The quantum mind or quantum consciousness is a group of hypotheses proposing that classical mechanics cannot explain consciousness.[1] It posits that quantum-mechanical phenomena, such as entanglement and superposition, may play an important part in the brain's function and could explain consciousness.
The hypotheses assert that consciousness is somehow quantum-mechanical and can overlap with quantum mysticism, a pseudoscientific movement that assigns supernatural characteristics to various quantum phenomena such as nonlocality and the observer effect.[2]
Eugene Wigner developed the idea that quantum mechanics has something to do with the workings of the mind. He proposed that the wave function collapses due to its interaction with consciousness. Freeman Dyson argued that "mind, as manifested by the capacity to make choices, is to some extent inherent in every electron".[3]
Other contemporary physicists and philosophers considered these arguments unconvincing.[4] Victor Stenger characterized quantum consciousness as a "myth" having "no scientific
basis" that "should take its place along with gods, unicorns and
dragons".[5]
David Chalmers argues against quantum consciousness. He instead discusses how quantum mechanics may relate to dualistic consciousness.[6] Chalmers is skeptical that any new physics can resolve the hard problem of consciousness.[7][8]
David Bohm viewed quantum theory and relativity as contradictory, which implied a more fundamental level in the universe.[9] He claimed that both quantum theory and relativity pointed to this
deeper theory, which he formulated as a quantum field theory. This more
fundamental level was proposed to represent an undivided wholeness and
an implicate order, from which arises the explicate order of the universe as we experience it.
Bohm's proposed order applies both to matter and consciousness.
He suggested that it could explain the relationship between them. He saw
mind and matter as projections into our explicate order from the
underlying implicate order. Bohm claimed that when we look at matter, we
see nothing that helps us to understand consciousness.
Bohm discussed the experience of listening to music. He believed
that the feeling of movement and change that make up our experience of
music derive from holding the immediate past and the present in the
brain together. The musical notes from the past are transformations
rather than memories. The notes that were implicated in the immediate
past become explicate in the present. Bohm viewed this as consciousness
emerging from the implicate order.
Bohm saw the movement, change or flow, and the coherence of
experiences, such as listening to music, as a manifestation of the
implicate order. He claimed to derive evidence for this from Jean Piaget's work on infants.[10] He held these studies to show that young children learn about time and
space because they have a "hard-wired" understanding of movement as part
of the implicate order. He compared this hard-wiring to Chomsky's theory that grammar is hard-wired into human brains.
Bohm never proposed a specific means by which his proposal could
be falsified, nor a neural mechanism through which his "implicate order"
could emerge in a way relevant to consciousness.[9] He later collaborated on Karl Pribram's holonomic brain theory as a model of quantum consciousness.[11]
According to philosopher Paavo Pylkkänen, Bohm's suggestion "leads naturally to the assumption that the physical correlate of the logical thinking process is at the classically describable level of the brain, while the
basic thinking process is at the quantum-theoretically describable
level".[12]
Theoretical physicist Roger Penrose and anaesthesiologist Stuart Hameroff collaborated to produce the theory known as "orchestrated objective reduction"
(Orch-OR). Penrose and Hameroff initially developed their ideas
separately and later collaborated to produce Orch-OR in the early 1990s.
They reviewed and updated their theory in 2013.[13][14]
Penrose's argument stemmed from Gödel's incompleteness theorems. In his first book on consciousness, The Emperor's New Mind (1989),[15] he argued that while a formal system cannot prove its own consistency,
Gödel's unprovable results are provable by human mathematicians.[16] Penrose took this to mean that human mathematicians are not formal
proof systems and not running a computable algorithm. According to
Bringsjord and Xiao, this line of reasoning is based on fallacious equivocation on the meaning of computation.[17] In the same book, Penrose wrote: "One might speculate, however, that
somewhere deep in the brain, cells are to be found of single quantum
sensitivity. If this proves to be the case, then quantum mechanics will
be significantly involved in brain activity."[15]: 400
Penrose determined that wave function collapse was the only possible physical basis for a non-computable process.
Dissatisfied with its randomness, he proposed a new form of wave
function collapse that occurs in isolation and called it objective reduction.
He suggested each quantum superposition has its own piece of spacetime
curvature and that when these become separated by more than one Planck length, they become unstable and collapse.[18] Penrose suggested that objective reduction represents neither randomness nor algorithmic processing but instead a non-computable influence in spacetime geometry from which mathematical understanding and, by later extension, consciousness derives.[18]
Hameroff provided a hypothesis that microtubules would be suitable hosts for quantum behavior.[19] Microtubules are composed of tubulin protein dimer subunits. The dimers each have hydrophobic pockets that are 8 nm apart and may contain delocalized π electrons. Tubulins have other smaller non-polar regions that contain π-electron-rich indole rings separated by about 2 nm. Hameroff proposed that these electrons are close enough to become entangled.[20] He originally suggested that the tubulin-subunit electrons would form a Bose–Einstein condensate, but this was discredited.[21] He then proposed a Frohlich condensate, a hypothetical coherent
oscillation of dipolar molecules, but this too was experimentally
discredited.[22]
Orch-OR has made numerous false biological predictions and is not an accepted model of brain physiology.[23] In other words, there is a missing link between physics and neuroscience.[24] For instance, the proposed predominance of A-lattice microtubules, more
suitable for information processing, was falsified by Kikkawa et al.,[25][26] who showed that all in vivo microtubules have a B lattice and a seam.
The proposed existence of gap junctions between neurons and glial cells was also falsified.[27] Orch-OR predicted that microtubule coherence reaches the synapses through dendritic lamellar bodies (DLBs), but De Zeeuw et al. proved this impossible[28] by showing that DLBs are micrometers away from gap junctions.[29]
In 2014, Hameroff and Penrose claimed that the discovery of quantum vibrations in microtubules by Anirban Bandyopadhyay of the National Institute for Materials Science in Japan in March 2013[30] corroborates Orch-OR theory.[14][31]
Although these theories are stated in a scientific framework, it
is difficult to separate them from scientists' personal opinions. The
opinions are often based on intuition or subjective ideas about the
nature of consciousness. For example, Penrose wrote:[32]
[M]y own point of view asserts that you can't even simulate conscious activity. What's going on in conscious thinking is something you couldn't properly imitate at all by computer.... If something behaves as though it's conscious, do you say it is conscious? People argue endlessly about that. Some people would say, "Well, you've got to take the operational viewpoint; we don't know what consciousness is. How do you judge whether a person is conscious or not? Only by the way they act. You apply the same criterion to a computer or a computer-controlled robot." Other people would say, "No, you can't say it feels something merely because it behaves as though it feels something." My view is different from both those views. The robot wouldn't even behave convincingly as though it was conscious unless it really was—which I say it couldn't be, if it's entirely computationally controlled.
Penrose continues:[33]
A lot of what the brain does you could do on a computer. I'm not saying that all the brain's action is completely different from what you do on a computer. I am claiming that the actions of consciousness are something different. I'm not saying that consciousness is beyond physics, either—although I'm saying that it's beyond the physics we know now.... My claim is that there has to be something in physics that we don't yet understand, which is very important, and which is of a noncomputational character. It's not specific to our brains; it's out there, in the physical world. But it usually plays a totally insignificant role. It would have to be in the bridge between quantum and classical levels of behavior—that is, where quantum measurement comes in.
W. Daniel Hillis responded: "Penrose has committed the classical mistake of putting
humans at the center of the universe. His argument is essentially that
he can't imagine how the mind could be as complicated as it is without
having some magic elixir brought in from some new principle of physics,
so therefore it must involve that. It's a failure of Penrose's
imagination.... It's true that there are unexplainable, uncomputable
things, but there's no reason whatsoever to believe that the complex
behavior we see in humans is in any way related to uncomputable,
unexplainable things."[33]
Lawrence Krauss is also blunt in criticizing Penrose's ideas. He
has said: "Roger Penrose has given lots of new-age crackpots ammunition
by suggesting that at some fundamental scale, quantum mechanics might be
relevant for consciousness. When you hear the term 'quantum
consciousness', you should be suspicious.... Many people are dubious
that Penrose's suggestions are reasonable, because the brain is not an
isolated quantum-mechanical system."[2]
Hiroomi Umezawa and collaborators proposed a quantum field theory of memory storage.[34][35] Giuseppe Vitiello and Walter Freeman proposed a dialog model of the mind. This dialog takes place between the classical and the quantum parts of the brain.[36][37][38] Their quantum field theory models of brain dynamics are fundamentally different from the Penrose–Hameroff theory.
Karl Pribram's holonomic brain theory (quantum holography) invoked quantum mechanics to explain higher-order processing by the mind.[39][40] He argued that his holonomic model solved the binding problem.[41] Pribram collaborated with Bohm in his work on quantum approaches to
mind and he provided evidence on how much of the processing in the brain
was done in wholes.[42] He proposed that ordered water at dendritic membrane surfaces might operate by structuring Bose–Einstein condensation supporting quantum dynamics.[43]
Henry Stapp proposed that quantum waves are reduced only when they interact with consciousness. He argues from the orthodox quantum mechanics of John von Neumann[clarify] that the quantum state collapses when the observer selects one among
the alternative quantum possibilities as a basis for future action. The
collapse, therefore, takes place in the expectation that the observer
associated with the state. Stapp's work drew criticism from scientists
such as David Bourget and Danko Georgiev.[44] Georgiev[45][46][47] criticized Stapp's model in two respects:
Stapp has responded to both of Georgiev's objections.[specify][48][49]
British philosopher David Pearce defends what he calls physicalistic idealism ("the non-materialist
physicalist claim that reality is fundamentally experiential and that
the natural world is exhaustively described by the equations of physics
and their solutions") and has conjectured that unitary conscious minds
are physical states of quantum coherence (neuronal superpositions).[50][51][52][53] This conjecture is, according to Pearce, amenable to falsification,
unlike most theories of consciousness, and Pearce has outlined an
experimental protocol describing how the hypothesis could be tested
using matter-wave interferometry to detect nonclassical interference patterns of neuronal superpositions at the onset of thermal decoherence.[54] Pearce admits that his ideas are "highly speculative", "counterintuitive", and "incredible".[52]
These
hypotheses of the quantum mind remain hypothetical speculation, as
Penrose and Pearce admit in their discussions. Until they make a
prediction that is tested by experimentation, the hypotheses aren't
based on empirical evidence. According to Krauss, "It is true that
quantum mechanics is extremely strange, and on extremely small scales
for short times, all sorts of weird things happen. And in fact, we can
make weird quantum phenomena happen. But what quantum mechanics doesn't
change about the universe is, if you want to change things, you still
have to do something. You can't change the world by thinking about it."[2]
The process of testing the hypotheses with experiments is fraught with conceptual/theoretical, practical, and ethical problems.
The
idea that a quantum effect is necessary for consciousness to function
is still in the realm of philosophy. Penrose proposes that it is
necessary, but other theories of consciousness do not indicate that it
is needed. For example, Daniel Dennett proposed a theory called multiple drafts model, which doesn't indicate that quantum effects are needed, in his 1991 book Consciousness Explained.[55] A philosophical argument on either side isn't scientific proof,
although philosophical analysis can indicate key differences in the
types of models and show what type of experimental differences might be
observed. But since there isn't a clear consensus among philosophers, it
isn't conceptual support that a quantum mind theory is needed.
There are computers that are specifically designed to compute using quantum-mechanical effects. Quantum computing is computing using quantum-mechanical phenomena, such as superposition and entanglement.[56] They are different from binary digital electronic computers based on transistors. Whereas common digital computing requires that the data be encoded into binary digits (bits), each of which is always in one of two definite states (0 or 1), quantum computation uses quantum bits, which can be in superpositions of states. One of the greatest challenges is controlling or removing quantum decoherence.
This usually means isolating the system from its environment, as
interactions with the external world cause the system to decohere. Some
quantum computers require their qubits to be cooled to 20 millikelvins
in order to prevent significant decoherence.[57] As a result, time-consuming tasks may render some quantum algorithms
inoperable, as maintaining the state of qubits long enough eventually
corrupts the superpositions.[58] There aren't any obvious analogies between the functioning of quantum
computers and the human brain. Some hypothetical models of quantum mind
have proposed mechanisms for maintaining quantum coherence in the brain,
but they have not been shown to operate.
Quantum entanglement is a physical phenomenon often invoked for quantum mind models. This effect occurs when pairs or groups of particles interact so that the quantum state of each particle cannot be described independently of the other(s),
even when the particles are separated by a large distance. Instead, a
quantum state has to be described for the whole system. Measurements of physical properties such as position, momentum, spin, and polarization, performed on entangled particles are found to be correlated.
If one particle is measured, the same property of the other particle
immediately adjusts to maintain the conservation of the physical
phenomenon. According to the formalism of quantum theory, the effect of
measurement happens instantly, no matter how far apart the particles
are.[59][60] It is not possible to use this effect to transmit classical information at faster-than-light speeds[61] (see Faster-than-light § Quantum mechanics). Entanglement is broken when the entangled particles decohere through interaction with the environment—for example, when a measurement is made[62] or the particles undergo random collisions or interactions. According
to Pearce, "In neuronal networks, ion–ion scattering, ion–water
collisions, and long-range Coulomb interactions from nearby ions all
contribute to rapid decoherence times; but thermally induced decoherence
is even harder experimentally to control than collisional decoherence."
He anticipated that quantum effects would have to be measured in
femtoseconds, a trillion times faster than the rate at which neurons
function (milliseconds).[54]
Another possible conceptual approach is to use quantum mechanics
as an analogy to understand a different field of study like
consciousness, without expecting that the laws of quantum physics will
apply. An example of this approach is the idea of Schrödinger's cat. Erwin Schrödinger described how one could, in principle, create entanglement of a
large-scale system by making it dependent on an elementary particle in a
superposition. He proposed a scenario with a cat in a locked steel
chamber, wherein the cat's survival depended on the state of a radioactive atom—whether it had decayed and emitted radiation. According to Schrödinger, the Copenhagen interpretation implies that the cat is both alive and dead until the state has been observed. Schrödinger did not wish to promote
the idea of dead-and-alive cats as a serious possibility; he intended
the example to illustrate the absurdity of the existing view of quantum
mechanics.[63] But since Schrödinger's time, physicists have given other interpretations of the mathematics of quantum mechanics, some of which regard the "alive and dead" cat superposition as quite real.[64][65] Schrödinger's famous thought experiment poses the question, "when does a quantum system stop existing as a superposition of states and
become one or the other?" In the same way, one can ask whether the act
of making a decision is analogous to having a superposition of states of
two decision outcomes, so that making a decision means "opening the
box" to reduce the brain from a combination of states to one state. This
analogy about decision-making uses a formalism derived from quantum
mechanics, but doesn't indicate the actual mechanism by which the
decision is made. In this way, the idea is similar to quantum cognition.
This field clearly distinguishes itself from the quantum mind, as it is
not reliant on the hypothesis that there is something micro-physical
quantum-mechanical about the brain. Quantum cognition is based on the
quantum-like paradigm,[66][67] generalized quantum paradigm,[68] or quantum structure paradigm[69] that information processing by complex systems such as the brain can be
mathematically described in the framework of quantum information and
quantum probability theory. This model uses quantum mechanics only as an
analogy, but doesn't propose that quantum mechanics is the physical
mechanism by which it operates. For example, quantum cognition proposes
that some decisions can be analyzed as if there is interference between
two alternatives, but it is not a physical quantum interference effect.
The
demonstration of a quantum-mind effect by experiment is necessary. Is
there a way to show that consciousness is impossible without a quantum
effect? Can a sufficiently complex digital, non-quantum computer be
shown to be incapable of consciousness? Perhaps a quantum computer will
show that quantum effects are needed. In any case, complex computers
that are either digital or quantum computers may be built. These could
demonstrate which type of computer is capable of conscious, intentional
thought. But they don't exist yet, and no experimental test has been
demonstrated.
Quantum mechanics is a mathematical model that can provide some extremely accurate numerical predictions. Richard Feynman called quantum electrodynamics, based on the quantum-mechanics formalism, "the jewel of physics" for its extremely accurate predictions of quantities like the anomalous magnetic moment of the electron and the Lamb shift of the energy levels of hydrogen.[70]: Ch. 1 So it is not impossible that the model could provide an accurate
prediction about consciousness that would confirm that a quantum effect
is involved. If the mind depends on quantum mechanical effects, the true
proof is to find an experiment that provides a calculation that can be
compared to experimental measurement. It has to show a measurable
difference between a classical computation result in a brain and one
that involves quantum effects.
The main theoretical argument against the quantum-mind hypothesis
is the assertion that quantum states in the brain would lose coherency
before they reached a scale where they could be useful for neural
processing. This supposition was elaborated by Max Tegmark. His calculations indicate that quantum systems in the brain decohere at sub-picosecond timescales.[71][72] No response by a brain has shown computational results or reactions on
this fast of a timescale. Typical reactions are on the order of
milliseconds, trillions of times longer than sub-picosecond timescales.[73]
Daniel Dennett uses an experimental result in support of his multiple drafts model of an optical illusion that happens on a time scale of less than a second or so. In this
experiment, two different-colored lights, with an angular separation of a
few degrees at the eye, are flashed in succession. If the interval
between the flashes is less than a second or so, the first light that is
flashed appears to move across to the position of the second light.
Furthermore, the light seems to change color as it moves across the
visual field. A green light will appear to turn red as it seems to move
across to the position of a red light. Dennett asks how we could see the
light change color before the second light is observed.[55] Velmans argues that the cutaneous rabbit illusion,
another illusion that happens in about a second, demonstrates that
there is a delay while modelling occurs in the brain and that this delay
was discovered by Libet.[74] These slow illusions that happen at times of less than a second don't
support a proposal that the brain functions on the picosecond time
scale.
According to David Pearce, a demonstration of picosecond effects
is "the fiendishly hard part – feasible in principle, but an
experimental challenge still beyond the reach of contemporary molecular
matter-wave interferometry. [...] The conjecture predicts that we'll
discover the interference signature of sub-femtosecond
macro-superpositions."[54]
Penrose says:[33]
The problem with trying to use quantum mechanics in the action of the brain is that if it were a matter of quantum nerve signals, these nerve signals would disturb the rest of the material in the brain, to the extent that the quantum coherence would get lost very quickly. You couldn't even attempt to build a quantum computer out of ordinary nerve signals, because they're just too big and in an environment that's too disorganized. Ordinary nerve signals have to be treated classically. But if you go down to the level of the microtubules, then there's an extremely good chance that you can get quantum-level activity inside them.
For my picture, I need this quantum-level activity in the microtubules; the activity has to be a large-scale thing that goes not just from one microtubule to the next but from one nerve cell to the next, across large areas of the brain. We need some kind of coherent activity of a quantum nature which is weakly coupled to the computational activity that Hameroff argues is taking place along the microtubules.
There are various avenues of attack. One is directly on the physics, on quantum theory, and there are certain experiments that people are beginning to perform, and various schemes for a modification of quantum mechanics. I don't think the experiments are sensitive enough yet to test many of these specific ideas. One could imagine experiments that might test these things, but they'd be very hard to perform.
A demonstration of a quantum effect in the brain has to explain this
problem or explain why it is not relevant, or that the brain somehow
circumvents the problem of the loss of quantum coherency at body
temperature. As Penrose proposes, it may require a new type of physical
theory.
According
to Lawrence Krauss, "You should be wary whenever you hear something
like 'Quantum mechanics connects you with the universe' ... or 'quantum
mechanics unifies you with everything else'. You can begin to be
skeptical that the speaker is somehow trying to use quantum mechanics to
argue fundamentally that you can change the world by thinking about
it."[2] A subjective feeling is not sufficient to make this determination.
Humans don't have a reliable subjective feeling for how we do a lot of
functions. According to Daniel Dennett, "On this topic, Everybody's an expert... but they think that they have a particular personal authority about the
nature of their own conscious experiences that can trump any hypothesis
they find unacceptable."[75]
Since humans are the only animals that can verbally communicate
their conscious experience, performing experiments to demonstrate
quantum effects in consciousness requires experimentation on a living
human brain.[citation needed] This is not automatically excluded or impossible, but it seriously
limits the kinds of experiments that can be done. Studies of the ethics
of brain studies are being actively solicited[76] by the BRAIN Initiative, a U.S. Federal Government funded effort to document the connections of neurons in the brain.
An ethically objectionable practice by proponents of quantum mind
theories involves the practice of using quantum-mechanical terms in an
effort to make the argument sound more impressive, even when they know
that those terms are irrelevant. Dale DeBakcsy notes that "trendy
parapsychologists, academic relativists, and even the Dalai Lama have all taken their turn at robbing modern physics of a few
well-sounding phrases and stretching them far beyond their original
scope in order to add scientific weight to various pet theories".[77] At the very least, these proponents must make a clear statement about
whether quantum formalism is being used as an analogy or as an actual
physical mechanism, and what evidence they are using for support. An
ethical statement by a researcher should specify what kind of
relationship their hypothesis has to the physical laws.
Misleading statements of this type have been given by, for example, Deepak Chopra. Chopra has commonly referred to topics such as quantum healing or quantum effects of consciousness. Seeing the human body as being
undergirded by a "quantum-mechanical body" composed not of matter but of
energy and information, he believes that "human aging is fluid and
changeable; it can speed up, slow down, stop for a time, and even
reverse itself", as determined by one's state of mind.[78] Robert Carroll states that Chopra attempts to integrate Ayurveda with quantum mechanics to justify his teachings.[79] Chopra argues that what he calls "quantum healing" cures any manner of
ailments, including cancer, through effects that he claims are literally
based on the same principles as quantum mechanics.[80] This has led physicists to object to his use of the term quantum in reference to medical conditions and the human body.[80] Chopra said: "I think quantum theory has a lot of things to say about the observer effect,
about non-locality, about correlations. So I think there’s a school of
physicists who believe that consciousness has to be equated, or at least
brought into the equation, in understanding quantum mechanics."[81] On the other hand, he also claims that "[quantum effects are] just a
metaphor. Just like an electron or a photon is an indivisible unit of
information and energy, a thought is an indivisible unit of
consciousness."[81] In his book Quantum Healing, Chopra stated the conclusion that quantum entanglement links everything in the Universe, and therefore it must create consciousness.[82] In either case, the references to the word "quantum" don't mean what a
physicist would claim, and arguments that use the word "quantum"
shouldn't be taken as scientifically proven.
Chris Carter includes statements in his book Science and Psychic Phenomena[83] of quotes from quantum physicists in support of psychic phenomena. In a
review of the book, Benjamin Radford wrote that Carter used such
references to "quantum physics, which he knows nothing about and which
he (and people like Deepak Chopra) love to cite and reference because it
sounds mysterious and paranormal.... Real, actual physicists I've
spoken to break out laughing at this crap.... If Carter wishes to posit
that quantum physics provides a plausible mechanism for psi, then it is
his responsibility to show that, and he clearly fails to do so."[84] Sharon Hill has studied amateur paranormal research groups, and these
groups like to use "vague and confusing language: ghosts 'use energy',
are made up of 'magnetic fields', or are associated with a 'quantum
state'".[85][86]
Statements like these about quantum mechanics indicate a
temptation to misinterpret technical, mathematical terms like
entanglement in terms of mystical feelings. This approach can be
interpreted as a kind of scientism, using the language and authority of science when the scientific concepts don't apply.
Perhaps the final question is, what difference does it make if
quantum effects are involved in computations in the brain? It is already
known that quantum mechanics plays a role in the brain since quantum
mechanics determines the shapes and properties of molecules like neurotransmitters and proteins, and these molecules affect how the brain works. This is the reason that drugs such as morphine affect consciousness. As Daniel Dennett said, "quantum effects are
there in your car, your watch, and your computer. But most things — most
macroscopic objects — are, as it were, oblivious to quantum effects.
They don't amplify them; they don't hinge on them."[33] Lawrence Krauss said: "We're also connected to the universe by gravity,
and we're connected to the planets by gravity. But that doesn't mean
that astrology is true.... Often, people who are trying to sell
whatever it is they're trying to sell try to justify it on the basis of
science. Everyone knows quantum mechanics is weird, so why not use that
to justify it? ... I don't know how many times I've heard people say,
'Oh, I love quantum mechanics because I'm really into meditation, or I
love the spiritual benefits that it brings me.' But quantum mechanics,
for better or worse, doesn't bring any more spiritual benefits than
gravity does."[2]
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