1,218 research outputs found
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
Classification of mixed three-qubit states
We introduce a classification of mixed three-qubit states, in which we define
the classes of separable, biseparable, W- and GHZ-states. These classes are
successively embedded into each other. We show that contrary to pure W-type
states, the mixed W-class is not of measure zero. We construct witness
operators that detect the class of a mixed state. We discuss the conjecture
that all entangled states with positive partial transpose (PPTES) belong to the
W-class. Finally, we present a new family of PPTES "edge" states with maximal
ranks.Comment: 4 pages, 1 figur
Spin squeezing inequalities and entanglement of qubit states
We derive spin squeezing inequalities that generalize the concept of the spin
squeezing parameter and provide necessary and sufficient conditions for genuine
2-, or 3- qubit entanglement for symmetric states, and sufficient condition for
general states of qubits. Our inequalities have a clear physical
interpretation as entanglement witnesses, can be relatively easy measured, and
are given by complex, but {\it elementary} expressions.Comment: formula (24) corrected, minor changes, final versio
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