A calculation that requires 10,000 years with a cutting-edge supercomputer was achieved in only 200 seconds by a quantum computer---. This surprising news made headlines around the world in October 2019. This is a dream computer that holds promise for applications such as climate change simulation and new drug development. This technology is expected to markedly increase human potential. However, Professor Takashi Yamamoto, specializing in quantum information and quantum optics at Osaka University’s Graduate School of Engineering Science, warns: “If a universal quantum computer becomes available, the greatest challenge will be protecting the confidentiality of communication. People in the modern age believe that the flow and exchange of important information through the Internet poses no problems because the information is provided in an encrypted form. However, in the future, people may see that raw information that is easy to decode is flowing through the Internet.” This resembles the password for a cash card being written on a postcard. So how can we secure communication? The answer is “a quantum network as a countermeasure against quantum computers,” according to Professor Yamamoto. What is the secret of controlling quantum with quantum?

To many people, computers in the current age appear to be able to do just about anything.“Artificial intelligence (AI)” is expected to make self-driving cars more precise and safer than human drivers in the near future. In the field of games, such as Shogi, Go and chess, computer programs stronger than human players have been introduced. Even a complicated calculation that cannot be completed by a human dedicating their entire life can be finished instantaneously with the use of a laptop computer. However, from a wider point of view encompassing outer space, mysteries that cannot be resolved will remain in an unlimited number despite advancements in the current type of computers. In this context, there is a growing expectation of quantum computers as a “supercomputer” of the near future. Professor Keisuke Fujii (Osaka University Graduate School of Engineering Science), who is one of the front-line researchers in this field, was asked about the current position and future perspectives for quantum computers.

“Quantum computers” are now held to progressively increasing expectations as a device capable of instantaneously solving the questions that cannot be solved by the latest supercomputer even when it is applied for many years. After entry into the 21st century, many breakthroughs have been achieved in this field, including even “verification of quantum supremacy” (surpassing the supercomputers in terms of calculation speed in some specific applications). At present, particularly close attention is being paid to the “superconducting” quantum computing system adopted by Google (USA) and some other developers, whereas other systems, such as “ion trapping” and “photons”, are also viewed as promising, and research results have been accumulated on these systems. Specially Appointed Associate Professor Kenji Toyoda, Center for Quantum Information and Quantum Biology, Osaka University (hereafter referred to as “Associate Prof. Toyoda”) is one of the leading researchers in the field of ion trap-based information processing. The path leading to the truth of nature is not confined to a single path. Associate Prof. Toyoda was asked about the current status of ion trap and its future perspectives.

The global competition over space development, represented by the Apollo Program, stimulated the creation of numerous advanced technologies. Resembling such a course of technological development, the technologies cultivated through the efforts for the development of quantum computers will benefit mankind in numerous aspects. The technology for increasing the sensitivity of magnetic resonance imaging (MRI), an imaging modality now commonly used during healthcare, is one such example. Japan is said to lead the world in terms of the percentage of medical facilities equipped with an MRI apparatus designed to take images of deep areas of the human body such as the brain, blood vessels and organs. It has been playing a significant role in diagnosis at many hospitals. With MRI, electromagnetic waves are applied to the water molecules of the body and the weak signals returning from the hydrogen atoms are analyzed. Nuclear magnetic resonance (NMR) actively used for chemical analysis also functions under the same principle. With the conventional apparatus for MRI, however, the sensitivity is not high because the signals emitted from the atomic nucleus are weak. At the Center for Quantum Information and Quantum Biology, Osaka University (QIQB), Specially Appointed Associate Professor (Full-time) Makoto Negoro (hereafter called “Associate Professor Negoro”) and his colleagues succeeded in increasing the signal intensity by approximately 10,000-times at room temperature, thus cultivating a path for the development of next-generation MRI technology. Associate Professor Negoro expresses his anticipation, saying: “This will enable real-time assessment of the metabolic status, showing which parts of the body are being favorably affected by a given drug and how such efficacy is manifested. This is sure to significantly change healthcare.” The technology used for this kind of MRI has markedly advanced during the course of quantum computer development. The technology for precise control of the quantum state is called “Quantum Technology 2.0”, and it has a broad-range potential of application to quantum simulation, quantum communications and quantum sensing.

The term “quantum computer” used in the context of “When will a quantum computer be realized?” often refers to an “all-purpose (almighty)” quantum computer with an ultra-high calculational capability that possesses the function of self-correcting errors in calculation results, which are also seen with the existing computers we routinely use at present. Now, the competition over research and development of quantum computers is intensifying worldwide. However, an additional two or three decades are estimated before a complete form of a quantum computer becomes available. If you now feel “I see. That is a dream story,” you are the very person for whom I recommend reading this article until the end. In around 5 years from now, it will be possible to utilize the amazing calculational capability expected of quantum computers in “some fields” before a complete form becomes available. Application of such a capability to the field of quantum chemistry is particularly attractive because of its large impact on the market and the availability of the research results accumulated over the past 90 years. “Chemistry”, which pertains to pharmaceutical and other industrial products, metabolism inside the living body, etc. is closely related to our daily life. There is a large demand for calculations for the prediction of complex chemical reactions and many mechanisms of chemical reactions remain unclarified even with the supercomputers currently available. Then, how can we utilize the power of an uncompleted quantum computer? This question will be answered by Specially Appointed Associate Professor (Full-time) Wataru Mizukami, Center for Quantum Information and Quantum Biology, Osaka University (QIQB), who is actively engaged in the development of new algorithms for computational chemistry (hereafter referred to as “Associate Prof. Mizukami”). The birth of an “ultimate microscope” enabling visualization of macroscopically invisible chemical reactions with a quantum computer is near.