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    Is our brain able to interpret quantum properties of light?

    September, 15th 2023

    Ado Jorio de Vasconcelos is a professor at the Department of Physics at the Federal University of Minas Gerais (UFMG), a member of the Brazilian Society of Physics, the Brazilian Academy of Sciences, the National Order of Scientific Merit and The World Academy of Sciences. His work comprises research and development of scientific instrumentation in optics for the study of nanostructures with applications in materials science and biomedicine.

    In this interview, Ado Jorio talks about his studies with a retinal analysis system to look for signs of Alzheimer’s disease and with optical spectroscopy and Raman scattering, which led him to the Quantum Vision project. He also describes the methodology and infrastructure developed in the project, which combines physics and neuroscience to study whether and how our visual system perceives quantum phenomena – and the next steps to be taken by the group of researchers. He also talks about the potential of the research, which fundamentally may lead to novel insight into how our brain works. For Ado, pioneer science is necessarily related to curiosity, humanity’s great driving force.

    Pioneer Science: Can you tell us a little about your work with quantum optics, in particular with Raman spectroscopy?

    Ado Jorio: Optics is a very broad field in which light is used to study different phenomena that may be related to its interaction with matter or with light itself. When we talk about quantum optics, we are concerned with the quantum properties of light. The work that we have been doing is on the interaction of light with matter: the photon, which is the indivisible amount of energy in light, enters a material and exchanges energy with this medium, generating another photon of greater or lesser energy. This is what we call Raman scattering, which is the inelastic scattering of light.

    And what we are studying, which is a very interesting phenomenon, happens when a photon transfers energy to the medium and this energy is then absorbed by another photon, generating two other photons that have a property called quantum correlation. Thus, we research the quantum properties of light formed, in essence, by two photons that are quantum-correlated by the interaction that took place within a medium – and this interaction is called Raman spectroscopy.

    In what ways did your work in this area lead to the Quantum Vision project?

    The Quantum Vision project, broadly speaking, poses the following question: is our brain capable of identifying quantum properties of light? If light carries different quantum information, is the great processor that is our brain capable of detecting and interpreting these properties? More specifically, our contribution to the project has to do with the Raman scattering process.

    In general, in daylight, our eyes capture an enormous amount of photons. So, the first thing we need to ask ourselves is: is our vision system capable of interpreting that you’ve detected a single photon? The second question is: if I shoot two photons, one in each eye, and these photons have quantum correlation information, will my brain somehow understand that?

    In other words: if we send in two photons that are uncorrelated and measure their effects in the brain, and then we send in two photons that are quantum correlated, does the brain detect a difference and interpret the quantum correlation? This is the question we are trying to answer in the Quantum Vision project.

    And what are your expectations for Quantum Vision?

    Expectations are very high. Because, despite being a pioneering and very fundamental question, it encompasses several important aspects: from helping to understand how the brain works, to knowing whether the brain interprets quantum properties; to the possible need to develop new devices capable, for example, of directing the photon to a specific detector on our retina and then being able to control it from an instrumental point of view.

    Thus, the question and the scientific work range from the development of an instrument that does not exist to do what we need to do, and the consequences of the answer to the question that we propose.

    One of your recent lines of research involved developing a retinal scanning system to look for signs of Alzheimer’s disease. How does it work? Can you tell us a little more about this research?

    Again, it comes from a very broad question: am I able to measure the optical spectroscopy signal from the back of my eye, from my retina? When the sun shines on a table, I may look at it and understand that it is a table; I am doing, in a way, a spectroscopic interpretation. But is it possible to do this in another way: throw light and capture the signal from inside a person’s retina? If the answer is positive, is it then possible to identify specific molecular arrangements in the retina? In the same way that I know that the table is made of wood, because I interpret colors and other types of information, if I can do spectroscopy inside my eye, I will be able to know what the molecular arrangements are and identify properties within it.

    Alzheimer’s disease mostly affects our brain, and what happens in the brain also happens in the optic nerve, which is an extension of the brain tissue. Consequently, changes caused by Alzheimer’s can be identified in the retina. Several diseases generate changes in the body that produce molecular markers and there is a specific marker related to the development of Alzheimer’s: a peptide called beta-amyloid. So, if it is possible to identify the presence of beta-amyloid in the back of my eye, I will identify that this protein is being accumulated in my brain tissue, which is related to the development of Alzheimer’s.

    Do you intend to move from the laboratory stage to researching with patients?

    For sure. Now, we have already developed all the instrumental methodology to generate the photons, shoot them into a molecular tissue that we know develops Alzheimer’s, and this showed us how to identify the molecular marker. But all of this was done in animal models or on dissected animal tissue. The next step now is to work through all the safety issues related to throwing a laser into a person’s eye without interfering with the eye’s functionality. Then, start testing on humans.

    What do you believe you’ll find? What are the potentials of this study?

    There is still no drug or treatment that reverses or cures an Alzheimer’s patient. And one of the major obstacles to this is our inability to detect the disease in its early stages and our lack of knowledge regarding its entire development. When a person is diagnosed with Alzheimer’s, in general, he or she already has an evolution of the disease that can reach up to twenty years, to the point of starting to show clinical symptoms, such as memory impairment. Treating a disease at such an advanced stage is very difficult. If we manage to diagnose early, monitor the evolution of the condition, try different interventions, and study their effect, this could lead to a cure for Alzheimer’s. And behind the cure is the scientific knowledge of how the disease develops and what you must do to stop it from evolving.

    And what about Quantum Vision?

    When we are talking about a disease, the result is obvious: the development of knowledge to end the disease. But in Quantum Vision, our question is almost philosophical: is our brain capable of understanding quantum properties of light? Let’s say the answer is: yes, it is. How? What allows our brain to differentiate two quantum-correlated photons from two quantum-uncorrelated photons?

    With these questions, we are fundamentally going to study and learn about the function of our brain, which, even today, is a big black box, even though we have accumulated a lot of knowledge on the subject.

    What are the challenges in producing such cutting-edge research?

    The challenges are many. If I want to generate quantum light, I need a laser that compresses many photons in a very short space of time – to then generate a few pairs of correlated photons. You can see that generating and understanding the source of quantum information itself is already a great challenge: to produce the quantum light of interest and to understand the properties of that light. Then comes the transference of these photons, directed towards a person’s eyes. And we need to be clear about how many photons we’re throwing at the eye, at what repetition rate. And, for that, it is necessary to develop a way for the person to be exposed to these photons.

    After this phase of technical challenges, we then enter the moment of learning and demonstrating how the person can truly identify a photon. There is still one last challenge: understanding whether the person can differentiate if a property is quantum. All this is very new! I’ll take a step back: when a newborn child sees a chair, does he or she know that it is a chair? Probably not, he or she will learn later on it’s a chair. So, there’s still the challenge that, for us to know if our brain is capable of differentiating something or not, maybe the big challenge is not even if the brain is doing the work but learning how to recognize it. These are pioneering, open-ended questions that we will need to understand and learn from.

    Is it at this moment that we enter a relationship with other areas of science?

    For sure: at this moment you enter neuroscience, which has a whole neurological part of interpretation and methodology, which is not a methodology that we, as physicists, learn. As a physicist my methods include tinkering with detectors, processors, and lasers, among other equipment. But when you approach the interpretation of a person, it is knowledge that we do not have and, therefore, we need to talk to researchers who work with psychophysics and with various issues that are related to the ability of human beings to say whether they saw a photon, for example. All these questions are important if you are measuring a certain phenomenon, because it depends on the interpretation of the person who is doing the experiment.

    It’s a step yet to be taken, right?

    The specific test with people has not yet been done. But, just as in the study on Alzheimer’s, we already worked on all the knowledge required to be able to test people today and, in the case of Quantum Vision, photons that carry quantum correlation, we have already developed all the knowledge to start testing on people. We’ve even developed part of the infrastructure to get these photons into a person’s eye. Although, as I said, this development has a very broad character: I can throw light into the back of a person’s eye in a controlled way and obtain a range of information – then I can apply this to quantum light, to the early diagnosis of Alzheimer’s – I can apply it to the limit of our imagination.

    Is it important to put yourself in that place, of the unknown, of risk, to provoke scientific leaps?

    I would say that curiosity is the great driving force of science. It’s the will to understand the workings of what you don’t know, it’s the will to know why that is the way it is. This is not just the prerogative of a physicist or a neurologist: a child has that curiosity; a journalist has that curiosity. It’s what moves us! And what is specific to scientists is that this is also our function: to answer the questions we all ask.

    See also the infographic “Quantum Vision in the laboratory“, to know how physicists produce and direct photons with quantum correlation into a person’s eyes; and how neuroscientists assess visual perception of light.


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