734 research outputs found
More on the Isomorphism
In this paper we revisit the isomorphism to
apply to some subjects in Quantum Computation and Mathematical Physics.
The unitary matrix by Makhlin giving the isomorphism as an adjoint action
is studied and generalized from a different point of view. Some problems are
also presented.
In particular, the homogeneous manifold which characterizes
entanglements in the case of is studied, and a clear-cut calculation of
the universal Yang-Mills action in (hep-th/0602204) is given for the abelian
case.Comment: Latex ; 19 pages ; 5 figures ; minor changes. To appear in
International Journal of Geometric Methods in Modern Physics (vol.4, no.3
Optical nonlinearity enhancement of graded metallic films
The effective linear and third-order nonlinear susceptibility of graded
metallic films with weak nonlinearity have been investigated. Due to the simple
geometry, we were able to derive exactly the local field inside the graded
structures having a Drude dielectric gradation profile. We calculated the
effective linear dielectric constant and third-order nonlinear susceptibility.
We investigated the surface plasmon resonant effect on the optical absorption,
optical nonlinearity enhancement, and figure of merit of graded metallic films.
It is found that the presence of gradation in metallic films yields a broad
resonant plasmon band in the optical region, resulting in a large enhancement
of the optical nonlinearity and hence a large figure of merit. We suggest
experiments be done to check our theoretical predictions, because graded
metallic films can be fabricated more easily than graded particles.Comment: 11 pages, 2 eps figures, submitted to Applied Physics Letter
Strong fields induce ultrafast rearrangement of H-atoms in HO
H-atoms in HO are rearranged by strong optical fields generated by
intense, 10 fs laser pulses to form H, against prevailing wisdom that
strong fields inevitably lead to multiple molecular ionization and the
subsequent Coulomb explosion into fragments. This atomic rearrangement is shown
to occur within a single 10 fs pulse. Comparison with results obtained with
300-attosecond long strong fields generated using fast Si ions
helps establish thresholds for field strength and time required for such
rearrangements. Quantum-chemical calculations reveal that H originates in
the A state of HO when the O-H bond elongates to 1.15 a.u. and
the H-O-H angle becomes 120. Bond formation on the ultrafast timescale of
molecular vibrations (10 fs for H) has hitherto not been reported.Comment: Submitted to Physical Review Lotter
Quantum dynamics of proton migration in H2O dications: formation of H2+ on ultrafast timescales
Irradiation of isolated water molecules by few-cycle pulses of intense
infrared laser light can give rise to ultrafast rearrangement resulting in
formation of the H2+ ion. Such unimolecular reactions occur on the potential
energy surface of the H2O2+ dication that is accessed when peak laser
intensities in the 1015 W cm-2 range and pulse durations as short as 9-10 fs
are used; ion yields of ~1.5% are measured. We also study such reactions by
means of time-dependent wavepacket dynamics on an ab initio potential energy
surface of the dication and show that a proton, generated from O-H bond
rupture, migrates towards the H-atom, and forms vibrationally-excited H2+ in a
well-defined spatial zone.Comment: To appear in J. Chem. Phys. (tentatively the 22 January 2012 issue
Optical nonlinearity enhancement of graded metal-dielectric composite films
We have derived the local electric field inside graded metal-dielectric
composite films with weak nonlinearity analytically, which further yields the
effective linear dielectric constant and third-order nonlinear susceptibility
of the graded structures. As a result, the composition-dependent gradation can
produce a broad resonant plasmon band in the optical region, resulting in a
large enhancement of the optical nonlinearity and hence a large figure of
merit.Comment: 11 pages, 2 figures. To be published in Europhysics Letter
Spectral representation of the effective dielectric constant of graded composites
We generalize the Bergman-Milton spectral representation, originally derived
for a two-component composite, to extract the spectral density function for the
effective dielectric constant of a graded composite. This work has been
motivated by a recent study of the optical absorption spectrum of a graded
metallic film [Applied Physics Letters, 85, 94 (2004)] in which a broad
surface-plasmon absorption band has been shown to be responsible for enhanced
nonlinear optical response as well as an attractive figure of merit. It turns
out that, unlike in the case of homogeneous constituent components, the
characteristic function of a graded composite is a continuous function because
of the continuous variation of the dielectric function within the constituent
components. Analytic generalization to three dimensional graded composites is
discussed, and numerical calculations of multilayered composites are given as a
simple application.Comment: Physical Review E, submitted for publication
Quantum Magnetic Deflagration in Mn12 Acetate
We report controlled ignition of magnetization reversal avalanches by surface
acoustic waves in a single crystal of Mn12 acetate. Our data show that the
speed of the avalanche exhibits maxima on the magnetic field at the tunneling
resonances of Mn12. Combined with the evidence of magnetic deflagration in Mn12
acetate (Suzuki et al., cond-mat/0506569) this suggests a novel physical
phenomenon: deflagration assisted by quantum tunneling.Comment: 4 figure
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