The key to this new research is the "exciton". This describes
the pairing of an electron that has been kicked into a higher
energy state by a photon, with a hole or gap it - or another
electron - leaves within the shell or orbit around the nucleus
of an atom. Despite its new high energy state the electron
remains paired with one of the holes or positions that has been
vacated by electrons moving to a higher energy state. When an
electron's high energy state decays again it is drawn back to
the hole it is linked to and a photon is once again emitted.
That cycle usually happens very quickly but if one could find a
way to freeze or hold an exciton in place for any length of time
one could delay the re-emitting of a photon and effectively slow
or even freeze light. The researchers, led by PhD researcher
Andrea Fischer and Dr. Rudolf A. Roemer from the University of
Warwick's Department of Physics, looked at the possibilities
presented by some tiny rings of matter accidentally made during
the manufacture quantum d