Somehow, as a single cell develops into a person, a mind arises out of nowhere inside our heads. It thinks, feels, and has a sense of self. We do not know how or why such a mind suddenly appears, nor do we actually understand how it works. Luckily, we at least have theories.

Most theories assume that consciousness arises through an incredible orchestra of 100 billion neurons and their interconnections. But not even that is enough for the quantum theory of consciousness. It claims that something even stranger and more fascinating is going on inside our heads.

To understand just how outrageous the quantum theory of consciousness really is, we first need to have a look at the two things that make it up separately: quantum mechanics and consciousness.

Part One: Quantum Mechanics

Quantum mechanics is essentially a toolbox. Open it, and you will find all sorts of shiny concepts and formulas that go by easy-to-remember names like: the Heisenberg uncertainty principle, the Planck constant, the Schrödinger equation (not to be confused with Schrödinger’s more famous, cat-murdering box), particle-wave duality, the Allen wrench, and quantum entanglement. Whenever theoretical physicists get an especially hard nut to crack, they rummage through the box until they find the right formulas to solve it.

Unfortunately, most of those quantum tools are counter-intuitive, and all of them confusing. At least, to non-theoretical physicists. (Even to most of them, they just won’t admit it.)
So, for today, let’s not worry too much about the individual tools, but let’s look at the box as a whole instead. What kinds of nuts can we actually crack with our quantum toolbox?

First, let’s get something out of the way: Quantum mechanics and quantum physics are essentially the same thing. They are just different names for our toolbox.

Second, let us dive into a thought experiment.

Imagine you have a large bowl filled with strawberries and blueberries. You would like to sort them into two piles. Also, you are too lazy to do it yourself. Naturally, you build a robot to do it for you. But for it to work, you have to come up with a way how your robot can tell the berries apart.
After some thinking (and snacking on the berries), you decide to give your robot a scale. You weigh some berries yourself and decide that 4 grams seem to be a good cut-off. You program your robot to sort all lighter berries as blueberries and all others as strawberries.

Your Strawberry/Blueberry Robot is what physics would call a model. Every berry the robot picks tests the 4 gram-hypothesis your model is built on. And because you are a great berry scientist, your model works. After an hour, all berries are sorted without a single mistake. Great.

But your luck runs out. Your neighbour has seen your robot and walks over to you with his own bowl, filled not only with blueberries and strawberries but also bananas, sesame seeds, flowers, ice cream, and old socks (neighbours are, without exception, weird). Your Prediction Robot fails. So, you revise your model. You build a new robot with a camera and a spectrometer to help it tell socks and strawberries apart. You add a thermometer so it can recognise the ice cream. Soon, your new robot is better than ever, but also much more complicated. And with your original strawberry/blueberry bowl, both robots work equally well. It really only makes sense to use your more complicated robot when you want to work with your weird neighbour’s sock-bowl.

This is precisely how you should also use quantum mechanics.
For everything you will ever encounter in your day-to-day life, regular physics does the trick just fine. Newton famously invented a formula to predict how fast an apple will fall to the ground, or how long it will take a car to drive somewhere at 50 km/h. This branch of physics is thus called Newtonian or classical mechanics.

But when you zoom in really far into apples and cars, down to the level of atoms, electrons, and photons, things get weird. And—just like your original robot when faced with the weird sock-bowl—classical mechanics suddenly stop working. So, physicists had to come up with more sophisticated solutions to their problems. Eventually, they came up with a set of models they called quantum mechanics. Theoretically, you can also use quantum mechanics to predict the behaviour of apples and cars, and your results will be just as good as those of classical mechanics. But while everyone with a smartphone can use Newton’s formulas, using quantum mechanics on the scale of apples and cars would be so ridiculously (and unnecessarily) difficult that even a supercomputer would throw the towel. That is why we only ever hear of quantum physics when someone tries to figure out something about ridiculously small and complex things, like electrons or the Higgs boson. That is the only time when we actually need to use them.
But what makes quantum physics so ridiculously difficult? Well, classical physics (like every sane person) assumes that there is only one correct answer to every question. If you know precisely how heavy an apple is, and how high the tree, you can calculate exactly how long it will take for it to fall to the ground.

Quantum theory, on the other hand, assumes the universe is random. It works not with certainties, but probabilities. An apple may be very likely to fall to the ground like we would expect it to, but it might just as well take twice that time. Or fly off into the air instead. Or grow ears and then vanish. It is very, very, very unlikely that it will. But it might.

And this might is a huge difference to Newtonian physics with its fixed ways. It’s also what drives supercomputers insane when they have to do the math involved. Weirdly, this randomness—however absurd it sounds—seems to be quite close to the truth. When we zoom in to the size of electrons, we can clearly see how randomly they behave. Trying to predict exactly where an electron will be, or how fast it zips around an atom, yields no consistent results. The only thing that still makes sense is to find a certain area in which the electron probably is. No guarantees, though.

This may leave you thinking: Why? Why would the universe be so weird at its core? All we experience seems so nice and predictable. When you drop a plate, it falls and shatters. It never floats in the air and turns green instead. Why is this not the same on very small scales?

The answer is as boring as it is frustrating: We do not know. Physicists can only look at how the world behaves and then extrapolate models that can predict this behaviour. And quantum theory is the best toolbox to make predictions about small things. So—until we discover a better toolbox—we just have to accept that the universe, like your neighbour, is weird.

Part Two: Consciousness

Let’s turn to the second half of the quantum theory of consciousness. Consciousness. What is it?

The answer is relatively simple: Consciousness is the thing inside us that experiences. It is where all of our senses, feelings, and thoughts come together to form a coherent whole.

Alright, but where is this consciousness that experiences? Surprisingly, modern medicine has a pretty good answer to that question: behind your ears. Specifically, inside a small chunk of both of your brain’s halves that sits just above and a little to the back of your ears. This region is called the Posterior Hot Zone, because it lights up bright-red on brain scans when subjects are experiencing something consciously—like when they focus on smelling a rose or watch a cat video.

If we loose parts of our brain outside of the Posterior Hot Zone, to tragedy or a surgeon’s scalpel, we loose all sorts of functions: coordination, eyesight, the ability to perform complex algebra, control over our hands, the list continues. But our experience of our surroundings and inner thoughts remains the same.

If the Posterior Hot Zone is damaged, however, the integration of our senses breaks down. We might still see just as well as before, but we lose all meaning behind that which we observe. We can still catch a basketball, but no longer recognise it for what it is. We no longer see it consciously.

Your next question about consciousness might be: Why is it?

Here, our understanding steps on thin ice. Maybe consciousness is a way to process all the information our senses pick up. Or maybe it only exists to provide easy access to data for the rest of your brain. There are also scientists who think that consciousness just kind of happens when a system becomes complex enough. Our minds, the entire fabric of who we are, might just be a by-product of our brain. Like warmth is only a by-product of a light bulb.

That leaves us with one more question: How? How does consciousness experience our feelings and the world around us? How does it give us a sense of self? Finally, we turn back to quantum physics.

Part Three: The Quantum Theory of Consciousness

Alright. So, quantum physics is a toolbox to predict how tiny things like electrons behave. Consciousness sits in our brains, behind our ears, where it processes data and experiences the world. But what could the two possibly have in common? Well, the simple fact that they are both horrifyingly difficult to understand led to an interesting idea: maybe the brain and quantum mechanics are somehow connected.

Maybe consciousness—and our entire brain, for that matter—cannot be explained with classical mechanics. Just like with photons and electrons, we need quantum mechanics to understand how it works. Many scientists have furiously rejected this idea. The mainstream opinion remains that classical physics will someday be able to explain our brains, and that we need not reach for the quantum toolbox. But no one has convincingly disproven the quantum theory of consciousness, and it offers fascinatingly straightforward answers to some of the still unsolved questions about the mind.

For instance, why it is still impossible to simulate an entire brain.

Even the most powerful, basement-filling supercomputers cannot accommodate the processing speeds required to recreate a digital human brain. And yet, your brain runs on about 20 Watt, and weighs just under 1.5 kilogram. You can read and understand this nub and only use up the calorie equivalent of a single bite of an apple. Maybe your brain can do that because is not a normal 1-or-0 computer. Maybe it is a quantum computer, harnessing all the strange powers of the quantum realm to its advantage.

Roger Penrose (a famous physicist) and Stuart Hameroff (a less famous medical doctor) proposed that the brain might use microtubuli—extremely small pipes which are commonly thought to fulfil basic functions such as contracting a muscle cell—to harness one of the quantum tools called superposition. This would allow the brain to not only process something as a one or zero but as several different numbers at once, vastly improving its processing capacity.

Other scientists proposed that our minds employ quantum entanglements, something none of our current computers can do. If that was true, it would be no wonder we cannot simulate a brain yet. We would first need to develop quantum computers.

And it gets wilder.

Our consciousness—and those of all living beings—may not only use quantum tools. Consciousness may very well be a tool itself.

To understand what that means, we need to look at the quantum tool called wave-particle-duality. When physicists developed quantum theory, they discovered that some predictions improved when they pretended everything—from electrons to cats in boxes—was made up not of particles, but waves.

This may sound woozy and esoteric, but the idea of wave-particle-duality is one of the most fundamental tools in our quantum toolbox. And quantum mechanics is not woozy at all. It brought us semiconductors and lasers. Quantum mechanics works.

The waves in the wave-particle-duality are often called wave functions; the word function implying that this trick is only a mathematical equation and not a real-world thing. Whether we are actually made up of waves in the real world is not important. The important thing is that if we pretend we are, our predictions improve.

But these wave functions do not exist forever. As soon as you look at them directly (if you measure the position of a particle in an otherwise empty box, for instance), the waves disappear and turn back into normal particles and objects. This process is called the collapse of a wave function.

It is critical to understand that this collapse of a wave is caused by an outside observer. In quantum theory, a conscious observation is everything that stands between a thing being a wave and it being a particle. This is true for electrons, apples, cars, cats, ourselves, and everything else in the universe. As you look around the room and spot a chair, you might actually make that chair. You collapse the wave function into the actual thing because you observe it.

Consciousness may be nothing more than this process of collapsing a wave into a particle. If that is true, it does not need to arise in our brains or anywhere else. It simply is. It is a fundamental building-block of the universe, just like the concept of warmth, or time, or gravity.

Maybe our brains do not make consciousness at all, but only use it—like our inner ear uses gravity to determine up and down. It would be absurd to argue our inner ears make gravity. Gravity exists already, and our inner ears only use it as a very convenient tool to make sense of the world around us. Maybe it is the same with consciousness. The only thing the Posterior Hot Zone in our brain does is access the consciousness that is already there and make good use of it.

No part of the quantum theory of consciousness has ever been conclusively proven. And no part of it has been entirely revoked. And both of those facts make it even more thrilling to think about.

Sources and Further Exploring:

Stephen Hawking, Brief Answers to The Big Questions (2018)

Dominic Walliman, Domain of Science,YouTube, www.youtube.com/channel/UCxqAWLTk1CmBvZFPzeZMd9A

Christof Koch, What Is Consciousness? (2018), Scientific American, https://www.scientificamerican.com/article/what-is-consciousness/

Van Gulick Robert, Consciousness, The Stanford Encyclopedia of Philosophy (Spring 2018 Edition), Edward N. Zalta (ed.), https://plato.stanford.edu/entries/consciousness/

Atmanspacher Harald, Quantum Approaches to Consciousness, The Stanford Encyclopedia of Philosophy (Summer 2020 Edition), Edward N. Zalta (ed.), https://plato.stanford.edu/archives/sum2020/entries/qt-consciousness

John Matson, What is Quantum Mechanics Good for? (2010), Scientific American, https://www.scientificamerican.com/article/everyday-quantum-physics/

Klaus S. Stiefel and Daniel S. Brooks, Why Is There no Successful Whole Brain Simulation (yet)? (2019), Biological Theory, https://link.springer.com/article/10.1007/s13752-019-00319-5

Philip Ball, The Strange Link Between the Human Mind and Quantum Physics (2017), BBC, http://www.bbc.com/earth/story/20170215-the-strange-link-between-the-human-mind-and-quantum-physics