In
an international scientific breakthrough, a Griffith University
research team has been able to photograph the shadow of a single atom
for the first time.
“We
have reached the extreme limit of microscopy; you cannot see anything
smaller than an atom using visible light,” Professor Dave Kielpinski of
Griffith University’s Centre for Quantum Dynamics in Brisbane.
“We
wanted to investigate how few atoms are required to cast a shadow and
we proved it takes just one,” Professor Kielpinski said.
Published
this week in Nature Communications, “Absorption imaging of a single
atom” is the result of work over the last 5 years by the
Kielpinski/Streed research team.
At
the heart of this Griffith University achievement is a super
high-resolution microscope, which makes the shadow dark enough to see.
No other facility in the world has the capability for such extreme
optical imaging.
Holding
an atom still long enough to take its photo, while remarkable in
itself, is not new technology; the atom is isolated within a chamber and
held in free space by electrical forces.
Professor
Kielpinski and his colleagues trapped single atomic ions of the element
ytterbium and exposed them to a specific frequency of light. Under this
light the atom’s shadow was cast onto a detector, and a digital camera
was then able to capture the image.
“By
using the ultra hi-res microscope we were able to concentrate the image
down to a smaller area than has been achieved before, creating a darker
image which is easier to see,” Professor Kielpinski said.
The precision involved in this process is almost beyond imagining.
“If
we change the frequency of the light we shine on the atom by just one
part in a billion, the image can no longer be seen,” Professor
Kielpinski said.
Research team member, Dr Erik Streed, said the implications of these findings are far reaching.
“Such experiments help confirm our understanding of atomic physics and may be useful for quantum computing,” Dr Streed said.
There are also potential follow-on benefits for biomicroscopy.
“Because
we are able to predict how dark a single atom should be, as in how much
light it should absorb in forming a shadow, we can measure if the
microscope is achieving the maximum contrast allowed by physics.”
“This
is important if you want to look at very small and fragile biological
samples such as DNA strands where exposure to too much UV light or
x-rays will harm the material.
“We
can now predict how much light is needed to observe processes within
cells, under optimum microscopy conditions, without crossing the
threshold and destroying them.”
And this may get biologists thinking about things in a different way.
“In the end, a little bit of light just might be enough to get the job done.”
