[extropy-chat] fermionic light

[Damien Broderick]

Bright future for ‘solid light’

[ 
<http://uninews.unimelb.edu.au/uninews.php?volume=16&number=7&publication=un>The 
University of Melbourne Voice Vol. 1, No. 4  30 April - 14 May 2007 ]

By Rebecca Scott

When photons interact they can behave like a solid.

Researchers from the universities of Melbourne 
and Cambridge have unveiled a new theory that 
shows light can behave like a solid.

“Solid light will help us build the technology of 
this century,” says research team member, 
University of Melbourne physicist Dr Andrew Greentree.

Dr Greentree and School of Physics colleagues 
Jared Cole and Professor Lloyd Hollenberg, with 
Dr Charles Tahan of the University of Cambridge, 
made their ‘solid light’ breakthrough by studying 
light with 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 interact with each other.

Mr Cole describes a phase transition as a change 
in the state of something – “such as when water becomes ice”.

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

He says phase transitions are important in 
science and technology, but only the simplest examples are as yet 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 collaborators to 
be leading the world in this new area,” he says.

The team’s work has been reported in Nature Physics and New Scientist.

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