Quantum Mechanics used in new computers

Aug 12, 2005

In 1945 the chairman of IBM said he saw a global market of four to five computers. In 2002 more than 45 million computers were sold in the US. Components for computers continue to shrink in size, and experts predict that by 2030 computer circuits will be measured on an atomic scale. On this scale scientists suggest using the physical properties of small particles, known as quantum mechanics, to do calculations.

Albert Einstein once described quantum mechanics, the physics of small particles, as spooky. The properties of quantum particles often contradict high school physics and cannot be fully explained by modern physicists. Nonetheless, scientists are beginning to harness these properties to develop a new level of computing, known as quantum computing.

Two properties of quantum mechanics are used.

In modern electronics information is encoded as a series of ones and zeroes. Each 1 or 0 is known as a bit. For a quantum computer the equivalent is a qubit, but at the quantum level a qubit can be one, zero, or a combination of both. Quantum particles can be in several states at the same time, known as superposition. This allows a computer to perform calculations simultaneously as if the qubit were at once both 1 and 0. Ohio State University physics professor Greg Lafyatis explains another property harnessed in quantum computing.

Lafyatis says, "The other feature is called entanglement, and entanglement is something that disturbed Albert Einstein to his grave, but it's a very, very bizarre feature of quantum mechanics where objects at a distance are somehow linked to one another in ways that we can't say we really understand, but ways that at least can be exploited to do certain calculations."

For two entangled particles a change in one instantaneously provides information about the state of the other. In this way information can be passed between qubits, regardless of distance, in an instant.

Currently, scientists are working to both build a functioning quantum computer and to develop uses for the completed machine.

Lafyatis' research focuses on building a device known as an atom trap. Quantum particles readily interact with the surrounding universe, and for quantum computing qubits need to be isolated. Lafyatis is working to trap and isolate over ten thousand Rubidium atoms on a small circular chip.

This feat is accomplished with lasers. Since lasers are beams of light they travel in a wave shape. Crossing two lasers creates an intersection of waves that results in a field of light that looks like an egg carton. Each small valley can hold and isolate a single atom.

Currently, Lafyatis is trying to place the Rubidium atoms in these valleys. Solid Rubidium is heated to form a gas, with each atom traveling at near the speed of sound in many directions. Using lasers once more, the atoms are slowed to the speed of a meandering beetle and contained in a vacuum. Graduate student Rajani Ayachitula describes the final collection of atoms as a pale ball of translucent red hovering in the vacuum chamber. Lafyatis and his team are working at moving this ball over the chip and placing the atoms into the valleys of light.

Lafyatis says the work is difficult and developing a working quantum computer will take many decades. He also says they will not be common.

Lafyatis says, "The one thing I want to make clear about quantum computing is basically, it's not going to replace your PC, I mean, what it can do is it can solve certain very, very special problems, and as time goes by it will probably be able to solve more and more and more important problems, but I don't want to give the impression that twenty years from now or fifty years from now that they'll just throw out regular computers and everyone will be using quantum ones."

The problems quantum computers will be used to solve will be the design of complex new materials that rely on quantum properties as well as the modeling of complex systems in nature. Experts add that a working quantum computer will be able to defeat modern codes that protect information and communications.

Ayachitula says the final goal of a working quantum computer is not the only reason to attempt the project. She says the process of learning to work with quantum mechanics provides deeper insights into a field that is anything but intuitive.