Holger Mueller Fall 2010 Abstract

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

Holger Mueller, UC Berkeley

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 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. The gravitational redshift has been measured using clocks on a tower, an aircraft and a rocket, currently reaching an accuracy of 7x10^-5. In this talk, I will show that laboratory experiments based on quantum interference of atoms enable a much more precise measurement, yielding an accuracy of 7x10^-9. We will also discuss the relationship of redshift measurements and tests of the universality of free fall, and propose new experiments that could improve the current bounds on redshift violations to 10^-14.