Quantum computers use quantum processors that use elementary particles such as neutrons, electrons and / or atoms instead of integrated circuits and transistors like conventional processors. Two of the most "crazy and magical" properties of these particles are:
- First, they are somehow constantly "attached" to other particles that are entangled with it after some interaction. For example, when the spin of one particle is measured in the "up" state, the other particle, even if it was very far away, would be immediately (ie faster than the speed of light) in the opposite "down" state. Large collections of complex particles (if present in the brain) could therefore behave in an "orchestrated" or coordinated manner over long distances.
- Second, there are in a superposition of states before any measurement. For example, an electron may be at two different energy levels or rotate up and down simultaneously. When measured, however, it will be at a certain energy level or in a certain spin direction - we say that it has "collapsed" in a certain state. When using classical processors, we assign a specific "1" or "0" to a bit. In a quantum processor, we could assign "1" to the spin-down state and "0" to the spin-up state of, say, an electron. However, until we measure the situation, it will be "1" and "0" at the same time - just as a coin that spins is neither a "crown" nor "letters" when it spins. Therefore, a quantum bit or "qubit" can represent "1" AND "0" at the same time, as opposed to the "bit" of a standard processor which can only represent "1" Ή "0" in a moment in time. The bit is binary and point, but the qubit is "spatial" and "fuzzy" - this allows much more information to be processed in parallel, taking advantage of the superposition property. A "bit" represents either a 1 or a 0 at a point in time, while a "qubit" can represent both at the same time.1
Various physical properties of elementary particles can be attributed to "1" and "0". For example, we can use the spin-up or spin-down states of an atom's nucleus, the different energy levels of electrons in an atom, or even the orientation of the polarization level of light particles or photons.
Quantum computers using phosphor atoms
In 2013, a research team led by Australian engineers from the University of New South Wales (UNSW) created the first functional quantum bit based on the single-atom phosphorus nucleus spin inside a zero-spin non-magnetic silicon atom bed. In a groundbreaking publication in the journal Nature, they reported a record accuracy in recording and reading quantum information using nuclear spin. 2
As the nucleus of a phosphor atom has a very weak magnetic field and has the lowest number of spins που (meaning that it is less sensitive to electric and magnetic fields), it is almost invulnerable to magnetic noise or electrical interference from the environment. It is further "shielded" by the noise from the surrounding bed of silicon atoms with zero spin. As a result, the nuclear spin has a longer coherence time that allows information to be stored on it for a longer period of time, leading to a much higher level of accuracy.
"The phosphor atom nucleus contains a nuclear spin, which could act as an excellent memory storage qubit thanks to its very weak sensitivity to ambient noise."
Andrew Zurak, referring to the work of the UNSW team, 3
In 2014, another team (this time in Dutch-US collaboration) used phosphor atom nuclear spins in quantum computing to achieve even greater 99.99% accuracy and a longer coherence time of over 35 seconds. 4.5
Quantum computers in our heads?
So what does all this have to do with our brain? There are numerous examples in quantum biology where quantum processing is suspect - for example, there is evidence that birds use quantum processes in their retinas to navigate the globe and that photosynthesis is evolving more efficiently with long-term consistency. It has also been observed that the human sense of smell and certain aspects of human vision would require quantum processing to occur. Thus, it is not surprising that we should look for quantum processing in the human brain.
One of the first popular hypotheses was proposed by Roger Penrose, a distinguished physicist, and Stuart Hammeroff, an anesthesiologist. They hypothesized that quantum processing could take place in the microtubules of neurons.6 However, most scientists were skeptical, as the brain was considered a hot, humid, and noisy environment, where quantum coherence, which usually takes place in extremely isolated environments. and cold temperatures, it would be impossible to achieve. Neither Penrose nor Hammeroff responded satisfactorily to this critique of their theory. However, there have been recent discoveries in extending cohesion times, and research teams around the world are rushing to extend cohesion times to room temperature with some success.7,8 Thus, jurors have not yet ruled on the Penrose-Hammeroff theory.
Fisher's pioneering ideas
Most recently, in 2015, Matthew Fisher, a physicist at the University of California, Berkeley, developed a model in which nuclear spins in phosphorus atoms can serve as qubits. This model is very similar to what was discussed in the previous section, as it was developed in a laboratory environment - the difference is that this time it was applied to the human brain, where phosphorus is abundant9.
"Could we ourselves be quantum computers and not just intelligent robots designing and building quantum computers?"
Matthew Fisher, 10
Fisher has argued quite convincingly that the spins of phosphorus atom nuclei can be sufficiently isolated (from the electron cloud around it and the protective shield of a zero-spin atom bed) and also to be less distracted by quantum noise due to weak magnetic field (due to its low spin number), thus allowing it to maintain quantum coherence. (The laboratory studies discussed in the previous section and the experimental results have verified and confirmed this fact). Thus, in an environment such as the brain, where electric fields abound, the nuclei of phosphorus atoms would be in a sufficiently isolated environment.
The process starts in the cell with a chemical called pyrophosphate. It consists of two phosphates bonded together - each consisting of a phosphorus atom surrounded by multiple oxygen atoms with zero spin (a situation similar to that of the laboratory study discussed above, where the phosphorus atom was nested in silicon atoms with zero σπιν). The interaction between the spins of the phosphates makes them complicated. One of the resulting configurations results in a zero spin or a "single" state of maximum interference. The enzymes then break down the entangled phosphates into two free phosphate ions, which continue to be entangled as they are removed. These complex phosphates are then combined separately with calcium ions and oxygen atoms to form Posner molecules, as shown below.
These clusters provide additional "shielding" to the intricate pairs from external interference, so that they can maintain coherence for much longer distances over long distances in the brain. When Fisher calculated the coherence time for these molecules, the incredible sum of 105 seconds resulted - a whole day.12
What Next?
Although Fischer does not seem to specify in detail what will happen next - which is important if we want to get the big picture - the author will try to do so. Numerous complex nuclei of phosphorus atoms (within Posner molecules) will be scattered over a large area of the brain. They would be in a supernatural state, existing as waves, for some time before collapsing. When the collapse occurs, the atom's electrons respond. Electrons determine the chemical properties of atoms. Thus, the collapse causes a change in the chemical properties of the phosphorus atoms, resulting in a cascade of chemical reactions that send a cascade of neurotransmitters to the synapses of neurons. The sequence of electrochemical signals is then incorporated to form a perception, which is interpreted based on the individual's life experiences.
This solves a long-standing neuroscience question that has occupied scientists: How is the brain able to integrate information from different parts of the brain to form a coherent perception? Perhaps with the "Fisher mechanism" (a term newly coined by the author), a simultaneous collapse of the nuclear spins of phosphorus atoms entangled in various layers and parts of the brain could be the answer.
Restrictions
The most obvious limitation is that Fischer's ideas have not yet been thoroughly tested, although some aspects (for example, the longer cohesion time of phosphorus atoms) have already been tested in the laboratory. However, there are plans to do so. The first test will be if there are Posner molecules in extracellular fluids and if they could be complicated. Fisher proposes to test this in the laboratory by causing chemical reactions to complicate the nuclear spin of phosphorus, then pouring the solution into two test tubes and looking for quantum correlations in the light emitted12.
Roger Penrose believes that Fisher's mechanism can only help explain long-term memory, but may not be sufficient to explain consciousness.12 He believes that the Penrose-Hammeroff formulation for microtubules, which he says is more massive than nuclei, is a more powerful explanation for this, although most scientists are skeptical. It would be interesting if Posner molecules (with complex particles) could be found in these microtubules - then both Fisher's hypothesis and the Penrose-Hammeroff hypothesis would be at least partially correct. (Everyone likes a happy ending!)
In a few words
1. It has been proven in the laboratory that quantum computing with isolated and shielded phosphor atoms leads to extremely accurate results and longer consistency times.
2. Phosphorus is abundant in the brain.
3. The human brain (and possibly the brains of other animals) can use the nuclear spins of phosphorus atoms as qubits to perform quantum calculations.
Report
1. Image: (2019, Sep 28). What makes quantum computing special? Medium.com.
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3. Dzurak, A. (2014, Oct 15). Silicon Qubits Could Be the Key to a Quantum Revolution, SciTech Daily.
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8. Miao, K., Blanton, J., Anderson, C., Bourassa, A., Crook, A., Wolfowicz, G., Abe, H., Ohshima, T., & Awschalom, D. (2020) . Universal cohesion protection in a solid state qubit spin. Science, eabc5186.
9. Fisher, MPA (2015). Quantum cognition: The ability to process nuclear spins in the brain. Annals of Physics, 362, 593-602.
10. Fernandes, S. (2018, Mar 27) Are We Quantum Computers? The Current (Science + Technology).
11. Swift, M., Van de Walle, C., & Fisher, M. (2018). Posner molecules: from atomic structure to nuclear spins. Physical Chemistry Chemical Physics, 20 (18), 12373-12380.
12. Brooks, M. (2015, Dec 15). Is quantum physics behind your brain's ability to think? New Scientist.
