133 research outputs found
Precision spectroscopy with two correlated atoms
We discuss techniques that allow for long coherence times in laser
spectroscopy experiments with two trapped ions. We show that for this purpose
not only entangled ions prepared in decoherence-free subspaces can be used but
also a pair of ions that are not entangled but subject to the same kind of
phase noise. We apply this technique to a measurement of the electric
quadrupole moment of the 3d D5/2 state of 40Ca+ and to a measurement of the
linewidth of an ultrastable laser exciting a pair of 40Ca+ ions
Growth and reproduction studies on gilthead seabream (Sparus aurata) in Beymelek Lagoon, Turkey
In the present study, age, growth, length-weight relationship and reproduction were investigated in gilthead seabream (Sparus aurata L., 1758) collected from Beymelek Lagoon (Antalya, Turkey) between February 2006 and July 2007. The age, total length and weight of samples ranged from 0+ to 4 years, 10.6 to 35.5cm, and 18 to 928g, respectively. Growth was described by the standard form of the von Bertalanffy growth equation and the estimated parameters were Lâ = 44.6cm, k = 0.394yr^-1 and t0 = -1.331yr. Length-weight relationship was determined as W=0.0174TL^2.9769 (R^2=0.965), and weight increased with size isometrically (b = 2.9769) for all fish. Sex inversion occurred mainly at 26 cm in total length and females reached sexual maturity at 28.5 cm. The spawning period was from December to February, while the gamete emission peaked in December
Quantum control, quantum information processing, and quantum-limited metrology with trapped ions
We briefly discuss recent experiments on quantum information processing using
trapped ions at NIST. A central theme of this work has been to increase our
capabilities in terms of quantum computing protocols, but we have also applied
the same concepts to improved metrology, particularly in the area of frequency
standards and atomic clocks. Such work may eventually shed light on more
fundamental issues, such as the quantum measurement problem.Comment: Proceedings of the International Conference on Laser Spectroscopy
(ICOLS), 10 pages, 5 figure
Diffusion Resonances in Action Space for an Atom Optics Kicked Rotor with Decoherence
We numerically investigate momentum diffusion rates for the pulse kicked
rotor across the quantum to classical transition as the dynamics are made more
macroscopic by increasing the total system action. For initial and late time
rates we observe an enhanced diffusion peak which shifts and scales with
changing kick strength, and we also observe distinctive peaks around quantum
resonances. Our investigations take place in the context of a system of
ultracold atoms which is coupled to its environment via spontaneous emission
decoherence, and the effects should be realisable in ongoing experiments.Comment: 4 Pages, RevTeX 4, 5 Figures. Updated Figures, Minor Changes to text,
Corrected Reference
'Designer atoms' for quantum metrology
Entanglement is recognized as a key resource for quantum computation and
quantum cryptography. For quantum metrology, the use of entangled states has
been discussed and demonstrated as a means of improving the signal-to-noise
ratio. In addition, entangled states have been used in experiments for
efficient quantum state detection and for the measurement of scattering
lengths. In quantum information processing, manipulation of individual quantum
bits allows for the tailored design of specific states that are insensitive to
the detrimental influences of an environment. Such 'decoherence-free subspaces'
protect quantum information and yield significantly enhanced coherence times.
Here we use a decoherence-free subspace with specifically designed entangled
states to demonstrate precision spectroscopy of a pair of trapped Ca+ ions; we
obtain the electric quadrupole moment, which is of use for frequency standard
applications. We find that entangled states are not only useful for enhancing
the signal-to-noise ratio in frequency measurements - a suitably designed pair
of atoms also allows clock measurements in the presence of strong technical
noise. Our technique makes explicit use of non-locality as an entanglement
property and provides an approach for 'designed' quantum metrology
Nanofabrication by magnetic focusing of supersonic beams
We present a new method for nanoscale atom lithography. We propose the use of
a supersonic atomic beam, which provides an extremely high-brightness and cold
source of fast atoms. The atoms are to be focused onto a substrate using a thin
magnetic film, into which apertures with widths on the order of 100 nm have
been etched. Focused spot sizes near or below 10 nm, with focal lengths on the
order of 10 microns, are predicted. This scheme is applicable both to precision
patterning of surfaces with metastable atomic beams and to direct deposition of
material.Comment: 4 pages, 3 figure
Squeezing of Atoms in a Pulsed Optical Lattice
We study the process of squeezing of an ensemble of cold atoms in a pulsed
optical lattice. The problem is treated both classically and
quantum-mechanically under various thermal conditions. We show that a dramatic
compression of the atomic density near the minima of the optical potential can
be achieved with a proper pulsing of the lattice. Several strategies leading to
the enhanced atomic squeezing are suggested, compared and optimized.Comment: Latex, 9 pages, 10 figures, submitted to PR
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