October 17, 2012

Quantum Physics’ Latest Parlor Trick

Ian Armas Foster

On July 4 of this year, physicists and journalists celebrated the finding of the elusive Higgs boson, a particle to verify the standard model of subatomic particles. And yet, this last week the Nobel Prize in Physics was awarded to Frenchman Serge Haroche and American David Wineland for a discovery that received relatively little fanfare, but may prove significantly more practical in paving the way for quantum computers.

Quantum computers could drastically change the world of HPC. While today’s high performance systems often attempt to simulate similar kinds of computing through parallel processing, it would come naturally to quantum computers.

The difference between today’s computers and a quantum computer is best exemplified by finding the most efficient route for a salesman to travel to all the places he needs to visit. Today’s computers would calculate the efficiency of each route individually and then compare the routes to find the result. Quantum computers, on the other hand, would be able to traverse each route simultaneously.

The bizarre realm of quantum physics allows tiny particles such as electrons and photons to essentially be in two places at once. This enables quantized bits to naturally process in parallel by contributing to multiple tasks at the same time.

Further, the quantum bits (or qubits) that would comprise a quantum machine’s computing power would be smaller than electronic bits such that, if a method is found to encapsulate them and keep them from interacting with their surroundings, the resulting bit density would far surpass that of today’s computers.

However, the principle seemed more theoretically interesting than experimentally determinable. The problem with utilizing quantized particles as bits is that the quantum properties are easily lost. Observing a particle’s quantum state destroys the effect, as does allowing the particle to interact with the external realm.

As the Nobel committee put it, “Single particles are not easily isolated from their surrounding environment, and they lose their mysterious quantum properties as soon as they interact with the outside world.”

That is, until Haroche and Wineland developed novel methods, which the Nobel committee noted were analogous to parlor tricks — Wineland using light particles (photons) to control particles of matter (electrons), and Haroche employing the reverse method. In a game-changing experiment, Wineland hit an atom with laser light and observed the atom at two different places a distance of 80 nanometers apart.

The techniques allowed the researchers to control photons and electrons in ways that were never thought possible. Per the Nobel committee, “Haroche and Wineland, together with their research groups, have managed to measure and control very fragile quantum states, which were previously thought inaccessible for direct observation. The new methods allow them to examine, control and count the particles.”

There, of course, remains a lot of work to be done. But being able to “examine, control, and count” electrons and photons represents a significant step in manipulating their quantum states for computing purposes.

The result would be dramatic. According to the Royal Swedish Academy of Sciences, “Perhaps the quantum computer will change our everyday lives in this century in the same radical way as the classical computer did in the last century.”

As exciting as the discovery and resulting Nobel prize is, Wineland urges cautious optimism. “I wouldn’t recommend anybody buy stock in a quantum computing company,” Wineland said before noting that it might be possible to eventually build one.