Letter

Nature 463, 926-929 (18 February 2010) | doi:10.1038/nature08776; Received 21 August 2009; Accepted 10 December 2009

There is a Brief Communication Arising (2 September 2010) associated with this document.

A precision measurement of the gravitational redshift by the interference of matter waves

Holger Müller1,2, Achim Peters3 & Steven Chu1,2,4

  1. Department of Physics, 366 Le Conte Hall MS 7300, University of California, Berkeley, California 94720, USA
  2. Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, California 94720, USA
  3. Institut für Physik, Humboldt-Universität zu Berlin, Hausvogteiplatz 5-7, 10117 Berlin, Germany
  4. US Department of Energy, 1000 Independence Avenue SW, Washington, District of Columbia 20585, USA

Correspondence to: Holger Müller1,2 Correspondence and requests for materials should be addressed to H.M. (Email: hm@berkeley.edu).

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 potential1. This effect, known as gravitational redshift, is important to the operation of the global positioning system2, timekeeping3, 4 and future experiments with ultra-precise, space-based clocks5 (such as searches for variations in fundamental constants). The gravitational redshift has been measured using clocks on a tower6, an aircraft7 and a rocket8, currently reaching an accuracy of 7×10-5. Here we show that laboratory experiments based on quantum interference of atoms9, 10 enable a much more precise measurement, yielding an accuracy of 7×10-9. 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 gravity11. 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 theories1.

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