69 research outputs found
Spatial properties of entangled photon pairs generated in nonlinear layered structures
A spatial quantum model of spontaneous parametric down-conversion in
nonlinear layered structures is developed expanding the interacting vectorial
fields into monochromatic plane waves. A two-photon spectral amplitude
depending on the signal- and idler-field frequencies and propagation directions
is used to derive transverse profiles of the emitted fields as well as their
spatial correlations. Intensity spatial profiles and their spatial correlations
are mainly determined by the positions of transmission peaks formed in these
structures with photonic bands. A method for geometry optimization of the
structures with respect to efficiency of the nonlinear process is suggested.
Several structures composed of GaN/AlN layers are analyzed as typical examples.
They allow the generation of photon pairs correlated in several emission
directions. Photon-pair generation rates increasing better than the second
power of the number of layers can be reached. Also structures efficiently
generated photon pairs showing anti-bunching and anti-coalescence can be
obtained. Three reasons for splitting the correlated area in photonic-band-gap
structures are revealed: zig-zag movement of photons inside the structure,
spatial symmetry and polarization-dependent properties. Also spectral splitting
can be observed in these structures.Comment: 13 pages, 17 figure
Photon-number distributions of twin beams generated in spontaneous parametric down-conversion and measured by an intensified CCD camera
The measurement of photon-number statistics of fields composed of photon
pairs, generated in spontaneous parametric down-conversion and detected by an
intensified CCD camera is described. Final quantum detection efficiencies,
electronic noises, finite numbers of detector pixels, transverse intensity
spatial profiles of the detected beams as well as losses of single photons from
a pair are taken into account in a developed general theory of photon-number
detection. The measured data provided by an iCCD camera with single-photon
detection sensitivity are analyzed along the developed theory. Joint
signal-idler photon-number distributions are recovered using the reconstruction
method based on the principle of maximum likelihood. The range of applicability
of the method is discussed. The reconstructed joint signal-idler photon-number
distribution is compared with that obtained by a method that uses superposition
of signal and noise and minimizes photoelectron entropy. Statistics of the
reconstructed fields are identified to be multi-mode Gaussian. Elements of the
measured as well as the reconstructed joint signal-idler photon-number
distributions violate classical inequalities. Sub-shot-noise correlations in
the difference of the signal and idler photon numbers as well as partial
suppression of odd elements in the distribution of the sum of signal and idler
photon numbers are observed.Comment: 14 pages, 14 figure
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
Properties of entangled photon pairs generated in one-dimensional nonlinear photonic-band-gap structures
We have developed a rigorous quantum model of spontaneous parametric
down-conversion in a nonlinear 1D photonic-band-gap structure based upon
expansion of the field into monochromatic plane waves. The model provides a
two-photon amplitude of a created photon pair. The spectra of the signal and
idler fields, their intensity profiles in the time domain, as well as the
coincidence-count interference pattern in a Hong-Ou-Mandel interferometer are
determined both for cw and pulsed pumping regimes in terms of the two-photon
amplitude. A broad range of parameters characterizing the emitted
down-converted fields can be used. As an example, a structure composed of 49
layers of GaN/AlN is analyzed as a suitable source of photon pairs having high
efficiency.Comment: 14 pages, 23 figure
Squeezed-light generation in a nonlinear planar waveguide with a periodic corrugation
Two-mode nonlinear interaction (second-harmonic and second-subharmonic
generation) in a planar waveguide with a small periodic corrugation at the
surface is studied. Scattering of the interacting fields on the corrugation
leads to constructive interference that enhances the nonlinear process provided
that all the interactions are phase matched. Conditions for the overall phase
matching are found. Compared with a perfectly quasi-phase-matched waveguide,
better values of squeezing as well as higher intensities are reached under
these conditions. Procedure for finding optimum values of parameters for
squeezed-light generation is described.Comment: 14 pages, 14 figure
Universal measurement of quantum correlations of radiation
A measurement technique is proposed which, in principle, allows one to
observe the general space-time correlation properties of a quantized radiation
field. Our method, called balanced homodyne correlation measurement, unifies
the advantages of balanced homodyne detection with those of homodyne
correlation measurements.Comment: 4 pages, 4 figures, small misprints were corrected, accepted to Phys.
Rev. Let
Stability and instability in parametric resonance and quantum Zeno effect
A quantum mechanical version of a classical inverted pendulum is analyzed.
The stabilization of the classical motion is reflected in the bounded evolution
of the quantum mechanical operators in the Heisenberg picture. Interesting
links with the quantum Zeno effect are discussed.Comment: 6 pages, 3 figure
Multiple-photon resolving fiber-loop detector
We show first reconstructions of the photon-number distribution obtained with
a multi-channel fiber-loop detector. Apart from analyzing the statistics of
light pulses this device can serve as a sophisticated postselection device for
experiments in quantum optics and quantum information. We quantify its
efficiency by means of the Fisher information and compare it to the efficiency
of the ideal photodetector.Comment: 5 pages, 6 figure
The 1/N-expansion, quantum-classical correspondence and nonclassical states generation in dissipative higher-order anharmonic oscillators
We develop a method for the determination of thecdynamics of dissipative
quantum systems in the limit of large number of quanta N, based on the
1/N-expansion of Heidmann et al. [ Opt. Commun. 54, 189 (1985) ] and the
quantum-classical correspondence. Using this method, we find analytically the
dynamics of nonclassical states generation in the higher-order anharmonic
dissipative oscillators for an arbitrary temperature of a reservoir. We show
that the quantum correction to the classical motion increases with time
quadratically up to some maximal value, which is dependent on the degree of
nonlinearity and a damping constant, and then it decreases. Similarities and
differences with the corresponding behavior of the quantum corrections to the
classical motion in the Hamiltonian chaotic systems are discussed. We also
compare our results obtained for some limiting cases with the results obtained
by using other semiclassical tools and discuss the conditions for validity of
our approach.Comment: 15 pages, RevTEX (EPSF-style), 3 figs. Replaced with final version
(stylistic corrections
Linear atomic quantum coupler
In this paper, we develop the notion of the linear atomic quantum coupler.
This device consists of two modes propagating into two waveguides, each of them
includes a localized and/or a trapped atom. These waveguides are placed close
enough to allow exchanging energy between them via evanescent waves. Each mode
interacts with the atom in the same waveguide in the standard way, i.e. as the
Jaynes-Cummings model (JCM), and with the atom-mode in the second waveguide via
evanescent wave. We present the Hamiltonian for the system and deduce the exact
form for the wavefunction. We investigate the atomic inversions and the
second-order correlation function. In contrast to the conventional linear
coupler, the atomic quantum coupler is able to generate nonclassical effects.
The atomic inversions can exhibit long revival-collapse phenomenon as well as
subsidiary revivals based on the competition among the switching mechanisms in
the system. Finally, under certain conditions, the system can yield the results
of the two-mode JCM.Comment: 14 pages, 3 figures; comments are most welcom
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