[EN] What is a quantum computer ?

In this article, I will explain what a quantum computer is, written for junior high and high school students.

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1. What is the difference from a regular computer?

First, the regular computers inside our smartphones and PCs are called classical computers.

Difference from Classical Computers

So, what is the difference between a classical computer and a quantum computer? Simply put, in certain areas, the calculation speed is orders of magnitude faster. Specifically, Google reported that its quantum computer (Willow) completed a calculation in 300 seconds that would take a supercomputer longer than the age of the universe (about 13.8 billion years). Based on this, it means it can calculate at a speed 1.5 quadrillion times faster. In this way, quantum computers can perform calculations incredibly fast.

Strengths and Weaknesses of Quantum Computers

However, it is a misunderstanding to think that quantum computers are always faster; they have their own strengths and weaknesses. The example of Willow mentioned earlier is also in a field where quantum computers excel. Therefore, there are some calculations where classical computers are faster than quantum computers.

2. What can they do?

So, what can we do when calculations become faster with quantum computers? The answer is simulation and optimization. Quantum computers can perform simulations in much finer detail, and for optimization, they can analyze far more patterns than classical computers. Let's look at what is currently being done and what will be possible in the future for these two areas.

Present

- Optimization of delivery routes and factory production lines (Japan Post, Denso, etc.)

- Financial simulation and analysis (UFJ, etc.)

- Exploring stable structures of chemical compounds used for medicines (PeptiDream, Fujitsu, etc.)

- Clarifying the mechanisms of chemical reactions and developing new materials (Mitsubishi Chemical, etc.)

As shown in the examples above, efficiency improvements in moving things and simulations in finance and chemistry are currently being conducted. In some cases, efficiency has improved dramatically by using quantum computers.

Future

- Further material development through simulations

-> Improving the efficiency of solar panels

New materials for carbon dioxide capture

- Drug development through molecular-level simulations

-> By simulating viruses, drugs, and the human body at the molecular level, it will be possible to create effective medicines without side effects.

- More accurate weather forecasts through detailed simulations

- Optimization of not only logistics and production processes but also infrastructure

-> Eliminating traffic jams

- New energy sources

-> Improving the efficiency of artificial synthesis

- Decryption of most current cryptography

-> This became a hot topic with Bitcoin for a while, but since current cryptography is highly likely to be broken by future quantum computers, migrating to cryptography that quantum computers cannot break (post-quantum cryptography) is recommended.

- Applications in physics

-> By using quantum computer simulations, there may be new discoveries in physics.

(I personally hope that quantum computers will bring us at least one step closer to the Theory of Everything.)

In this way, quantum computers will be deeply involved in our daily lives and in solving current social problems.

3. How long until it is completed?

When will a quantum computer capable of doing these things be completed?

Actually, as of 2026, quantum computers have entered the practical application phase. However, these quantum computers are still far from perfect. It is said that near-perfect quantum computers will be built around 2030, and general-purpose quantum computers will be available around 2050.

4. What should students do?

So, as quantum computers become increasingly important, what should we do as students?

For those who want to proactively learn

Quantum computers are highly advanced, and learning paths are not fully established, so I think many people want to learn but don't know how.

In conclusion, I recommend first reading an introductory book that clearly explains quantum computers using diagrams. If you try to tackle difficult concepts from the beginning, you will definitely stumble. So, please read an introductory book to get a general understanding and grasp the concept first. (I will continue to post articles about quantum computers for students, so reading those articles is also a good option.)

Also, please try participating in events related to quantum computers. Reading books or watching videos is completely different from actually going there and listening to talks in person. You can find event information by searching online, so check occasionally and attend if you have the chance.

After that, once you have gained some knowledge, try actually using a quantum computer over the internet. Companies like IBM offer such services. I think you will become even more interested once you actually try using one.

For those who are just interested

If you don't necessarily want to take major action but are interested, try reading articles about quantum computers occasionally. There is a huge difference between knowing and not knowing. I believe knowledge about quantum computers will become even more important in the future, so please continue reading articles.

For those with little interest

If you're not interested, you don't have to do anything, but please try to remember at least a little bit of the content of this article.

I will be posting articles about the principles of quantum computers in the future, so please look forward to them.

While every effort is made to ensure the accuracy of the content, we do not guarantee the completeness or accuracy of the information. We assume no responsibility for any damages arising from the use of this site.

Daily experiments and code are available on my GitHub repository (nmr-qc-project)
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* All images in this article were generated by Gemini.