Using clouds of ultra-cold atoms and a pair of lasers
operating at optical wavelengths, researchers have reached a quantum network
milestone: entangling light with an optical atomic coherence composed of
interacting atoms in two different states. The development could help pave the
way for functional, multi-node quantum networks.
The research, done at the Georgia Institute of Technology,
used a new type of optical trap that simultaneously confined both ground-state
and highly-excited (Rydberg) atoms of the element rubidium. The large size of
the Rydberg atoms – which have a radius of about one micron instead of a usual
sub-nanometer size – gives them exaggerated electromagnetic properties and
allows them to interact strongly with one another.