The computer of the future that overcomes the limitations of existing computing technology.
The revolutionary changes brought about by quantum computers have already begun!

A quantum computer is a new, innovative computing system that processes information using the principles of quantum mechanics. It uses qubits instead of the 0 and 1 bits of conventional computers, and is based on superposition and entanglement, which allow qubits to exist in both 0 and 1 states simultaneously.
Quantum computers can use superposition states to calculate multiple cases simultaneously, and entangled states can dramatically increase computational speed.
This book explores what quantum computers are, how they work, and how they will change our lives.
Furthermore, it shows that quantum computers have the potential to bring about revolutionary changes in cryptography, drug development (e.g., Google's Sycamore), and artificial intelligence.

In this book, we will explore these future technologies together.
I'm not going to teach you quantum theory.
You won't even learn how to solve the Schrödinger equation.
...
I'll tell you about the latest, most exciting, and most unexpected discoveries—things already in use, things that may never see the light of day, and, most importantly, the ones I think will truly transform our daily lives tomorrow.
--- p.9-10 "Prologue: The Second Revolution?"

Without us even realizing it, the quantum revolution has already shaken up our understanding of time and space.
Not only do our smartphones adjust their time to Coordinated Universal Time, measured by atomic clocks in laboratories, but GPS also measures our location based on quantum experiments conducted inside satellites.
Beyond these applications, these watches could also find use in an even more unexpected field: geophysics.
To understand this, we need to go through general relativity! --- p.34 "What time is it now?"

Until now, experiments have been nothing more than technical devices for observing nature.
Experiments are no longer content to simply measure phenomena; they are now creating unprecedented phenomena.
This is the essence of the second quantum revolution.
In the first step, physicists create a phenomenon in the laboratory and observe it closely.
Then use it for other purposes.
They create interference and use it to invent accelerometers.
We create an entanglement and use it to encrypt messages.
We create superpositions and use them to design computers.
--- p.53 "Atoms on the Top of Mount Etna"

Quantum computers are a challenge to the mass adoption of quantum technology, perhaps the ultimate challenge.
It is based on the most abstract theories and the most cutting-edge technologies.
What's worse is that it carries all the illusions with it.
It attracts and captivates the most adventurous and daring investors in the high-tech world.
But it also gives me fear.
--- p.71 "Draw a Quantum Computer"

Any discussion of the future of quantum computing requires a serious consideration of the error problem.
There are so many errors, such as 'gate errors', 'phase errors', and 'bit errors'.
Where do these errors come from? Which errors are the most serious? How can we fix them? Let's start by explaining what these errors are specifically.
--- p.144 "Bugs"

Of all the qubits studied to date, there is no guarantee that any type will be successfully scaled in the future.
Each has serious problems, and those who invest time and resources in them are taking a real risk.
But nothing is as dangerous as topological qubits.
Topological qubits are perhaps the most adventurous challenge of this second quantum revolution.
--- p.180 "Outsiders"

Quantum computers could spark small revolutions in unexpected places.
It is the agricultural sector.
Currently, nitrogen fertilizer is one of the major energy costs our society pays to support our population.
To produce this fertilizer, nitrogen must be converted into ammonia.
This chemical reaction requires a reactor at temperatures exceeding 400°C, consumes 1-2% of the world's energy, and emits an equivalent amount of CO2 into the atmosphere.
This is a disaster.
Fortunately, a simple protein, nitrogenase, can perform the same task without the need to heat the nitrogen.
If quantum computers could decipher how it works, and factories could replicate it, polluting reactors would be no longer needed!

--- p.207 "A real simulator, not a game"