Some Thoughts on Quantum Mechanics and Consciousness
Today I wanted to veer slightly off-topic and write about two of my favorite topics… quantum mechanics and consciousness!
In particular, I want to write about the Many-Worlds Interpretation (MWI) of quantum mechanics (QM), which was proposed by Hugh Everett III in 1957. If you’re interested in foundations of physics I would encourage giving it a go and reading it.
QM is a fundamental framework within which most of our understanding of the world sits. QM’s ontological implications — what it says about ‘the way things really are’ — are unfortunately unclear. Different interpretations of QM disagree on the nature of reality.
The lack of clarity about the reality that QM is supposed to be describing is a very strange situation. What we want from a physical theory is for it to explain the nature of the thing it describes in some profound way, not just be a tool for calculating things. In QM, it seems that changing some things about its axioms dramatically changes what it appears to say about how our world works, and our role in it. In particular, different interpretations range from placing consciousness (matter having a subjective feeling of what it’s like to be itself) as fundamental to the fabric of reality, to it having no special role at all. That these dramatically different descriptions of the world seem to make no difference to QM’s utility as a tool for calculating properties of the world is remarkable.
What I’d like to do here is first introduce the MWI to first show you what it is. I’ll compare it to the standard introductory textbook view of QM which is called the Copenhagen Interpretation. I’ll then show you what MWI implies about the nature of the world and how this differs from other interpretations, with a specific emphasis on what each might say about whether consciousness could be a fundamental aspect of reality.
The Many-Worlds Interpretation
All interpretations of QM come with sets of fundamental axioms. For the MWI, they are:
Quantum Mechanics Describes Everything
The Schrödinger equation completely describes the evolution of all physical systems, including the entire universe.
The wavefunction never collapses; it evolves unitarily and deterministically according to quantum mechanics.
Entanglement and Branching
When a quantum system interacts with anything at all, including things we call measurement devices, the system and device become entangled.
Instead of a single definite outcome, all possible outcomes occur, leading to a branching of the universe.
Each branch represents a set of different outcomes, or ‘consistent histories’, and they evolve independently.
No Wavefunction Collapse
Unlike the Copenhagen Interpretation, there is no postulated wavefunction collapse.
Apparent randomness arises because observers experience only one branch at a time, but all branches continue to exist.
Observer as Part of the Wavefunction
Observers are quantum systems that obey the same physical laws as everything else.
Consciousness does not influence or collapse the wavefunction; instead, the observer splits into multiple versions across different branches.
Born Rule as an Emergent Statistical Probability
The Born Rule, which gives the probability of measuring an outcome, is not fundamental but emerges from the structure of the branching worlds.
Branches with larger amplitudes correspond to more probable experiences.
Key Implications
Every quantum event creates a vast (but mostly non-communicating) set of parallel branches.
Decoherence explains why these branches do not interfere with each other on macroscopic scales.
Reality is fundamentally deterministic, but subjective experience appears probabilistic.
The Copenhagen Interpretation
The Copenhagen Interpretation, largely developed by Niels Bohr and Werner Heisenberg, is usually taught as ‘what QM is’ to people first learning QM. It has a very different flavor. Here’s the axioms for this interpretation.
The Wavefunction Represents Probabilistic Knowledge
The wavefunction (Ψ) describes all the possible states of a quantum system.
It does not necessarily represent an objectively real entity but rather our knowledge of the system.
Wavefunction Evolution and Collapse
The wavefunction evolves deterministically according to the Schrödinger equation when not observed.
Upon measurement, the wavefunction collapses instantaneously into a single eigenstate corresponding to the observed outcome.
The Principle of Superposition
Before measurement, a quantum system exists in a superposition of all possible states.
The probability of each outcome is given by the Born Rule.
The Measurement Postulate (Observer Role)
Measurement causes an irreversible collapse of the wavefunction, selecting a single outcome.
The act of measurement is fundamental but remains conceptually undefined (the "measurement problem").
Classical-Quantum Divide
There is a conceptual separation between the quantum system (described by Ψ) and the classical measuring apparatus.
Indeterminism and Probability
Unlike classical mechanics, quantum mechanics is intrinsically probabilistic.
The outcome of a measurement is fundamentally random, and only probabilities can be predicted.
Key Implications
The Copenhagen Interpretation provides a single reality, in contrast to Many-Worlds.
The collapse of the wavefunction is non-deterministic, introducing an element of randomness into nature.
The observer’s role in measurement is central but remains philosophically debated.
Here’s a table with some of the key differences noted.
The Key Difference is The Special Role of ‘The Observer’
The main difference between these two interpretations is the nature of the observer. In the Copenhagen Interpretation, the observer is the entity that ends a quantum system’s quantumness by deciding to measure something. In this worldview, the mind of a person fundamentally affects the nature of reality. Your decision to measure a thing changed something fundamental about the world. And there is only one world that exists — the one ‘you’ are in. Quantum things pop into and out of existence, but ‘measurement’ tames their weirdness and extracts a classical world out of them.
In contrast, the Many-Worlds Interpretation removes the observer from the main stage, and ‘measurement’ as a process separate from interaction, and instead treats everything as being quantum mechanical. In MWI an observer has no special status — all matter and energy is on an equal footing and there is nothing special about ‘observers’ or ‘measurements’.
Both of these pictures generate the same predictions about what happens when a person measures the properties of a quantum system (the Born probabilities) but they describe vastly different underlying realities.
Why Was ‘The Observer’ Introduced?
I think the likely reason for this was that back in the early days of QM, the folks who proposed it wanted to make it easy to use and understand for people running and designing experimental tests. From this perspective the only thing that mattered was how user-friendly it was. What was needed was a simple prescription for doing calculations to predict things people at the time were measuring. Those things were perfectly well described by the Copenhagen set-up, where the experimentalist played the central role of ‘the observer’, deciding how to set up an experiment, what to measure and the like.
In these early days, the conceptual frame that QM was only relevant for exotic systems and that the ‘real world’ was fundamentally classical was likely very appealing.
Here’s Everett on the Copenhagen Interpretation:
While undoubtedly safe from contradiction, due to its extreme conservatism, it is perhaps overcautious. We do not believe that the primary purpose of theoretical physics is to construct "safe" theories at severe cost in the applicability of their concepts, which is a sterile occupation, but to make useful models which serve for a time and are replaced as they are outworn.
‘The Observer’ is a Good Approximation
In the Many-Worlds Interpretation, classical physics emerges as something like a thermodynamic limit. What any particular conscious observer sees in the world around them is a statistical property of reality. Just like the temperature in the room you are in arises from the statistical properties of a huge number of molecules bouncing around, your classical reality emerges from the quantum mechanical interplay of all the degrees of freedom of the world you interact with.
In the specific case where an isolated part of the world (what in the Copenhagen Interpretation would be called a ‘quantum system’) is connected to a large system (a ‘measurement device’, with or without a human observer), the Copenhagen Interpretation works because the large system is … large. It’s a fine approximation to what is really going on. But it’s critical to understand that it is just an approximation. The separation of ‘small and isolated quantum system’ from ‘large system’ is just a conceptual and computational convenience. It has nothing to do with anything fundamental.
Nothing is Lost by Removing ‘The Observer’
Physicist Sean Carroll has an expression that I quite like. He calls the MWI ‘taking quantum mechanics seriously’. The reason he calls it this is that if we assume everything is quantum mechanical — and why wouldn’t we? — we get the MWI.
This is really important to understand. QM is a beautiful theory of nature that works very well without having to add unnecessary additional unsupported assumptions to it. While the historical reasons for doing this are understandable, a hundred years have passed since then. We don’t need them. They don’t add anything.
Here’s Everett on this subject:
… the probabilistic assertions of the usual interpretation of quantum mechanics can be deduced from this theory, in a manner analogous to the methods of classical statistical mechanics, as subjective appearances to observers - observers which were regarded simply as physical systems subject to the same type of description and laws as any other systems, and having no preferred position. The theory is therefore capable of supplying us with a complete conceptual model of the universe, consistent with the assumption that it contains more than one observer.
If it was just helpful cruft to frame QM for experimental physicists that would be one thing. But unfortunately, the whole introduction of ‘the observer’ has really damaged understanding of what QM really is and says about the world. Some people believe that consciousness and QM are fundamentally linked because of this, for example pointing to the existence of quantum mechanical effects in biological systems, joined together with a Copenhagen-style understanding of QM itself, to proclaim things like ‘quantum fields are conscious’. What a claim to make!
People have a natural tendency to want to be at the center of things. I personally know a person who goes so far as to effectively be a solipsist, believing she is the only conscious entity in the universe, creating the rest of reality with her mind. This may sound crazy, but there really are people who think this way.
History has not been kind to the ‘we are special’ viewpoints of the world. The earth is not the center of the universe. Evolution does not select just for humans. If we apply the prior that ‘we are not special’ to the QM interpretations question, and ask if we can put all the stuff in the universe on an equal footing and still have the whole thing work, the answer is a resounding yes. The MWI (quantum mechanics taken seriously) does this.
The Search For Meaning in Life
Many people these days are searching for deeper meaning in their lives. That’s good. The unexamined life is not worth living and all that. The search for purpose will always be part of what makes us human.
If we believe we are connected to, or part of, the mysterious and divine, meaning becomes easier to find.
Up until recently, religious belief supplied this connection. It’s a central feature of nearly all religious belief systems that our existence is deeply intertwined with something mysterious and divine—a God or Gods who are both immanent (present within all things) and transcendent (beyond our full understanding).
Nowadays, people are dissatisfied with simple faith. We want to feel like we are part of a larger purposeful whole, but it’s not enough to just believe it. We now want our desired beliefs to align with and be backed by science. Somehow this makes us feel like our beliefs are ‘more correct’.
Our desire for our beliefs to have scientific backing creates fertile ground for believing ‘scientific-sounding but false’ claims about the way our world works. The average person doesn’t have the background to distinguish between ‘scientific-sounding but false’ and claims that accurately reflect what a scientific theory actually says.
‘There Are Quantum Effects in Biology’ Doesn’t Mean Anything
In the MWI, everything is quantum mechanical. If you see effects that are not classical, this just means that the aspect of the system you’re looking at is very well isolated from the rest of the world. There is nothing magic or special about it.
I think that people think that ‘quantum effects’ are like some bubble of magic that gives the bubble superpowers or something. That’s not how it works. Everything is quantum mechanical. ‘Quantum effects’ is just shorthand for ‘pretty well isolated from everything else’. That’s all!
‘QM is a Mechanism For Free Will’ Doesn’t Make Sense
Some people claim that QM provides a mechanism for free will. After all, you chose to make a measurement of that quantum system, didn’t you?
Unfortunately this argument is incoherent, because QM is unitary. It is deterministic. It’s only the introduction of the concept of a measurement that introduces randomness and irreversibility into the picture, and there’s no reason to do so.
When we take QM seriously, the pattern of matter and energy that is ‘you’ is a subsystem in the evolution of the universe with the consistent history encoded in your memories. You share this subsystem with all of the other constituents of the universe that have that same consistent history. This includes all of the ‘free will decisions’ you have made.
But there are an enormous number of other ‘yous’, who made different decisions. Each of them see different consistent histories. When you take QM seriously, ‘free will’ is a much more complex topic. Our subjective experience is real, but so is the subjective experience of the enormous number of other conscious observers who are ‘you’ who made different decisions and were subject to different outcomes.
The idea that free will is rescued by appeal to QM is rooted in a belief that the Copenhagen Interpretation ‘is’ QM, and that the decisions of a conscious observer affect the fabric of reality. But the Copenhagen Interpretation is NOT QM. It is just the MWI with unnecessary cruft. In the MWI, the you who is reading this is a particular substate of the wavefunction of the universe, and all the ‘yous’ all feel like they are the only one.
Penrose’s Theory of Quantum Consciousness Doesn’t Make Sense
Roger Penrose, in collaboration with anesthesiologist Stuart Hameroff, proposed the Orchestrated Objective Reduction (Orch-OR) theory, which suggests that consciousness arises from quantum processes in the brain. The core ideas are:
Quantum Coherence in Microtubules
They claim microtubules (structural components inside neurons) support quantum coherence, which means degrees of freedom that are largely decoupled from the rest of the universe, in the brain. (As an aside, this claim is highly suspect — it is very difficult to make anything in a complex system completely isolated from its environment, and if you can, that means they don’t affect anything (because they are isolated!)).
Objective Reduction (OR) by Gravity
Penrose argues that gravitational effects cause spontaneous collapse of the wavefunction. This is an interesting idea, but at least in the brain, gravity is about 10⁴² times weaker than electromagnetic forces, so this is highly unlikely to matter in the brain.
This collapse is non-random but non-computable.
Orchestrated OR (Orch-OR)
The brain somehow "orchestrates" these quantum collapses in microtubules to create meaningful, structured consciousness.
This is Incompatible with Quantum Mechanics
Quantum Mechanics Requires Strict Unitary Evolution
QM taken seriously assumes that the wavefunction never collapses.
Penrose's Objective Reduction (OR) directly contradicts this by proposing that wavefunctions must collapse due to gravity, selecting only one real outcome.
Non-Computability vs. MWI's Determinism
MWI is fundamentally deterministic: the wavefunction evolves predictably and branches.
Penrose argues that consciousness is non-computable, meaning it cannot be derived from purely algorithmic evolution (as required in QM).
The Role of Observers
In MWI, observers are quantum systems that branch along with the universe.
In Orch-OR, the act of conscious observation plays a fundamental role in causing wavefunction collapse.
Penrose’s Orch-OR theory requires real, objective wavefunction collapse, which fundamentally contradicts QM’s purely unitary evolution without collapse. If QM is correct, then Penrose’s proposal cannot be a valid description of reality.
QM is Not Magic
When we take QM seriously, everything is quantum mechanical. This includes you, your brain, your brain’s bits, your cells, your neurons, all of it. This makes it pretty clear that if isolating some part of the world from the rest, to take advantage of quantum effects that would otherwise be smeared out, gives some major evolutionary advantage, systems will hijack that and use it. Therefore it’s not surprising that living beings could evolve structures that are isolated from their environments, providing whatever effects these produce to benefit the organism carrying them. It is easy to find ‘quantum effects’ in biology — after all, everything is quantum mechanical, and there are many physical systems that are inherently isolated from the world (such as photons, neutrinos, nuclear spins, the list goes on).
However (and this is crucial) this does not have any significance whatsoever to philosophy of mind, artificial intelligence, or consciousness, unless the information processing the system is purported to be performing is complex enough so that it can’t be simulated classically.
To see why this is, let’s say that evolution found a way to isolate and use a system for some reason. The one I’ll pick on here is something called superradiance, which is related to lasers (yes lasers are highly quantum mechanical devices!), and photosynthesis (more quantum biology!). Here’s a paper on the topic, where some theoretical work calculates that it should be present in microtubules and groups of microtubules, which are ubiquitous molecules in living structures.
Superradiance is where a collection of excited atoms or molecules emits light in a cooperative, coherent manner that's much more intense than what would occur if each atom emitted light independently.
In conventional spontaneous emission, excited atoms emit photons randomly and independently. However, in superradiance, the atoms become quantum mechanically correlated through their interaction with a shared electromagnetic field (photons are the excitations of this field), causing them to emit light collectively and in phase.
If a molecule could capture and transmit light more effectively, that would be better for organisms that use the energy of the light, right? That’s how photosynthesis evolved. Specific molecules evolved that manipulate the isolation of parts of the molecule from the rest of the world thereby creating more efficient antennas for capturing the energy of light.
This is cool, but not surprising. If an antenna can evolve that’s say 10x better at absorbing and transmitting the energy in light, that makes an enormous difference to the organism’s survivability. But this is not even remotely related to the speedups in quantum computation.
For ‘quantum effects’ to matter in making a distinction between classical and quantum information processing, there must be a system performing a quantum computation that exhibits quantum supremacy — where a quantum system is performing a computation better than a classical computer could. This requires a level of isolation from the rest of the world that has never been observed in nature, and even in our most advanced quantum computing technologies, only claims have been made, and it is possible that these claims may not hold up. The level of engineering that goes into shielding quantum computers from the rest of the world is staggering. Consider this: in the systems we built at D-Wave, the temperatures required are about 200 times colder than interstellar space, and never occur anywhere naturally (they must be engineered); and the magnetic fields are shielded down to something like 50,000 times lower than the Earth’s magnetic field!
Just because there are quantum effects in biological systems (of course there are, everything is quantum mechanical), does not mean these quantum effects are useful for, or important to, anything to do with minds, intelligence, or consciousness. This … is not how any of this works. It’s like saying because we observe rocks rolling downhill (‘I see classical effects in rocks’) they are GPUs (‘GPUs are classical, rocks exhibit classical effects, therefore rocks are GPUs’!). This is nonsensical. But claiming brains are quantum computers because you see quantum effects in molecules that are in the brain is the same argument.
Back to superradiance in microtubules. This effect is trivial to simulate classically and does nothing at all to change the information processing capability of the system. Is it probably helpful somehow to the organism? Sure. But it has nothing whatsoever to do with conscious first-person experience.
‘Quantum Consciousness’ is a Cargo Cult
The people who want quantum mechanics to underlie our conscious experience are doing so because they are looking for a ‘science-adjacent’ reason for their lives to have deep meaning. It is essentially replacing ‘God’ in traditional religious belief with ‘quantum mechanics’. It is a cargo cult, where the cargo is the real science of QM, with the cultists building a set of beliefs and rituals around the misunderstanding of QM in the same way Pacific Islanders during WW2 misunderstood the advanced Western technology and material goods ("cargo") brought by military forces during the war.
For these folks, QM is a kind of God, and historically when you tell zealots that their God isn’t what they think it is, you don’t get an intellectually stimulating dialogue. The easiest thing for these folks to do is to continue to repeat whatever mantras their cults preach, cherry-pick results that align with their views, create conferences and journals that are isolated from actual science to reinforce the cult, and ignore or attack ‘mainstream science’ for being close-minded.
(As an aside, most of the people who are quantum consciousness cargo cultists seem to have had psychotic breaks that triggered these obsessions. There seems to be a strong correlation between psychedelic drug use, psychosis, and obsessions with consciousness being magical.)
Science doesn’t work based on what you want to be true. It is a constantly evolving matching of what we measure about the world around us and the models we create of those observations.
I have a lot of sympathy for people on a quest for deeper meaning. But you won’t find it by being a part of a cargo cult. There is nothing wrong with some things just being a matter of belief. You don’t need to try to science it up.