For the first time, light has been recorded to behave as a wave as well as a particle.
While one of the oldest conundrums surrounding light have been time and again proven to be right, to date, the phenomenon was never actually witnessed, much less recorded. Swiss scientists have, for the first time, captured light behaving as a wave as well as a particle.
Researchers at the Ecole Polytechnique Federale de Lausanne (EPFL) – managed to pull off the trick by forcing an interaction between electrons and the photons in the standing wave. As it certainly isn’t easy to observe light, what with its super-hyper-speed, scientists had to get creative.
First, they got the light behaving as a wave. To get the standing wave, scientists fired laser pulses at a metallic nanowire. The laser pulses excited the nanowire’s charged particles and caused them to vibrate. The surface of the nanowire acted as a sort of waveguide. When the waves travelling in the opposite directions met, they formed standing waves.
Professor Ben Eggleton of Sydney University’s CUDOS research group explained that photons can be guided along a metallic wire in the form of plasmons (surface plasmon polaritons).
“The light is coupled to the electron, and its path will therefore follow the path of the nanowire.”
To get the image of the standing wave, the EPFL researchers fired a stream of electrons from an electron microscope. Where the electrons interacted with the standing wave, it either added quanta or energy to the electrons (speeding them up, as the release says), or took energy away (slowing them down). That change in energy provided the information that let the researchers visually capture the light’s wave-like nature. The same information the light imparted to the electrons also demonstrated its particle aspect.
The change in the speed of the electrons suggests an exchange of quanta, or energy. This clearly demonstrates that the waves of light on the nanowire were acting as particles and waves at the same time. In simpler terms, though light was flowing like a wave, it also had energy. When the energy exchange took place, the speed of the flow varied.
The dual nature of light to behave as a particle or a wave has always puzzled scientists, though they have accepted the phenomenon for more than 100 years. However, all of the experiments to corroborate the conundrum have either ended up proving either light behaved as a particle or a wave.
As EPFL’s Fabrizio Carbone observes, this is the first direct imaging showing the paradoxical nature of quantum mechanics. Scientists hope being able to record light behaving as a particle could open up new ways for quantum computing, which relies on light to store and process information.
[Image Credit: EPFL]