Resonant Rydberg Dressing of Alkaline-Earth Atoms via Electromagnetically Induced Transparency

Giant nonlocal Kerr nonlinearity and polaritonic solitons in a Rydberg-dressed Bose-Einstein condensate

We present a scheme to generate nonlocal optical Kerr nonlinearity and polaritonic solitons via matter-wave superradiance in a Rydberg-dressed Bose-Einstein condensate (BEC). We show that the polariton spectrum of the scattered field generated by the superradiance is changed significantly due to the existence of the long-range Rydberg-Rydberg interaction between atoms, i.e. it has a roton-maxon form; moreover, the BEC structure factor displays a strong dependence on the Rydberg-dressing, which can be tuned in a controllable way. We also show that such a Rydberg-dressed BEC system can support a giant nonlocal optical Kerr nonlinearity, and hence allow the formation and stable propagation of polaritonic solitons, which have ultraslow propagation velocity and ultralow generation power. The results reported here are useful to understand the unique properties of Rydberg-dressing in BECs and have potential applications in optical information processing and transmission.

Quench Dynamics of a Fermi Gas with Strong Nonlocal Interactions

We induce strong nonlocal interactions in a 2D Fermi gas in an optical lattice using Rydberg dressing. The system is approximately described by a t - V model on a square lattice where the fermions experience isotropic nearest-neighbor interactions and are free to hop only along one direction. We measure the interactions using many-body Ramsey interferometry and study the lifetime of the gas in the presence of tunneling, finding that tunneling does not reduce the lifetime. To probe the interplay of nonlocal interactions with tunneling, we investigate the short-time-relaxation dynamics of charge-density waves in the gas. We find that strong nearest-neighbor interactions slow down the relaxation. Our work opens the door for quantum simulations of systems with strong nonlocal interactions such as extended Fermi-Hubbard models.

Transverse-Field Ising Dynamics in a Rydberg-Dressed Atomic Gas

We report on the realization of long-range Ising interactions in a cold gas of cesium atoms by Rydberg dressing. The interactions are enhanced by coupling to Rydberg states in the vicinity of a Förster resonance. We characterize the interactions by measuring the mean-field shift of the clock transition via Ramsey spectroscopy, observing one-axis twisting dynamics. We furthermore emulate a transverse-field Ising model by periodic application of a microwave field and detect dynamical signatures of the paramagnetic-ferromagnetic phase transition. Our results highlight the power of optical addressing for achieving local and dynamical control of interactions, enabling prospects ranging from investigating Floquet quantum criticality to producing tunable-range spin squeezing.

Coherent population trapping based atomic reservoir for almost perfect higher-order squeezing

Due to either coherent or dissipative interactions with the coherent population trapping (CPT)-based atoms, the evolutions of the Bogoliubov modes towards the vacuum states have been shown to lead to second-order squeezing of the involved optical fields. Here we push the CPT-based dissipative interactions towards higher-order squeezing, which is not simply determined by second-order squeezing but instead by different criteria involving higher-order moments. It is shown that the CPT-based atomic reservoir supports the dissipative evolution of the Bogoliubov modes almost completely to the vacuum states and then yields almost perfect fourth-order squeezing (90%∼100%). The present mechanism is robust against spontaneous emission since the atoms stay largely in the ground states. As a by-product, a comparison is given with two-level atoms, in which the excitation of a large fraction reduces the degree of higher-order squeezing.

Rydberg-Dressed Magneto-optical Trap

We propose and demonstrate the laser cooling and trapping of Rydberg-dressed Sr atoms. By off-resonantly coupling the excited state of a narrow (7 kHz) cooling transition to a high-lying Rydberg state, we transfer Rydberg properties such as enhanced electric polarizability to a stable magneto-optical trap operating at <1  μK. Simulations show that it is possible to reach a regime where the long-range interaction between Rydberg-dressed atoms becomes comparable to the kinetic energy, opening a route to combining laser cooling with tunable long-range interactions.

Floquet Symmetry-Protected Topological Phases in Cold-Atom Systems

We propose and analyze two distinct routes toward realizing interacting symmetry-protected topological (SPT) phases via periodic driving. First, we demonstrate that a driven transverse-field Ising model can be used to engineer complex interactions which enable the emulation of an equilibrium SPT phase. This phase remains stable only within a parametric time scale controlled by the driving frequency, beyond which its topological features break down. To overcome this issue, we consider an alternate route based upon realizing an intrinsically Floquet SPT phase that does not have any equilibrium analog. In both cases, we show that disorder, leading to many-body localization, prevents runaway heating and enables the observation of coherent quantum dynamics at high energy densities. Furthermore, we clarify the distinction between the equilibrium and Floquet SPT phases by identifying a unique micromotion-based entanglement spectrum signature of the latter. Finally, we propose a unifying implementation in a one-dimensional chain of Rydberg-dressed atoms and show that protected edge modes are observable on realistic experimental time scales.