QMB: Living Systems and Quantum Physics

The Orderliness of Living Systems

It has long been clear that the main feature and main mystery of living tissue is its amazing orderliness. On the one hand, any organism is an unsettled, non-equilibrium system driven by chemical reactions with essentially stochastic kinetics. But at the same time, living organisms are incredibly ordered — both structurally and functionally. The same chemical reactions, though governed by probabilistic laws, are arranged in highly complex, strictly deterministic chains. Cells, tissues and organs form; myriad interactions take place — and all of this encompasses a huge amount of spatial and temporal order [1].

The question naturally arises: what is responsible for this order; where does it come from? Answers were sought in statistical methods, attempting to derive orderliness from stochastic processes, such as diffusion. It was proposed that all combinations of large and small molecules are possible, but only the most probable of them are realized, and they, again in accordance with probabilities, constitute complex chains and sequences. However, these attempts failed miserably. Ordered chains of reactions in a random environment, on the contrary, quickly collapsed, ruined by genuine chaos [2]. It was impossible to get by without some form of guiding influence — and it would have to act not just between nearby molecules but at macroscopic distances.

Basically, by the 1960s, a critical mass of awareness had developed – the realization that we knew almost nothing about the organization of living systems. This applied equally to the brain and its functions – memory and thinking. As I already noted in the introduction, the fundamental puzzles became the nonlocality and stability of the products of brain activity—our memories and thoughts. And they remain enigmatic to this day, at least within the framework of mainstream scientific paradigms.

Nonlocality contradicts traditional notions of the direct responsibility of certain neurons (or small groups of them) for certain fragments of memory: conventional science considers these to be static 'imprints' of lived experiences in the synaptic connections between neurons. The essence of nonlocality is that during the processes of recollection, memorization, and thinking, very different parts of the brain suddenly begin to act in unison: the waves coming from them change their amplitudes together and become synchronized – their phases seem to “lock” to one another. Memories are “blurred” almost throughout the entire neocortex – at least, that is what the experiments assert. According to them, large “communities” of neurons from different areas of the brain – not small localized groups – work in concert. And what is even more inexplicable, the synchronization is established instantly – significantly faster than the neurons could “reach out” to each other through electrochemistry. It is known for certain that chemical reactions are way too slow, and the fields from ion currents are way too weak, to produce effects so quickly and at such distances.

The stability of memory is also inexplicable. Those very "imprints" of lived experiences simply cannot be stable. The brain tissue shows amazing plasticity, evolving and undergoing a complex internal life: the brain constantly reacts to the outside world and adjusts to it. Streams of stimuli, signals from receptors, continually reorganize neural connections, and it is impossible to predict in advance exactly where and how they will change – or, perhaps, disappear altogether. No neuron group – including “memory imprints” – can remain for even a month in a static, unchanged form. But our memories are tenacious – many of them last for decades...

Are these issues acknowledged within mainstream science? Certainly. Science continues to seek explanations – but mainly within the boundaries of officially accepted views. To date, these efforts have not yielded substantial breakthroughs – although now we know much more about the orderliness of living systems. As for the workings of the brain, official scientific paradigms have not progressed far. More on this here.

But let's return to the second half of the last century. It became clear that purely local interactions between neurons through synapses could not explain the results of the experiments [3]. It was also shown that individual neurons could not be solely responsible for the functioning of the brain as a whole, and their local (synaptic) interconnections could not explain the details of these workings [4]. For the operation of living systems in general and the brain in particular, some unknown coordinating factor is needed, propagating rapidly, almost instantaneously, over large areas [5].

On the other hand, by that same time, quantum physics had flourished, producing remarkable results and elucidating many mysteries. For example, quantum mechanics explained how chemistry works — and, of course, on the crest of this wave, some tried to apply its approaches to living systems. This was not a success, but nevertheless, the idea that some form of quantum correlations underlie the order in living tissues kept recurring among inquiring minds. And when the newest and most complex discipline, quantum field theory, got involved, the light began to dawn – and the right paths emerged.

Spontaneous Symmetry Breaking

Quantum field theory deals with systems consisting of a very large number of elements. It describes the internal micro-dynamics of these systems, leading to the emergence of macro-effects. As a result, micro-elements “sense” each other over large, macroscopic distances. A macro-order appears in a quantum system — the system becomes both quantum and classical. This is not ephemeral theoretical musing: in fact, we are surrounded by such systems; we encounter them every day. A good example is crystals; another familiar example is magnets. And so, one researcher, contemplating the nature of memory, saw in it a hint of quantum macro-order. One that emerges from the central phenomenon of quantum field theory, thanks to which crystals and magnets exist — spontaneous symmetry breaking [6].

What’s that? It is a kind of phase transition of a quantum system from a less ordered to a more ordered state — or, equivalently, to a more energetically favorable one. The process is easy to understand using crystals as an example: melt some metal, such as bismuth, and then let it cool. Once it has cooled sufficiently, that is, after crossing a certain critical temperature, the metal will transition to a new phase, a crystalline one. In the melt, atoms could occupy any position — the system was completely symmetrical. After cooling, the positions of the atoms are constrained by the parameters of the crystal lattice: they have to be located at certain angles and at certain distances from each other. The system has lost some of its symmetry, gaining orderliness in return! This has happened by itself, spontaneously — no one has ‘glued’ the bismuth atoms together; they organized themselves into a lattice, realizing a certain universal dynamic mechanism. The same molten state can produce a huge variety of crystalline forms — this is the meaning of the initial symmetry of the system. In each specific case, only one of the possibilities is realized depending on the initial conditions — for example, on the distribution of heterogeneities in the melt. This is the essence of the loss of the original symmetry — mathematically speaking, the symmetry of translation. The continuous translational symmetry of the molten state — atoms could be shifted, that is, translated, in any direction to any distance — turned into a more limited discrete translational symmetry of the crystal lattice!

The resulting crystal is very stable and hard; it cannot be shaken like the melt. How is this stability achieved? First, because the positions of the atoms in the lattice minimize potential energy – with respect to interatomic interactions and the Pauli exclusion principle. This is "static" stability: it is always advantageous for the atoms to occupy positions at an energy minimum. However, they do not stand still (unless the crystal is cooled to absolute zero); they continuously vibrate, deviating slightly from their ideal positions. What, then, prevents these vibrations from resonating, amplifying uncontrollably, and causing the crystal to decay? What ensures the "dynamic" stability of the crystal? The answer lies in quantum correlations: the atoms of the crystal form a single quantum whole, so the vibrations of each particle are linked to those of all the others. As a result, perturbations do not accumulate but instead propagate through the lattice in the form of elastic waves. Figuratively speaking, all the atoms of the crystal lattice, no matter how distant their location, constantly exchange information about each other — this is what allows the lattice to maintain its order. In a mathematical sense, this means the following: if, as a result of a quantum dynamic process, part of the original symmetry is lost, then inevitably — mathematically inevitably! — new quantum entities emerge — collective oscillations of all elements of the system. They are called quasi-particles — ‘quasi,’ because they exist only as long as the order they support is maintained. If a crystal is disassembled into atoms, these quasi-particles cannot be found there. And at the same time, they are completely real — other particles, such as photons, can scatter off them, as has been observed in many experiments.

In the case of crystals, Goldstone bosons are also called phonons. As mentioned earlier, these are quanta of elastic waves, that is, waves of displacement of atoms in the crystal lattice. Another popular example of the spontaneous violation of symmetry is a ferromagnet — for instance, the sort that we bring from our travels and stick on the fridge door. Magnetization is the result of the loss of the rotational symmetry of the magnetic moments — in metals, these are the magnetic dipole moments of electrons. Roughly speaking, if we denote dipole moments with arrows, then a nonzero magnetization means that all the electrons point their arrows in one direction. In this case, the Goldstone bosons supporting such co-direction are called magnons and represent the quanta of magnetic dipole waves — also called spin waves — that is, the collective oscillations of all the ‘arrows,’ the magnetic moments of all the electrons. As with the atoms in a crystal, they all signal to one another about their direction and thus maintain their order.

The hardness of a crystal and the magnetization of a magnet are macroscopic effects; we observe them in real life, on our space-time scales. Yet, they are the result of essentially quantum dynamic processes, which cannot be described by classical physics. So, quantum field theory, dealing with the interaction of a very large number of quantum objects, builds a bridge between the micro and the macro. The macro emerges from the micro because a vast number of microscopic constituents behave as a single whole. And it is the Goldstone quasi-particle-bosons, the collective quantum oscillations, that are responsible for this.

Quantum Condensate

The term ‘bosons’ means that Goldstone quasiparticles obey Bose-Einstein statistics, that is, any number of them can occupy the same quantum state. One of the important features of such particles is their ability to form a Bose-Einstein Condensate (BEC), a special phase of matter in which a multitude of identical bosons occupies a single lowest-energy level ("condenses into the ground state," as they say in theoretical physics), behaving collectively as a unified macroscopic quantum object. Usually, this implies an equilibrium BEC, a regime where the system's properties are determined exclusively by temperature and energy balance, without any continuous external pumping or dissipation. Such a condensate can only form if the bosons are “real” particles whose number is approximately conserved, as, for example, in atomic gases cooled to almost absolute zero. A classic example is the condensate of rubidium or sodium, first obtained in 1995, where billions of atoms move in unison, like a coherent quantum wave.

Phonons in crystals and magnons in ferromagnets – collective excitations of an already ordered medium – are not "real" particles in this sense. Their "number" is constantly changing: they can be created or destroyed as the system redistributes energy internally or exchanges heat with its surroundings. Moreover, their ground (lowest-energy) state is equivalent to a perfectly ordered crystal or magnet, that is, simply to their absence. This is why phonons and magnons in general cannot form an equilibrium BEC (except in some very exotic situations); the ordered lattice or the state of magnetization themselves represent the "condensed" phase, from which these bosons emerge as fluctuations.

But crystals and magnets are forms of non-living matter. Their microscopic components may move or vibrate, but the system as a whole is closed: it does not maintain a continuous, directed exchange of energy with the external world and therefore can reach thermodynamic equilibrium. On the other hand, living matter never reaches this equilibrium and doesn't even approach it – this is the very meaning of its existence! Thermodynamic equilibrium means death. Every living system is an open structure that constantly exchanges energy and matter with the environment, maintaining internal order through metabolic flows. Because of this, the concept of an equilibrium BEC has no direct meaning in biological systems; their internal processes do not arrive at a state determined solely by temperature and energy balance. There is never a static balance; life is always dynamic, sustained by external input.

Nevertheless, the idea of condensation itself remains relevant: with a constant energy supply, collective excitations (those same quasiparticle-bosons) can transition into highly ordered states resembling a BEC, but one that is non-equilibrium and imposed by the external world. One example is the so-called Fröhlich condensate [30], in which the quantum oscillations of biomolecules can synchronize via a continuous energy inflow, forming large coherent regions. This is an analog of Bose-Einstein condensation, but one that occurs far from an equilibrium state and at high (room) temperature. Herbert Fröhlich demonstrated that if energy is constantly "injected" from the outside into a system of bosons (collective vibrations of quantum objects), this energy, under certain conditions, does not simply "heat" the entire system by making the objects vibrate more strongly (as one would naturally assume from classical physics or everyday experience). Instead, it concentrates into a single (the lowest-frequency) vibrational mode of the bosons, as if forcibly transferring them all into this one identical mode. Thus, all the bosons end up (condense) in the very same state and behave as a single quantum object – in complete analogy with a classical, equilibrium BEC.

Fröhlich himself applied this concept to biological systems, aiming to explain how quantum effects could manifest as macro-correlations within living cells. He treated the biological medium as a system of electric (micro) dipoles – charged molecular groups like C=O, N-H, and so on – that constitute large (macro) biomolecules. The vibrations of these dipoles, when synchronized via the mechanism described above, form a single "bioelectric wave": a macroscopic quantum object analogous to a Bose-Einstein condensate. It is precisely this type of quantum condensate that is discussed later in the context of the quantum model of the brain.

Let me stress again: the macro emerges from the micro due to an enormous number of particles behaving as a single whole. This is an essentially quantum effect; there is no analog for it in classical physics. I will try, however, to provide a very crude and not entirely accurate (but at least some) metaphor:

Imagine a medium-sized room where 20 people are locked. They are bustling about randomly, walking back and forth, bumping into each other, looking around: in short, they are behaving chaotically. All possible movements are permitted; the system is completely symmetrical.

Then, the experimenter begins to pump cold air into the room. Soon, it becomes freezing. At some point, the people realize they cannot cope with the cold individually. They form a circle, putting their arms around each other's shoulders, creating a single figure: this way, they are slightly warmer. Now they can only make small movements within the confines of this unified figure – jostling, stretching, changing arm positions, etc. The system has lost its symmetry, leaving only one narrow set of actions. I must note: no one told the participants how to stand or what figure to form; no one led them by the hand. They gathered into a group (as a result of which the system lost its symmetry) spontaneously, all by themselves, because it seemed right (i.e., energetically favorable) to them.

Then the temperature drops further – and further and further... Soon, all movement within the figure ceases. The people huddle into an optimally dense group – to conserve heat most effectively – standing motionless, maintaining maximum contact area, and staring at the floor... Their collective state is an analog of a classical, equilibrium Bose-Einstein condensate: they have lost their individuality, becoming indistinguishable components of a single whole, and their collective vibrations have ceased (like in crystals cooled to almost absolute zero). Even their thoughts are probably the same: When will this experiment finally end?...

A sad picture. But now, let's imagine that instead of lowering the temperature, the experimenter turns on loud rhythmic music (that is, by analogy with a living organism, provides a metabolic influx of energy). Soon, everyone is dancing, all in the same frequency mode. If we assume they are all graduates of the same dance class, they will even move identically, looking like a single whole from the outside. We once again have a highly ordered collective state – but we didn't have to cool the room! And if the music is turned off (i.e., cellular metabolism is interrupted), everyone will stop, the order will disappear (i.e., the cells in the organism will die).

In conclusion, let me emphasize: non-equilibrium quantum condensation in living systems is not speculation. It is a real, existing, and repeatedly verified mechanism.