2,095 research outputs found
Two-mode entanglement in two-component Bose-Einstein condensates
We study the generation of two-mode entanglement in a two-component
Bose-Einstein condensate trapped in a double-well potential. By applying the
Holstein-Primakoff transformation, we show that the problem is exactly solvable
as long as the number of excitations due to atom-atom interactions remains low.
In particular, the condensate constitutes a symmetric Gaussian system, thereby
enabling its entanglement of formation to be measured directly by the
fluctuations in the quadratures of the two constituent components [Giedke {\it
et al.}, Phys. Rev. Lett. {\bf 91}, 107901 (2003)]. We discover that
significant two-mode squeezing occurs in the condensate if the interspecies
interaction is sufficiently strong, which leads to strong entanglement between
the two components.Comment: 22 pages, 4 figure
Hydrogen interactions in aluminum-lithium alloys
A program is described which seeks to develop an understanding of the effects of dissolved and trapped hydrogen on the mechanical properties of selected Al-Li-Cu-X alloys. A proposal is made to distinguish hydrogen (H2) induced EAC from aqueous dissolution controlled EAC, to correlate H2 induced EAC with mobile and trapped concentrations, and to identify significant trap sites and hydride phases (if any) through use of model alloys and phases. A literature review shows three experimental factors which have impeded progress in the area of H2 EAC for this class of alloys. These are as listed: (1) inter-subgranular fracture in Al-Li alloys when tested in the S-T orientation in air or vacuum make it difficult to readily detect H2 induced fracture based on straight forward changes in fractography; (2) the inherently low H2 diffusivity and solubility in Al alloys is further compounded by a native oxide which acts as a H2 permeation barrier; and (3) H2 effects are masked by dissolution assisted processes when mechanical testing is performed in aqueous solutions
K-shell photoionization of ground-state Li-like boron ions [B]: Experiment and Theory
Absolute cross sections for the K-shell photoionization of ground-state
Li-like boron [B(1s2s S)] ions were measured by employing the
ion-photon merged-beams technique at the Advanced Light Source synchrotron
radiation facility. The energy ranges 197.5--200.5 eV, 201.9--202.1 eV of the
[1s(2s\,2p)P]P and [1s(2s\,2p)P] P
resonances, respectively, were investigated using resolving powers of up to
17\,600. The energy range of the experiments was extended to about 238.2 eV
yielding energies of the most prominent
[1s(2\,n)]P resonances with an absolute accuracy
of the order of 130 ppm. The natural linewidths of the [1s(2s\,2p)P]
P and [1s(2s\,2p)P] P resonances were measured
to be meV and meV, respectively, which compare
favourably with theoretical results of 4.40 meV and 30.53 meV determined using
an intermediate coupling R-matrix method.Comment: 6 figures and 2 table
K-shell photoionization of ground-state Li-like carbon ions [C]: experiment, theory and comparison with time-reversed photorecombination
Absolute cross sections for the K-shell photoionization of ground-state
Li-like carbon [C(1s2s S)] ions were measured by employing the
ion-photon merged-beams technique at the Advanced Light Source. The energy
ranges 299.8--300.15 eV, 303.29--303.58 eV and 335.61--337.57 eV of the
[1s(2s2p)P]P, [1s(2s2p)P]P and [(1s2s)S 3p]P
resonances, respectively, were investigated using resolving powers of up to
6000. The autoionization linewidth of the [1s(2s2p)P]P resonance was
measured to be meV and compares favourably with a theoretical result
of 26 meV obtained from the intermediate coupling R-Matrix method. The present
photoionization cross section results are compared with the outcome from
photorecombination measurements by employing the principle of detailed balance.Comment: 3 figures and 2 table
Mach-Zehnder Interferometry at the Heisenberg Limit with coherent and squeezed-vacuum light
We show that the phase sensitivity of a Mach-Zehnder
interferometer fed by a coherent state in one input port and squeezed-vacuum in
the other one is i) independent from the true value of the phase shift and ii)
can reach the Heisenberg limit , where is the
average number of particles of the input states. We also show that the
Cramer-Rao lower bound, , can be saturated for arbitrary values of the squeezing parameter
and the amplitude of the coherent mode by a Bayesian phase
inference protocol.Comment: 4 pages, 4 figure
Few-Body Bound Complexes in One-dimensional Dipolar Gases and Non-Destructive Optical Detection
We consider dipolar interactions between heteronuclear molecules in
low-dimensional geometries. The setup consists of two one-dimensional tubes. We
study the stability of possible few-body complexes in the regime of repulsive
intratube interaction, where the binding arises from intertube attraction. The
stable dimers, trimers, and tetramers are found and we discuss their properties
for both bosonic and fermionic molecules. To observe these complexes we propose
an optical non-destructive detection scheme that enables in-situ observation of
the creation and dissociation of the few-body complexes. A detailed description
of the expected signal of such measurements is given using the numerically
calculated wave functions of the bound states. We also discuss implications on
the many-body physics of dipolar systems in tubular geometries, as well as
experimental issues related to the external harmonic confinement along the tube
and the prospect of applying an in-tube optical lattice to increase the
effective dipole strength.Comment: 16 pages, 15 figures, published versio
Nuclear quantum optics with x-ray laser pulses
The direct interaction of nuclei with super-intense laser fields is studied.
We show that present and upcoming high-frequency laser facilities, especially
together with a moderate acceleration of the target nuclei, do allow for
resonant laser-nucleus interaction. These direct interactions may be utilized
for the optical measurement of nuclear properties such as the transition
frequency and the dipole moment, thus opening the field of nuclear quantum
optics. As ultimate goal, one may hope that direct laser-nucleus interactions
could become a versatile tool to enhance preparation, control and detection in
nuclear physics.Comment: 5 pages, 3 eps figures, revised versio
Coupling of Surface and Volume Dipole Oscillations in C-60 Molecules
We first give a short review of the ``local-current approximation'' (LCA),
derived from a general variation principle, which serves as a semiclassical
description of strongly collective excitations in finite fermion systems
starting from their quantum-mechanical mean-field ground state. We illustrate
it for the example of coupled translational and compressional dipole
excitations in metal clusters. We then discuss collective electronic dipole
excitations in C molecules (Buckminster fullerenes). We show that the
coupling of the pure translational mode (``surface plasmon'') with
compressional volume modes in the semiclasscial LCA yields semi-quantitative
agreement with microscopic time-dependent density functional (TDLDA)
calculations, while both theories yield qualitative agreement with the recent
experimental observation of a ``volume plasmon''.Comment: LaTeX, 12 pages, 5 figures (8 *.eps files); Contribution to XIV-th
Nuclear Physics Workshop at Kazimierz Dolny, Poland, Sept. 26-29, 200
A symmetry analyser for non-destructive Bell state detection using EIT
We describe a method to project photonic two-qubit states onto the symmetric
and antisymmetric subspaces of their Hilbert space. This device utilizes an
ancillary coherent state, together with a weak cross-Kerr non-linearity,
generated, for example, by electromagnetically induced transparency. The
symmetry analyzer is non-destructive, and works for small values of the
cross-Kerr coupling. Furthermore, this device can be used to construct a
non-destructive Bell state detector.Comment: Final published for
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