194 research outputs found
Collapse and Revival of the Matter Wave Field of a Bose-Einstein Condensate
At the heart of a Bose-Einstein condensate lies its description as a single
giant matter wave. Such a Bose-Einstein condensate represents the most
"classical" form of a matter wave, just as an optical laser emits the most
classical form of an electromagnetic wave. Beneath this giant matter wave,
however, the discrete atoms represent a crucial granularity, i.e. a
quantization of this matter wave field. Here we show experimentally that this
quantization together with the cold collisions between atoms lead to a series
of collapses and revivals of the coherent matter wave field of a Bose-Einstein
condensate. We observe such collapses and revivals directly in the dynamical
evolution of a multiple matter wave interference pattern, and thereby
demonstrate a striking new behaviour of macroscopic quantum matter
Sub-Hz line width diode lasers by stabilization to vibrationally and thermally compensated ULE Fabry-Perot cavities
We achieved a 0.5 Hz optical beat note line width with ~ 0.1 Hz/s frequency
drift at 972 nm between two external cavity diode lasers independently
stabilized to two vertically mounted Fabry-Perot (FP) reference cavities.
Vertical FP reference cavities are suspended in mid-plane such that the
influence of vertical vibrations to the mirror separation is significantly
suppressed. This makes the setup virtually immune for vertical vibrations that
are more difficult to isolate than the horizontal vibrations. To compensate for
thermal drifts the FP spacers are made from Ultra-Low-Expansion (ULE) glass
which possesses a zero linear expansion coefficient. A new design using Peltier
elements in vacuum allows operation at an optimal temperature where the
quadratic temperature expansion of the ULE could be eliminated as well. The
measured linear drift of such ULE FP cavity of 63 mHz/s was due to material
aging and the residual frequency fluctuations were less than 40 Hz during 16
hours of measurement. Some part of the temperature-caused drift is attributed
to the thermal expansion of the mirror coatings. High-frequency thermal
fluctuations that cause vibrations of the mirror surfaces limit the stability
of a well designed reference cavity. By comparing two similar laser systems we
obtain an Allan instability of 2*10-15 between 0.1 and 10 s averaging time,
which is close to the theoretical thermal noise limit.Comment: submitted to Applied Physics
A scanning cavity microscope
Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1, 700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm(2);we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems
Coherent manipulation of Bose-Einstein condensates with state-dependent microwave potentials on an atom chip
Entanglement-based technologies, such as quantum information processing,
quantum simulations, and quantum-enhanced metrology, have the potential to
revolutionise our way of computing and measuring and help clarifying the
puzzling concept of entanglement itself. Ultracold atoms on atom chips are
attractive for their implementation, as they provide control over quantum
systems in compact, robust, and scalable setups. An important tool in this
system is a potential depending on the internal atomic state. Coherent dynamics
in this potential combined with collisional interactions allows entanglement
generation both for individual atoms and ensembles. Here, we demonstrate
coherent manipulation of Bose-condensed atoms in such a potential, generated in
a novel way with microwave near-fields on an atom chip. We reversibly entangle
atomic internal and motional states, realizing a trapped-atom interferometer
with internal-state labelling. Our system provides control over collisions in
mesoscopic condensates, paving the way for on-chip generation of many-particle
entanglement and quantum-enhanced metrology with spin-squeezed states.Comment: 9 pages, 6 figure
New Measurement of the 2S Hyperfine Interval in Atomic Hydrogen
An optical measurement of the 2S hyperfine interval in atomic hydrogen using
two-photon spectroscopy of the 1S-2S transition gives a value of 177 556
834.3(6.7) Hz. The uncertainty is
2.4 times smaller than achieved by our group in 2003 and more than 4 times
smaller than for any independent radio-frequency measurement. The specific
combination of the 2S and 1S hyperfine intervals predicted by QED theory
Hz is in good
agreement with the value of 48 923(54) Hz obtained from this experiment.Comment: 4 pages, 4 figure
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.
Application potential of high performance steels for weight reduction and efficiency increase in commercial vehicles
New Limits to the Drift of Fundamental Constants from Laboratory Measurements
We have remeasured the absolute - transition frequency in atomic hydrogen. A comparison with the result of the previous
measurement performed in 1999 sets a limit of Hz for the drift of
with respect to the ground state hyperfine splitting in Cs. Combining this result with the recently published
optical transition frequency in Hg against and a
microwave Rb and Cs clock comparison, we deduce separate limits
on yr and the
fractional time variation of the ratio of Rb and Cs nuclear magnetic moments
equal to
yr. The latter provides information on the temporal behavior of the
constant of strong interaction.Comment: 4 pages, 3 figures, LaTe
Pathway to the PiezoElectronic Transduction Logic Device
The information age challenges computer technology to process an
exponentially increasing computational load on a limited energy budget - a
requirement that demands an exponential reduction in energy per operation. In
digital logic circuits, the switching energy of present FET devices is
intimately connected with the switching voltage, and can no longer be lowered
sufficiently, limiting the ability of current technology to address the
challenge. Quantum computing offers a leap forward in capability, but a clear
advantage requires algorithms presently developed for only a small set of
applications. Therefore, a new, general purpose, classical technology based on
a different paradigm is needed to meet the ever increasing demand for data
processing.Comment: in Nano Letters (2015
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