Quantum theory, discovered more than 100 years ago, has changed the rules of the game. It seems to be a disaster and also a boon. In this article, I would like to introduce this rarely known game changer that transformed classic into modern, analog into digital, and certainty into uncertainty. Few people notice that quantum appears everywhere, not only in the field of science, but also in a context closely related to technology, thus contributing to our modern world. Let's take a look at the amazing quantum world. By the time Max Plank discovered light quanta in 1900, modern quantum physics had begun. A few years later, Niels Bohr discovered the quantum leap and gave birth to quantum theory. Quantum theory creates a completely mysterious world, redefining our understanding of reality. It seems to be a disaster that classical physics is completely wrong. No one can predict where a quantum will go before taking an action based on the uncertainty principle. This leads to a contrast with what we believed in classical physics. (Davies, 1982) Fortunately, this inte...