Scientists have long known that light can behave as both a particle and a wave—Einstein first predicted it in 1909. But no experiment has been able to show light in both states simultaneously. Now, researchers at the École Polytechnique Fédérale de Lausanne in Switzerland have taken the first ever photograph of light as both a wave and a particle. The key was a new experimental technique that uses electrons to capture the light’s movement. The work was published today in the journal Nature Communications.
To get this snapshot, the researchers shot laser pulses at a nanowire. The wavelengths of light moved in two different directions along the metal. When the waves ran into each other, they look liked a wave standing still, which is effectively a particle.
In order to see how the waves were moving, the researchers shot a beam of electrons at the nanowire, like dropping dye in a river to see the currents. The particles in the light wave changed the speed at which the electrons moved. That enabled the researchers to capture an image just as the waves met.
“This experiment demonstrates that, for the first time ever, we can film quantum mechanics – and its paradoxical nature – directly,” said Fabrizio Carbone, one of the authors of the study, in a press release. Carbone hopes that a better understanding of how light functions can jumpstart the field of quantum computing.