136 research outputs found
Generation of Superposition Spin States in an Atomic Ensemble
A method for generating a mesoscopic superposition state of the collective
spin variable of a gas of atoms is proposed. The state consists of a
superposition of the atomic spins pointing in two slightly different
directions. It is obtained by using off resonant light to carry out Quantum Non
Demolition Measurements of the spins. The relevant experimental conditions,
which require very dense atomic samples, can be realized with presently
available techniques. Long-lived atomic superposition states may become useful
as an off-line resource for quantum computing with otherwise linear operations.Comment: 5 pages, 2 figures, accepted in Phys. Rev. Let
1D Bose gases in an optical lattice
We report on the study of the momentum distribution of a one-dimensional Bose gas in an optical lattice. From the momentum distribution we extract the condensed fraction of the gas and thereby measure the depletion of the condensate and compare it with a theoretical estimate. We have measured the coherence length of the gas for systems with average occupation n̄>1 and n̄<1 per lattice sit
Assessing short-term feed efficiency and its association with biological markers in herbage-fed dairy cows.
Feed efficiency is an important trait of dairy production. However, assessing feed efficiency is constrained by the associated cost and difficulty in measuring individual feed intake, especially on pastures. The objective of this study was to investigate short-term feed efficiency traits of herbage-fed dairy cows and screening of potential biomarkers (n = 238). Derived feed efficiency traits were ratio-based (i.e., feed conversion ratio (FCR) and N use efficiency (NUE)) or residual-based (i.e., residual feed intake (RFI), residual energy intake (REI), and residual N intake (RNI)). Thirty-eight Holstein and 16 Swiss Fleckvieh dairy cows underwent a 7-d measurement period during mid- and/or late-lactation. The experimental data (n = 100 measurement points) covered different lactational and herbage-fed system situations: mid-lactation grazing (n = 56), late-lactation grazing (n = 28), and late-lactation barn feeding (n = 16). During each measuring period, the individual herbage intake of each cow was estimated using the n-alkane marker technique. For each cow, biomarkers representing milk constituents (n = 109), animal characteristics (n = 13), behaviour, and activity (n = 46), breath emissions (n = 3), blood constituents (n = 35), surface, and rectal temperature (n = 29), hair cortisol (n = 1), and near-infrared (NIR) spectra of faeces and milk (n = 2) were obtained. The relationships between biomarkers and efficiency traits were statistically analysed with univariate linear regression and for NIR spectra using partial least squares regression with feed efficiency traits. The feed efficiency traits were interrelated with each other (r: -0.57 to -0.86 and 0.49-0.81). The biomarkers showed varying R2 values in explaining the variability of feed efficiency traits (FCR: 0.00-0.66, NUE: 0.00-0.74, RFI: 0.00-0.56, REI: 0.00-0.69, RNI: 0.00-0.89). Overall, the feed efficiency traits were best explained by NIR spectral characteristics of milk and faeces (R2: 0.25-0.89). Biomarkers show potential for predicting feed efficiency in herbage-fed dairy cows. NIR spectra data analysis of milk and faeces presents a promising method for estimating individual feed efficiency upon further validation of prediction models. Future applications will depend on the ability to improve the robustness of biomarkers to predict feed efficiency in a greater variety of environments (locations), managing conditions, feeding systems, production intensities, and other aspects
1D Bose Gases in an Optical Lattice
We report on the study of the momentum distribution of a one-dimensional Bose
gas in an optical lattice. From the momentum distribution we extract the
condensed fraction of the gas and thereby measure the depletion of the
condensate and compare it with a theorical estimate. We have measured the
coherence length of the gas for systems with average occupation and
per lattice site.Comment: 4 pages, 3 figure
Superfluid to Mott insulator transition in one, two, and three dimensions
No Heading: We have created one-, two-, and three-dimensional quantum gases and study the superfluid to Mott insulator transition. Measurements of the transition using Bragg spectroscopy show that the excitation spectra of the low-dimensional superfluids differ significantly from the three-dimensional cas
Mapping a quantum state of light onto a long-lived atomic spin state: towards quantum memory
We report an experiment on mapping a quantum state of light onto the ground
state spin of an ensemble of Cs atoms with the life time of 2 milliseconds.
Quantum memory for one of the two quadrature phase operators of light is
demonstrated with vacuum and squeezed states of light. The sensitivity of the
mapping procedure at the level of approximately one photon/sec per Hz is shown.
The results pave the road towards complete (storing both quadrature phase
observables) quantum memory for Gaussian states of light. The experiment also
sheds new light on fundamental limits of sensitivity of the magneto-optical
resonance method.Comment: 5 pages, 4 figures, RevTe
Characterizing the spin state of an atomic ensemble using the magneto-optical resonance method
Quantum information protocols utilizing atomic ensembles require preparation
of a coherent spin state (CSS) of the ensemble as an important starting point.
We investigate the magneto-optical resonance method for characterizing a spin
state of cesium atoms in a paraffin coated vapor cell. Atoms in a constant
magnetic field are subject to an off-resonant laser beam and an RF magnetic
field. The spectrum of the Zeeman sub-levels, in particular the weak quadratic
Zeeman effect, enables us to measure the spin orientation, the number of atoms,
and the transverse spin coherence time. Notably the use of 894nm pumping light
on the D1-line, ensuring the state F=4, m_F=4 to be a dark state, helps us to
achieve spin orientation of better than 98%. Hence we can establish a CSS with
high accuracy which is critical for the analysis of the entangled states of
atoms.Comment: 12 pages ReVTeX, 6 figures, in v2 added ref. and corrected typo
A New Measurement of the 1S0 Neutron-Neutron Scattering Length using the Neutron-Proton Scattering Length as a Standard
The present paper reports high-accuracy cross-section data for the 2H(n,nnp)
reaction in the neutron-proton (np) and neutron-neutron (nn)
final-state-interaction (FSI) regions at an incident mean neutron energy of
13.0 MeV. These data were analyzed with rigorous three-nucleon calculations to
determine the 1S0 np and nn scattering lengths, a_np and a_nn. Our results are
a_nn = -18.7 +/- 0.6 fm and a_np = -23.5 +/- 0.8 fm. Since our value for a_np
obtained from neutron-deuteron (nd) breakup agrees with that from free np
scattering, we conclude that our investigation of the nn FSI done
simultaneously and under identical conditions gives the correct value for a_nn.
Our value for a_nn is in agreement with that obtained in pion-deuteron capture
measurements but disagrees with values obtained from earlier nd breakup
studies.Comment: 4 pages and 3 figure
The three-nucleon bound state using realistic potential models
The bound states of H and He have been calculated using the Argonne
plus the Urbana three-nucleon potential. The isospin state
have been included in the calculations as well as the - mass difference.
The H-He mass difference has been evaluated through the charge
dependent terms explicitly included in the two-body potential. The calculations
have been performed using two different methods: the solution of the Faddeev
equations in momentum space and the expansion on the correlated hyperspherical
harmonic basis. The results are in agreement within 0.1% and can be used as
benchmark tests. Results for the CD-Bonn interaction are also presented. It is
shown that the H and He binding energy difference can be predicted
model independently.Comment: 5 pages REVTeX 4, 1 figures, 6 table
Narrowband frequency tunable light source of continuous quadrature entanglement
We report the observation of non-classical quantum correlations of continuous
light variables from a novel type of source. It is a frequency non-degenerate
optical parametric oscillator below threshold, where signal and idler fields
are separated by 740MHz corresponding to two free spectrum ranges of the
parametric oscillator cavity. The degree of entanglement observed, - 3.8 dB, is
the highest to-date for a narrowband tunable source suitable for atomic quantum
memory and other applications in atomic physics. Finally we use the latter to
visualize the Einstein-Podolsky-Rosen paradox.Comment: 11 pages, 9 figures, LaTe
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