Is the Brain a Quantum Computer?

A Quantum Computer is complex. Quantum brain dynamics may hold the answer to this question. If the essential mechanism within a human brain involves quantum entanglement and superposition, then, given the uncertainty principle, humans are unpredictable.

This newest explanation of the so-called “free will” reveals the fundamental difference between humans and robots: we humans have free will and free thoughts. Therefore, without quantum artificial intelligence algorithms, AIs would never fully replace humans in the world. 

But this is a big “if” and scientists have been trying to answer this question for decades: are quantum dynamics involved in the formation of consciousness? Current theories and experiments have not yet shown any evidence for a definitive answer but promising breakthroughs are pointing to a possible yes to this question.

Nobel Laureate Roger Penrose was among the first pioneers that tried to explain consciousness with quantum dynamics. He developed interests in quantum brain dynamics when he was told that doctors had no idea how the prescribed lithium pill would cure his depression, but it somehow did.

After years of research, in 1989, Penrose claimed that classical physics could not explain the very existence of consciousness, rendering the necessity of a bridge between classical and quantum physics to explain brain dynamics. He believed that brains may be taking advantage of the collapse of the wave function during quantum measurement, so the current computer driven by traditional architecture alone is not strong enough to achieve strong artificial intelligence that can fully mimic human brains.

Marvin Minsky, the founder of MIT’s AI laboratory, on the other hand, rebutted Penrose’s view in 1991. He believed that humans were essentially classical computing machines. Despite the complicated functions of human brains, they can still be fully explained by contemporary physics and thus replicated by algorithms. This marked the foundation of the continuous research on machine learning and artificial intelligence like the neural network.

But Penrose believed that brains were far more complex than problem solving networks and algorithms. In response, he worked with Stuart Hameroff to further polish the quantum brain dynamics theories with their model on the quantum gravitational effect of neural microtubules.

Simply put, traditional view on consciousness claimed that consciousness originated from the connections among neuron cells and complicated chemical reactions. Yet, the new theory proposed that consciousness actually originated at the quantum level inside the neuron cells, that is orchestrated by cellular structures called microtubules. This incited lasting debates in academia, with the main focus on the retention time of quantum coherence in these microtubes.

Indeed, microtubules can form quantum entanglement just like all other microscopic structures, but the quantum decoherence happens in the time scale of 10^-20 to 10^-13 seconds, which is far shorter than the time we take to form a thought. This is the quantum coherence retention time or quantum decoherence problem, and this is the key problem when trying to explain everyday objects with quantum theories. 

Essentially, we are all built by small particles like molecules and atoms, but the random thermal motions among countless particles would prevent meaningful connections among the wave functions. So, even if two particles can form entanglement, it would be immediately destroyed by the chaotic surrounding environment. One of the many reasons building a quantum computer is a challenge.

Simply put, it is virtually impossible for quantum entanglement to last long enough to have a meaningful impact on the ordinary world, and this is why classical physics has been doing a great job explaining everyday objects. 

Of course, quantum effects can sometimes be impactful on the macroscopic scale, like supercurrent and superconductivity, but it requires the temperature to be as low as 4K or -452.47 F.

Only at this temperature, the random thermal motion of atoms and electrons can cool down and cause a superconductivity or supercurrent phenomena. Human bodies, however, are normally 310K. Therefore, many believe that quantum effects are not related to life functions in such a hot, humid, “noisy” and “chaotic” environment.  

However, Matthew Fisher, a physicist at the University of California, Santa Barbara, believed that microtubules may produce long enough entanglement to form consciousness. He published a paper in the Annals of Physics on September 3, 2015, entitled “Quantum cognition, the possibility of processing with nuclear spins in the brain”.

Fisher demonstrated the possibility of quantum neural mechanisms based on the nuclear spins of phosphorus atoms. The Posner molecular cluster of calcium phosphate can be used as a storage of qubits with its quantum coherence retention time lasting as long as 10^5 seconds, or more than a day. In neuroscience, memory formation and learning occurs on the timescale of several hours to one day, so such a long lasting quantum coherence could be used by the brain.. 

This works because the Posner molecule in the water rotates at a high speed of 10^11 revolutions per second. The amplitude and the direction of the magnetic field at the phosphorus nucleus change rapidly in the matter of 10 picoseconds, meaning that it can offset the magnetic field from the protons in the surrounding water molecules. Therefore, the entanglement can last for a meaningful time in this protected environment. 

If this theory can be proven in subsequent experiments, then this new model of quantum computing, inspired by, according to Fisher, the human brain dynamics, will outperform the best quantum computers we have, which are made by rare materials and cost billions of dollars. Currently, Professor Fisher is taking a sabbatical at Stanford University to work with experimental physicists to prove his theory that would possibly mark the beginning of a new way to look at our brains. 

However, while the real answer to our quantum computer question remains unclear until further experiments and theories, scientists have nonetheless found quantum effects in life. 

One area where quantum effects have been observed is within enzymes, one of the most important molecules in the human body. Every living thing is created by enzymes, including viruses which can live without DNA but not without enzymes. One of the most important effects of enzymes is the power of accelerating reactions from tens of thousands of years to a matter of seconds, yet the reason why this happens remains a mystery until recently.

Judith Klinman of University of California, Berkeley and Nigel Scrutton of University of Manchester discovered the quantum tunneling effects in enzymes. Electrons and protons would disappear at one point and instantly reappear somewhere else when enzymes are involved. In other words, teleportation was discovered. 

More recently, Graham Fleming of UC Berkeley discovered quantum effects in the photosynthesis process. Photosynthesis is a complicated process with the photons (light) traveling from one molecule to another almost precisely. However, photons are not charged so unlike electrons they do not know where to go. In theory, 99% of light should have ended up in the wrong position based on basic statistics, but we all know this is not the case: photosynthesis has an efficiency rate of almost 34% even after the waste of sunlight on the surface of the leaves. 

So how do photons know where to go? Fleming noticed that light tends to travel like waves in the process. It seems like a photon produces countless copies of itself and travels simultaneously on all possible paths. It will then pick the path with the least energy, which is the path in photosynthesis, and the wave function collapses.

To better understand this, suppose that you are travelling from home to work but do not know which path to choose. So, you make countless copies of yourself and all of you simultaneously travel on all possible paths. At the end, the first one that gets to work will become the winner and continue to live while all other copies will disappear. 

These findings rock academia as it turns out that plants may actually operate like quantum computers to efficiently harvest the light energy. Given that human computers are still not capable of replicating the photosynthesis process in the most efficient way, next time when you are eating a bowl of salad, you are actually eating a quantum computer!

These pieces of evidence and theories point to exciting possibilities that brains may also operate on a quantum level as a quantum computer. With more scientific discoveries happening everyday, the answer to the question may be clear sooner that we expect. 

Written by Tianyi Li

Edited by Mike Pena & Alexander Fleiss