Quantum computers are said to change society as the "next-generation computer."
With its computing power that is orders of magnitude higher than that of conventional computers, it is expected to solve various problems such as the development of new drugs and forecasting financial markets.
What is different from conventional computers? We will explain how it works and the challenges for practical application.
Japan's first quantum computer in full-scale operation
The "quanta" of quantum computers are extremely small materials such as light particles and electrons, and it is said that ultra-high-speed calculations are possible by applying physical phenomena that occur in this "quantum" world.
RIKEN developed the first domestically produced machine and started a service available to researchers on the 27th.
RIKEN Director Yasunobu Nakamura
It was developed by a research group consisting of Yasunobu Nakamura, director of RIKEN, a leading Japan expert in quantum computer research, and domestic companies.
Director Nakamura commented on the significance of the development, saying, "The realization of a large-scale quantum computer is a challenging issue, and it is a technology that still has high hurdles even from a global perspective.
The first RIKEN unit began full-scale operation on the 27th. For the time being, we would like researchers from universities and companies with which we have signed contracts to conduct joint research to use the system, and accelerate further improvements and related software development.
What makes ultra-fast computation possible?
How are quantum computers different from conventional computers such as supercomputers? I will explain how it works.
First, a traditional computer.
When the computer performs calculations, it replaces it with an electrical switch.
At this time, there are two choices: to conduct current or not.
All information is represented by "0" or "1" and processed in this combination. This state is "bit" and is the basic unit.
In practice, the calculation is as follows:
For example, in the case of 3 digits, there are 000 combinations of "001", "010", "011", "100", "101", "110", "111", and "8".
For this reason, a conventional computer requires a total of eight processes.
On the other hand, it is the case with quantum computers.
In the quantum world, there is a special physical phenomenon called "superposition" that is both "0" and "1", which is "qubit".
By applying this "superposition", the process that required eight processes with conventional computers has been reduced to just one.
This mechanism makes it possible to perform ultra-fast calculations.
In the case of a quantum computer developed by RIKEN, there are 64 "qubits" arranged in a grid shape in an integrated circuit, which is the brain, and it means that information "2 to the power of 64" can be expressed at the same time by "superposition".
It has the potential to reduce the number of calculations compared to conventional computers that repeat calculations at high speed, and depending on the target of the calculation, it is expected to be able to solve problems at an order of magnitude faster speed than supercomputers.
Intensifying competition for practical application
Concepts and prototype ideas for quantum computers were proposed in the 1980s, and in 1994, American researchers discovered a calculation method that can use quantum computers to factorize huge numbers used in cryptography at high speed, which attracted attention.
In Japan, Director Yasunobu Nakamura, who leads a team at RIKEN, succeeded in creating the world's first "qubit" as an electric circuit in 1999.
By being able to handle "qubits" in the same way as conventional electrical circuits, research and development of quantum computers has accelerated, and IT giants such as Google and IBM are now leading the world in the development race with the aim of practical use using similar "qubits".
In Japan, the University of Tokyo, Osaka University, and the National Institutes of Natural Sciences have also devised "qubits" with different mechanisms and are conducting research and development.
Noise and temperature and technical barriers
Quantum computers are being developed around the world.
The "superposition" of "qubits" makes ultra-high-speed calculations possible, but the biggest challenge for practical application is that this state is extremely vulnerable to "noise" such as electromagnetic waves and heat, and whether accurate calculations can be performed depends greatly on the surrounding environment.
In the case of RIKEN's quantum computer, an integrated circuit consisting of "qubits" covers it with multiple layers of cylindrical containers to block "noise" and keeps it close to 273 degrees below zero, which is called "absolute zero."
However, "noise" can also be caused by cables that read electrical signals from "qubits" and impurities in circuits, which can lead to malfunctions.
Therefore, a mechanism for "error correction" has been devised to detect errors due to malfunctions in advance and calculate them while correcting them.
If there is only one qubit, it is theoretically thought that 1,1 times that number of qubits is required to reliably perform error correction.
IBM, which completed a 433-qubit quantum computer last year, plans to develop 1121,100 qubits, but it will need at least <> million qubits to put it into practical use.
In order to increase the number of "qubits" that affect the computing power of quantum computers, not only a large number of communication cables that control and read signals according to the number of qubits, but also large refrigerators that maintain an environment close to "absolute zero" are required.
Quantum computers have the potential to solve specific problems in various fields of society, such as drug discovery, finance, and material development, but the key to enabling ultra-high-speed computation is whether they can overcome these issues, and it is attracting attention whether they can achieve further evolution.
Chief Cabinet Secretary Matsuno: "A big step"
Chief Cabinet Secretary Matsuno said at a press conference on the afternoon of March 27, "Competition for the development of quantum computers is intensifying internationally, and the first domestically produced quantum computer is a major step toward practical application in Japan. Since October last year, the government has been considering a new strategy to present policies and action plans for the practical application and industrialization of quantum technology, and will steadily advance these strategies."