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Manga artist Kotobuki Shiriagari, who describes himself as “totally hopeless at math and physics,” will ask researcher Hiroyuki Mizuno about quantum and quantum computers to know the unknown and visualize the invisible. The artist will then attempt to visualize quantum, qubit, superposition, entanglement, and more.
Kotobuki Shiriagari
Attempts to Visualize the Quantum World
Kotobuki Shiriagari (Manga Artist)×Hiroyuki Mizuno (Distinguished Researcher at the Center for Exploratory Research, and Director of the Hitachi Kyoto University Laboratory, Research & Development Group, Hitachi, Ltd.)
Moderator: Masako Taniguchi (AXIS)
DATE | 2025.3.12 WED. | 12:00－13:00 JST
Prior to the webinar, Kotobuki Shiriagari and Hiroyuki Mizuno also had a dialogue in December 2024. This article introduces their conversation with text and illustrations by Mr. Shiriagari. It explains why manga iconography was featured in the webinar, while Mr. Mizuno provides easy-to-understand explanations of basic topics such as quantum, quantum computers, and the current state of development.
Kotobuki Shiriagari explores the mind of a quantum computer scientist
“Basically, quantum computers are also for predicting the future.”
Shiriagari: I’d like to start with what a mathematical formula is. I have no idea what it means when I see one. But I also think it would be interesting if it could be expressed in words.
Mizuno: Formulas are a tool to accurately describe physical phenomena. But it is not easy to explain mathematical formulas in words. In a sense, it is a world of imagination. No one has actually seen wave-particle duality, but things make sense if you think of it that way. It might be proven wrong in the future when human beings become more intelligent.
Shiriagari: When I heard about particles and waves, I thought of skipping stones in a river. Do ripples on the surface of the water have anything to do with quantum computers?
Mizuno: Yes, they do. Young’s double-slit experiment is well known for demonstrating both particle-like and wave-like properties of electrons. In this experiment, electrons passing through two slits spread out like a wave and show an interference pattern, but it was also observed that as a particle, each electron hit the detection screen behind the slits.
Shiriagari: ??? So, we should just accept the formula based on the experiment [laughs].
Mizuno: Exactly. The quantum world is invisible and unknown, so we only deem that “it is understood with this concept.” If you ask, “Is there an intermediate between particle and wave,” I’d say there isn’t at this point. But in the future, another interpretation may emerge that will be considered more appropriate. The point is that right now, particles and waves are the only terms we know.
Shiriagari: You mean there is no border between a particle and wave?
Mizuno: It means that the quantum effects at the microscopic scale average out at the macroscopic scale and cannot be observed by humans. This is not a matter of observational technology. You might then think that it would have no impact on the world, but a chain of microscopic changes does have an effect on the macroscopic scale. Every reaction of different materials is the result of quantum effects, and the resulting macroscopic changes become visible to us from the outside.
Shiriagari: Is it like, when you look from the outside, you can’t understand individuals, but you can understand Japan as a country?
Mizuno: Right. The quantum effect is that each individual human behavior becomes unobservable at some point. Nevertheless, the relationship between microscopic phenomena and the collective larger phenomena is not fully understood. Unless we understand the microscopic phenomena, we cannot understand the whole.
Shiriagari: Manga is the other way around. It’s like each electron and each quantum has its own individuality and moves on its own, but when they come together, they fit into a formula. So, there are some manga artists who think that from the perspective of the universe, human beings are also a type of mathematical formula.
Mizuno: The behavior in the microscopic realm isn’t necessarily continuous with the behavior of a larger phenomenon that emerges from it. This is one of the future challenges for humanity. Human understanding is not quite there yet. On one hand, I think that manga and art are a way to enjoy things that are too complex to understand through mathematical formulas. Because a world where everything is predictable would be boring. On the other hand, I have no doubt that all scientists want to understand everything and express it with formulas.
Shiriagari: What kind of knowledge do you gain from understanding formulas?
Mizuno: They enable us to predict the future. Launching a rocket is impossible without predicting what will happen when the thrust is increased. Basically, quantum computers are also for predicting the future.
Shiriagari: Are there any particular formulas that are important for the development of quantum computers?
Mizuno: The Schrödinger equation.
Shiriagari: It mostly consists of symbols. What does this “h” stand for?
Mizuno: He is a constant value called Planck’s constant. It is a long-digit number like π, so it is symbolized by the letter h. The bar on h indicates the constant equal to h divided by 2π.
Shiriagari: I see. How would you describe this equation in words?
Mizuno: The Schrödinger equation represents the relationship between the energy of an electron and the wave function that describes its state. As I mentioned earlier, an electron appears to be a particle but actually has the properties of a wave, and its state can be described by a wave function. The shape of the wave function is determined by the energy of the electron. The Schrödinger equation is the fundamental equation that determines the shape of this wave function.
Shiriagari: What is so revolutionary about it?
Mizuno: It makes it possible to precisely describe the quantum behavior of electrons in mathematical terms as a wave function. This led to theoretical explanations of the energy and probability of electron behavior, which could not be explained by classical physics.
Shiriagari: So you can do the calculation by putting in numbers. What is the wave function?
Mizuno: It’s a mathematical function that describes the state of an electron, showing where the particle is and how it moves.
Shiriagari: The position can be determined from this data?
Mizuno: Yes. The value of the wave function itself doesn’t represent anything directly, but by squaring its absolute value, it calculates the probability of finding an electron at a given point in space. For example, the shape of the wave function can be used to predict where an electron is most likely located in an atom. However, to complicate matters further, there is a principle that the position and momentum (product of velocity and mass) of a particle can’t be determined exactly at the same time. This is known as the uncertainty principle. If the position is given precisely, the velocity will be vague, and conversely, if we try to know the precise velocity, the position will be fuzzy. This property is closely related to the fact that electrons behave as waves.
Shiriagari: Please tell me about quantum computers.
Mizuno: Let me start with how classical computers work. Classical computers use only 0s and 1s to represent numbers and do calculations. 0s and 1s indicate whether information is present or not. Even if there is noise, say as small as 0.1, it still only takes a value of either 0 or 1, so the noise can be recalibrated to one of these two values, which was revolutionary. It retains its accuracy even after repeated calculations and copying.
Quantum computers, on the other hand, are different. They can handle not only 0 and 1, but any value in between. But this flexibility poses a challenge to maintaining accuracy when there is noise in the computation. Implementation of a system to correct errors is a major challenge in the development of quantum computers today.
I said earlier that quantum computers are innovative because they can handle not only 0 and 1, but any value in between. To be more precise, it’s a property called superposition. It allows there to be both states 0 and 1 simultaneously at a given ratio, which leads to the potential to efficiently perform complex computations that are impossible with classical computers. For example, if we liken a quantum state to the surface of a sphere, 0 corresponds to the north pole and 1 to the south pole, and the equator represents equal superpositions of 0 and 1.
The phenomenon of changing the qubit state by radiation at a certain frequency is called Rabi oscillation, and by observing the changes, we can follow the quantum state. See, doesn’t this sound easy?
Shiriagari: Well, wait a moment. I feel like I’m being tricked [laughs]. The sphere is based on a formula?
Mizuno: The sphere (Bloch Sphere) isn’t a physically existing one, but a model to represent a state described by a formula. The state is called the wave function, which clearly shows information about the state of an electron.
The flexibility of the qubit state enables a quantum computer to have enormous computational power even on a small scale. However, the system has a flaw. It’s prone to error accumulation. So it’s extremely important to build a system to correct errors.
Shiriagari: In that case, quantum computers are somewhat analog in nature, aren’t they?
Mizuno: Exactly. An analog computer with infinite precision would be the most powerful computer ever. But it would be impossible to create. A quantum computer can be potentially the next most powerful computer.
Shiriagari: Does it have to be digitized when you extract quantum results?
Mizuno: The moment an observation is made, the result is digitized. This is a concept called the Copenhagen Interpretation or the Standard Interpretation. At the moment of observation, the wave-like state collapses into either 0 or 1.
Shiriagari: I see. All you need is 0 or 1 at the end.
Mizuno: That is the case when connecting to the current system. But in the future, we may be able to input the quantum state into the subsequent system.
Shiriagari: A superposition of waves happens within the sphere, right?
Mizuno: That’s right. A quantum computer is characterized by its ability to process a superposition state, in addition to 0 and 1. This enables computations that are beyond the capabilities of conventional computers. It has the potential to solve complex problems such as prime factorization faster. This is why it is said to change the limits of cryptography. It can crack encryption without a password.
Shiriagari: Does that mean it can break encryption by repetitive superpositions with a vague guess?
Mizuno: Encryption is based on a method called public-key cryptography. This encryption method uses very large numbers that are the product of prime numbers. To decrypt, you need to find the prime numbers. This requires prime factorization of very large numbers, which takes a great deal of time to compute. Therefore, it takes too long to break the encryption, and it can’t be decoded. But a quantum computer has the potential to solve this prime factorization in an instant.
This is the background to the recent popularization of more secure systems that combine methods other than password protection, such as two-factor authentication.
Shiriagari: I also heard that drug discovery may become easier.
Mizuno: In new drug development, it’s crucial to be able to predict how molecules and atoms interact. If accurate simulations are possible, the need for animal and clinical testing may ultimately become obsolete. Right now, experiments are necessary because we don’t know which drug will work for what type of person or what side effects it will cause. But a quantum computer has the potential to significantly shorten this process, because it can directly simulate reactions using the Schrödinger equation.
Shiriagari: You mean it can predict the outcome.
Mizuno: Yes, although not completely. Humans are extremely complex. Today, it takes an enormous number of experiments to find a drug that can be tested for its efficacy through animal experiments. If we can make such a discovery process more efficient, wouldn’t that in itself be worthwhile?
Another thing is that new drugs for rare diseases tend to be less of a priority. Unlike drugs for COVID-19, for example, that had been developed at a tremendous pace worldwide. I think it would be really great if the development of new drugs for rare diseases were accelerated.
Shiriagari: I want a computer that will prevent me from pushing my wife’s buttons [laughs].
Mizuno: [laughs] ChatGPT is a kind of prediction machine. It predicts and returns the most probable answer based on past data in response to the prompt. In the same way, if it learns data about a specific individual, it may be possible in the future to predict responses that are unique to that individual. It might even be possible to have a tool that predicts your wife’s reaction [laughs].
Shiriagari: The competition to develop quantum computers is heating up, and it seems that there is potential for Japan as well.
Mizuno: There are many excellent Japanese researchers in the field of quantum mechanics, and many Nobel Prize winners in the past. However, the challenge lies in the productization and commercialization of the basic research. Successful commercialization requires a good bridge between academia and business. This is where we are trying to play a role.
We are working on silicon technology. It’s highly integrated and easy to downsize, so we believe it’s ideal for implementing, say, a million qubits. Several types of quantum computer systems are currently being developed in Japan, and we don’t know which is the best. But for now, it’s important to tackle various technologies, because such competition will lead to the final selection. I expect that in ten years, we will be able to narrow down which method is likely to become mainstream.
Shiriagari: I am beginning to get excited about ten years from now. Do you keep prototyping and experimenting, and experimenting and prototyping, day after day?
Mizuno: Exactly. The experimental data I showed you earlier is about two weeks old, and this week’s data becomes better than last week’s.
Shiriagari: Amazing! What do you find difficult?
Mizuno: Fierce competition and the rapid pace of advancement. Nevertheless, we all spend our days in research dreaming of a view that only a vanguard can see. But the world a vanguard sees is pitch black. But you turn back and see so many people following you [laughs]. If you are at the forefront, you never know which way to go, and you don’t know if there’s a cliff ahead. But you can be a pioneer and be the first to see a new landscape. I think enjoying such things is the best part of being a researcher.
Shiriagari: It’s interesting to imagine how technology emerging from such strenuous efforts might affect our daily lives.
Today I came here with the idea of visually representing the invisible world of quantum in manga. For example, the concepts of quantum uncertainty and superposition could be conveyed intuitively by using symbols, like manga iconography. How about fluffy-looking lines for a superposition of waves, and drawing a particle with a dot and a line? I want to transform complex mathematical formulas into something that people can intuitively understand.
Mizuno: That sounds like a very interesting attempt. Visual communication of scientific concepts can lead to new discoveries for researchers. For example, attempts have been made to visualize quantum states since the early days of quantum mechanics. Symbolic representations are easier for the general public to understand, so I’m looking forward to it.
……To be continued in a webinar on March 12.
Hiroyuki Mizuno
Distinguished Researcher at the Center for Exploratory Research, and Director of the Hitachi Kyoto University Laboratory, Research & Development Group, Hitachi, Ltd.
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Mizuno joined Hitachi in 1993 and engaged in research and development of integrated circuits such as microcomputers. He was a visiting scholar at Stanford University in the U.S. from 2002 to 2003. In 2015, he presented CMOS Annealing quantum-inspired technology, and in 2020, he became a project manager of the Silicon Quantum Computer Project in the Moonshot Research and Development Program ` . At the Hitachi Kyoto University Laboratory ` , he promotes research on the social implementation of new value and AI in collaboration with philosophers. D.Eng. and Institute of Electrical and Electronics Engineers (IEEE) Fellow.
Kotobuki Shiriagari
Manga Artist
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Shiriagari made his debut as a manga artist in 1985 with Ereki na Haru (Electric Spring). In 2000, he won the Bungeishunju Manga Award for Jiji-Oyaji 2000 and Yuruyuru-Oyaji, and in 2001, the Tezuka Osamu Cultural Prize Excellence Award for Yajikita in DEEP. His manga, Chikyu boeike no hitobito (The Earth Defender Family), has been serialized in the evening edition of the Asahi Shimbun since 2002. In addition to manga in many genres, from gag to socially conscious works, he is active in a wide range of fields, including video and contemporary art. He received the Medal with Purple Ribbon in 2014.
