries out the equivalent quantum-behavior-destroying function outside the physics laboratory?

Living cells were thought to be composed mostly of water and biomolecules in a constant state of molecular agitation that would be expected to instantly measure and scatter those weird quantum effects.

What we are talking about here is what happens when a water molecule bumps into one of a pair of entangled particles: its subsequent motion will be affected by the state of that particle, so that if you were to study the water molecule’s subsequent motion you could deduce some of the properties of the particle it had bumped into. So, in this sense, the water molecule has carried out a “measurement” because its motion provides a record of the state of the entangled pair, whether or not anyone is there to examine it. This kind of accidental measurement is usually sufficient to destroy entangled states.

Familiarity renders this extraordinary transformation unremarkable, but it is worth remembering that even in this age of genetic engineering and synthetic biology, nothing living has ever been made by humans entirely from nonliving materials.

Life appears to have one foot in the classical world of everyday objects and the other planted in the strange and peculiar depths of the quantum world. Life, we will argue, lives on the quantum edge.

We have already mentioned Aristotle’s view of objects possessing tendencies to move toward the earth, away from the earth or around the earth, all of which he considered to be natural motions. He also recognized that solid objects could be pushed, pulled and thrown, all motions that he called “violent” and considered to be initiated by some kind of force provided by another object, such as the throwing person. But what produced the throwing motion—or the flight of a bird? There appeared to be no external cause. Aristotle claimed that living creatures, unlike inanimate objects, were capable of initiating their own motion, and that in this case the cause of such motion was the creature’s soul.

He was impressed by the mechanical clocks, toys and automata dolls that provided amusement for the courts of Europe at the time, and was inspired by their mechanisms to make the revolutionary claim that the bodies of plants and animals, including humans, were merely elaborate machines composed of conventional materials and driven by mechanical devices such as pumps, cogs, pistons and cams that were in turn subject to those same forces that governed the motion of inanimate matter.

In fact, almost all of the nonbiological (physical and chemical) processes that cause change in our world are driven by thermodynamic principles. Ocean currents, violent storms, the weathering of rocks, the burning of forests and the corrosion of metals are all controlled by the inexorable forces of chaos that underpin thermodynamics.

Well, you’ll have guessed where this is going. Our imaginary DIY project has constructed a billiard-ball-driven equivalent of life. Just like a bird, a fish or a human, our imaginary device is able to sustain and replicate itself by harvesting free energy from random molecular collisions.

free energy harvested from random molecular collisions (and their chemical reactions) is directed to maintain a body and make a copy of that body.

Every animal presents itself as a sum of vital entities, every one of which manifests all the characteristics of life.

Life, it was generally believed, was indeed just elaborate thermodynamics.

Life is different. No one has ever discovered a condition that favors the direction: dead cell → live cell. This was of course the puzzle that prompted our ancestors to come up with the idea of a soul. We no longer believe that a cell possesses any kind of soul; but what is it then that is irrevocably lost when a cell or a person dies?

The Nobel Prize–winning physicist Richard Feynman is credited with insisting that “what we can’t make, we don’t understand.” By this definition, we do not understand life because we have not yet managed to make it.

So Planck proposed the radical idea that the matter in the walls of these hot bodies vibrated at certain discrete frequencies, which had the consequence that the heat energy was only radiated in tiny discrete lumps, or “quanta,” that could not be subdivided.

His theory suggested that energy, instead of flowing out of matter like water pouring continuously from a tap, came out as a collection of separate, indivisible packages—as if from a slowly dripping tap.

Albert Einstein extended this idea and suggested that all electromagnetic radiation, including light, is “quantized” rather than continuous, coming in discrete packets, or particles, which we now call photons.

photoelectric effect,

In a similar way, fundamental particles, such as electrons, can only be associated with certain characteristic wave frequencies, each associated with its own discrete energy level.

When it jumps from one energy state to another it must absorb or emit radiation corresponding to the energy difference between the level from which it jumps and the level at which it lands.

Heisenberg showed that this process reveals only those features that it is specifically designed to measure—much as the individual instruments on the dashboard of a car each give information about just one aspect of its operation, such as its speed, the distance traveled or the temperature of the engine.

But Heisenberg showed mathematically that it is impossible to set up a single experiment in which we can measure, as accurately as we wish, both where an electron is and how fast it is moving, simultaneously.

In the quantum world, the solution of the Schrödinger equation is a mathematical quantity called the wave function, which does not tell us the precise location of, say, an electron at a particular moment in time, but instead provides a whole set of numbers that describe the likelihood of the electron’s being found at different locations in space if we were to look for it there.

The quantum wave function is spread out over all space—meaning that in describing an electron, say, the best we can do is work out a set of numbers that give the probability of finding it not at a single location, but at every point in space simultaneously.

Likewise, if the electron is detected in a certain location then its wave function is instantly altered. At the moment of detection there will be zero probability of finding it anywhere else.

But, in stark contrast to the burglar, when we are not tracking the motion of an electron we cannot assume it nevertheless exists in some definite place at some particular time. Instead, all we have to describe it is the wave function, which is everywhere at once. Only through the act of looking (carrying out a measurement) can we “force” the electron to become a localized particle.

Thermodynamics works like this: it is the average behavior of lots of molecules that is predictable, not the behavior of individual molecules.

Schrödinger pointed out that statistical laws, such as those of thermodynamics, cease to accurately describe systems composed of just a small number of particles.

The important point is that the singular object that is the balloon strictly obeys the gas law because the orderly motion of its single continuous elastic surface arises from the disorderly motions of very large numbers of particles, generating, as Schrödinger put it, order from disorder.