title: A precision measurement of the gravitational redshift by the interference of matter waves.
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.
authors.affiliation: Department of Physics, 366 Le Conte Hall MS 7300, University of California, Berkeley, California 94720, USA. hm@berkeley.edu
authors.forename: Holger
authors.initials: H
authors.lastname: Müller
authors.forename: Achim
authors.initials: A
authors.lastname: Peters
authors.forename: Steven
authors.initials: S
authors.lastname: Chu