Light’s wave-particle duality imaged for the first time (Wired UK)


Fabrizio Carbone/EPFL


The weird way that light can behave as both a wave and a
particle has been known to physicists for about a century, but a
team in Lausanne has only now managed to capture it doing both at the same time.

The achievement comes after decades of attempts which
successfully observed both wave-like and particle-like behaviour.
But the physics researchers at the École polytechnique fédérale de
Lausanne took a radically different approach, using one of the only
two ultrafast energy-filtered transmission electron microscopes
that exist in the world.

They first fired a laser at a metallic nanowire, making charged
particles inside vibrate. The light waves travel along the nanowire
in two directions, but when they meet they form a ‘standing’ wave
that remains stationary — creating the source of light for the
experiment.

Then comes the novel part — the physicists shot a stream of electrons close
to the nanowire. As those electrons interacted with the light
source, hitting the confined photons, they either sped up or slowed
down, and the microscope allowed the researchers to image the
position where the change in speed — nd therefore the standing
wave — occurred. That shows the wave nature of light.

But at the same time, the impact of the electrons on the photons
and the resulting change in speed (showing up as an exchange of
energy in discrete ‘packets’, or quanta) 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, who led
the team.


Fabrizio Carbone/EPFL – Annotations by Wired.co.uk


We can explain what you’re seeing in the top image in the
annotated version here. It shows a graph where one axis (let’s call
it x) shows distance along the wire, the another (let’s call it y)
is the change in energy from the collisions, and the height (and
colour) shows how often the collisions happen.

The change in colour along the x axis shows the standing waves
that display the wave nature of light, while the change in colour
along the y axis shows discrete packets of energy that display
light’s particle nature — the first row shows the electrons that
have gained the energy of one photon, the second two, and so on. In
short, if it wasn’t a wave, the colour wouldn’t vary on the x axis,
and if it wasn’t a particle the colour wouldn’t vary on the y
axis.

The practical applications for this research into fundamental
physics are somewhat distant, but could help unlock the power of
quantum computers. “Being able to image and control quantum
phenomena at the nanometer scale like this opens up a new route
towards quantum computing,” said
Carbone.

The research, which was a collaborative effort between EPFL,
Trinity College and the Lawrence Livermore National Laboratory, has
been published in the journal Nature
Communications
.

If the article suppose to have a video or a photo gallery and it does not appear on your screen, please Click Here

3 March 2015 | 12:09 pm – Source: wired.co.uk

[ad_2]

Leave a Reply

Your email address will not be published.