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L'émergence de la conscience
The Sense of Self

Help Lien : CQC Introductions : Quantum Entanglement Lien : Physique quantique Lien : Principe de superposition quantique
Lien : The Strange World of Quantum Entanglement Lien : Quantum entanglement Lien : 9 formulations de la mécanique quantique Lien : Mind, Matter, and Quantum Mechanics, by Henry P. Stapp
Lien : Evolution of Consciousness Lien : Quantum Approaches to Consciousness Lien : Moving Forward on the Problem of Consciousness Lien : Quantum Consciousness
Lien : Comment la conscience contrôle le cerveau Lien : Neuroscience and the Soul: The Dualism of John Carew Eccles Lien : Quantum Models of Consciousness Lien : QUANTUM THEORY AND CONSCIOUSNESS: AN OVERVIEW WITH SELECTED EXAMPLES
Lien : STAPP AND DESCARTES Lien : Quantum mind

Heisenberg’s uncertainty principle, also known as Heisenberg’s non-determination principle or Heisenberg’s inequalities, was presented by German physicist Werner Karl Heisenberg in the spring of 1927. This principle states that it is impossible to obtain precise measurements of both the position of a particle and its momentum at the same time. The more precisely we determine the one, the less we can know about the other. In other words, we can either know the particle’s precise position while accepting great uncertainty as to its momentum, or vice versa, but we can never know both of these values precisely.

One way to try to explain this paradox is to assume that we cannot observe anything unless we expose it to light—in other words, to photons, which will strike it and be reflected by it. But on the scale of the infinitely small, even the tiniest photon that strikes an elementary particle such as an electron will alter its initial trajectory or make it change orbital. On this scale, the photon becomes a veritable projectile that may let us determine the electron’s position but will simultaneously alter its momentum and trajectory, so that we cannot know them at the same time as its position (but see the links below for an update of these explanations)..

Lien : Inégalités de Heisenberg Lien : Inégalités de Heisenberg Lien : Uncertainty principle

For the most part, quantum mechanics describes physical systems in terms of wave functions that change deterministically over time, in accordance with Schrödinger’s equation. Developed by Austrian physicist Erwin Schrödinger in 1925, this fundamental equation of quantum physics describes how an elementary particle evolves over time.

In this sense, this equation lets us do the same thing as dynamic equations in classical mechanics: predict the position and momentum of any system of particles that evolve deterministically over time. The difference is that what is known as the quantum wave does not specify the particles’ position and momentum as such, but rather the probability that some of the particles will have a given position and a given momentum when “measurements” are taken. Quotation marks are used here because the truly strange thing about quantum mechanics is that it does not provide a real explanation of what happens during such measurements (see preceding sidebar).

The idea of the collapse or the decoherence of the quantum wave is used to attempt to describe what happens at the time of measurement. Because, in some way that is not clearly understood, the act of measurement causes the quantum wave (which usually has a range of possible positions and velocities) to collapse in an indeterminate manner into definite values.

It’s a little like playing “heads or tails” in the dark. The probability of the coin’s being heads up or tails up when you pull your hand away is the same, but so long as you have not turned on the light, you can say that the coin lying immobile under your hand is in a superposition of states. When you turn on the light and actually take a “measurement”, you collapse the superposed states into a single one: heads or tails.

Though this analogy depicts the mechanism of this collapse fairly well, it is not described by Schrödinger’s equation and is the subject of much controversy.

Lien : Physique quantique : Superposition quantique Lien : Quantum entanglement Lien : Du monde quantique au monde macroscopique : la décohérence prise sur le fait

There are many different theories that try to explain consciousness in terms of molecular phenomena. For example, Flohr’s hypothesis posits the involvement of NMDA receptor molecules in our conscious processes. But another large group of theories draws on the principles of quantum physics to try to explain consciousness in terms of the infinitely small.

Some of these latter theories are purely speculative and allude to the strange properties of quantum systems in a metaphorical sense only. These theories may inspire new hypotheses that can be tested experimentally, but the theories themselves do not represent any real scientific progress so long as they remain nothing but vague analogies.

But other approaches apply current quantum theory to develop causal models linking specific biological microstructures to the physiological and psychological mechanisms of consciousness. For example, in the 1990s, Beck and Eccles suggested that the probabilistic nature of the release of neurotransmitters from the synaptic vesicles into the synaptic gap was of quantum origin. According to these authors, the extremely small size of the sites where the exocytosis of the synaptic vesicles occurs enables quantum uncertainty to play a role in this process.

Eccles describes structures called “dendrons” composed of groups of about 100 dendrites of pyramidal neurons in the cortex. He theorizes that consciousness operates by reciprocally linking each dendron with its associated unit of mental experience, or “psychon”. The effect of the psychon on the dendron would then increase the probability of the synaptic vesicles’ releasing neurotransmitters into the excitatory synapses of this dendron’s dendrites.

Eccles thus offers a dualist hypothesis,one that posits two distinct worlds. In this hypothesis, quantum physics at the level of the synaptic vesicles plays a role somewhat like the role of the pineal gland in the philosophy of Descartes: the site where the two worlds interact. Such dualism is intriguingly consistent with Eccles’s religious background: though he received the Nobel Prize for Medicine in 1963 for his important discoveries regarding synaptic mechanisms, he was a practicing Catholic who never disguised his faith in a human soul of divine origin.

Of all the theories of consciousness that draw directly on quantum physics, the one with the longest history was proposed by John von Neumann in the 1930s, developed further by Eugene Wigner in the 1960s, and refined a bit further by Henry Stapp starting in the 1980s.

In his 1955 monograph on the mathematical bases of quantum physics, von Neumann addressed the thorny issue of measurement in the context of quantum physics—the famous Heisenberg uncertainty principle (see sidebar). According to this principle, the more closely we approach the infinitely small, the more we realize that what we call reality tends toward a state that is more potential than real. This suggests that the only thing that can be considered fixed at this level arises from the act of observation itself, which in a sense determines one particular state at the expense of others.

From this came Von Neumann’s idea that what we call the “observer”of a measurement can be regarded as the measuring instrument just as much as it can be regarded as the human brain that takes note of this measurement. Other authors go even further and state that it is human consciousness that actually completes the quantum measurement, thus ascribing to this consciousness a critical role in taking this quantum measurement.


Inspired by these predecessors, Stapp developed his own interpretation of this approach. His hypothesis is based on the application of the uncertainty principle to the ion channels in neurons. The opening of these channels results in the release of neurotransmitters into the synaptic gap. And because it is these synapses that determine our thoughts through the interplay of neuronal assemblies, Stapp believes that quantum effects in these ion channels may influence our conscious thoughts.

(To view more diagrams of this receptor, click here.)

To support his hypothesis, Stapp notes that for an ion channel with a diameter of 1 nanometre (10-9 metres), the uncertainty for momentum is of the order of 1 metre per second, according to Heisenberg’s principle. In Stapp’s view, these effects are sufficient to give rise to a superposition of quantum states (see sidebar) that consciousness could then reduce to a single classic macroscopic state.

In simpler terms, Stapp believes that quantum waves collapse when intelligent brains select certain of the available quantum alternatives to decide their future behaviour.


Hence this interpretation of quantum mechanics is also a theory of consciousness inasmuch as the parts of the brain that are involved in the collapse of the quantum wave (see sidebar) are the ones that participate directly in consciousness. Human consciousness would thus have the singular ability to make the quantum wave collapse—in other words, the ability not only to describe physical reality, but also to influence it and hence to influence, in particular, the activity of the brain itself.

Thus Stapp does not so much try to explain in quantum terms how consciousness may be constituted as he takes it as given and states that it can influence a quantum phenomenon such as the collapse of the wave function. And for Stapp, this perspective can explain two essential things: first, the adaptive function of human consciousness, which lets us eliminate alternative realities so that we can choose a more effective course of action, and second, free will, which is so precious to us as human beings.

This can be regarded as a somewhat radical version of what neurobiologists who research attention call “top-down mechanisms”. In any case, this version goes too far for the reductionist materialists, who reject it outright. At the very most, according to some commentators, it can be seen as having some points of convergence with the materialist approach known as the “dual-aspect theory”.

Other theories that postulate quantum effects as the basis for consciousness find current quantum theory incomplete and rely on future developments in quantum theory to validate their intuitions. This is the case, for example, with Penrose and Hameroff’s model.

Decoherence theory attempts to resolve the difficult question of why the macroscopic world is not quantum.

The famous thought experiment known as Schrödinger’s cat demonstrates just how difficult this question is. In this thought experiment, a cat is placed in a closed, opaque box along with a flask containing a lethal gas. The flask will not release this poison unless an electron shot from a gun slightly farther away strikes the upper half of a sensor (and not its lower half).

Now, the quantum wave of this system gives the electron just as much chance of striking the upper half of the sensor as the lower half. The cat’s fate therefore remains undecided so long as the wave function has not collapsed (see sidebar) and so long as we do not know whether the electron has struck the upper or the lower portion of the sensor.

But when does this happen? When do things become determined and definite: when the flask breaks? when the cat inhales the poison gas? or only when it either lives or dies? And this is where things get really strange, because if we rely solely on Schrödinger’s equation, it doesn’t help us at all: according to that equation, the cat is in a superposition of two states: dead and alive! In precisely the same way, this equation sees the electron as a superposition of two trajectories, toward the upper and bottom halves of the sensor.

Thus physics alone does not seem able to tell us when things become definite. From this comes the idea, championed by Stapp, that the wave function may collapse only at the moment when it interacts with consciousness. Thus nothing would need to be definite until it was consciously perceived by an observer. If that is true, then Schrödinger’s cat would be neither dead nor alive until an observer opened the box and looked inside.

Link : Le chat de Schrödinger Link : Un chat à la rescousse des informaticiens Link : La décohérence

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