Scientists working in Switzerland say they've managed to capture the first-ever snapshot of light behaving as both a wave and a particle, confirming one of the foundation tenets of quantum mechanics.
Quantum mechanical theory holds that light can be both a wave and a particle -- simultaneously -- but no experiment has ever managed to capture that dual behavior until now.
A team of Swiss and American researchers, using an advanced electron microscope at the Swiss Federal Institute of Technology in Lausanne (EPFL) has managed the feat, reporting the accomplishment in the journal Nature Communications.
The Swiss institute's ultrafast energy-filtered transmission electron microscope is one of only two such instruments on the planet.
When light of a certain wavelength strikes a metal surface, the result is an emission of electrons in what is known as the "photoelectric" effect.
This effect long puzzled scientists until Albert Einstein proposed that light -- always considered a wave -- could also be a stream of particles.
Ever since, researchers have conducted experiments confirming both the particle behavior and the wave-like behavior of light, but always separately and at different instances.
What has eluded scientists is capturing both behaviors simultaneously.
The team at EPFL, headed by Fabrizio Carbone, set up an experiment with a novel twist; they would use electrons to capture an image of light.
They fired laser light at a metallic wire just nanometers thick, causing the light -- as a wave -- to move back and forth along the length of the wire.
Light waves moving in opposite directions would meet to form "standing waves" that would then emit further light -- as particles known as photons -- radiating from around the nanowire.
The team sent a stream of electrons close to the nanowire, which in hitting the photons caused them to release "packets" of energy, known as quanta.
The result is an image demonstrating the simultaneous particle nature and wave nature of light, the researchers say.
"This experiment demonstrates that, for the first time ever, we can film quantum mechanics -- and its paradoxical nature -- directly," says Carbone.
Although the finding confirms a basic theory of physics, it could also lead to applications in the real world in future technologies, he says.
"Being able to image and control quantum phenomena at the nanometer scale like this opens up a new route toward quantum computing," he explains.
Carried out at the Swiss institute, the research involved scientists from EPFL, Trinity College in Harford, Connecticut, and the Lawrence Livermore National Laboratory in California.