Optical Devices for Cold Atoms and Bose-Einstein Condensates

The manipulation of cold atoms with optical fields is a very promising technique for a variety of applications ranging from laser cooling and trapping to coherent atom transport and matter wave interferometry. Optical fields have also been proposed as interesting tools for quantum information processing with cold atoms. In this paper, we present a theoretical study of the dynamics of a cold 87Rb atomic cloud falling in the gravity field in the presence of two crossing dipole guides. The cloud is either deflected or split between the two branches of this guide. We explore the possibilities of optimization of this device and present preliminary results obtained in the case of zero-temperature dilute Bose-Einstein condensates.Comment: Proceedings of the International Spectroscopy Conference ISC-2007, Sousse, Tunisi

Atom interferometry with Bose-Einstein condensates on the International Space Station

Quantum technologies are on the rise to change our daily life and thinking triggered by enormous advances in quantum enhanced communication, computation, metrology, and sensing. For many of these fields an operation in space will be essential to improve the relevance and significance of future applications. In particular, space-based quantum sensing will enable Earth observation missions, studies of relativistic geodesy, and tests of fundamental physical concepts with outstanding precision. The basis for these prospects is the realization of ultracold quantum gases in a microgravity environment. Ultracold quantum gases like Bose-Einstein condensates (BECs) offer an excellent control over their external as well as internal degrees of freedom allowing for extremely low expansion energies. Under microgravity conditions this control enables unrivaled long free observation times which render BECs exquisite sources for atom interferometry, where the sensitivity typically scales quadratically with the interrogation time. Here we report on a series of BEC experiments performed with NASA's Cold Atom Lab aboard the International Space Station demonstrating first atom interferometers in orbit. By employing various Mach-Zehnder-type geometries we have realized magnetic gradiometers and successfully compared their outcome to complementary non-interferometric measurements. Moreover, we have characterized the atom source in great detail and have analyzed the current experimental limitations of the apparatus. Finally, we will provide an outlook on future experiments with CAL and beyond. These results pave the way towards future precision measurements with atom interferometers in space

Species-selective lattice launch for precision atom interferometry

Long-baseline precision tests based on atom interferometry require drastic control over the initial external degrees of freedom of atomic ensembles to reduce systematic effects. The use of optical lattices (OLs) is a highly accurate method to manipulate atomic states in position and momentum allowing excellent control of the launch in atomic fountains. The simultaneous lattice launch of two atomic species, as required in a quantum test of the equivalence principle, is however problematic due to crosstalk effects. In this article, we propose to selectively address two species of alkalines by applying two OLs at or close to magic-zero wavelengths of the atoms. The proposed scheme applies in general for a pair of species with a vastly different ac Stark shift to a laser wavelength. We illustrate the principle by studying a fountain launch of condensed ensembles of 87Rb and 41K initially co-located. Numerical simulations confirm the fidelity of our scheme up to few nm and nm s−1 in inter-species differential position and velocity, respectively. This result is a pre-requisite for the next performance level in precision tests.DAADDFG/SFB/geo-QDLR/50WM1131-1137Federal Ministry of Economic affairs and Energy (BMWi

Testing the universality of free fall with rubidium and ytterbium in a very large baseline atom interferometer

We propose a very long baseline atom interferometer test of Einstein's equivalence principle (EEP) with ytterbium and rubidium extending over 10m of free fall. In view of existing parametrizations of EEP violations, this choice of test masses significantly broadens the scope of atom interferometric EEP tests with respect to other performed or proposed tests by comparing two elements with high atomic numbers. In a first step, our experimental scheme will allow reaching an accuracy in the E\"otv\"os ratio of $7\times 10^{-13}$. This achievement will constrain violation scenarios beyond our present knowledge and will represent an important milestone for exploring a variety of schemes for further improvements of the tests as outlined in the paper. We will discuss the technical realisation in the new infrastructure of the Hanover Institute of Technology (HITec) and give a short overview of the requirements to reach this accuracy. The experiment will demonstrate a variety of techniques which will be employed in future tests of EEP, high accuracy gravimetry and gravity-gradiometry. It includes operation of a force sensitive atom interferometer with an alkaline earth like element in free fall, beam splitting over macroscopic distances and novel source concepts

Quantum description of atomic diffraction by material nanostructures

We present a theoretical model of matter-wave diffraction through a material nanostructure. This model is based on the numerical solution of the time-dependent Schr{\"o}dinger equation, which goes beyond the standard semi-classical approach. In particular, we consider the dispersion force interaction between the atoms and the material, which is responsible for high energy variations. The effect of such forces on the quantum model is investigated, along with a comparison with the semi-classical model. In particular, for atoms at low velocity and close to the material surface, the semi-classical approach fails, while the quantum model accurately describes the expected diffraction pattern. This description is thus relevant for slow and cold atom experiments where increased precision is required, e.g. for metrological applications

Quantum description of atomic diffraction by material nanostructures

We present a theoretical model of matter-wave diffraction through a material nanostructure. This model is based on the numerical solution of the time-dependent Schrödinger equation, which goes beyond the standard semiclassical approach. In particular, we consider the dispersion force interaction between the atoms and the material, which is responsible for high energy variations. The effect of such forces on the quantum model is investigated, along with a comparison with the semiclassical model. In particular, for atoms at low velocity and close to the material surface, the semiclassical approach fails, while the quantum model accurately describes the expected diffraction pattern. This description is thus relevant for slow and cold atom experiments where increased precision is required, e.g., for metrological applications

Efficient numerical description of the dynamics of interacting multispecies quantum gases

We present a highly efficient method for the numerical solution of coupled Gross-Pitaevskii equations describing the evolution dynamics of a multi-species mixture of Bose-Einstein condensates in time-dependent potentials. This method, based on a moving and expanding reference frame, compares favorably to a more standard but much more computationally expensive solution based on a frozen frame. It allows an accurate description of the long-time behavior of interacting, multi-species quantum mixtures including the challenging problem of long free expansions relevant to microgravity and space experiments. We demonstrate a successful comparison to experimental measurements of a binary Rb-K mixture recently performed with the payload of a sounding rocket experiment

Large-momentum-transfer atom interferometers with μ\murad-accuracy using Bragg diffraction

Large-momentum-transfer~(LMT) atom interferometers using elastic Bragg scattering on light waves are among the most precise quantum sensors to date. To advance their accuracy from the mrad to the $\mu$rad regime, it is necessary to understand the rich phenomenology of the Bragg interferometer, which differs significantly from that of a standard two-mode interferometer. We develop an analytic model for the interferometer signal and demonstrate its accuracy using comprehensive numerical simulations. Our analytic treatment allows the determination of the atomic projection noise limit of an LMT Bragg interferometer, and provides the means to saturate this limit. It affords accurate knowledge of the systematic phase errors as well as their suppression by two orders of magnitude down to a few $\mu\mathrm{rad}$ using appropriate light pulse parameters.Comment: 7 pages, 5 figures,comments welcome!; Assembled supplemental material together with mansucrip