4,459 research outputs found
Generation and detection of a sub-Poissonian atom number distribution in a one-dimensional optical lattice
We demonstrate preparation and detection of an atom number distribution in a
one-dimensional atomic lattice with the variance dB below the Poissonian
noise level. A mesoscopic ensemble containing a few thousand atoms is trapped
in the evanescent field of a nanofiber. The atom number is measured through
dual-color homodyne interferometry with a pW-power shot noise limited probe.
Strong coupling of the evanescent probe guided by the nanofiber allows for a
real-time measurement with a precision of atoms on an ensemble of some
atoms in a one-dimensional trap. The method is very well suited for
generating collective atomic entangled or spin-squeezed states via a quantum
non-demolition measurement as well as for tomography of exotic atomic states in
a one-dimensional lattice
Bogoliubov theory of entanglement in a Bose-Einstein condensate
We consider a Bose-Einstein condensate which is illuminated by a short
resonant light pulse that coherently couples two internal states of the atoms.
We show that the subsequent time evolution prepares the atoms in an interesting
entangled state called a spin squeezed state. This evolution is analysed in
detail by developing a Bogoliubov theory which describes the entanglement of
the atoms. Our calculation is a consistent expansion in , where
is the number of particles in the condensate, and our theory predict that it is
possible to produce spin squeezing by at least a factor of . Within
the Bogoliubov approximation this result is independent of temperature.Comment: 14 pages, including 5 figures, minor changes in the presentatio
Structure of boson systems beyond the mean-field
We investigate systems of identical bosons with the focus on two-body
correlations. We use the hyperspherical adiabatic method and a decomposition of
the wave function in two-body amplitudes. An analytic parametrization is used
for the adiabatic effective radial potential. We discuss the structure of a
condensate for arbitrary scattering length. Stability and time scales for
various decay processes are estimated. The previously predicted Efimov-like
states are found to be very narrow. We discuss the validity conditions and
formal connections between the zero- and finite-range mean-field
approximations, Faddeev-Yakubovskii formulation, Jastrow ansatz, and the
present method. We compare numerical results from present work with mean-field
calculations and discuss qualitatively the connection with measurements.Comment: 26 pages, 6 figures, submitted to J. Phys. B. Ver. 2 is 28 pages with
modified figures and discussion
Spin Squeezing in the Ising Model
We analyze the collective spin noise in interacting spin systems. General
expressions are derived for the short time behaviour of spin systems with
general spin-spin interactions, and we suggest optimum experimental conditions
for the detection of spin squeezing. For Ising models with site dependent
nearest neighbour interactions general expressions are presented for the spin
squeezing parameter for all times. The reduction of collective spin noise can
be used to verify the entangling powers of quantum computer architectures based
on interacting spins.Comment: 7 pages, including 3 figure
Doped coupled frustrated spin-1/2 chains with four-spin exchange
The role of various magnetic inter-chain couplings is investigated by
numerical methods in doped frustrated quantum spin chains. A non-magnetic
dopant introduced in a gapped spin chain releases a free spin-1/2 soliton. The
formation of a local magnetic moment is analyzed in term of soliton
confinement. A four-spin coupling which might originate from cyclic exchange is
shown to produce such a confinement in contrast to transverse magnetic
exchange. Dopants on different chains experience an effective space-extended
non-frustrating pairwise spin interaction.Comment: Few modifications and references added. Submitted to PR
Few-body resonances of unequal-mass systems with infinite interspecies two-body s-wave scattering length
Two-component Fermi and Bose gases with infinitely large interspecies s-wave
scattering length exhibit a variety of intriguing properties. Among these
are the scale invariance of two-component Fermi gases with equal masses, and
the favorable scaling of Efimov features for two-component Bose gases and
Bose-Fermi mixtures with unequal masses. This paper builds on our earlier work
[D. Blume and K. M. Daily, arXiv:1006.5002] and presents a detailed discussion
of our studies of small unequal-mass two-component systems with infinite
in the regime where three-body Efimov physics is absent. We report on
non-universal few-body resonances. Just like with two-body systems on
resonance, few-body systems have a zero-energy bound state in free space and a
diverging generalized scattering length. Our calculations are performed within
a non-perturbative microscopic framework and investigate the energetics and
structural properties of small unequal-mass two-component systems as functions
of the mass ratio , and the numbers and of heavy and
light atoms. For purely attractive Gaussian two-body interactions, we find that
the and systems exhibit three-body and four-body
resonances at mass ratios and 10.4(2), respectively. The
three- and four-particle systems on resonance are found to be large. This
suggests that the corresponding wave function has relatively small overlap with
deeply-bound dimers, trimers or larger clusters and that the three- and
four-body systems on resonance have a comparatively long lifetime. Thus, it
seems feasible that the features discussed in this paper can be probed
experimentally with present-day technology.Comment: 17 pages, 17 figure
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