Southampton scientist searches for quantum limit using polystyrene balls

A physicist at the University of Southampton is using polystyrene balls of increasing size to recreate classic experiments in physics to test the limits of quantum mechanics.

Dr Hendrik Ulbricht has been awarded a Foundational Questions Institute (FQXi) grant of $140,000 to carry out experiments which could reveal where the quantum realm ends and the classical world begins. He describes the experiment in a YouTube video.

Dr Ulbricht will look at interference patterns of the balls and recreate a polystyrene test which has all the elements of Thomas Young’s two-slit experiment, in which light from a single source is shone through a pair of slits and onto a screen, where an interference pattern of light and dark bands appear. In physics, interference is something that happens when two light waves come together. In quantum physics, even a single particle itself can interfere.

Over the years, single particle interference patterns have been created by firing electrons, atoms and even large molecules at the slits. Dr Ulbricht hopes to push the quantum-classical boundary a big step further by demonstrating interference using polystyrene balls that are a thousand times heavier than the largest molecules tested so far.

“Nobody has done this with polystyrene before, but it looks very promising,” said Dr Ulbricht. “These experiments will help us understand the mechanism which links the quantum to the classical world in a consistent picture.”

The Microstructured Optical Fibre group led by Professor David Richardson at the University of Southampton’s Optoelectronics Research Centre developed the optical fibres to guide the particles through the process.