188 research outputs found
Light shifts in atomic Bragg diffraction
Bragg diffraction of an atomic wave packet in a retroreflective geometry with
two counterpropagating optical lattices exhibits a light shift induced phase.
We show that the temporal shape of the light pulse determines the behavior of
this phase shift: In contrast to Raman diffraction, Bragg diffraction with
Gaussian pulses leads to a significant suppression of the intrinsic phase shift
due to a scaling with the third power of the inverse Doppler frequency.
However, for box-shaped laser pulses, the corresponding shift is twice as large
as for Raman diffraction. Our results are based on approximate, but analytical
expressions as well as a numerical integration of the corresponding
Schr\"odinger equation.Comment: 6 pages, 5 figure
A representation-free description of the Kasevich-Chu interferometer: a resolution of the redshift controversy
Motivated by a recent claim by Muller et al (2010 Nature 463 926-9) that an atom interferometer can serve as an atom clock to measure the gravitational redshift with an unprecedented accuracy, we provide a representation-free description of the Kasevich-Chu interferometer based on operator algebra. We use this framework to show that the operator product determining the number of atoms at the exit ports of the interferometer is a c-number phase factor whose phase is the sum of only two phases: one is due to the acceleration of the phases of the laser pulses and the other one is due to the acceleration of the atom. This formulation brings out most clearly that this interferometer is an accelerometer or a gravimeter. Moreover, we point out that in different representations of quantum mechanics such as the position or the momentum representation the phase shift appears as though it originates from different physical phenomena. Due to this representation dependence conclusions concerning an enhanced accuracy derived in a specific representation are unfounded.German Space Agency (DLR)BMWi/DLR 50 WM 0837Alexander von Humboldt StiftungTempleton Foundation/2153
Regimes of atomic diffraction: Raman versus Bragg diffraction in retroreflective geometries
We provide a comprehensive study of atomic Raman and Bragg diffraction when
coupling to a pair of counterpropagating light gratings (double diffraction) or
to a single one (single diffraction) and discuss the transition from one case
to the other in a retroreflective geometry as the Doppler detuning changes. In
contrast to single diffraction, double Raman loses its advantage of high
diffraction efficiency for short pulses and has to be performed in a Bragg-type
regime. Moreover, the structure of double diffraction leads to further
limitations for broad momentum distributions on the efficiency of mirror
pulses, making the use of (ultra) cold ensembles essential for high diffraction
efficiency.Comment: 16 pages, 14 figure
The space atom laser: An isotropic source for ultra-cold atoms in microgravity
Atom laser experiments with Bose-Einstein condensates (BECs) performed in ground-based laboratories feature a coherent and directed beam of atoms which is accelerated by gravity. In microgravity the situation is fundamentally different because the dynamics is entirely determined by the repulsive interaction between the atoms and not by the gravitational force. As a result, the output of a space atom laser is a spherical wave slowly expanding away from the initial BEC. We present a thorough theoretical study of this new source of matter waves based on rf outcoupling which exhibits an isotropic distribution both in position and momentum even for an initially anisotropic trap. The unique geometry of such a freely expanding, shell-shaped BEC offers new possibilities for matter waves in microgravity and is complementary to other matter-wave sources prepared by delta-kick collimation or adiabatic expansion. Our work paves the way for the upcoming experimental realization of a space atom laser making use of NASA's Cold Atom Laboratory on the International Space Station
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 .
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
Reply to Comment on 'Species-selective lattice launch for precision atom interferometry'
Reply to: Alexander D Cronin and Raisa Trubko: Comment on 'Species-selective lattice launch for precision atom interferometry'. In: New Journal of Physics 18 (2016), Nr. 11, 118001. DOI: https://doi.org/10.1088/1367-2630/18/11/11800
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
Quantum Test of the Universality of Free Fall
We simultaneously measure the gravitationally-induced phase shift in two
Raman-type matter-wave interferometers operated with laser-cooled ensembles of
Rb and K atoms. Our measurement yields an E\"otv\"os ratio of
. We briefly estimate possible
bias effects and present strategies for future improvements
Atom Strapdown: Toward Integrated Quantum Inertial Navigation Systems
We present an alternative technique for estimating the response of a cold atom interferometer (CAI). Using data from a conventional inertial measurement unit (IMU) and common strapdown terminology, the position of the atom wave packet is tracked in a newly introduced sensor frame, enabling hybridization of both systems in terms of acceleration and angular rate measurements. The sensor frame allows for an easier mathematical description of the CAI measurement and integration into higher-level navigation systems. The dynamic terms resulting from the transformation of the IMU frame into the CAI sensor frame are evaluated in simulations. The implementation of the method as a prediction model in an extended Kalman filter is explained and demonstrated in realistic simulations, showing improvements of over two orders of magnitude with respect to the conventional IMU strapdown solution. Finally, the implications of these findings for future hybrid quantum navigation systems are discussed
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