There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
One of the central predictions of metric theories of gravity, such as general relativity,
is that a clock in a gravitational potential U will run more slowly by a factor of
1 + U/c(2), where c is the velocity of light, as compared to a similar clock outside
the potential. This effect, known as gravitational redshift, is important to the operation
of the global positioning system, timekeeping and future experiments with ultra-precise,
space-based clocks (such as searches for variations in fundamental constants). The
gravitational redshift has been measured using clocks on a tower, an aircraft and
a rocket, currently reaching an accuracy of 7 x 10(-5). Here we show that laboratory
experiments based on quantum interference of atoms enable a much more precise measurement,
yielding an accuracy of 7 x 10(-9). Our result supports the view that gravity is a
manifestation of space-time curvature, an underlying principle of general relativity
that has come under scrutiny in connection with the search for a theory of quantum
gravity. Improving the redshift measurement is particularly important because this
test has been the least accurate among the experiments that are required to support
curved space-time theories.