Researchers at the Kohei Itoh Group in Keio University are working to create the ultimate silicon computer, which does calculations using individual silicon atoms.
The brain of a computer is made from silicon semiconductor integrated circuits, or silicon chips. In the semiconductor industry, to make silicon chips run faster and consume less power, people have worked to increase circuit integration. This trend is known as Moore's Law. However, if Moore's Law is pursued, by 2025, we will have reached the stage where a single silicon atom stores a one or a zero to do calculations in binary.
Q. Because computers calculate using ones and zeros, computing is done just by switching currents on and off. The shorter the distance the current flows, the faster computing can be done, and lower power consumption can also be achieved. At present, currents are switched in areas consisting of about 200 atoms. But it is predicted that in 2020-2030, switching on and off will be done in areas the size of a single atom. Our research began with the question of whether computing can be done with individual atoms.
There are three isotopes of silicon, Si-28, Si-29, and Si-30, where the number of neutrons in the silicon atom is 14, 15, and 16. Among the three isotopes, only Si-29 has a nuclear spin, making it magnetic. In 2002, the Itoh Group suggested a method of computing using Si-29 magnets placed on a silicon wafer made of Si-28, which is not magnetic. By counting zero if the Si-29 magnet points upward and one if it points downward, computing can be performed using individual silicon atoms.
Q. Computing with individual atoms is truly the cutting edge of nanotechnology. So we are trying to do the ultimate in nanotech. To read the individual magnets, we have to develop extremely sensitive instruments. So we've started this research by developing equipment. The world of individual atoms is very different from the world that normally surrounds us, where Newtons Law describes behavior of motion. At the level of individual atoms, the world of quantum mechanics pioneered by people like Einstein emerges, where each atom can carry both one and zero simultaneously. That's the most difficult thing to grasp. Ordinarily, we would have one or zero, but here, we can have one and zero at the same time. We try to control quantum mechanics. Ultimately, we may even be able to make new discoveries in quantum mechanics.
A device for computing with individual silicon atoms, which are dominated by quantum mechanics, will be an entirely new kind of computer, called a quantum computer. This is what the Itoh Group is pursuing to develop.
To achieve a silicon quantum computer, the Itoh Group is studying various topics. The first is the ultimate in nanotechnology, for arranging the individual atoms. Then quantum physics research to align all the magnets in the same direction, and quantum operation technology for freely manipulating the orientation of each atomic magnet, which corresponds to calculation. The Itoh Group is also developing measurement technology to detect the orientation of each magnet after a calculation.
