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Quantum Computing Closer To Reality

August 11, 2011

Physicists at the National Institute of Standards and Technology (NIST) have discovered that the quantum properties of ions can be manipulated using microwaves, instead of lasers.

Using microwaves enables the experiments to be made with a system that is one-tenth the size of conventional laser based systems. Compared to the laser sources, microwave components could be expanded to build practical quantum computing systems using thousands of ions for quantum computing and simulations.

Microwaves have been used in past experiments to manipulate single ions, but the NIST group is the first to position microwave sources close enough to the ions and create the conditions enabling the quantum phenomenon.

Dietrich Liebfried, a coauthor of the paper, says, “It’s conceivable a modest-sized quantum computer could eventually look like a smart phone combined with a laser pointer-like device, while sophisticated machines might have an overall footprint comparable to a regular desktop PC.”

Digital computers use what is known as a binary system, each bit is either a one or zero. The quantum computer manipulates the ion, which can be imagined to be a tiny bar magnet, to exploit a weird discovery of particle physics, superposition or entanglement. In superposition the quantum bit (qubit) can be positioned as a one, or zero, or one and zero simultaneously.

This system increases the potential computing power to help solve many number intensive computing problems such as running climate-change models and breaking encrypted codes.

The use of microwaves reduces errors that are introduced with laser beams, but microwave operations need to be improved to enable practical quantum computations. The NIST researchers achieved entanglement 76 percent of the time, as opposed to laser based systems that reach entanglement 99.3 percent of the time.

The researchers published their study in the August 11 issue of Nature.

Image Caption: Composite photo of microwave apparatus used in NIST quantum computing experiments. A pair of ions (electrically charged atoms) are trapped by electric fields and manipulated with microwaves inside a glass chamber at the center of the apparatus. The chamber is illuminated by a green light-emitting diode for visual effect. An ultraviolet laser beam used to cool the ions and detect their quantum state is colorized to appear blue. Credit: Y. Colombe/NIST

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