Quantum Optics and Photonics 1. Single-zone Atom Interferometer : Experimental Observation

In a typical atomic interferometer, the atomic wavepacket is split first by what can be considered effectively as an atomic beamsplitter. The split components are then redirected towards each other by atomic mirrors. Finally, the converging components are recombined by another atomic beam splitter. Here, we demonstrate a novel atomic interferometer where the atomic split is split and recmobined in a continuous manner. Specifically, in this interferometer, the atom simply passes through a single-zone optical beam, consisting of a pair of bichromatic counterpropagating beams that cause optically off-resonant Raman excitations. During the passage, the atomic wave packets in two distinct internal states couple to each other continuously. The two internal states trace out a complicated trajectory, guided by the optical beams, with the amplitude and spread of each wavepacket varying continuously. Yet, at the end of the single-zone excitation, there is an interference with fringe amplitudes that can reach a visibility close to unity. One can consider this experiment as a limiting version of π/2-π-π/2 Raman atom interferometer, proposed originally by Borde, and demonstrated by Chu et al. Specifically, the distances between the first π/2 Raman pulse and the π Raman pulse and between the π Raman pulse and the second π/2 Raman pulse are zero. This configuration is considerably simpler that the Borde-Chu interferometer (BCI), eliminating the need for precise alignment of the multiple zones. In situations of practical interest, the BCI and the continuos interferometer (CI) can achieve comparable performance (e.g., rotational sensitivity. As such, the relative simplicity of the CI may make it an attractive candidate for measuring rotation. Furthermore, it opens up the possibility of realizing trajectories with multipler loops in a manner that is able to measure other effects while the rotational sensitivity vanishes.