1,578 research outputs found
Quantum control of spin-correlations in ultracold lattice gases
We demonstrate that it is possible to prepare a lattice gas of ultracold
atoms with a desired non-classical spin-correlation function using atom-light
interaction of the kind routinely employed in quantum spin polarization
spectroscopy. Our method is based on quantum non-demolition (QND) measurement
and feedback, and allows in particular to create on demand exponentially or
algebraically decaying correlations, as well as a certain degree of
multi-partite entanglement.Comment: 2 figure
Clustered Integer 3SUM via Additive Combinatorics
We present a collection of new results on problems related to 3SUM,
including:
1. The first truly subquadratic algorithm for
1a. computing the (min,+) convolution for monotone increasing
sequences with integer values bounded by ,
1b. solving 3SUM for monotone sets in 2D with integer coordinates
bounded by , and
1c. preprocessing a binary string for histogram indexing (also
called jumbled indexing).
The running time is:
with
randomization, or deterministically. This greatly improves the
previous time bound obtained from Williams'
recent result on all-pairs shortest paths [STOC'14], and answers an open
question raised by several researchers studying the histogram indexing problem.
2. The first algorithm for histogram indexing for any constant alphabet size
that achieves truly subquadratic preprocessing time and truly sublinear query
time.
3. A truly subquadratic algorithm for integer 3SUM in the case when the given
set can be partitioned into clusters each covered by an interval
of length , for any constant .
4. An algorithm to preprocess any set of integers so that subsequently
3SUM on any given subset can be solved in
time.
All these results are obtained by a surprising new technique, based on the
Balog--Szemer\'edi--Gowers Theorem from additive combinatorics
Estimating the plasmonic field enhancement using high-order harmonic generation: The role of inhomogeneity of the fields
In strong field laser physics it is a common practice to use the high-order
harmonic cutoff to estimate the laser intensity of the pulse that generates the
harmonic radiation. Based on the semiclassical arguments it is possible to find
a direct relationship between the maximum value of the photon energy and the
laser intensity. This approach is only valid if the electric field driving HHG
is spatially homogenous. In laser-matter processes driven by plasmonics fields,
the enhanced fields present a spatial dependence that strongly modifies the
electron motion and consequently the laser driven phenomena. As a result, this
method should be revised in order to more realistically estimate the field. In
this work, we demonstrate how the inhomogeneity of the fields will effect this
estimation. Furthermore, by employing both quantum mechanical and classical
calculations, we show how one can obtain a better estimation for the intensity
of the enhanced field in plasmonic nanostructure.Comment: 7 pages and 2 figure
Numerical studies of light-matter interaction driven by plasmonic fields: the velocity gauge
Theoretical approaches to strong field phenomena driven by plasmonic fields
are based on the length gauge formulation of the laser-matter coupling. From
the theoretical viewpoint it is known there exists no preferable gauge and
consequently the predictions and outcomes should be independent of this choice.
The use of the length gauge is mainly due to the fact that the quantity
obtained from finite elements simulations of plasmonic fields is the plasmonic
enhanced laser electric field rather than the laser vector potential. In this
paper we develop, from first principles, the velocity gauge formulation of the
problem and we apply it to the high-order harmonic generation (HHG) in atoms. A
comparison to the results obtained with the length gauge is made. It is
analytically and numerically demonstrated that both gauges give equivalent
descriptions of the emitted HHG spectra resulting from the interaction of a
spatially inhomogeneous field and the single active electron (SAE) model of the
helium atom. We discuss, however, advantages and disadvantages of using
different gauges in terms of numerical efficiency.Comment: 19 pages, 5 figures, submitted to Journal of Computational Physic
Fractional Quantum Hall States in Ultracold Rapidly Rotating Dipolar Fermi Gases
We demonstrate the experimental feasibility of incompressible fractional
quantum Hall-like states in ultra-cold two dimensional rapidly rotating dipolar
Fermi gases. In particular, we argue that the state of the system at filling
fraction is well-described by the Laughlin wave function and find a
substantial energy gap in the quasiparticle excitation spectrum. Dipolar gases,
therefore, appear as natural candidates of systems that allow to realize these
very interesting highly correlated states in future experiments.Comment: 4 pages, 2 figure
Orbital physics of polar Fermi molecules
We study a system of polar dipolar fermions in a two-dimensional optical
lattice and show that multi-band Fermi-Hubbard model is necessary to discuss
such system. By taking into account both on-site, and long-range interactions
between different bands, as well as occupation-dependent inter- and intra-band
tunneling, we predict appearance of novel phases in the strongly-interacting
limit
Many body population trapping in ultracold dipolar gases
A system of interacting dipoles is of paramount importance for understanding
of many-body physics. The interaction between dipoles is {\it anisotropic} and
{\it long-range}. While the former allows to observe rich effects due to
different geometries of the system, long-range () interactions lead to
strong correlations between dipoles and frustration. In effect, interacting
dipoles in a lattice form a paradigmatic system with strong correlations and
exotic properties with possible applications in quantum information
technologies, and as quantum simulators of condensed matter physics, material
science, etc. Notably, such a system is extremely difficult to model due to a
proliferation of interaction induced multi-band excitations for sufficiently
strong dipole-dipole interactions. In this article we develop a consistent
theoretical model of interacting polar molecules in a lattice by applying the
concepts and ideas of ionization theory which allows us to include highly
excited Bloch bands. Additionally, by involving concepts from quantum optics
(population trapping), we show that one can induce frustration and engineer
exotic states, such as Majumdar-Ghosh state, or vector-chiral states in such a
system.Comment: many interesting page
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