A laser cooling method for trapped atoms is described which achieves ground state cooling by exploiting quantum interference in a driven L-shaped arrangement of atomic levels. The scheme is technically simpler than existing methods of sideband cooling, yet it can be significantly more efficient, in particular when several motional modes are involved, and it does not impose restrictions on the transition linewidth. We study the full quantum mechanical model of the cooling process for one motional degree of freedom and show that a rate equation provides a good approximation.
A chain of singly-charged particles, confined by a harmonic potential, exhibits a sudden transition to a zigzag configuration when the radial potential reaches a critical value, depending on the particle number. This structural change is a phase transition of second order, whose order parameter is the crystal displacement from the chain axis. We study analytically the transition using Landau theory and find full agreement with numerical predictions by [J. Schiffer Phys. Rev. Lett. 70, 818 (1993)] and [Piacente et al Phys. Rev. B 69, 045324 (2004)]. Our theory allows us to determine analytically the system's behaviour at the transition point.Comment: 12 pages, 8 figures. Revised version, to appear in Phys. Rev.
Understanding strongly correlated quantum systems is a central problem in many areas of physics. The collective behavior of interacting particles gives rise to diverse fundamental phenomena such as confinement in quantum chromodynamics, phase transitions, and electron fractionalization in the quantum Hall regime. While such systems typically involve massive particles, optical photons can also interact with each other in a nonlinear medium. In practice, however, such interactions are often very weak. Here we describe a novel technique that allows the creation of a strongly correlated quantum gas of photons using one-dimensional optical systems with tight field confinement and coherent photon trapping techniques. The confinement enables the generation of large, tunable optical nonlinearities via the interaction of photons with a nearby cold atomic gas. In its extreme, we show that a quantum light field can undergo fermionization in such one-dimensional media, which can be probed via standard photon correlation measurements.
Trapped and laser-cooled ions are increasingly used for a variety of modern high-precision experiments, for frequency standard applications, and for quantum information processing. Therefore laser cooling of trapped ions is reviewed, the current state of the art is reported, and several new cooling techniques are outlined. The principles of ion trapping and the basic concepts of laser cooling for trapped atoms are introduced. The underlying physical mechanisms are presented, and basic experiments are briefly sketched. Particular attention is paid to recent progress by elucidating several milestone experiments. In addition, a number of special cooling techniques pertaining to trapped ions are reviewed; open questions and future research lines are indicated.
We study the low temperature physics of an ultracold atomic gas in the potential formed inside a pumped optical resonator. Here, the height of the cavity potential, and hence the quantum state of the gas, depends not only on the pump parameters, but also on the atomic density through a dynamical ac-Stark shift of the cavity resonance. We derive the Bose-Hubbard model in one dimension and use the strong coupling expansion to determine the parameter regime in which the system is in the Mott-insulator state. We predict the existence of overlapping, competing Mott-insulator states, and bistable behavior in the vicinity of the shifted cavity resonance, controlled by the pump parameters. Outside these parameter regions, the state of the system is in most cases superfluid. DOI: 10.1103/PhysRevLett.100.050401 PACS numbers: 05.30.Jp, 03.75.Hh, 37.10.Jk, 67.90.+z Ultracold atomic gases in optical lattices offer the unprecedented and unique possibility to study paradigmatic systems of quantum many-body physics [1,2]. These systems allow one to realize various versions of Hubbard models [3], a prominent example of which is the BoseHubbard model [4], exhibiting the superfluid (SF)-Mottinsulator (MI) quantum phase transition [5]. The realization of the Bose-Hubbard model with ultracold atoms has been proposed in the seminal theoretical work in Ref. [6] and has been demonstrated in the milestone experiments in Ref. [7]. Several aspects and modifications of the SF-MI quantum phase transition (or crossover [8]) are the objects of intense studies [2].Optical lattices in free space are not affected by the presence of the atoms. This scenario is, however, strongly modified when the atoms move in the optical potential which is formed inside a pumped resonator: Here, the atoms interact with the cavity mode while the cavity field, determining the optical lattice, may critically depend on the density of the atoms [9,10]. Several recent studies address cavity quantum electrodynamics (CQED) with cold atoms. CQED techniques were used to measure pair correlations in the atom laser [11] and have been proposed for characterizing quantum states of ultracold matter [12]. Self-organization of atoms in transversally pumped cavities was observed in [13] and was theoretically described in [14]. Bragg scattering of atomic structures inside optical resonators has been investigated in [15]. Most recently, Bose-Einstein condensed atoms have been loaded inside cavities [16]. This experimental progress calls for theoretical development of CQED combined with many-body physics.In this Letter we determine the ground state of ultracold atomic gases in the optical lattice of a cavity. The cavity is driven by a laser, and the atoms shift the cavity resonance, thus affecting the intracavity field amplitude, which in turn determines the depth of the cavity potential and the ground state of the atomic gas itself. The problem is hence highly nonlinear, as the optical lattice and the state of the atoms have to be evaluated in a self-consistent way. The derivat...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.