Title: Photon
Molecule
Description: Researchers
show that two photons, depicted in this artist?s conception
as waves (left and
right), can be locked together at a short distance. Under certain
conditions the
photons can form a state resembling a two-atom molecule,
represented as the
blue dumbbell shape at center. Credit: E. Edwards/JQI
(September 10, 2015) It’s
not lightsaber time, not yet. But a team including theoretical physicists from
the National Institute of Standards and Technology (NIST) has taken another
step toward building objects out of photons, and the findings* hint that
weightless particles of light can be joined into a sort of “molecule” with its
own peculiar force.
The findings build on previous research that several team
members contributed to before joining NIST. In 2013, collaborators from
Harvard, Caltech and MIT found a way to bind two photons together so that one
would sit right atop the other, superimposed as they travel. Their experimental
demonstration was considered a breakthrough, because no one had ever
constructed anything by combining individual photons—inspiring some to imagine
that real-life lightsabers were just around the corner.
Now, in a paper forthcoming in Physical Review Letters, the
NIST and University of Maryland-based team (with other collaborators) has
showed theoretically that by tweaking a few parameters of the binding process,
photons could travel side by side, a specific distance from each other. The
arrangement is akin to the way that two hydrogen atoms sit next to each other
in a hydrogen molecule.
“It’s not a molecule per se, but you can imagine it as
having a similar kind of structure,” says NIST’s Alexey Gorshkov. “We’re
learning how to build complex states of light that, in turn, can be built into
more complex objects. This is the first time anyone has shown how to bind two
photons a finite distance apart."