November 8, 2012
A Quantum Kiss Can Change The Color Of Empty Space
April Flowers for redOrbit.com - Your Universe Online
Our world is made of color, even the empty gaps have a color of their own.
The findings of this study, published in the current issue of Nature, set a fundamental quantum limit on how tightly light can be trapped.
The Cambridge team collaborated with scientists from the Donostia International Physics Center (DIPC), the Materials Physics Center in Donostia-San SebastiÃ¡n (CFM) and the University of Paris-Sud to combine masterfully crafted experiments with advanced theories. Their work shows how light interacts with matter at nanometer sizes, and how one can literally see quantum mechanics in action in the air at room temperature.
Electrons in a metal move easily, so shining a white light onto a tiny crack pushes electric charges onto and off each crack face in turn, at optical frequencies. A plasmonic color is produced for the ghostly region in between by the oscillating charge across the gap, but only when the gap is small enough.
Consider this charge to be like the building tension between a flirting couple staring into each other's eyes. Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory says as their faces get closer the tension increases and only a kiss will discharge the energy.
The gap is shrunk below 1 nanometer in the new experiments, strongly reddening the gap color as the charge builds up. Electrons can jump across the gap by a process known as quantum tunneling, however, so the charge can drain away when the gap is below 0.35 nanometers. This can be seen as a blue-shifting of the color.
Baumberg says: “It is as if you can kiss without quite touching lips.”
Another team member, Matt Hawkeye from Cambridge, says, “Lining up the two nano-balls of gold is like closing your eyes and touching together two needles strapped to the end of your fingers. It has taken years of practice to get good at it.”
Professor Javier Aizpurua, leader of the theoretical team from San Sebastian explains: “Trying to model so many electrons oscillating inside the gold just cannot be done with existing theories.” To achieve this result, Aizpurua had to fuse classical world views with quantum theory to even predict the color shifts seen in the physical experiment.
The findings of this study are important as they suggest ways to measure the world down to the scale of single atoms and molecules as well as strategies to make useful tiny devices.