We've seen light as a wave, and we've seen light as a particle, but for the first time, we now have one image with light playing the role of both wave and particle at the same time.
What you're looking at here is a major breakthrough. The image reveals a property of light that has never been witnessed before by human eyes, though we've long known about it. But at last, thanks in an ingenious imaging experiment, we can now see how light behaves as a wave and a particle at the same time.
The image was published today in Nature Communications by a team of scientists based in Europe.
According to a release from Ecole Polytechnique Fédérale de Lausanne about the paper:
The experiment is set up like this: A pulse of laser light is fired at a tiny metallic nanowire. The laser adds energy to the charged particles in the nanowire, causing them to vibrate. Light travels along this tiny wire in two possible directions, like cars on a highway. When waves traveling in opposite directions meet each other they form a new wave that looks like it is standing in place. Here, this standing wave becomes the source of light for the experiment, radiating around the nanowire.
This is where the experiment's trick comes in: The scientists shot a stream of electrons close to the nanowire, using them to image the standing wave of light. As the electrons interacted with the confined light on the nanowire, they either sped up or slowed down. Using the ultrafast microscope to image the position where this change in speed occurred, Carbone's team could now visualize the standing wave, which acts as a fingerprint of the wave-nature of light.
While this phenomenon shows the wave-like nature of light, it simultaneously demonstrated its particle aspect as well. As the electrons pass close to the standing wave of light, they "hit" the light's particles, the photons. As mentioned above, this affects their speed, making them move faster or slower. This change in speed appears as an exchange of energy "packets" (quanta) between electrons and photons. The very occurrence of these energy packets shows that the light on the nanowire behaves as a particle.
"This experiment demonstrates that, for the first time ever, we can film quantum mechanics - and its paradoxical nature - directly," says Fabrizio Carbone. In addition, the importance of this pioneering work can extend beyond fundamental science and to future technologies. As Carbone explains: "Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route towards quantum computing."
Read the full scientific paper at Nature Communications