A recent experiment accomplished the feat of simultaneously capturing light as both a particle and a wave for the first time.
When UV light hits a metal surface it creates a stream of electrons, École polytechnique fédérale de Lausanne reported. Albert Einstein believed this "photoelectric" effect could be explained by the idea that light is not only a wave, but also a stream of particles. Past experiments have been able to observe both the particle and wave behaviors of light, but never at the same time.
In order to accomplish this a team of researchers used electrons to image the light, allowing them to capture light behaving as both a wave and a stream of particles in one single "snapshot." In the experiment a pulse of laser light was fired at a metallic nanowire, adding energy to the charged particles in the wire and prompting them to vibrate. Light travels along these ultra-small wires in two possible directions, and when waves traveling in opposite directions meet it forms a new wave that looks like it is "standing in place"; in this scenario, the standing wave becomes a light source for the experiment.
Once this wave was achieved the researchers shot a stream of electrons close to the nanowire, using them to create a clear image of the stationary wave. As the electrons interacted with the light on the nanowire, they either sped up or slowed down. An ultrafast microscope allowed the scientists to image these changes in speed and position, allowing them to see the standing wave that acts as a "fingerprint of the wave-nature of light." The experiment also revealed the particle properties of light by demonstrating an exchange of energy "packets" (quanta) between electrons and photons.
"This experiment demonstrates that, for the first time ever, we can film quantum mechanics - and its paradoxical nature - directly," said Fabrizio Carbone. "Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing."
The findings were published in a recent edition of the journal Nature Communications.
