2,906 research outputs found
Matter-wave diffraction in time with a linear potential
Diffraction in time of matter waves incident on a shutter which is removed at
time is studied in the presence of a linear potential. The solution is
also discussed in phase space in terms of the Wigner function. An alternative
configuration relevant to current experiments where particles are released from
a hard wall trap is also analyzed for single-particle states and for a
Tonks-Girardeau gas.Comment: 11 pages, 6 figure
Reflection of a Lieb-Liniger wave packet from the hard-wall potential
Nonequilibrium dynamics of a Lieb-Liniger system in the presence of the
hard-wall potential is studied. We demonstrate that a time-dependent wave
function, which describes quantum dynamics of a Lieb-Liniger wave packet
comprised of N particles, can be found by solving an -dimensional Fourier
transform; this follows from the symmetry properties of the many-body
eigenstates in the presence of the hard-wall potential. The presented formalism
is employed to numerically calculate reflection of a few-body wave packet from
the hard wall for various interaction strengths and incident momenta.Comment: revised version, improved notation, Fig. 5 adde
Shortcuts to adiabaticity in a time-dependent box
A method is proposed to drive an ultrafast non-adiabatic dynamics of an
ultracold gas trapped in a box potential. The resulting state is free from
spurious excitations associated with the breakdown of adiabaticity, and
preserves the quantum correlations of the initial state up to a scaling factor.
The process relies on the existence of an adiabatic invariant and the inversion
of the dynamical self-similar scaling law dictated by it. Its physical
implementation generally requires the use of an auxiliary expulsive potential
analogous to those used in soliton control. The method is extended to a broad
family of many-body systems. As illustrative examples we consider the ultrafast
expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in
different dimensions, where the method exhibits an excellent robustness against
different regimes of interactions and the features of an experimentally
realizable box potential.Comment: 6 pp, 4 figures, typo in Eq. (6) fixe
Exact propagators for atom-laser interactions
A class of exact propagators describing the interaction of an -level atom
with a set of on-resonance -lasers is obtained by means of the Laplace
transform method. State-selective mirrors are described in the limit of strong
lasers. The ladder, V and configurations for a three-level atom are
discussed. For the two level case, the transient effects arising as result of
the interaction between both a semi-infinite beam and a wavepacket with the
on-resonance laser are examined.Comment: 13 pages, 6 figure
One-dimensional anyons with competing -function and derivative -function potentials
We propose an exactly solvable model of one-dimensional anyons with competing
-function and derivative -function interaction potentials. The
Bethe ansatz equations are derived in terms of the -particle sector for the
quantum anyonic field model of the generalized derivative nonlinear
Schr\"{o}dinger equation. This more general anyon model exhibits richer physics
than that of the recently studied one-dimensional model of -function
interacting anyons. We show that the anyonic signature is inextricably related
to the velocities of the colliding particles and the pairwise dynamical
interaction between particles.Comment: 9 pages, 2 figures, minor changes, references update
A single atom detector integrated on an atom chip: fabrication, characterization and application
We describe a robust and reliable fluorescence detector for single atoms that
is fully integrated into an atom chip. The detector allows spectrally and
spatially selective detection of atoms, reaching a single atom detection
efficiency of 66%. It consists of a tapered lensed single-mode fiber for
precise delivery of excitation light and a multi-mode fiber to collect the
fluorescence. The fibers are mounted in lithographically defined holding
structures on the atom chip. Neutral 87Rb atoms propagating freely in a
magnetic guide are detected and the noise of their fluorescence emission is
analyzed. The variance of the photon distribution allows to determine the
number of detected photons / atom and from there the atom detection efficiency.
The second order intensity correlation function of the fluorescence shows
near-perfect photon anti-bunching and signs of damped Rabi-oscillations. With
simple improvements one can boost the detection efficiency to > 95%.Comment: 24 pages, 11 figure
Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo
One of the greatest questions for modern physics to address is how elements
heavier than iron are created in extreme, astrophysical environments. A
particularly challenging part of that question is the creation of the so-called
p-nuclei, which are believed to be mainly produced in some types of supernovae.
The lack of needed nuclear data presents an obstacle in nailing down the
precise site and astrophysical conditions. In this work, we present for the
first time measurements on the nuclear level density and average strength
function of Mo. State-of-the-art p-process calculations systematically
underestimate the observed solar abundance of this isotope. Our data provide
stringent constraints on the NbMo reaction rate,
which is the last unmeasured reaction in the nucleosynthesis puzzle of
Mo. Based on our results, we conclude that the Mo abundance
anomaly is not due to the nuclear physics input to astrophysical model
calculations.Comment: Submitted to PR
Adiabatic dynamics of an inhomogeneous quantum phase transition: the case of z > 1 dynamical exponent
We consider an inhomogeneous quantum phase transition across a multicritical
point of the XY quantum spin chain. This is an example of a Lifshitz transition
with a dynamical exponent z = 2. Just like in the case z = 1 considered in New
J. Phys. 12, 055007 (2010) when a critical front propagates much faster than
the maximal group velocity of quasiparticles vq, then the transition is
effectively homogeneous: density of excitations obeys a generalized
Kibble-Zurek mechanism and scales with the sixth root of the transition rate.
However, unlike for z = 1, the inhomogeneous transition becomes adiabatic not
below vq but a lower threshold velocity v', proportional to inhomogeneity of
the transition, where the excitations are suppressed exponentially.
Interestingly, the adiabatic threshold v' is nonzero despite vanishing minimal
group velocity of low energy quasiparticles. In the adiabatic regime below v'
the inhomogeneous transition can be used for efficient adiabatic quantum state
preparation in a quantum simulator: the time required for the critical front to
sweep across a chain of N spins adiabatically is merely linear in N, while the
corresponding time for a homogeneous transition across the multicritical point
scales with the sixth power of N. What is more, excitations after the adiabatic
inhomogeneous transition, if any, are brushed away by the critical front to the
end of the spin chain.Comment: 10 pages, 6 figures, improved version accepted in NJ
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