32 research outputs found
Photoelectron spectra in an autoionization system interacting with a neighboring atom
Photoelectron ionization spectra of an autoionization system with one
discrete level interacting with a neighbor two-level atom are discussed. The
formula for long-time ionization spectra is derived. According to this formula,
the spectra can be composed of up to eight peaks. Moreover, the Fano-like zeros
for weak optical pumping have been identified in these spectra. The conditional
ionization spectra depending on the state of the neighbor atom exhibit
oscillations at the Rabi frequency. Dynamical spectral zeros occurring once per
the Rabi period have been revealed in these spectra.Comment: 10 pages, 13 figure
Surface spontaneous parametric down-conversion
Surface spontaneous parametric down-conversion is predicted as a consequence
of continuity requirements for electric- and magnetic-field amplitudes at a
discontinuity of chi2 nonlinearity. A generalization of the usual two-photon
spectral amplitude is suggested to describe this effect. Examples of nonlinear
layered structures and periodically-poled nonlinear crystals show that surface
contributions to spontaneous down-conversion can be important.Comment: 4 pages, 3 figure
Field quantization in inhomogeneous absorptive dielectrics
The quantization of the electromagnetic field in a three-dimensional
inhomogeneous dielectric medium with losses is carried out in the framework of
a damped-polariton model with an arbitrary spatial dependence of its
parameters. The equations of motion for the canonical variables are solved
explicitly by means of Laplace transformations for both positive and negative
time. The dielectric susceptibility and the quantum noise-current density are
identified in terms of the dynamical variables and parameters of the model. The
operators that diagonalize the Hamiltonian are found as linear combinations of
the canonical variables, with coefficients depending on the electric
susceptibility and the dielectric Green function. The complete time dependence
of the electromagnetic field and of the dielectric polarization is determined.
Our results provide a microscopic justification of the phenomenological
quantization scheme for the electromagnetic field in inhomogeneous dielectrics.Comment: 19 page
Emission of photon pairs at discontinuities of nonlinearity in spontaneous parametric down-conversion
In order to fulfil the continuity requirements for electric- and
magnetic-field amplitudes at discontinuities of chi2 nonlinearity additional
photon pairs have to be emitted in the area of discontinuity. Generalized
two-photon spectral amplitudes can be used to describe properties of photon
pairs generated in this process that we call surface spontaneous parametric
down-conversion. The spectral structure of such photon pairs is similar to that
derived for photon pairs generated in the volume. Surface and volume
contributions to spontaneous down-conversion can be comparable as an example of
nonlinear layered structures shows.Comment: 11 pages, 8 figure
Nonclassical properties of states engineered by superpositions of quantum operations on classical states
We consider an experimentally realizable scheme for manipulating quantum
states using a general superposition of products of field annihilation
() and creation () operators of the type (), with . Such an
operation, when applied on states with classical features, is shown to
introduce strong nonclassicality. We quantify the generated degree of
nonclassicality by the negative volume of Wigner distribution in the phase
space and investigate two other observable nonclassical features,
sub-Poissonian statistics and squeezing. We find that the operation introduces
negativity in the Wigner distribution of an input coherent state and changes
the Gaussianity of an input thermal state. This provides the possibility of
engineering quantum states with specific nonclassical features.Comment: 19 pages, IOPclass(iopart.cls
Sudden vanishing and reappearance of nonclassical effects: General occurrence of finite-time decays and periodic vanishings of nonclassicality and entanglement witnesses
Analyses of phenomena exhibiting finite-time decay of quantum entanglement
have recently attracted considerable attention. Such decay is often referred to
as sudden vanishing (or sudden death) of entanglement, which can be followed by
its sudden reappearance (or sudden rebirth). We analyze various finite-time
decays (for dissipative systems) and analogous periodic vanishings (for unitary
systems) of nonclassical correlations as described by violations of classical
inequalities and the corresponding nonclassicality witnesses (or quantumness
witnesses), which are not necessarily entanglement witnesses. We show that
these sudden vanishings are universal phenomena and can be observed: (i) not
only for two- or multi-mode but also for single-mode nonclassical fields, (ii)
not solely for dissipative systems, and (iii) at evolution times which are
usually different from those of sudden vanishings and reappearances of quantum
entanglement.Comment: 10 pages, 3 figure
Asymptotical photon distributions in the dissipative Dynamical Casimir Effect
Asymptotical formulas for the photon distribution function of a quantum
oscillator with time-dependent frequency and damping coefficients, interacting
with a thermal reservoir, are derived in the case of a large mean number of
quanta. Different regimes of excitation of an initial thermal state with an
arbitrary temperature are considered. New formulas are used to predict the
statistical properties of the electromagnetic field created in the experiments
on the Dynamical Casimir Effect which are now under preparation.Comment: 11 pages, accepted contribution to CEWQO 2009 proceedings (to appear
in Physica Scripta
Number phase uncertainty relations: verification by homodyning
It is shown that fundamental uncertainty relations between photon number and
canonical phase of a single-mode optical field can be verified by means of
balanced homodyne measurement. All the relevant quantities can be sampled
directly from the measured phase-dependent quadrature distribution.Comment: 1 Ps figure (divided in 3 subfigures) using REVTE
Dynamics of quantum light in integrated nonlinear waveguide arrays and generation of robust continuous variable entanglement
We study a class of nonlinear waveguide arrays where the waveguides are
endowed with quadratic non- linearity and are coupled through the evanescent
overlap of the guided modes. We study both the stimulated and spontaneous
process in the array and show the viability of such an array as a platform for
generating both bipartite and tripartite continuous variable entanglement on
demand. We explicitly address the affect of realistic losses on the
entanglement produced, briefly discuss the possible types of nonlinear
materials that could be used, and suggest solutions to the possible phase
matching issues in the waveguides. The simultaneous generation and manipulation
of the light on a single waveguide chip circumvents the usual bandwidth
problems associated with the use of external bulky optical elements and makes
this avenue promising for further investigation.Comment: 5 pages, 5 figure
Wigner-function description of quantum teleportation in arbitrary dimensions and continuous limit
We present a unified approach to quantum teleportation in arbitrary
dimensions based on the Wigner-function formalism. This approach provides us
with a clear picture of all manipulations performed in the teleportation
protocol. In addition within the framework of the Wigner-function formalism all
the imperfections of the manipulations can be easily taken into account.Comment: 8 pages, LaTeX, 1 figure (included). Accepted for publication in
Phys. Rev. A A minor correction added on May 2