Quantum information in quantum consciousness

Original author: Nicole Yunger Halpern
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It is generally accepted that a graduate student physicist should not even touch on some scientific tasks with the very tip of a long spear - this applies especially to gaps in the foundations of quantum theory. These tasks are so complex that there is not the slightest chance of progress. These tasks are so vague that there is not the slightest chance of convincing anyone to pay attention to progress. An example of such a task is the role of quantum physics in the formation of consciousness.

Credit: dailygalaxy.com

Disclaimer! From a translator: I translated this post in an attempt to figure out an idea. The concept itself is quite controversial, and not all points are clear (or insufficiently complete) in the original. I do not take the responsibility to invent the original and leave a post as a starting point for your thoughts and discussions.

There was already a post on Habré about Fisher’s idea, but it’s always interesting to hear explanations from actors (authors). Some places are adapted, links are added.

In fact, we know that quantum physics definitely plays a role in our minds: the laws of quantum physics allow atoms to remain stable, and decayed atoms definitely cannot affect consciousness.

But most physicists are convinced that useful quantum entanglement cannot exist in the brain. Entanglement is manifested in quantum correlations between quantum systems, which are stronger than any achievable in classical systems. Entanglement decays very quickly in hot, humid, and noisy environments.
And the brain is just such an environment. Imagine you put the entangled molecules A and Binto someone’s brain. Water, ions and other particles will collide with these molecules. The higher the temperature of the medium, the more collisions. Particles of the medium will become entangled with molecules A and B through electromagnetic interaction. The larger A confused with the environment, the less A can be confused with B . Ultimately, A will be slightly confused with many particles of the medium. But such a weak entanglement cannot be used for some useful calculations. So it seems that quantum physics is unlikely to significantly affect consciousness.

Do not touch

However, my supervisor, John Prescill, offered to think about whether it would be interesting for me to work on this topic.

Try a completely new topic, ”he said,“ take a chance. ” If it doesn’t work out, okay. All the same, they do not expect much from graduate students. Have you seen Matthew Fisher 's article on quantum consciousness?

Matthew Fisher is a theoretical physicist at the University of California at Santa Barbara. He is praised and revered, especially for his work on superconductors . A couple of years ago, Matthew became interested in biochemistry. He knew, of course, that most physicists doubt the participation of quantum processes in the formation of consciousness. But what if this were not so, he thought, how could they participate? Thought - and in 2015 wrote an articleto the Annals of Physics, in which, using reverse engineering, he proposed a variant of quantum consciousness.

A graduate student in no case should concern such tasks, even a three-meter radio antenna, claims common sense. But I trust John Preskill like no other on Earth.
I will look at the article , I said.

Matthew suggested that quantum physics can influence consciousness as follows ( approx. Per. Also article on Habré ). Experimenters have already done quantum computing using one hot, wet, and random system: nuclear magnetic resonance (NMR) . NMR is used in magnetic resonance imaging(MRI) for imaging the human brain. A standard NMR system consists of liquid molecules at high temperature. The molecules, in turn, are composed of atoms, whose nuclei possess a quantum property called spin . Spins of nuclei can encode quantum information (CI).

Matthew reasoned: what could prevent the spins of the nuclei from storing quantum information in our brains? He compiled a list of things that could destroy quantum information, and concluded that hydrogen ions pose the greatest threat. They can become entangled with spins (and lead to decoherence ) through a dipole – dipole interaction .

How can spin avoid this threat? For example, a spin of magnitudezero the electric quadrupole moment of the nucleus; quadrupole interactions cannot lead to decoherence of such a spin. And in what atoms in our body does the spin equal ? In hydrogen and phosphorus. Only hydrogen is susceptible to other sources of decoherence, so Matthew came to the conclusion that phosphorus atoms can store CIs in our brain, while the spins of the phosphorus nucleus work like qubits (quantum bits).

Phosphorus is protected from electrical interactions, but what about magnetic dipole-dipole interactions? Such interactions depend on the orientation of the spins relative to their position in space. If phosphorus is part of a small molecule dangling in biological fluid, the position of the nucleus changes randomly, and on average the interaction will be zero.

There are other atoms in the molecules besides phosphorus. The nuclei of these atoms can interact with the phosphorus spin, and destroy its quantum state. This will not happen in only one case: when all the spins of these nuclei are equal to zero. In which atoms in the human body are the backs of the nucleus equal to zero? In oxygen and calcium. So phosphorus will be protected from interaction with other atoms in the molecules with calcium and oxygen.

Matthew proposed his own version of a molecule that would protect phosphorus from decoherence. And then I discovered that such a molecule is indeed described in the scientific literature. A molecule called a Posner cluster or Posner molecule(I will call her Posner for short). Posner can exist in artificial bi-fluids - fluids created to simulate fluids within us. It is believed that Posners can exist in our bodies and participate in bone formation. Matthew estimates that Posners can protect phosphorus backs from decoherence for 1-10 days.

Posner's molecule (image courtesy of Swift et al. )

But how can Posners affect consciousness? Matthew proposed the following option. The adenosine triphosphate molecule (ATP) is an energy source for biochemical reactions. "Triphosphate" means that it contains three phosphate ions - compoundsconsisting of one phosphorus atom and three oxygen atoms. Two phosphates can separate from the ATP molecule, while remaining connected to each other.

A pair of phosphates will drift until it encounters an enzyme called pyrophosphatase. This enzyme can split a pair of phosphates into two independent phosphates. Moreover, as Matthew suggested, together with Leo Rajihovsky , the spins of the phosphorus nuclei are projected into a singlet state , which is a state with maximum entanglement.

Imagine a lot of phosphates in biofluids. Six phosphates can combine with nine calcium ions to form a Posner molecule. Each Posner can have six common singles with other Pozners - this is how entire clouds of entangled Posner molecules form.
One bunch of Posner can get into one neuron, while another bunch - into another neuron. Posners can be transferred across cell membranes with the VGLUT protein (BNPI). So two neurons are also confused. Imagine two Posners, P and Q, converging in the neuron N. Calculations of quantum chemistry show that these Posners can combine with each other. Suppose P was entangled with Posner P ' in neuron N' . If P and Q are combined in N neuron , entanglement between P and P ' will increase the likelihood of combining P' and Q '.

United Posners will move slowly - they will have to overcome the resistance of water. Hydrogen and magnesium can replace calcium in Posner, breaking molecules. Negatively charged phosphates will attract positively charged ones, and just like phosphates will attract . Released calcium will fill the N and N 'neurons. An increase in calcium concentration leads to the appearance of a chemical potential on the axon and the release of neurotransmitters that transmit a signal between two neurons. If two neurons N and N 'are entangled through Posner molecules, two neurons can ignite simultaneously.

We do not know if the mechanism suggested by Matthew works in our brains. However, last year the Heising-Simons Foundation singled outMatthew and colleagues $ 1.2 million for experiments.

John Preskill told me: for example, Matthew’s idea is at least partially true, and Posner’s molecules can really store quantum information. Quantum systems process information differently than classical systems. How fast can Posner process quantum information?
I threw my spear in the fifth year of graduate school, and went from Caltech for a five-month internship, having vowed to return with an article answering John's question. And so I did: the article was published in the Annals of Physics this month.

Fortunately, I was able to interest Elizabeth Crosson.in my project. Elizabeth, now an assistant professor at the University of New Mexico, was then a postdoc in John’s group. We both dealt with the theory of quantum information, but our qualifications, abilities, and strengths varied. We complemented each other, possessing the same obstinacy, which forced us to continue to send letters and exchange messages day and night.

Elizabeth and I translated Matthew's ideas from the language of biochemistry into the mathematical language of CI theory. We divided Matthew's narrative into a sequence of biochemical steps, and found out how each of these steps will convert the CI recorded in phosphorus nuclei. We presented each transformation in the form of an equation and an element of a flowchart (flowchart elements are images that can be created together to create circuits of working algorithms). We called this set of transformations Posner operations.

Imagine that you can perform Posner operations by preparing molecules, trying to connect them, etc. How can you handle CI with such operations? Elizabeth and I have found applications in quantum messaging, quantum error recording, and quantum computing. Our results are based on one assumption - possibly erroneous - that Matthew made the right conclusions. We characterized what Pozners can achieve if they are actively managed, although random influences would direct them in biological fluids. But this is at least a good starting point for further research.

We found several CI effects that can be realized with Posner molecules. At first,CI can be teleported from one Posner to another, but noise occurs. Its nature is in the effective dimension that Posner performs on one another when combined. This dimension transforms the subspace of the Hilbert space of two Posners through the rough Bell dimension. The Bell measurement gives one of four possible outcomes, or two bits. If one of the bits is discarded, the measurement result will be coarse. Quantum teleportation requires a Bell measurement, and coarsening this measurement leads to noise.

This noisy teleportation is also called super dense encoding.. A bit is a random parameter that takes one of two values, and “trit” is a random parameter that can take one of three possible values. A trit can be effectively teleported from one Posner to another using entanglement if one bit is directly transmitted between them.

Secondly, Matthew argued that the Posner structure protects CI from decoherence. Scientists have developed error correction and detection programs to protect CI from decoherence. Can Pozner realize such programs in our model? It turns out that yes: Elizabeth and I (with the help of a former postdoc from Caltech Fernando Pastavsky) developed a program for detecting errors that can work on Posners. One Posner encodes a logical kutrit (quantum version of the trit), and the code detects any error that occurs in one of the six qubits in Pozner.

Third, how complex can a quantum state be that can be prepared using Posner operations? Quite complicated, as we have discovered: suppose you can measure this state locally so that the results of previous measurements will influence the measurements in the future. You can do any quantum calculation. That is, the Posner operation allows you to prepare a state that can be used to create a universal quantum computer .

Finally,we found a numerical estimate of the effect of entanglement on the rate of Posner association. Imagine that you have prepared two Posner P and P ', which are confused only with other particles. If Posners come closer to the correct orientation, the probability of their association in our model is 33.6%. And if each qubit in P is maximally confused with a qubit in P ', the probability of combining increases to 100%.

Elizabeth and I present the process described by Matthew in a 2015 article as flowcharts.

I was afraid that other scientists would ridicule our work as insane. To my surprise, she was enthusiastically received: her colleagues praised the riskiness of research in a new direction. In addition, our work is not crazy at all: we do not claim that quantum physics affects consciousness. We build on Matthew’s assumptions, noting that they may be erroneous, and examine the consequences of his assumptions. We are not biochemists, nor experimenters, so we confine ourselves to statements in the theory of CI.

Pozner may not be able to maintain coherence long enough to use quantum effects in information processing. Will Matthew's mistakes put an end to our research? Not. Posner prompted us to ideas and questions in the theory of CI. For example, our quantum circuits illustrate interactions (unitary gates) and measurements made by combining Pozners. These schemes partially motivated the emergence of a new field of research that arose last summer and is now gaining momentum. Let's take random unitary gates interspersed with measurements. Unitary interactions entangle qubits, and dimensions destroy entanglement. Which of the influences will be more significant? Will the system go from a state of “largely confused” to “largely confused" at a given measurement frequency? Researchers fromSanta Barbara and Colorado ; MIT; Oxford ; Lancaster, UK ; Berkeley; stanford ; and Princeton tackled this issue.  

The aspirant physicist, as is commonly believed, should not touch quantum consciousness even with the halberd of the Swiss guard. But I'm glad I tried: I learned a lot, made a contribution to science, and it was an adventure. And if someone does not approve of such impudence, I can blame John Preskill.

The article “Quantum information in the Posner model of quantum cognition” can be found here . The version for arXiv is here , and here is the report on the article.

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