'Magic dust' may help develop powerful supercomputers

A type of 'magic dust' which combines light and matter can be used to solve complex problems and could eventually surpass the capabilities of even the most powerful supercomputers, scientists say.
Researchers from Cambridge, Southampton and Cardiff Universities in the UK have used quantum particles known as polaritons - which are half light and half matter - to act as a type of 'beacon' showing the way to the simplest solution to complex problems.
This entirely new design could form the basis of a new type of computer that can solve problems that are currently unsolvable, in diverse fields such as biology, finance or space travel, researchers said.

Our technological progress - from modelling protein folding and behaviour of financial markets to devising new materials and sending fully automated missions into deep space - depends on our ability to find the optimal solution of a mathematical formulation of a problem: the absolute minimum number of steps that it takes to solve that problem.
"This is exactly the problem to tackle when the objective function to minimise represents a real-life problem with many unknowns, parameters, and constraints," said Professor Natalia Berloff of Cambridge University, first author of the research paper published in the journal Nature Materials.
Modern supercomputers can only deal with a small subset of such problems when the dimension of the function to be minimised is small or when the underlying structure of the problem allows it to find the optimal solution quickly even for a function of large dimensionality.

Even a hypothetical quantum computer, if realised, offers at best the quadratic speed-up for the "brute-force" search for the global minimum, researchers said.

The 'magic dust' polaritons are created by shining a laser at stacked layers of selected atoms such as gallium, arsenic, indium, and aluminium. The electrons in these layers absorb and emit light of a specific colour.
Polaritons are ten thousand times lighter than electrons and may achieve sufficient densities to form a new state of matter known as a Bose-Einstein condensate, where the quantum phases of polaritons synchronise and create a single macroscopic quantum object that can be detected through photoluminescence measurements, researchers said.

"We are currently scaling up our device to hundreds of nodes, while testing its fundamental computational power. The ultimate goal is a microchip quantum simulator operating at ambient conditions," said Professor Pavlos Lagoudakis, from the University of Southampton.