News in Science

Physicists create light out of nothing

Spooky science Scientists have used the spooky properties of quantum physics to create light out of empty space.

Researchers including Professor Tim Duty from the University of New South Wales in Sydney, used a strange phenomenon called the dynamical Casimir effect to force a mirror to make its own light rather than simply reflecting the light around it.

The study reported in the journal Nature uses the weird science of quantum fluctuations in which virtual sub-atomic elementary particle pairs continuously pop in and out of existence in a vacuum.

"Understanding vacuum fluctuations will help scientists researching physics raging from gravity waves to the evaporation of black holes," says Duty.

Duty and colleagues were able to scatter half of the virtual particle pairs before the particles could reconnect and pop out of existence, forcing them to become real.

"That's where the dynamical Casimir effect comes in allowing scientists to generate a virtual photon particle," says Duty.

Faster than the speed of light

To achieve the effect, the mirror needs to be moving close to the speed of light, 300,000 kilometres per second in a vacuum.

"In practical terms that's impossible because it would take the output of a nuclear power plant to accelerate a mirror to such high velocities," says Duty.

"So instead, we used a tiny microcircuit called a superconducting quantum interference device, or SQUID".

"It acts as a tuneable electronic mirror for virtual microwave photons, causing some to be scattered in the real world before they can disappear again," he explains.

Duty and colleagues found the mirror then started radiating its own photons in microwaves.

"It's a bit like shaking a sealed black box really hard, opening it and suddenly a flash of light comes out".

"The real photons produced in the experiment collectively retain a peculiar quantum signature that ordinary light lacks."

"We measure strange correlations in the microwaves and found waves at one frequency correlate to waves at another frequency. And that doesn't normally happen for classical microwaves," says Duty.

The static Casimir effect

Duty says the experiment builds on the static Casimir effect which describes a force generated when virtual particles are squeezed out as two light-impenetrable boundaries — such as mirrors or metal plates — are brought closer and closer together.

"Eventually this restricts the ability of some quantum fluctuation particles to pop into the space between the mirrors. However because there's no restriction on virtual particles popping in and out of existence beyond the mirror boundary, they generate force pushing the two mirrors together."

While the static Casimir effect does this in the three dimensions of space, the dynamical Casimir effect does it in the dimension of time.