«Anyone who is not shocked by the quantum theory does not understand it. »
Niels Bohr
Does our brain, memory and/or consciousness have a quantum component, underlying the neural network?
After a brief description of the matter, we will present the main principles of quantum mechanics.
Then we will describe their applications to the development of the quantum computer.
We will end with the presentation of theories supporting a quantum functioning of the brain and the consciousness.
5.1 Matter structure
The universe presents a great homogeneity at its fundamental structure level, the matter being energy and vice versa.
The space is made of energy and vacuum, on average one atom per cubic meter. It is the same for the atom whose nucleus counts for a 100.000th of its size.
The temperature in the outer space* of -272°C is very close to absolute zero*.
A hundred elements, thirty particles and four forces are enough to describe the matter, its elementary structure remaining identical from the infinitely small to the infinitely large.
Particles
We distinguish matter particles: 12 fermions (quarks, electron, neutrinos) from force ones: 13 bosons (photons, gluons).
The stable matter consists of 4 fermions: quark up, quark down, electron and electron neutrino.
Neutrinos are present throughout the universe and travel 42
through the matter at a speed close to that of the light one.
Every second 60 billions of them reach every skin square inch.
Forces
There are four fundamental forces: strong nuclear force, weak nuclear force, electromagnetic force and gravitational force.
The weak nuclear force ensures with the strong nuclear one the matter cohesion.
The electromagnetic force results from interactions between electrically charged particles.
The gravitational force is responsible for the attraction of massive bodies, the gravity holding us to the ground.
Waves
There are three types of wave with different frequencies: the mechanical ones requiring support, the electromagnetic and the gravitational ones crossing the vacuum.
Mechanical waves propagate through a substance by
temporarily deforming it. Electromagnetic waves correspond to oscillations of electric and magnetic fields. Gravitational waves result from space-time distortions.
Summary
At the level of the messenger: quantum particles as well as of the vector: electromagnetic or gravitational waves, there are candidates for the information relay at a global level.
5.2 Quantum physics
Understanding the quantum physics is a challenge for our Cartesian mind and requires a certain amount of imagination.
The quantum mechanics describes the behaviour of the
infinitely small and is based on 7 fundamental principles.
Wave-particle duality
43
Every quantum object behaves both as an intangible wave and as a material corpuscle.
It is represented by the wave function that determines the probability for a particle to be at a specific location.
Quantum
A quantum particle can pass from one state to another but in a non-linear way i.e., by step or quantum.
These discontinuous states concern the energy level, the velocity or the spin* of the particle.
State superposition
A quantum object can be in several states at once: an electron can rotate on itself in two opposite directions simultaneously and an atom can both be in fundamental and excited state.
The superposition is equal to the sum of the probabilities for the particle to be in each of distinct states.
Decoherence
A quantum particle is sensitive to minute variations in light, temperature, magnetic field or position leading to the collapse of its superposition.
During this decoherence, the object randomly takes one of the possible states and behaves then like a material corpuscle.
As a result, the measurement of a quantum state gives results randomly alternating.
Uncertainty
The Heisenberg uncertainty principle underlines the
impossibility of knowing at the same time and with precision the speed and position of a quantum particle.
Tunnel effect
Due to its wave-particle duality, a quantum object can cross a 44
physical obstacle thanks to its wave part, as if it was walking through a tunnel.
Entanglement
When two particles of the same system are separated, they continue to behave as a single quantum object.
They must be considered as still belonging to the same object, described by a single wave function.
Regardless of the distance between them, the particles react simultaneously, they remain entangled.
Any modification of one changes the other instantaneously, we speak of entanglement or else of non quantum locality.
Summary
On our scale the quantum theory is bewildering but has never been put in default, its predictions having been one after the other confirmed experimentally.
If man were a quantum object, he could be in two places, turning left and right at the same time, aligning his behaviour instantly with that of his entire family or walk through walls.
5.3 Quantum computer
The quantum theory of information combines the quantum
mechanics and the information sciences and has led to the development of the quantum computer.
The bit* is the basic unit in computing and can only take the values 0 or 1, expressing the yes-no alternative.
The qubit* is the quantum counterpart of the classic one, but it can be in a fuzzy state, superimposing states 0 and 1, and non-local, covering any linear combination of these values.
The superposition and entanglement allow thus the
simultaneous analysis of all possible solutions, leveraging the computering power.
45
A 300-bit computer would surpass the combined power of all conventional computers. The largest to date totalizes 53 ones.
The instability of the superposition and of the non-locality, requiring extremely low ambient temperature and vacuum, are the major problems to be overcome in its development.
5.4 Quantum brain
Facing difficulties of identifying the ultimate nature of consciousness, the thesis of a brain operating in a quantum mode is more and more often evoked.
Where the functioning of the brain and the emergence of the consciousness would be based as in a quantum computer on the state superposition and entanglement.
The challenge is to identify subcellular components that can behave as quantum objects at body temperature, so well above absolute zero.
Several physicists and neurobiologists support this hypothesis and propose different molecular candidates.
N.Bohr having been the first to propose that the probabilistic and non-mechanical character of the quantum theory may be at the source of consciousness.
Microtubules*
The cytoskeleton* of neurons consists of actin microfilaments and tubulin microtubules, tubulin molecules containing
hydrophobic pockets*.
According to the mathematician R.Penrose and the
anesthesiologist S.Hameroff, these pockets contain delocalized electrons that can be remotely entangled.
These entangled electrons ensuring then the quantum
coherence of neurons, the material basis of the consciousness.
The activity of synapses influencing that of microtubules, the transmission of nerve impulses would regulate the mind.
46
Physicists G.Bernroider and S.Roy suggest that the quantum coherence lies in the ion channels of the neuronal membranes.
These channels can be superimposed on lipids, proteins, other membrane channels and neurons.
Potassium and oxygen ions would form a superimposed
quantum network, like that of quantum computers.
Phosphorus nuclei
How to inhibit quantum decoherence in the brain, knowing that quantum computer can only function under vacuum and at very low temperatures.
According to Fisher, the spin of the phosphorus nucleus plays a major role in maintaining neural quantum coherence.
This assumption is based on the following observations:
- Qubits can be kept at 25°c for 39 minutes using
phosphorus atoms contained in a silicon block.
- Small magnetic pulses allowing the superposition of
the phosphorus core spin.
- Phosphorus is present in the human body as tiny
clusters of calcium phosphate.
Thus the qubits of the neuronal phosphorus nucleus would inhibit decoherence at body temperature.
Summary
The thesis of an underlying quantum activity in the brain is more and more evoked and subject to experimental researches.
Various atomic structures that could be involved in the
emergence of a quantum consciousness having been identified.
The spin of the phosphorus atom nucleus could promote the maintenance of neuronal quantum coherence.
47
The matter elementary structure remains identical from the infinitely small to the infinitely large and is summed up in 4
stable particles.
The qubit can be in a fuzzy state, superimposing states 0 and 1, and non-local, covering any combination of these values.
Applied to the computer, these quantum properties leverage the computating power, allowing the simultaneous analysis of all possible options.
The brain functioning and the consciousness emergence could also depend on the state superposition and the entanglement.
Some neuronal molecules could behave as quantum objects at body temperature.
Thus, the existence in the brain of quantum activities,
underlying biological processes, is gradually emerging.
48