Using Atom Interferometry to Detect Dark Energy
  We review the tantalising prospect that the first evidence for the dark
energy driving the observed acceleration of the Universe on giga-parsec scales
may be found through metre scale laboratory based atom interferometry
experiments. To do that, we first introduce the idea that scalar fields could
be responsible for dark energy and show that in order to be compatible with
fifth force constraints these fields must have a screening mechanism which
hides their effects from us within the solar system. Particular emphasis is
placed on one such screening mechanism known as the chameleon effect where the
field's mass becomes dependent on the environment. The way the field behaves in
the presence of a spherical source is determined and we then go on to show how
in the presence of the kind of high vacuum associated with atom interferometry
experiments, and when the test particle is an atom, it is possible to use the
associated interference pattern to place constraints on the acceleration due to
the fifth force of the chameleon field - this has already been used to rule out
large regions of the chameleon parameter space and maybe one day will be able
to detect the force due to the dark energy field in the laboratory.
