21,772 research outputs found
Enstrophy Dynamics of Stochastically Forced Large-Scale Geophysical Flows
Enstrophy is an averaged measure of fluid vorticity. This quantity is
particularly important in {\em rotating} geophysical flows. We investigate the
dynamical evolution of enstrophy for large-scale quasi-geostrophic flows under
random wind forcing. We obtain upper bounds on the enstrophy, as well as
results establishing its H\"older continuity and describing the small-time
asymptotics
Trapped ion quantum computation with transverse phonon modes
We propose a scheme to implement quantum gates on any pair of trapped ions
immersed in a large linear crystal, using interaction mediated by the
transverse phonon modes. Compared with the conventional approaches based on the
longitudinal phonon modes, this scheme is much less sensitive to ion heating
and thermal motion outside of the Lamb-Dicke limit thanks to the stronger
confinement in the transverse direction. The cost for such a gain is only a
moderate increase of the laser power to achieve the same gate speed. We also
show how to realize arbitrary-speed quantum gates with transverse phonon modes
based on simple shaping of the laser pulses.Comment: 5 page
Implementation of controlled SWAP gates for quantum fingerprinting and photonic quantum computation
We propose a scheme to implement quantum controlled SWAP gates by directing
single-photon pulses to a two-sided cavity with a single trapped atom. The
resultant gates can be used to realize quantum fingerprinting and universal
photonic quantum computation. The performance of the scheme is characterized
under realistic experimental noise with the requirements well within the reach
of the current technology.Comment: 4 page
Generalized Stable Multivariate Distribution and Anisotropic Dilations
After having closely re-examined the notion of a L\'evy's stable vector, it
is shown that the notion of a stable multivariate distribution is more general
than previously defined. Indeed, a more intrinsic vector definition is obtained
with the help of non isotropic dilations and a related notion of generalized
scale. In this framework, the components of a stable vector may not only have
distinct Levy's stability indices 's, but the latter may depend on its
norm. Indeed, we demonstrate that the Levy's stability index of a vector rather
correspond to a linear application than to a scalar, and we show that the
former should satisfy a simple spectral property
Topology of Knotted Optical Vortices
Optical vortices as topological objects exist ubiquitously in nature. In this
paper, by making use of the -mapping topological current theory, we
investigate the topology in the closed and knotted optical vortices. The
topological inner structure of the optical vortices are obtained, and the
linking of the knotted optical vortices is also given.Comment: 11 pages, no figures, accepted by Commun. Theor. Phys. (Beijing, P.
R. China
Arbitrary-speed quantum gates within large ion crystals through minimum control of laser beams
We propose a scheme to implement arbitrary-speed quantum entangling gates on
two trapped ions immersed in a large linear crystal of ions, with minimal
control of laser beams. For gate speeds slower than the oscillation frequencies
in the trap, a single appropriately-detuned laser pulse is sufficient for
high-fidelity gates. For gate speeds comparable to or faster than the local ion
oscillation frequency, we discover a five-pulse protocol that exploits only the
local phonon modes. This points to a method for efficiently scaling the ion
trap quantum computer without shuttling ions.Comment: 4 page
Nonlocal Entanglement Transformations Achievable by Separable Operations
For manipulations of multipartite quantum systems, it was well known that all
local operations assisted by classical communication (LOCC) constitute a proper
subset of the class of separable operations. Recently, Gheorghiu and Griffiths
found that LOCC and general separable operations are equally powerful for
transformations between bipartite pure states. In this letter we extend this
comparison to mixed states and show that in general separable operations are
strictly stronger than LOCC when transforming a mixed state to a pure entangled
state. A remarkable consequence of our finding is the existence of entanglement
monotone which may increase under separable operations.Comment: v2 has rephrased Theorem 1 and corrected Kraus operators in Theorem
2. Additional comments are welcome
Generally Covariant Conservative Energy-Momentum for Gravitational Anyons
We obtain a generally covariant conservation law of energy-momentum for
gravitational anyons by the general displacement transform. The energy-momentum
currents have also superpotentials and are therefore identically conserved. It
is shown that for Deser's solution and Clement's solution, the energy vanishes.
The reasonableness of the definition of energy-momentum may be confirmed by the
solution for pure Einstein gravity which is a limit of vanishing Chern-Simons
coulping of gravitational anyons.Comment: 12 pages, Latex, no figure
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