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| Energy-space photography of light confined on a nanowire, simultaneously shows both spatial interference and energy quantization. Credit: Fabrizio Carbone/EPFL |
For the first time, scientists have managed to capture the dual natures of
light - particle and wave - in a single electron microscope image.
Until now, scientists have only ever been able to capture an image of light
as either a particle or a wave, and never both at the same time. But a team
from the École Polytechnique Fédérale de Lausanne in Switzerland have
managed to overcome the obstacles that stood in the way of previous
experiments by using electrons to image light in this very strange
state.
The key to their success is their unusual experiment design. First they fire
a pulse of laser light at a single strand of nanowire suspended on a piece
of graphene film. This causes the nanowire to vibrate, and light particles -
or photons - are sent travelling along it in two possible directions. When
light particles that are travelling on opposite directions meet and overlap
on the wire, they form a wave. Known as a ‘standing wave’, this state
creates light that radiates around the nanowire.
So far so good, but that’s not going to give you an image of the two light
states. The scientists figured that out by feeding a stream of electrons
into the area nearby the nanowire, they could force an interaction between
the electrons and the light that had been confined on the nanowire.
This interaction caused the electrons to either speed up or slow down, and
the team used an ultrafast electron microscope to capture this exact moment,
so they could visualise the standing wave, "which acts as a fingerprint of
the wave-nature of light," the press release explains. Publishing their
results in Nature Communications, the team discusses how this collision
between the photons and electrons and the consequential speed-change
experienced by the electrons appears as an exchange of energy, which can be
visualised by the microscope.
So the top part of the image is the standing wave, while the bottom shows
where the photons are located.
"This experiment demonstrates that, for the first time ever, we can film
quantum mechanics - and its paradoxical nature - directly," one of the team,
physicist Fabrizio Carbone, said in a press release. "Being able to
image and control quantum phenomena at the nanometer scale like this opens
up a new route towards quantum computing."
The team in Switzerland has put together an adorable little video explaining
their experiment. Just imagine if every time light appeared in particle form
it actually made those weird little noises. What an utter nightmare.
Reference:
Piazza, L., Lummen, T., Quiñonez, E. et al. Simultaneous observation of the
quantization and the interference pattern of a plasmonic near-field. Nat
Commun 6, 6407 (2015).
DOI: 10.1038/ncomms7407