A single photon of light can assume a different shape depending on the conditions of the creation of the photon and the measurement instruments. The concepts that a high energy process like lasers can change the shape of single light particles called photons has been around for 35 years but the actual measurement of the effect and a photograph of the behavior were considered to be impossible. Professor Mete Atature, a Fellow of Saint John’s College at the University of Cambridge, and colleagues have achieved the impossible according to their report in the edition of the journal Nature.
The problem with observing the squeezed photon is stated in Heisenberg’s uncertainty principle. Heisenberg’s uncertainty principle indicates that it is impossible to measure the shape of a particle that has two linked properties like momentum and position. One of the properties will always be an uncertainty and that is why physicists despaired of ever seeing a squeezed photon. The researchers at the University of Cambridge changed the rules of the game and produced the first photo of a squeezed photon of light.
The researchers used a man-made unit of matter called a quantum dot. Among other unique properties, a quantum dot can be excited by a very low level of laser light and emit single photons. The researchers reduced the noise created by the electromagnetic field necessary to produce single photons of light below the detectable limit of the most precise instruments. The change in parameters means the researchers were only measuring one quantity and had escaped the limits on quantum physics that are imposed by the uncertainty principle.