Can consciousness be explained with quantum physics?
One of the most important open questions in science is how our consciousness is established. In the 1990s, long before he won the 2020 Nobel Prize in Physics for his prediction of black holes, physicist Roger Penrose teamed up with anesthetist Stuart Hameroff to propose an ambitious answer.
They both claimed that the brain's neural system forms an intricate network and that the consciousness it produces should obey the rules of quantum mechanics , the theory that determines how tiny particles like electrons move. According to these researchers, this could explain the mysterious complexity of human consciousness.
Penrose and Hameroff's thesis was greeted with disbelief. The laws of quantum mechanics usually only apply at very low temperatures . Quantum computers, for example, currently operating at about -272 ° C . At higher temperatures, classical mechanics prevail. Since our body operates at room temperature, it is to be expected that it is governed by the classical laws of physics. For this reason, the theory of quantum consciousness has been dismissed outright by many scientists, although others are staunch supporters .
Rather than enter this debate, I decided to join forces with colleagues from China, led by Professor Xian-Min Jin of Shanghai Jiaotong University, to put some of the principles underlying the quantum theory of consciousness to the test.
In our new article , we have investigated how quantum particles could move in a complex structure like the brain, but in a laboratory environment.
If our findings can one day be compared to activity measured in the brain, we might be one step closer to validating or discarding the controversial Penrose and Hameroff theory .
Brain and fractals
Our brains are made up of cells called neurons, and their combined activity is believed to generate consciousness. Each neuron contains microtubules , which carry substances to different parts of the cell. The Penrose-Hameroff theory of quantum consciousness holds that microtubules are structured in a fractal pattern that would allow quantum processes to occur.
Fractals are structures that are neither two-dimensional nor three-dimensional, but have some fractional value in between. In mathematics, fractals emerge as beautiful patterns that repeat endlessly, generating what is seemingly impossible: a structure that has a finite area, but an infinite perimeter.
This may seem impossible to visualize, but in reality fractals occur quite frequently in nature . If we look closely at the bouquets of a cauliflower or the branches of a fern , we will see that both are made up of the same basic shape that is repeated over and over again, but on increasingly smaller scales. That is a key feature of fractals.
The same is true if we look inside our own body: the structure of the lungs , for example, is fractal, just like the blood vessels of the circulatory system. Fractals also appear in the lovely repetitive works of art by MC Escher and Jackson Pollock , and have been used for decades in technology, such as antenna design . They are all examples of classical fractals, that is, fractals that are governed by the laws of classical physics and not quantum physics.
It is easy to see why fractals have been used to explain the complexity of human consciousness. Since they are infinitely intricate and allow complexity to emerge from simple repeating patterns, they could be the structures that underpin the mysterious depths of our minds.
But if this is the case, it could only be happening at the quantum level, with tiny particles moving in fractal patterns within neurons in the brain. That is why Penrose and Hameroff's proposal is called "quantum consciousness" theory.
Quantum consciousness
We cannot yet measure the behavior of quantum fractals in the brain, if they exist at all. But advanced technology allows us to measure quantum fractals in the laboratory. In recent research using a scanning tunnel microscope (STM), my colleagues from Utrecht and I carefully arranged the electrons in a fractal pattern, creating a quantum fractal.
When we measured the wave function of electrons, which describes their quantum state, we found that they also lived in the fractal dimension dictated by the physical pattern we had created. In this case, the pattern that we used on the quantum scale was the Sierpiński triangle , which is a shape that is between one-dimensionality and two-dimensionality.
This was an exciting finding, but STM techniques cannot probe how quantum particles move, which would tell us more about how quantum processes might occur in the brain. So in our latest research , my colleagues at Shanghai Jiaotong University and I went one step further. Using state-of-the-art photonic experiments, we were able to reveal the quantum motion that takes place within fractals in unprecedented detail.
We achieve this by injecting photons (particles of light) into an artificial chip carefully designed to form a tiny Sierpiński triangle. We injected photons at the tip of the triangle and observed how they propagated through its fractal structure in a process called quantum transport . Next, we repeat this experiment on two different fractal structures, both shaped like squares instead of triangles. And in each of these structures we carry out hundreds of experiments.
Our observations from these experiments reveal that quantum fractals actually behave differently than classics. Specifically, we discovered that the propagation of light through a fractal is governed by different laws in the quantum case compared to the classical case.
This new knowledge of quantum fractals could lay the groundwork for scientists to experimentally test the theory of quantum consciousness. If quantum measurements of the human brain are ever made, they could be compared to our results to definitively decide whether consciousness is a classical or quantum phenomenon.
Our work could have profound implications in other scientific fields as well. By investigating quantum transport in our artificially designed fractal structures, we may have taken the first small steps toward unifying physics, mathematics, and biology, which could greatly enrich our understanding of the world around us, as well as the world. that exists in our heads.
Cristiane de Morais Smith, Professor, Theoretical Physics, Utrecht University
This article was originally published on The Conversation. Read the original.