124 research outputs found
Penning collisions of laser-cooled metastable helium atoms
We present experimental results on the two-body loss rates in a
magneto-optical trap of metastable helium atoms. Absolute rates are measured in
a systematic way for several laser detunings ranging from -5 to -30 MHz and at
different intensities, by monitoring the decay of the trap fluorescence. The
dependence of the two-body loss rate coefficient on the excited state
() and metastable state () populations is also investigated.
From these results we infer a rather uniform rate constant
cm/s.Comment: 8 pages, 9 figures, Revte
Extended coherence time on the clock transition of optically trapped Rubidium
Optically trapped ensembles are of crucial importance for frequency
measurements and quantum memories, but generally suffer from strong dephasing
due to inhomogeneous density and light shifts. We demonstrate a drastic
increase of the coherence time to 21 s on the magnetic field insensitive clock
transition of Rb-87 by applying the recently discovered spin self-rephasing.
This result confirms the general nature of this new mechanism and thus shows
its applicability in atom clocks and quantum memories. A systematic
investigation of all relevant frequency shifts and noise contributions yields a
stability of 2.4E-11 x tau^(-1/2), where tau is the integration time in
seconds. Based on a set of technical improvements, the presented frequency
standard is predicted to rival the stability of microwave fountain clocks in a
potentially much more compact setup.Comment: 5 pages, 4 figure
Efficient magneto-optical trapping of a metastable helium gas
This article presents a new experiment aiming at BEC of metastable helium
atoms. It describes the design of a high flux discharge source of atoms and a
robust laser system using a DBR diode coupled with a high power Yb doped fiber
amplifier for manipulating the beam of metastable atoms. The atoms are trapped
in a small quartz cell in an extreme high vacuum. The trapping design uses an
additional laser (repumper) and allows the capture of a large number of
metastable helium atoms (approximately ) in a geometry favorable for
loading a tight magnetostatic trap.Comment: 12 pages, 7 figures, Late
Influence of optical aberrations in an atomic gyroscope
In atom interferometry based on light-induced diffraction, the optical
aberrations of the laser beam splitters are a dominant source of noise and
systematic effect. In an atomic gyroscope, this effect is dramatically reduced
by the use of two atomic sources. But it remains critical while coupled to
fluctuations of atomic trajectories, and appears as a main source of noise to
the long term stability. Therefore we measure these contributions in our setup,
using cold Cesium atoms and stimulated Raman transitions
New frontiers at the interface of general relativity and quantum optics
In the present paper we follow three major themes: (i) concepts of rotation in general relativity, (ii) effects induced by these generalized rotations, and (iii) their measurement using interferometry. Our journey takes us from the Foucault pendulum via the Sagnac interferometer to manifestations of gravito-magnetism in double binary pulsars and in Gödel\u27s Universe. Throughout our article we emphasize the emerging role of matter wave interferometry based on cold atoms or Bose-Einstein condensates leading to superior inertial sensors. In particular, we advertise recent activities directed towards the operation of a coherent matter wave interferometer in an extended free fall. © 2009 Springer Science+Business Media B.V
Doppler cooling and trapping on forbidden transitions
Ultracold atoms at temperatures close to the recoil limit have been achieved
by extending Doppler cooling to forbidden transitions. A cloud of ^40Ca atoms
has been cooled and trapped to a temperature as low as 6 \mu K by operating a
magneto-optical trap on the spin-forbidden intercombination transition.
Quenching the long-lived excited state with an additional laser enhanced the
scattering rate by a factor of 15, while a high selectivity in velocity was
preserved. With this method more than 10% of pre-cooled atoms from a standard
magneto-optical trap have been transferred to the ultracold trap. Monte-Carlo
simulations of the cooling process are in good agreement with the experiments
Absolute frequency measurement of the magnesium intercombination transition
We report on a frequency measurement of the clock
transition of Mg on a thermal atomic beam. The intercombination
transition has been referenced to a portable primary Cs frequency standard with
the help of a femtosecond fiber laser frequency comb. The achieved uncertainty
is which corresponds to an increase in accuracy of six
orders of magnitude compared to previous results. The measured frequency value
permits the calculation of several other optical transitions from to
the -level system for Mg, Mg and Mg. We describe in
detail the components of our optical frequency standard like the stabilized
spectroscopy laser, the atomic beam apparatus used for Ramsey-Bord\'e
interferometry and the frequency comb generator and discuss the uncertainty
contributions to our measurement including the first and second order Doppler
effect. An upper limit of in one second for the short term
instability of our optical frequency standard was determined by comparison with
a GPS disciplined quartz oscillator.Comment: 8 pages, 8 figure
Inertial sensing with quantum gases: a comparative performance study of condensed versus thermal sources for atom interferometry
Abstract: Quantum sensors based on light pulse atom interferometers allow for measurements of inertial and electromagnetic forces such as the accurate determination of fundamental constants as the fine structure constant or testing foundational laws of modern physics as the equivalence principle. These schemes unfold their full performance when large interrogation times and/or large momentum transfer can be implemented. In this article, we demonstrate how interferometry can benefit from the use of BoseâEinstein condensed sources when the state of the art is challenged. We contrast systematic and statistical effects induced by BoseâEinstein condensed sources with thermal sources in three exemplary science cases of Earth- and space-based sensors. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s)
Optical Clocks in Space
The performance of optical clocks has strongly progressed in recent years,
and accuracies and instabilities of 1 part in 10^18 are expected in the near
future. The operation of optical clocks in space provides new scientific and
technological opportunities. In particular, an earth-orbiting satellite
containing an ensemble of optical clocks would allow a precision measurement of
the gravitational redshift, navigation with improved precision, mapping of the
earth's gravitational potential by relativistic geodesy, and comparisons
between ground clocks.Comment: Proc. III International Conference on Particle and Fundamental
Physics in Space (SpacePart06), Beijing 19 - 21 April 2006, to appear in
Nucl. Phys.
- âŠ