Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.
We simultaneously measure the gravitationally-induced phase shift in two
Raman-type matter-wave interferometers operated with laser-cooled ensembles of
$^{87}$Rb and $^{39}$K atoms. Our measurement yields an E\"otv\"os ratio of
$\eta_{\text{Rb,K}}=(0.3\pm 5.4)\times 10^{-7}$. We briefly estimate possible
bias effects and present strategies for future improvements
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