Communications of the ACM
Tossing a Coin in the Microcosm
The demonstration of the quantum walk is an important step toward the development of quantum computers, says Dr. Artur Widera from the Bonn Institute of Applied Physics.
Credit: Institute of Applied Physics
Physicists at the University of Bonn say they have demonstrated for the first time the "quantum walk" effect in an experiment with cesium. At the microscopic level, the phenomenon of superposition allows atoms to maintain several quantum mechanical states simultaneously, which means that an atomic "coin" can be heads and tails at the same time. The physicists held a single cesium atom with lasers, and then pulled the atom in two opposite directions, with the "heads" part being pulled to the right and the "tails" part to the left. Following that, the researchers once more placed each of both atomic components into a heads/tails superposition state. The repetition of this procedure eventually leads to the cesium atom being distributed everywhere, and only when one measures the atom's position does it "decide" where it wants to turn up because of the quantum mechanical property of interference, in which two parts of the atom are able to reinforce themselves or cancel each other out. This quantum walk can be executed numerous times, producing a curve that mirrors the atom's likelihood of presence.
Artur Widera from the Bonn Institute of Applied Physics says that his team's demonstration of the quantum walk is an important step toward the development of quantum computers. "With the effect we have demonstrated, entirely new algorithms can be implemented," he says.
From Bonn University
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