2,429 research outputs found
Enhancement of laser cooling by the use of magnetic gradients
We present a laser cooling scheme for trapped ions and atoms using a
combination of laser couplings and a magnetic gradient field. In a
Schrieffer-Wolff transformed picture, this setup cancels the carrier and blue
sideband terms completely resulting in an improved cooling behaviour compared
to standard cooling schemes (e.g. sideband cooling) and allowing cooling to the
vibrational ground state. A condition for optimal cooling rates is presented
and the cooling behaviour for different Lamb-Dicke parameters and spontaneous
decay rates is discussed. Cooling rates of one order of magnitude less than the
trapping frequency are achieved using the new cooling method. Furthermore the
scheme turns out to be robust under deviations from the optimal parameters and
moreover provides good cooling rates also in the multi particle case.Comment: 14 pages, 8 figure
Trapped ion chain as a neural network
We demonstrate the possibility of realizing a neural network in a chain of
trapped ions with induced long range interactions. Such models permit to store
information distributed over the whole system. The storage capacity of such
network, which depends on the phonon spectrum of the system, can be controlled
by changing the external trapping potential and/or by applying longitudinal
local magnetic fields. The system properties suggest the possibility of
implementing robust distributed realizations of quantum logic.Comment: 4 pages, 3 figure
Franck-Condon Physics in A Single Trapped Ion
We propose how to explore the Franck-Condon (FC) physics via a single ion
confined in a spin-dependent potential, formed by the combination of a Paul
trap and a magnetic field gradient. The correlation between electronic and
vibrational degrees of freedom, called as electron-vibron coupling, is induced
by a nonzero gradient. For a sufficiently strong electron-vibron coupling, the
FC blockade of low-lying vibronic transitions takes place. We analyze the
feasibility of observing the FC physics in a single trapped ion, and
demonstrate various potential applications of the ionic FC physics in quantum
state engineering and quantum information processing.Comment: 7 pages, 5 figure
Spin gating electrical current
We use an aluminium single electron transistor with a magnetic gate to
directly quantify the chemical potential anisotropy of GaMnAs materials.
Uniaxial and cubic contributions to the chemical potential anisotropy are
determined from field rotation experiments. In performing magnetic field sweeps
we observe additional isotropic magnetic field dependence of the chemical
potential which shows a non-monotonic behavior. The observed effects are
explained by calculations based on the kinetic
exchange model of ferromagnetism in GaMnAs. Our device inverts the conventional
approach for constructing spin transistors: instead of spin-transport
controlled by ordinary gates we spin-gate ordinary charge transport.Comment: 5 pages, 4 figure
Individual addressing of trapped ions and coupling of motional and spin states using rf radiation
Individual electrodynamically trapped and laser cooled ions are addressed in
frequency space using radio-frequency radiation in the presence of a static
magnetic field gradient. In addition, an interaction between motional and spin
states induced by an rf field is demonstrated employing rf-optical double
resonance spectroscopy. These are two essential experimental steps towards
realizing a novel concept for implementing quantum simulations and quantum
computing with trapped ions.Comment: Replaced with published versio
Radio Sources in the 2dF Galaxy Redshift Survey. I. Radio Source Populations
We present the first results from a study of the radio continuum properties
of galaxies in the 2dF Galaxy Redshift Survey, based on thirty 2dF fields
covering a total area of about 100 square degrees. About 1.5% of galaxies with
b(J) < 19.4 mag are detected as radio continuum sources in the NRAO VLA Sky
Survey (NVSS). Of these, roughly 40% are star-forming galaxies and 60% are
active galaxies (mostly low-power radio galaxies and a few Seyferts). The
combination of 2dFGRS and NVSS will eventually yield a homogeneous set of
around 4000 radio-galaxy spectra, which will be a powerful tool for studying
the distriibution and evolution of both AGN and starburst galaxies out to
redshift z=0.3.Comment: 14 pages, 7 figures, accepted for publication in PAS
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