Annual Review of Cold Atoms and Molecules

The following section is included:

• CONTENTS

Degenerate quantum gases of alkaline-earth-like elements open new opportunities in research areas ranging from molecular physics to the study of strongly correlated systems. These experiments exploit the rich electronic structure of these elements, which is markedly different from the one of other species for which quantum degeneracy has been attained. Specifically, alkaline-earth-like atoms, such as strontium, feature metastable triplet states, narrow intercombination lines, and a nonmagnetic, closed-shell ground state. This review covers the creation of quantum degenerate gases of strontium and the first experiments performed with this new system. It focuses on laser-cooling and evaporation schemes, which enable the creation of Bose–Einstein condensates and degenerate Fermi gases of all strontium isotopes, and shows how they are used for the investigation of optical Feshbach resonances, the study of degenerate gases loaded into an optical lattice, as well as the coherent creation of Sr₂ molecules.

We briefly review recent progress on ultracold atomic Fermi gases with different types of synthetic spin–orbit coupling, including the one–dimensional (1D) equal weight Rashba–Dresselhaus and two-dimensional (2D) Rasbha spin–orbit couplings. Theoretically, we show how the single-body, two-body and many-body properties of Fermi gases are dramatically changed by spin–orbit coupling. In particular, the interplay between spin–orbit coupling and interatomic interaction may lead to several long-sought exotic superfluid phases at low temperatures, such as anisotropic superfluid, topological superfluid and inhomogeneous superfluid. Experimentally, only the first type — equal weight combination of Rasbha and Dresselhaus spin–orbit couplings — has been realized very recently using a two-photon Raman process. We show how to characterize a normal spin–orbit coupled atomic Fermi gas in both non-interacting and strongly-interacting limits, using particularly momentum-resolved radio-frequency spectroscopy. The experimental demonstration of a strongly-interacting spin–orbit coupled Fermi gas opens a promising way to observe various exotic superfluid phases in the near future.

Ultracold atoms in optical lattices can realize nearly perfect analogs to condensed matter model systems without the complexity present in materials. In this chapter, we thoroughly describe our experimental characterization of the transition from superfluid (SF, for shallow optical lattices) to Mott insulator (MI, for deep optical lattices) using trapped ultracold bosonic atoms in optical lattices. Our measurements are based on the time-of-flight (TOF) technique, where we focus on the atoms' momentum distribution and correlations therein. In this review, we discuss three main measurements: (i) the properties of the Mott state including the effects of non-zero, but small, tunneling; (ii) the critical value at which an inhomogeneous ensemble of systems fully departs the SF phase; and (iii) the state diagramdescribing a single harmonically trapped system as a function of a characteristic density and lattice depth using a magnetic resonance imaging (MRI) technique to eliminate inhomogeneous averaging.

The propagation of light in periodic structures with high optical density is suppressed if the light frequency lies within certain bands called photonic band gaps. The effect is well-known from dielectric photonic crystals, but also exists in optical lattices and has recently been observed experimentally. While it is usually modelled using the transfer matrix approach, we show here that the phenomenon is also efficiently captured by a cooperative scattering model in the multiple scattering limit which, apart from providing a more fundamental understanding of the phenomenon, has the advantage of allowing incorporation of finite-size and disorder effects.

Atomic physics experiments, based on hot vapors or laser-cooled atomic samples, may be useful to simulate some astrophysical problems, where radiation pressure, radiative transport or light amplification are involved. We discuss several experiments and proposals, dealing with multiple-scattering of light in hot and cold atomic vapors, random lasing in cold atoms and light-induced long-range forces, which may be relevant in this context.

The creation of ultracold molecules has opened up new possibilities for studies on molecular matter waves, strongly interacting superfluids, high-precision molecular spectroscopy and coherent molecular optics. In an atomic Bose–Einstein condensate (BEC) and a degenerate Fermi–Fermi or Fermi–Bose mixture, magnetic Feshbach resonance or optical photoassociation (PA) technique has been used to create not only diatomic molecules but also more complex molecules. In this chapter, we focus on many issues of nonlinear dynamics of atom–molecule systems. In Sec. 1, on the basis of the two-channelmean-field approach, we study the manybody effects on the Landau–Zener(LZ) picture of two-body molecular production through dramatically distorting the energy levels near the Feshbach resonance. In Sec. 2, we investigate the Feshbach resonance with modulation of an oscillating magnetic field. In Sec. 3, we include the nonlinear interparticle collisions and focus on the linear instability induced by the collisions and the adiabatic fidelity of the atom–trimer dark state in a stimulated Raman adiabatic passage (STIRAP). In Sec. 4, we theoretically investigate conversion problem from atom to N-body polyatomic molecule in an ultracold bosonic system by implementing the generalized STIRAP. In the last section, we discuss role of two-body interactions in the Feshbach conversion of fermionic atoms to bosonic molecules.

Quantum metrology is the science that aims to achieve precision measurements by making use of quantum principles. Attribute to the well-developed techniques of manipulating and detecting cold atoms, cold atomic systems provide an excellent platform for implementing precision quantum metrology. In this chapter, we review the general procedures of quantum metrology and some experimental progresses in quantum metrology with cold atoms. Firstly, we give the general framework of quantum metrology and the calculation of quantum Fisher information, which is the core of quantum parameter estimation. Then, we introduce the quantum interferometry with single and multiparticle states. In particular, for some typical multiparticle states, we analyze their ultimate precision limits and show how quantum entanglement could enhance the measurement precision beyond the standard quantum limit. Further, we review some experimental progresses in quantum metrology with cold atomic systems.

The following section is included:

• INDEX