An ensemble of cold atoms in its free fall on a parabolic trajectory is coherently split, redirected and recombined with beam splitters made out of light. This coherent beam splitting process is based on Raman-transitions between two atomic hyperfine states. Furthermore, these two interferometer states are correlated with two different momentum states resulting in the mentioned spatial splitting of the atomic ensemble.
The two atomic wave packets enclose on their trajectories an area which results in a rotation sensitive Sagnac Interferometer configuration. The imprinted rotation phase
on the atoms is converted to a variation in the population of the two interferometer states by the last light pulse. This population difference is then finally detected with a state selective fluorescence detection. Indeed, the presented interferometer configuration is also sensitive to accelerations with the phase
and has its application in atomic gravimeters. Due to the dependence of the rotation phase shift on the velocity, it is possible to distinguish between these two inertial phase shifts by using a differential interferometry scheme. As shown in Fig. 1, our differential setup consists of two interferometers launching atoms in opposite directions (vleft = -vright) but use the same beam splitter pulses.