The CPU, or central processing unit in computers we use today, is made of semiconductors that carry out computations through "On" and "Off" electric signals, but there are limits to the improvements that can be made to this method of computation. Computers of the future are likely to make use of the quantum-mechanical properties of materials, or, in other words, the behavior of particles such as atoms and molecules. Such computers are known as quantum computers, and optical computers are considered to be one of them. Optical computers would process data at ultrahigh-speed, making use of the way light particles (photons) spin to the left or right.