Can Quantum Physics Be Used to Explain the Existence of Consciousness?

illustration of quantum physics
CC0/Public Domain

How does the human brain generate our subjective experiences? How does it manifest human consciousness? The general sense that "I" am a "me" that has experiences distinct from other things?

Trying to explain where these subjective experiences come from is often called the "hard problem" of consciousness and, at first glance, it would seem to have little to do with physics, but some scientists have speculated that perhaps the deepest level of theoretical physics contain exactly the insights needed to illuminate this question by suggesting that quantum physics can be used to explain the very existence of consciousness.

Is Consciousness Related to Quantum Physics?

First, let's get the easy aspect of this answer out of the way:

Yes, quantum physics is related to consciousness. The brain is a physical organism that transmits electrochemical signals. These are explained by biochemistry and, ultimately, are related to the fundamental electromagnetic behaviors of molecules and atoms, which are dictated by the laws of quantum physics. In the same way that every physical system is governed by quantum physical laws, the brain is certainly governed by them as well and consciousness - which is clearly in some way related to the functioning of the brain - must therefore be related to the quantum physical processes going on within the brain.

Problem solved, then? Not quite. Why not? Just because quantum physics is generally involved in the operation of the brain, that doesn't actually answer the specific questions that come up in regard to consciousness and how it may be related to quantum physics.

As with much of the problems that continue to remain open in our understanding of the universe (and human existence, for that matter), the situation is quite complex and requires a fair amount of background.

What Is Consciousness?

This question itself can and does easily occupy volumes of well thought out scholarly texts, ranging from modern neuroscience to philosophy, both ancient and modern (with some helpful thinking on the issue even showing up in the realm of theology).

I will, therefore, be brief in laying the groundwork of the discussion, by citing some key points of consideration:

  • We all have subjective experiences that feel a certain way, which cannot at present be decisively linked to specific neurological locations in the human brain
  • Attempts to simulate the fullness of human consciousness within a computer (artificial intelligence) has not succeeded

The Observer Effect and Consciousness

One of the first ways that consciousness and quantum physics come together is through the Copenhagen interpretation of quantum physics. In this interpretation of quantum physics, the quantum wave function collapses due to a conscious observer making a measurement of a physical system. This is the interpretation of quantum physics which sparked the Schroedinger's cat thought experiment, demonstrating some level of the absurdity of this way of thinking ... except that it does completely match the evidence of what we observe at the quantum level!

One extreme version of the Copenhagen interpretation was proposed by John Archibald Wheeler and is called the Participatory Anthropic Principle. In this, the entire universe collapsed into the state we see specifically because there had to be conscious observers present to cause the collapse.

Any possible universes that do not contain conscious observers (say because that universe expands or collapses too quickly to form them via evolution) is automatically ruled out.

Bohm's Implicate Order and Consciousness

The physicist David Bohm argued that since both quantum physics and relativity were incomplete theories, they must point at a deeper theory. He believed that this theory would be a quantum field theory that represented an undivided wholeness in the universe. He used the term "implicate order" to express what he thought this fundamental level of reality must be like, and believed that what we are seeing are broken reflections of that fundamentally ordered reality. He proposed the idea that consciousness was somehow a manifestation of this implicate order and that attempting to understand consciousness purely by looking at matter in space was doomed to failure.

However, he never proposed any real scientific mechanism for studying consciousness (and his theory of implicate order never got sufficient traction in its own right), so this concept never became a fully-developed theory.

Roger Penrose and The Emperor's New Mind

The concept of using quantum physics to explain human consciousness really took off with Roger Penrose's 1989 book The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics (see "Books on Quantum Consciousness"). The book was written specifically in response to the claim of old school artificial intelligence researchers, perhaps most notably Marvin Minsky, who believed that the brain was little more than a "meat machine" or a biological computer. In this book, Penrose argues that the brain is far more sophisticated than that, perhaps closer to a quantum computer. In other words, instead of operating on a strictly binary system of "on" and "off," the human brain works with computations that are in a superposition of different quantum states at the same time.

The argument for this involves a detailed analysis of what conventional computers can actually accomplish. Basically, computers run through programmed algorithms. Penrose delves back into the origins of the computer, by discussing the work of Alan Turing, who developed a "universal Turing machine" that is the foundation of the modern computer. However, Penrose argues that such Turing machines (and thus any computer) have certain limitations which he doesn't believe the brain necessarily has.

Specifically, any formal algorithmic system (again, including any computer) is constrained by the famous "incompleteness theorem" formulated by Kurt Godel in the early twentieth century. In other words, these systems can never prove their own consistency or inconsistency. However, the human mind can prove some of these results. Therefore, according to Penrose's argument, the human mind cannot be the sort of formal algorithmic system that can be simulated on a computer.

The book ultimately rests on the argument that the mind is more than the brain, but that this cannot ever be truly simulated within a conventional computer, no matter the degree of complexity within that computer. In a later book, Penrose proposed (together with his collaborator, the anesthesiologist Stuart Hammeroff) that the physical mechanism for the quantum physical interactions in the brain are "microtubules" within the brain. Several formulations of how this would work have been discredited and Hameroff has had to revise his hypotheses about the exact mechanism. Many neuroscientists (and physicists) have expressed skepticism that microtubules would have this sort of effect, and I've heard it said in off-hand ways by many that his case was more compelling before he proposed an actual physical location.

Free Will, Determinism, and Quantum Consciousness

Some proponents of quantum consciousness have put forth the idea that quantum indeterminacy -- the fact that a quantum system can never predict an outcome with certainty, but only as a probability from among the various possible states - would mean that quantum consciousness resolves the problem of whether or not humans actually have free will. So the argument goes, if our consciousness is governed by quantum physical processes, then they are not deterministic, and we, therefore, have free will.

There are a number of problems with this, which are summed up quite well in these quotes from neuroscientist Sam Harris in his short book Free Will (where he is arguing against free will, as commonly understood):

... if certain of my behaviors are truly the result of chance, they should be surprising even to me. How would neurological ambushes of this kind make me free? [...]

The indeterminacy specific to quantum mechanics offers no foothold: If my brain is a quantum computer, the brain of a fly is likely to be a quantum computer, too. Do flies enjoy free will? [...] quantum indeterminacy does nothing to make the concept of free will scientifically intelligible. In the face of any real independence from prior events, every thought and action would seem to merit the statement "I don't know what came over me."

If determinism is true, the future is set -- and this includes all our future states of mind and our subsequent behavior. And to the extent that the law of cause and effect is subject to indeterminism--quantum or otherwise--we can take no credit for what happens. There is no combination of these truths that seems compatible with the popular notion of free will.

Let's consider what Harris is talking about here. For example, one of the best-known cases of quantum indeterminacy is the quantum double slit experiment, in which quantum theory tells us that there is absolutely no way to predict with certainty which slit a given particle is going to go through unless we actually make an observation of it going through the slit. However, there is nothing about our choice of making this measurement which determines which slit the particle will go through. In the basic configuration of this experiment, there is an even 50% chance it'll go through either slit and if we're observing the slits then the experimental results will match that distribution randomly.

The place in this situation where we do appear to have some sort of "choice" (in the sense it is commonly understood) is that we can choose whether or not we're going to make the observation. If we don't make the observation, then the particle doesn't go through a specific slit. It instead goes through ​both slits and the result is an interference pattern on the other side of the screen. But that's not the part of the situation that philosophers and pro-free will advocates invoke when they're talking about quantum indeterminacy because that is really an option between doing nothing and doing one of two deterministic outcomes.

In short, the whole conversation related to quantum consciousness is quite complex. As more intriguing discussions about it unfold, there's no doubt this article will adapt and evolve, growing more complex in its own right. Hopefully, at some point, there'll be some interesting scientific evidence on the subject to present.