'Funky effects' of quantum theory could lead to efficient computing

Washington, Feb 17 : Quantum mechanics can offer a way to exceed limits in speed, efficiency and accuracy of computing, communications and measurement, according to a new study. Quantum mechanics is the set of physical theories that explain the behaviour of matter and energy at the scale of atoms and subatomic particles. It includes a number of strange properties that differ significantly from the way things work at sizes that people can observe directly, which are governed by classical physics.

"There are limits, if you think classically," said lead researcher Seth Lloyd, a professor in MIT's Research Laboratory of Electronics and Department of Mechanical Engineering. But while classical physics imposes limits that are already starting to restrict things like computer chip development and precision measuring systems, "once you think quantum mechanically you can start to surpass those limits," he added.

"Over the last decade, a bunch of my colleagues and postdocs and I have been looking at how quantum mechanics can make things better," he said.
What Lloyd refers to as the "funky effects" of quantum theory, such as squeezing and entanglement, could ultimately be harnessed to make measurements of time and distance more precise and computers more efficient.

"Once you open your eyes to the quantum world, you see a whole lot of things you simply cannot do classically," he said. Among the ways that these quantum effects are beginning to be harnessed in the lab, he said, is in prototypes of new imaging systems that can precisely track the time of arrival of individual photons, the basic particles of light. "There's significantly greater accuracy in the time-of-arrival measurement than what one would expect," he said.

Lloyd said that this could eventually lead to systems that can sense finer detail, for example in a microscope's view of a minuscule object, than what were thought to be the ultimate physical limitations of optical systems set by the dimensions of wavelengths of light.

In addition, quantum effects could be used to make much-more-efficient memory chips for computers, by drastically reducing the number of transistors that need to be used each time data is stored or retrieved in a random-access memory location. Lloyd and his collaborators devised an entirely new way of addressing memory locations, using quantum principles, which they call a "bucket brigade" system.

Another example of the potential power of quantum effects, he said, is in making more accurate clocks, using the property of entanglement, in which two separate particles can instantaneously affect each other's characteristics. Lloyd presented his study at the American Association for the Advancement of Science annual meeting in Boston.

ANI