Quantum computers a step closer to reality

Physicists have brought quantum computers - which could solve problems too complex for today's most advanced machines - a step closer to reality by successfully stopping light in a new experiment.
Lead researcher Jesse Everett from Australian National University (ANU) said controlling the movement of light was critical to developing future quantum computers.
"Optical quantum computing is still a long way off, but our successful experiment to stop light gets us further along the road," said Everett.
He said quantum computers based on particles of light - photons - could connect easily with communication technology such as optic fibres and have potential applications in fields such as medicine, defence, telecommunications and financial services.

The research team's experiment - which created a light trap by shining infrared lasers into ultra-cold atomic vapour - was inspired by Everett's discovery of the potential to stop light in a computer simulation.
"It's clear that the light is trapped, there are photons circulating around the atoms," Everett said.

"The atoms absorbed some of the trapped light, but a substantial proportion of the photons were frozen inside the atomic cloud," he said.
Everett likened the team's experiment to a scene from Star Wars: The Force Awakens when the character Kylo Ren used the Force to stop a laser blast mid-air.

"It's pretty amazing to look at a sci-fi movie and say we actually did something that's a bit like that," he said.
Associate Professor Ben Buchler, who leads the ANU research team, said the light-trap experiment demonstrated incredible control of a very complex system.
"Our method allows us to manipulate the interaction of light and atoms with great precision," said Buchler.
Co-researcher Geoff Campbell from ANU said photons mostly passed by each other at the speed of light without any interactions, while atoms interacted with each other readily.
"Corralling a crowd of photons in a cloud of ultra-cold atoms creates more opportunities for them to interact," said Campbell.

"We're working towards a single photon changing the phase of a second photon. We could use that process to make a quantum logic gate, the building block of a quantum computer," he said.
The research was published in the journal Nature Physics.