Novel ordered states of matter in ultracold atomic gases

Maciej Lewenstein

Laurent Sanchez-Palencia

Lingran Kong, Tianyou Gao, Shi-Guo Peng +7 more

Generating the vortex-state superposition in a matter wave is demanded in many quantum processes such as quantum memory and quantum metrology. Here we report the experimental generation of macroscopic superposition of vortex states in ultracold quantum gases. By transferring an optical vortex-state superposition to the center-of-mass rotational state of ultracold atoms using the Raman coupling technique, we realize two-vortex and three-vortex superposition states in quantum gases, demonstrating the high dimensionality of the vortex state. We show the controllability of the superposition states on the Bloch sphere. The lifetime of the vortex superposition state in quantum gases is as large as 25 ms, about two orders of magnitude longer than the storage time in atomic ensembles. This work paves the way for high dimensional quantum processing in matter waves.

Claude N. Cohen-Tannoudji

Sylvain Nascimbène

This proceedings presents recent advancements in the realization of topological states of matter using ultracold atomic gases. We focus on the simulation of the quantum Hall effect, originally discovered in two-dimensional electron gases subjected to a magnetic field. Given that ultracold atoms are neutral, simulating the effect of a magnetic field requires an ad-hoc technique. We review various methods developed for this purpose, highlighting their respective advantages and limitations. Furthermore, we explore the extension of these techniques to interacting quantum gases within topological bands, aiming to create analogs of fractional quantum Hall states. These many-body states are distinguished by their topological order, which is characterized by long-range entanglement among particles and the emergence of low-lying excitations exhibiting fractional quantum statistics. The discussion will encompass the current state of research and potential future directions in the field.

Xu Zhi-Jun, Xiayin Liu

Atoms in the Mott insulator state trapped in an optical lattice are incoherence matter wave source. It is not the first-order, but the second-order interference effect (density correlation) that will appear for this incoherence wave source after being released. A density correlation function of the freely expanding ultracold gases is obtained theoretically, which presents sharp peaks of interference, and the stripes structure is similar to the diffraction gratings. It is further pointed out that the peak structure of the density correlation function depends on the relative position between two detectors. The phenomenon of subwavelength interference of matter waves is also proposed in this paper.