Could Light Behave As A Solid? A New Theory

“Solid light will help us build the technology of this century,” says Dr Andrew Greentree of the School of Physics at the University of Melbourne.

Dr Greentree and colleagues Jared Cole and Professor Lloyd Hollenberg of the University of Melbourne with Dr Charles Tahan of the University of Cambridge made their ‘solid light’ breakthrough using tools more commonly used to study matter.

“Solid light photons repel each other as electrons do. This means we can control photons, opening the door to new kinds of faster computers,” says Dr Greentree.

“Many real-world problems in quantum physics are too hard to solve with today’s computers. Our discovery shows how to replicate these hard problems in a system we can control and measure.”

He says photons of light do not normally interact with each other. In contrast, the electrons used by computers strongly repel each other.

The team has shown theoretically how to engineer a ‘phase transition’ in photons, leading them to change their state so that they do not interact with each other.

“A phase transition occurs when something changes its state, for example when water becomes ice,” says team member Jared Cole.

“Usually, photons flow freely, but in the right circumstances, they repel each other, and form a crystal.”

He says phase transitions are very important in science and technology, but only the simplest phase transitions can be understood.

Dr Greentree says the solid light phase transition effect ties together two very different areas of physics, optics and condensed matter “to create a whole new way of thinking”.

“It is very exciting for the University of Melbourne and its international collaborations to be leading the world in this new area,” he says.

The team’s work has been reported in the prestigious scientific journals Nature Physics and New Scientist.

Funding has come from international and national sources, including the Australian Research Council, the Australian Government, US National Security Agency, the US-based Advanced Research and Development Activity, Army Research Office and the US National Science Foundation.