With the development of artificial intelligence, virtual reality, etc., the amount of data to be processed is increasing, but the limits of integrated circuits are approaching. So instead of gates made of transistors, quantum computers that use the principles of quantum mechanics as their operational rules are emerging as an alternative. What exactly is quantum, and how can it be an alternative? A reporter who has no connection with science takes a close look at everything from quantum to the recently popular quantum computer with a learning mind.


Richard Feynman said this at a computational physics conference hosted by IBM and MIT in May 1981:

“The world we live in is not classical, it is quantum. Therefore, to simulate this world, we need quantum mechanics.”

That's right. When classical mechanics established by Isaac Newton failed to explain the atomic world, quantum mechanics was born, and physicists discovered through quantum mechanics that this world is quantum. The reason why quantum computers are needed is because the world we live in is not classical but quantum.


The power of quantum computers
Why can't you sleep when you drink a beverage containing caffeine? Scientists still don't know why. It's because they can't analyze the caffeine molecule, and to analyze it with a current computer, you need ¹⁰⁴⁸ bits. In contrast, a quantum computer needs 160 qubits.

As the number of qubits increases, their processing power doubles. As the number of qubits increases, the performance increases by a factor of two. 50 qubits provide ²⁵⁰ times the performance of 1 qubit.
A quantum computer is a computer that can compute multiple pieces of information simultaneously by utilizing quantum mechanical phenomena such as quantum superposition and entanglement. It is an ultra-high-speed, large-capacity computing technology optimized for specific operations.

Based on parallel processing capabilities, it boasts computational performance that is incomparably superior to that of existing computers, and it is expected to have a significant impact on existing industries based on this.


When will quantum computers become commercially available?
So when will quantum computers become fully commercially available?

There are already computers on the market that claim to be quantum computers. Of course, the price of that computer, the D-Wave 2000Q, is 15 million dollars, or 16.6 billion won in Korean currency.

Canada's D-Wave Systems is credited with being the first company to build a quantum computer.
In 2011, Canada's D-Wave Systems developed the 128-qubit quantum computer, the D-Wave 1. The following year, it released the 512-qubit D-Wave 2, followed by the 1,152-qubit D-Wave 2X in 2015 and the 2,048-qubit D-Wave 2000Q in 2017.

But if 160 qubits can reveal the structure of molecules, why can't we explain why coffee doesn't make us sleepy even though quantum computers with over 2,000 qubits exist? That's because D-Wave's computer is different from the quantum computers that are generally talked about.


D-Wave's computer observes quantum annealing
D-Wave is a "special-purpose computer" built to observe quantum annealing, a far cry from a general-purpose quantum computer that uses quantum gates.

D-Wave solves only optimization problems. An optimization problem is finding the best conditions. When the degree of badness is called the 'badness index', the optimization problem is to find the condition for minimizing the badness index.

In order to find the lowest point in a specific area of ^10km2 , we have to measure the elevation above sea level one by one. But how can we prove that the lowest point is the lowest point when we find the lowest point? When we consider the elevation above sea level of each point as a badness index, this problem becomes an optimization problem.

Here's how to solve an optimization problem. First, jump around quickly to find the lowest point. High speed means high temperature. Temperature is the average kinetic energy of many particles. When the particles move quickly as a whole, the momentum is high. This movement is random. They don't all move in one direction. If they move randomly, they can find the lowest point and pass, but they don't stay at a point that is slightly shallower than the surroundings.

If you gradually lower the temperature here, the shallow part will be passed over and the probability of being near the much deeper part increases. This is called annealing because the temperature is gradually lowered to find the lowest point.
D-Wave uses the tunneling phenomenon to speed up this process. In quantum mechanics, tunneling is the phenomenon in which nucleons constituting the nucleus probabilistically escape from the atom even at an energy state lower than the potential well of the nuclear force that binds it.

When solving the above optimization problem, it is possible to move from one location to another location at a similar depth at once by utilizing the tunneling phenomenon. This allows the problem to be solved quickly.


Is D-Wave's computer a true quantum computer?
There has been much debate over whether D-Wave is a true quantum computer.

In 2014, a research team led by Matthias Troyer of ETH Zurich in Switzerland had a D-Wave and a regular computer solve specific computational problems and compared them by measuring how much the problem-solving time increased as the size of the computational problem increased.

The research team said in the abstract that they found no evidence of a breakthrough in computational speed that would be seen on quantum computers. The research team reported that in several computational comparisons, in some problem-solving cases, the D-Wave showed computational speed performance that was several times faster, but in other problem-solving cases, a general computer showed much higher performance.
Meanwhile, in 2016, Google reported that its D-Wave 2X had achieved 100 million times the speed of conventional computers using the same algorithm, and in 2017, D-Wave claimed that its D-Wave 2000Q had achieved 2,600 times the speed of the fastest conventional computer.

Nowadays, everyone recognizes that D-Wave's computer is a computer that can perform quantum annealing. Since quantum annealing can only solve certain problems and cannot perform general calculations, it is not what we usually call a quantum computer. It is just another type of computer that utilizes quantum phenomena. Of course, it is still true that D-Wave is an extraordinary computer.

Also, major countries such as the US, Europe, China, and Japan are actively supporting the development of quantum computers. Global companies such as IBM, Google, Microsoft, and Intel are also sparing no effort in investing in the development of quantum computers. And no one can deny that D-Wave was the one who started it all.


The growing interest in quantum computers
Gartner selected quantum computing as the last of the 10 ICT trends that companies should pay attention to in 2019.
“CIOs and IT leaders should plan for quantum computing, learn about the technology while it is still emerging, identify real-world problems where quantum computing has potential, and consider the security implications,” said David Cearley, vice president at Gartner.

“Most organizations should be learning about and monitoring quantum computing by 2022,” he said, adding that “quantum computing won’t be viable until 2023 or 2025.”

As interest in quantum computers grows, one of the most active companies in quantum computing is IBM. IBM hosted the May 1981 Computational Physics Conference, the conference where Richard Feynman proposed quantum computers.

The following article will discuss IBM's quantum computer development history and quantum computer policy.

References - Kim Sang-wook's Quantum Study, Science Books, 2017.