The discovery of a new way of storing and "echoing" pulses of light is likely to help usher in future long-distance communication systems protected by high-security quantum cryptography.
The research, which has just been published in the prestigious journal Nature, was undertaken by a team of scientists based at the ARC Centre of Excellence in Quantum-Atom Optics at the Australian National University in Canberra.
It was led by Prof Ping Koy Lam.
Dr Jevon Longdell, a physicist at the University of Otago's Jack Dodd Centre for Quantum Technology, is a member of the team.
The scientists demonstrated how photon echoes could be used to create a quantum memory device, with pulses of light captured, stored and released on demand.
Bursts of laser light and a cloud of atoms work as a flexible optical memory.
Such a device would be an important part of a quantum repeater, which could extend the range of secure quantum communication, scientists said.
Quantum cryptography uses photons, which are individual particles of light, and their intrinsic quantum properties to develop an unbreakable coding system.
The approach uses the principles of quantum physics and is regarded as even more secure than current mathematically-based codes.
A quantum system can also detect eavesdropping.
In quantum cryptography, secure information is coded on to light beams which are sent from one point to another.
But present systems cannot operate beyond about 50 to 100km, because, at greater distances, too much information is lost.
Dr Longdell says the new approach is likely to help make quantum communication over thousands of kilometres an eventual reality.
"It makes long-distance quantum cryptography much closer to being realised.
"Before, I thought it might be something that's achievable.
"Now I think it's something that probably will be achieved.
"I imagine that in five years' time we'll have the ability to do long-distance quantum communication."
