68 research outputs found
Progress in atom chips and the integration of optical microcavities
We review recent progress at the Centre for Cold Matter in developing atom
chips. An important advantage of miniaturizing atom traps on a chip is the
possibility of obtaining very tight trapping structures with the capability of
manipulating atoms on the micron length scale. We recall some of the pros and
cons of bringing atoms close to the chip surface, as is required in order to
make small static structures, and we discuss the relative merits of metallic,
dielectric and superconducting chip surfaces. We point out that the addition of
integrated optical devices on the chip can enhance its capability through
single atom detection and controlled photon production. Finally, we review the
status of integrated microcavities that have recently been demonstrated at our
Centre and discuss their prospects for future development.Comment: 12 pages, 6 figures, proceedings of the ICOLS07 conferenc
Atom detection and photon production in a scalable, open, optical microcavity
A microfabricated Fabry-Perot optical resonator has been used for atom
detection and photon production with less than 1 atom on average in the cavity
mode. Our cavity design combines the intrinsic scalability of microfabrication
processes with direct coupling of the cavity field to single-mode optical
waveguides or fibers. The presence of the atom is seen through changes in both
the intensity and the noise characteristics of probe light reflected from the
cavity input mirror. An excitation laser passing transversely through the
cavity triggers photon emission into the cavity mode and hence into the
single-mode fiber. These are first steps towards building an optical
microcavity network on an atom chip for applications in quantum information
processing.Comment: 4 pages, 4 figures. A typographical error in the published paper has
been corrected (equation of the corrected normalized variance, page 3, 2nd
paragraph
The effect of self-affine fractal roughness of wires on atom chips
Atom chips use current flowing in lithographically patterned wires to produce
microscopic magnetic traps for atoms. The density distribution of a trapped
cold atom cloud reveals disorder in the trapping potential, which results from
meandering current flow in the wire. Roughness in the edges of the wire is
usually the main cause of this behaviour. Here, we point out that the edges of
microfabricated wires normally exhibit self-affine roughness. We investigate
the consequences of this for disorder in atom traps. In particular, we consider
how closely the trap can approach the wire when there is a maximum allowable
strength of the disorder. We comment on the role of roughness in future
atom--surface interaction experiments.Comment: 7 pages, 7 figure
Recent progress on the manipulation of single atoms in optical tweezers for quantum computing
This paper summarizes our recent progress towards using single rubidium atoms
trapped in an optical tweezer to encode quantum information. We demonstrate
single qubit rotations on this system and measure the coherence of the qubit.
We move the quantum bit over distances of tens of microns and show that the
coherence is reserved. We also transfer a qubit atom between two tweezers and
show no loss of coherence. Finally, we describe our progress towards
conditional entanglement of two atoms by photon emission and two-photon
interferences.Comment: Proceedings of the ICOLS07 conferenc
Demonstration and frequency noise characterization of a 17 m quantum cascade laser
We describe the properties of a continuous-wave room-temperature quantum
cascade laser operating at the long wavelength of 17 m. Long wavelength
mid-infrared quantum cascade lasers offer new opportunities for chemical
detection, vibrational spectroscopy and metrological measurements using
molecular species. In particular, probing low energy vibrational transitions
would be beneficial to the spectroscopy of large and complex molecules,
reducing intramolecular vibrational energy redistribution which acts as a
decoherence channel. By performing linear absorption spectroscopy of the v2
fundamental vibrational mode of N2O molecules, we have demonstrated the
spectral range and spectroscopic potential of this laser, and characterized its
free-running frequency noise properties. Finally, we also discuss the potential
application of this specific laser in an experiment to test fundamental physics
with ultra-cold molecules
Measuring the Boltzmann constant by mid-infrared laser spectroscopy of ammonia
We report on our ongoing effort to measure the Boltzmann constant,
using the Doppler broadening technique on ammonia. This paper presents some of
the improvements made to the mid-infrared spectrometer including the use of a
phase-stabilized quantum cascade laser, a lineshape analysis based on a refined
physical model and an improved fitting program 2 increasing the confidence in
our estimates of the relevant molecular parameters, and a first evaluation of
the saturation parameter and its impact on the measurement of k B. A summary of
the systematic effects contributing to the measurement is given and the optimal
experimental conditions for mitigating those effects in order to reach a
competitive measurement of at a part per million accuracy level are
outlined
Near-to mid-IR spectral purity transfer with a tunable frequency comb: methanol frequency metrology over a record frequency span
We report the development and operation of a frequency-comb-assisted
high-resolution mid-infrared molecular spectrometer combining high spectral
purity, SI-traceability, wide tunability and high sensitivity. An optical
frequency comb is used to transfer the spectral purity of a SI-traceable 1.54
m metrology-grade frequency reference to a 10.3 m quantum cascade
laser (QCL). The near-infrared reference is operated at the French
time/frequency metrology institute, calibrated there to primary frequency
standards, and transferred to Laboratoire de Physique des Lasers via the
REFIMEVE fiber network. The QCL exhibits a sub-10 --15 frequency stability from
0.1 to 10 s and its frequency is traceable to the SI with a total uncertainty
better than 4 x 10 --14 after 1-s averaging time. We have developed the
instrumentation allowing comb modes to be continuously tuned over 9 GHz
resulting in a QCL of record spectral purity uninterruptedly tunable at the
precision of the reference over an unprecedented span of 1.4 GHz. We have used
our apparatus to conduct sub-Doppler spectroscopy of methanol in a multi-pass
cell, demonstrating state-of-art frequency uncertainties down to the few
kilohertz level. We have observed weak intensity resonances unreported so far,
resolved subtle doublets never seen before and brought to light discrepancies
with the HITRAN database. This demonstrates the potential of our apparatus for
probing subtle internal molecular processes, building accurate spectroscopic
models of polyatomic molecules of atmospheric or astrophysical interest, and
carrying out precise spectroscopic tests of fundamental physics
Experiments on a videotape atom chip: fragmentation and transport studies
This paper reports on experiments with ultra-cold rubidium atoms confined in
microscopic magnetic traps created using a piece of periodically-magnetized
videotape mounted on an atom chip. The roughness of the confining potential is
studied with atomic clouds at temperatures of a few microKelvin and at
distances between 30 and 80 microns from the videotape-chip surface. The
inhomogeneities in the magnetic field created by the magnetized videotape close
to the central region of the chip are characterized in this way. In addition,
we demonstrate a novel transport mechanism whereby we convey cold atoms
confined in arrays of videotape magnetic micro-traps over distances as large as
~ 1 cm parallel to the chip surface. This conveying mechanism enables us to
survey the surface of the chip and observe potential-roughness effects across
different regions.Comment: 29 pages, 22 figures
Stark deceleration of CaF molecules in strong- and weak-field seeking states
We report the Stark deceleration of CaF molecules in the strong-field seeking
ground state and in a weak-field seeking component of a rotationally-excited
state. We use two types of decelerator, a conventional Stark decelerator for
the weak-field seekers, and an alternating gradient decelerator for the
strong-field seekers, and we compare their relative merits. We also consider
the application of laser cooling to increase the phase-space density of
decelerated molecules.Comment: 10 pages, 8 figure
Progress towards an accurate determination of the Boltzmann constant by Doppler spectroscopy
In this paper, we present significant progress performed on an experiment
dedicated to the determination of the Boltzmann constant, k, by accurately
measuring the Doppler absorption profile of a line in a gas of ammonia at
thermal equilibrium. This optical method based on the first principles of
statistical mechanics is an alternative to the acoustical method which has led
to the unique determination of k published by the CODATA with a relative
accuracy of 1.7 ppm. We report on the first measurement of the Boltzmann
constant by laser spectroscopy with a statistical uncertainty below 10 ppm,
more specifically 6.4 ppm. This progress results from improvements in the
detection method and in the statistical treatment of the data. In addition, we
have recorded the hyperfine structure of the probed saQ(6,3) rovibrational line
of ammonia by saturation spectroscopy and thus determine very precisely the
induced 4.36 (2) ppm broadening of the absorption linewidth. We also show that,
in our well chosen experimental conditions, saturation effects have a
negligible impact on the linewidth. Finally, we draw the route to future
developments for an absolute determination of with an accuracy of a few ppm.Comment: 22 pages, 11 figure
- …